Aquatic Invasions (2017) Volume 12, Issue 4: 415–434 DOI: https://doi.org/10.3391/ai.2017.12.4.01 © 2017 The Author(s). Journal compilation © 2017 REABIC Open Access Review Local ecological knowledge versus published literature: a review of non-indigenous Mollusca in Greek marine waters Fabio Crocetta 1, † , * , Serge Gofas 2 , Carmen Salas 2 , Lionello Paolo Tringali 3 and Argyro Zenetos 1 1 Hellenic Centre for Marine Research, Institute of Marine Biological Resources and Inland Waters, GR-19013, Anavyssos, Greece Departamento de Biología Animal, Universidad de Málaga, Campus de Teatinos s/n, E-29071 Málaga, Spain 3 Via Elio Lampridio Cerva 100, I-00143, Roma, Italy 2 *Corresponding author † Present address: Stazione Zoologica Anton Dohrn - Benthos Ecology Center, Villa Dohrn - Punta San Pietro 1, I-80077 - Ischia Porto (Napoli), Italy E-mail: fabio.crocetta@szn.it Received: 26 May 2017 / Accepted: 28 July 2017 / Published online: 12 September 2017 Handling editor: John Mark Hanson Abstract A review of the scientific literature and an analysis of unpublished material identified ~ 50 possible alien molluscs from Greece, four of which were newly reported here. Records of ~ 100 additional taxa, which would strongly inflate the alien species numbers, were excluded. Among the ~ 50 candidate species, 43 were confirmed as alien and 12 as cryptogenic. Twenty-nine alien species were considered established, and four deemed invasive. Our results are consistent with the position of Greece in the east-west Mediterranean gradient, as well as the Aegean marine environment. The contribution of well-informed citizen scientists appears to be crucial to our overall knowledge of alien molluscan biotas because only 12 alien taxa were detected during formal research projects, while 31 were first found by amateurs. No molluscan introductions were confirmed from Greece pre-1960s, and subsequent periods had variable numbers of introductions, ranging from 0 (1976–1980) to 9.5 (2006–2010). The areas with the highest alien species concentrations were the Saronikos Gulf, near the Piraeus port area, and the Dodekanisa, near the Levantine coastline. Despite a general decline in taxonomic expertise and in local knowledge, we show that these are still needed when compiling and analyzing alien species inventories that subsequently influence policy and management decisions. Key words: biological invasion, alien species, citizen science, biogeography, Mediterranean Sea Introduction The increase in human activities and the recent climate change have made ecosystems progressively more disturbed and susceptible to biological invasions worldwide (Stachowicz et al. 1999). Alien species spreading in marine environments has received less attention than those in terrestrial and freshwater habitats (Vilà et al. 2010). However, the importance of species introductions is now attracting substantial interest in the marine and coastal ecosystems. Indeed, the number of alien marine species detected in European waters has nearly doubled every 20 years since the beginning of the twentieth century (Hulme 2009), and these introductions are considered to be one of the main anthropogenic threats to biodiversity (Molnar et al. 2008). Mollusca are a major component of the marine fauna worldwide, accounting for 20–25% of the species, and among the taxa that contain the highest number of invasive species with high ecological impacts (Molnar et al. 2008). Mediterranean alien molluscan taxa have been widely studied (Gofas and Zenetos 2003; Zenetos et al. 2004) and > 200 species have been documented in this sea so far (Sabelli and Taviani 2014). The greatest number of confirmed alien species in the Mediterranean Sea originated in the Red Sea, entering via the Suez Canal (through the so-called Lessepsian migration) (Zenetos et al. 2010, 2012). After Israel (Galil 2007), Lebanon (Crocetta et al. 2013a, 2013b, 2014; Bitar 2014), and Turkey (Öztürk et al. 2014), Greece has the fourth highest number of alien and cryptogenic Mollusca in the Mediterranean (Zenetos et al. 2009c, 2011b). 415 F. Crocetta et al. The alien malacofauna of Greece has been the subject of numerous works focusing either on individual species (e.g., Koutsoubas and VoultsiadouKoukoura 1991; Zenetos et al. 2009a, 2009b; Crocetta and Russo 2013; Karachle et al. 2016) or reporting data and new records in local checklists (e.g., Zenetos et al. 2005b; Manousis and Galinou-Mitsoudi 2013, 2014; Crocetta et al. 2015c). Several local or national reviews have been published in which the Greek Mollusca were included (e.g., Zenetos et al. 2009c, 2011b; Corsini-Foka et al. 2015). In addition, potential records of alien molluscs from Greece have been reported in Greek and Mediterranean molluscan books (e.g., Koronéos 1979; Tenekides 1989; Manousis 2012; Perna 2013). Unfortunately, several recent articles and reviews are based on records that were not confirmed, e.g., records uncritically taken from checklists in old literature, grey literature, and records not supported by photos of the species and suspected to be based on misidentifications. Moreover, the rationale for possible inclusion or exclusion has not always been explained, therefore leaving the reader in doubt as to the validity of these records. Thus, the re-evaluation of earlier reports is needed in the light of modern knowledge and taxonomic studies. In addition, the Convention on Biological Diversity (2000) requires the “compilation and dissemination of information on alien species that threaten ecosystems, habitats, or species, to be used in the context of any prevention, introduction and mitigation activities”. Moreover, while establishing Good Environmental Status (GES) parameters, the D2 Descriptor (addressing NIS - Non Indigenous Species) of the European Union’s Marine Strategy Framework Directive (MSFD) proposes a qualitative/ normative definition to be used among GES criteria. To perform species-presence inventories or to list species encountered in widespread locations is now considered more accurate and cost-effective, and these assessments of species spatial occurrence/ distributions may be considered as surrogates for species abundance and level of invasiveness. Consequently, among the main criteria for assessing GES, an inventory of NIS present in a marine area/country/region, as well as temporal occurrence and trends in new introductions, were recently included (European Commission 2015). Alien species inventories therefore play definitive roles in informing regional policy and management decisions, as well as in identifying resource allocation priorities. At the same time, the scientific community is called upon to assess carefully the accuracy and veracity of the inventories (Ojaveer et al. 2014). Within the framework of several projects supporting the study of Mediterranean alien fauna, we compiled 416 and verified existing records (published and institutional reports) to set up an updated and annotated list of alien, intra-Mediterranean transfer, and cryptogenic marine molluscs in Greece (Figure 1) based upon the analysis of published information and unpublished material coming from dedicated research programmes and citizen scientists. Material and methods The definition of alien species (non-native, nonindigenous, exotic) used herein follows that of the European Commission (2008): “a species, subspecies or lower taxon, introduced outside its natural past or present distribution; includes any part, gametes, seeds, eggs, or propagules of such species that might survive and subsequently reproduce”. We also retained the term intra-Mediterranean transfers (Gofas and Zenetos 2003): “species moved by humans within the same macro area”—e.g., native from the Adriatic and introduced in the western Mediterranean. However, some species recently recorded from the Mediterranean Sea, or even present in the area for centuries, cannot be ascribed with certainty to a native or an alien/intra-Mediterranean transfer status, and may fall into the category of cryptogenic species (Carlton 1996): “a species that cannot be included with confidence among native nor among introduced ones”, a term that is here used in sensu lato and includes all species for which uncertainties occurred. Bibliographic data This study is based on an extensive literature survey where no boundary dates were fixed; therefore, this review covers literature published about Greece since the beginning of scientific writing and observations. We searched for records of alien molluscan species in the waters of Greece in both indexed and nonindexed journals (often manually), as well as relevant institutional reports and grey literature. However, we particularly focused on recent records of species labelled as aliens in Greek waters, species considered to be alien in the Mediterranean basin and recorded from Greece, and species already included in previous alien-species check-lists. Particular attention was given to the reliability of published records and to the status of species labelled as non-indigenous. All species identifications were confirmed by the examination of voucher material preserved in museums and private/institutional collections, and of photographs included in published articles. We excluded several categories of records: ─ species only recorded on the basis of shells, unless their presence is confirmed by published Non-indigenous marine Mollusca in Greece Figure 1. A. Geographical position of Greece within the Mediterranean Sea. Black arrows indicate the Strait of Gibraltar (left) and the Suez Canal (right). B. Greek locations mentioned in the present paper (main manuscript and Appendix 1–2). records of living specimens in other Mediterranean countries or by their significant presence in biogenic sediments in Greece or nearby countries; ─ species reported upon based on incorrect identifications, or incorrect or spurious locality data; ─ old records of alien or potentially alien species unless supported by clear images or by the direct examination of specimens, and there are no doubts with regards to the existence of living individuals. All confirmed species identifications were updated to the latest nomenclature available, following the World Register of Marine Species (WoRMS Editorial Board 2017). Unpublished data Unpublished data were obtained from ongoing research projects within the Hellenic Centre for Marine Research (HCMR) and from informed citizens (the so called citizen scientists: Delaney et al. 2008; Thiel et al. 2014). The latter have been the subject of a targeted leaflet covering the most popular alien taxa, including molluscs (Crocetta and Zenetos 2015). Key contributors were amateur shell collectors, followed by underwater photographers, fishermen, and tourists. However, internet-based contributions in the Mediterranean are also a valuable source of information (e.g., Azzurro et al. 2013; Kleitou et al. in Crocetta et al. 2015a). We therefore screened 417 F. Crocetta et al. photos stored in several web groups, including: “Hellenic Conches” (https://www.facebook.com/groups/ helleniconches/) and “Underwater photography in Greece” (https://www.facebook.com/groups/331466433724867/), both mostly contributed to by Greek subscribers. In the case of straightforward identifications, we asked the contributors for the permission to use the data as well as any relevant additional information. These data were augmented by additional information obtained through the Ellenic Network on Aquatic Invasive Species (ELNAIS), a dynamic online information platform aiming to collect and report spatial information on aquatic alien species in Greek waters (Zenetos et al. 2015a). Records reported to ELNAIS were further validated before being included in this study. Finally, unpublished data for Siphonaria pectinata (Linnaeus, 1758), a species not included in previous reviews, were sought in the Goulandris Natural History Museum (GNHM) to better determine its first detection in Greece. Database development A database of taxa recently reported from Greece was developed for the present study. In contrast to rejected species, where mostly the rationale for exclusion was explained, detailed information was provided for each included alien taxon, including: i) taxonomic notes; ii) date and literature reference of the first sighting/collection; iii) presence of additional confirmed records; iv) possible misspellings, synonyms, different genus/species combinations or misidentifications published from Greece; v) presence of unpublished records; vi) various notes on accuracy of identification and/or finding data; vii) status as alien or cryptogenic in the Mediterranean Sea as a whole; viii) establishment success in Greece and possible invasiveness; ix) most likely primary or secondary pathway/s in the Mediterranean and in Greece (see detailed explanations in Appendix 2). Results and discussion Unpublished data The different groups of citizen scientists contacted allowed us to obtain records that spanned three molluscan classes. While amateur shell collectors are mostly interested in shelled molluscs, including microshells that can be only found by the analysis of sediments under a stereo-microscope, underwater photographers are mostly interested in conspicuous and photogenic taxa, such as the large alien sea slugs or cephalopods. We obtained 173 unpublished records, covering 29 taxa (25 aliens and 4 cryptogenics, including one possible intra-Mediterranean transfer) 418 (Appendix 1). To these should be added 4 lots of Siphonaria pectinata (Linnaeus, 1758) from GNHM (Appendix 1), one of which confirmed the presence of this species from Greece as early as 1973. Due to the presence of some earlier reports (e.g., Zenetos et al. 2008a, 2008b, 2011b, 2013), the majority of new unpublished data (138 records) are from 2010 to 2015. However, some researchers/amateurs not contacted previously had older records of some alien taxa in their logbooks or photo archives. Moreover, some shell collectors preserve their specimens with full data and often collect large amounts of biogenic sediment that may remain unsorted for decades. Thus we obtained some older, unreported, data, the three oldest ones (apart those of S. pectinata) dating back to 1994. Records of four gastropods constituted new sightings for Greece, namely Cerithidium perparvulum (Watson, 1886), Cerithiopsis pulvis (A. Issel, 1869), Cerithiopsis tenthrenois (Melvill, 1896), and Pyrunculus fourierii (Audouin, 1826) (Table 2; Figure 2; Appendix 1–2) (for a previous record of C. tenthrenois from Greece based on a misidentification of Cerithiopsis cf. nana Jeffreys, 1867 see Appendix 2). All these four species are here reported from Greece from empty shells (single ones for three of them, 10 shells for C. perparvulum) found in biogenic sediments in Astypalaia and Rodos (Dodekanisa). However, they are well documented invaders from nearby Turkish shores (Çinar et al. 2011; Öztürk et al. 2014), and their presence in Greece is not surprising, and is likely to be confirmed by future work. Their late local discovery may be easily based on the fact that most of the past benthic studies in Greece have focused on soft substrates; consequently, species living on hard substrates may easily have been overlooked unless Greek research was reinforced by the help of citizen science. In addition, records of two bivalve species were of interest for analyzing temporal trends and establishment success (see below). The mollusc species most often reported to us were Conomurex persicus (Swainson, 1821) and Pinctada imbricata radiata (Leach, 1814), accounting for 27 and 25 records, respectively, followed by Bursatella leachii (Blainville, 1817) (18 records), Brachidontes pharaonis (P. Fischer, 1870), and Cerithium scabridum Philippi, 1848 (10 records each) (Appendix 1). Although depth was often not reported, or records were based on beached specimens (26 records), the deepest an alien species was found was 24 m for Bursatella leachii (Blainville, 1817), and 22 m for Melibe viridis (Kelaart, 1858) and Flabellina rubrolineata (O’ Donoghue, 1929). These depths agree with the common bathymetric range of Mediterranean alien species, usually limited Non-indigenous marine Mollusca in Greece Figure 2. Alien molluscan species newly recorded from Greece (see Appendix 1–2 for further details). Specimens not to scale, sizes reported as total height. A. Cerithidium perparvulum (Watson, 1886) – 2.1 mm (Carlo Sbrana private collection); B. Cerithiopsis pulvis (A. Issel, 1869) – 1.6 mm (Carlo Sbrana private collection); C. Cerithiopsis tenthrenois (Melvill, 1896) – 1.9 mm (Lionello Paolo Tringali private collection); D. Pyrunculus fourierii (Audouin, 1826) – 3.2 mm (Lionello Paolo Tringali private collection). Photographs by Stefano Bartolini (A–B) and Andrea Nappo (C–D). to the infralittoral zone. From a geographical point of view, the majority of records came from the Dodekanisa (67 records), followed by the Saronikos Gulf (54 records). Bibliographic data: species excluded from Greece Taxonomic knowledge has progressed greatly in the last few decades, and it is now clear that some species widely reported in early literature (usually from 1700 to around 1980) never actually lived in areas where they were recorded. In Greece, in particular, many records of Atlantic species have now been falsified; e.g., Littorina littorea (Linnaeus, 1758), Littorina obtusata (Linnaeus, 1758), Buccinum undatum Linnaeus, 1758, and Colus jeffreysianus (P. Fischer, 1868) (see Athanassopoulos 1917; Belloc 1948). Despite methodological advances, we identified a number of similar cases even in the recent literature, with taxa that still are mistakenly reported as being present in Greek waters; e.g., Chamelea striatula (da Costa, 1778), Mytilus edulis Linnaeus, 1758, Cerastoderma edule (Linnaeus, 1758), Nassarius reticulatus (Linnaeus, 1758), and Modiolus modiolus (Linnaeus, 1758) (De Smit and Bába 2000, 2002; Goigne 2001; Dimitriadis and Koutsoubas 2008; Manousis et al. 2010). Although potentially alien species, they were not included in previous alien species lists (Zenetos et al. 2005a, 2009c), and were excluded a priori also in this study. By excluding these taxa, the number of potential alien molluscs from Greece was estimated as ~ 150. However, we also excluded a priori an additional ~ 50 potential alien species illustrated in a recent popular guidebook of molluscs from Greece (Manousis 2012), where a number of native and alien species included are based on misidentifications (see Appendix 2 for details on some of them subsequently published in scientific literature). Moreover, many taxa included in the guide are inconsistent with the known biogeographical distribution of the species, which suggests that many of the illustrated specimens were not even collected in Greek waters. Examples are Gibbula cineraria (Linnaeus, 1758), a species that does not occur in the Mediterranean Sea (see Templado 2011; Nekhaev 2013), as well as Arctica islandica (Linnaeus, 1767), only known from the Mediterranean Sea as a fossil (Zenetos et al. 2005b) but illustrated in the guidebook as a living specimen with an intact periostracum. The number of species to be reassessed was in this way reduced to ~ 100 taxa. Of these, 58 species recorded in the recent literature as aliens or as (potentially) locally introduced by man were rejected, in addition to two further potential alien species, namely Trochus squarrosus Lamarck, 1822 and Murex trapa Röding, 1798, whose presence in Greece was never formally published, and the material 419 F. Crocetta et al. Table 1. Marine Mollusca recorded from Greece as aliens whose presence or whose status is here rejected, rationale for rejection (RAT), and correct identifications proposed here (in case of misidentifications). See Appendix 2 for bibliographic references and further details. Unpublished rejections with respect to the most recent bibliography or species rejected for the first time from Greek lists are highlighted in bold. Abbreviations used: D – incorrect or invalid locality data; M – misidentification/s; P – possible misidentification/s due to similarities with native species and impossibility to check the original material; R – misreading/s; S – records based on empty shells, or records based on material presumably imported through the souvenir trade; U – unchecked data excluded due to unreliability of the source. TAXA reported in literature Cellana rota (Gmelin, 1791) Emarginula decorata Deshayes, 1863 Scissurella jucunda Smith, 1890 Tectus fenestratus (Gmelin, 1791) Clanculus jussieui [var. striata] Monterosato, 1880 Trochus erithreus Brocchi, 1821 Trochus squarrosus Lamarck, 1822 Umbonium vestiarium (Linnaeus, 1758) Angaria delphinus (Linnaeus, 1758) Tricolia miniata (Monterosato, 1884) Cerithium litteratum (Born, 1778) Planaxis sulcatus (Born, 1778) Alvania dorbignyi (Audouin, 1826) Alvania pagodula (Bucquoy, Dautzenberg and Dollfus, 1884) Rissoa guerinii Récluz, 1843 Rissoina bertholleti A. Issel, 1869 Conomurex decorus (Röding, 1798) Crepidula porcellana Lamarck, 1801 Erronea caurica (Linnaeus, 1758) Notocochlis cernica (Jousseaume, 1874) Boreotrophon clathratus (Linnaeus, 1767) Coralliophila monodonta (Blainville, 1832) Murex forskoehlii forskoehlii Röding, 1798 Rapana rapiformis (Born, 1778) Murex trapa Röding, 1798 Gibberula cf. olivella Cossignani, 2001 Nassarius crenulatus (Bruguière, 1792) Nassarius stolatus (Gmelin, 1791) Conus inscriptus Reeve, 1843 Pyrgulina fischeri Hornung and Mermod, 1925 Bulla ampulla Linnaeus, 1758 Liloa mongii (Audouin, 1826) Pleurobranchus forskalii Rüppell and Leuckart, 1828 Acar plicata (Dillwyn, 1817) Tegillarca granosa (Linnaeus, 1758) Arcuatula senhousia (Benson in Cantor, 1842) Brachidontes variabilis (Krauss, 1848) Pinctada margaritifera (Linnaeus, 1758) Spondylus cf. multisetosus Reeve, 1856 Crassostrea virginica (Gmelin, 1791) Magallana angulata (Lamarck, 1819) Magallana gigas (Thunberg, 1793) Dendostrea frons (Linnaeus, 1758) Lima marioni P. Fischer, 1882 Limatula cf. pusilla (H. Adams, 1871) Centrocardita akabana (Sturany, 1899) Transkeia bogii van Aartsen, 2004 Transkeia globosa (Forsskål in Niebuhr, 1775) Ungulina rubra de Roissy, 1804 Chama aspersa Reeve, 1846 Pseudochama corbierei (Jonas, 1846) Fulvia australis (G. B. Sowerby II, 1834) Fulvia laevigata (Linnaeus, 1758) Circe scripta (Linnaeus, 1758) Circenita callipyga (Born, 1778) Clausinella punctigera (Dautzenberg and H. Fischer, 1906) Dosinia erythraea Römer, 1860 Ruditapes philippinarum (Adams and Reeve, 1850) Cucurbitula cymbium (Spengler, 1783) Teredothyra dominicensis (Bartsch, 1921) 420 RAT P M M S U M S U S U S P M U U U M D D M U S R, M D S M M S S M M M M M S M M M M P P P M U M M M M U M M M M S M M M P M D Correct identifications ? Emarginula divae van Aartsen and Carrozza, 1995 or Emarginula huzardii (Payraudeau, 1826) – NATIVE Sinezona sp. or Scissurella sp. – NATIVE? Trochus squarrosus Lamarck, 1822 + Trochidae sp. Alvania colossophilus Oberling, 1970 – NATIVE Conomurex persicus (Swainson, 1821) – ALIEN Notocochlis dillwynii (Payraudeau, 1826) – NATIVE Murex trapa Röding, 1798 Gibberula sp. – NATIVE? nomen dubium Odostomella bicincta (Tiberi, 1868) – NATIVE Bulla arabica Malaquias and Reid, 2008 – ALIEN Cephalaspidea sp. Pleurobranchus testudinarius Cantraine, 1835 – NATIVE Acar clathrata (Defrance, 1816) – NATIVE Musculus costulatus (Risso, 1826) – NATIVE Brachidontes pharaonis (P. Fischer, 1870) – ALIEN Pinctada imbricata radiata (Leach, 1814) – ALIEN Spondylus cf. spinosus Schreibers, 1793 – ALIEN Crassostrea/Magallana sp./spp. – ALIEN Crassostrea/Magallana sp./spp. – ALIEN Crassostrea/Magallana sp./spp. – ALIEN Dendostrea cf. folium (Linnaeus, 1758) – ALIEN ? Limatula cf. gwyni (Sykes, 1903) or Limatula sp. – NATIVE? Cardites antiquatus (Linnaeus, 1758) – NATIVE ? Diplodonta rotundata (Montagu, 1803) – NATIVE? Diplodonta brocchii (Deshayes, 1850) – NATIVE Chama asperella Lamarck, 1819 – ALIEN Pseudochama gryphina (Lamarck, 1819) – NATIVE Laevicardium crassum (Gmelin, 1791) – NATIVE Fulvia fragilis (Forsskål in Niebuhr, 1775) – ALIEN Gouldia minima (Montagu, 1803) – NATIVE Clausinella fasciata (da Costa, 1778) – NATIVE Dosinia exoleta (Linnaeus, 1758) – NATIVE Rocellaria dubia (Pennant, 1777) – NATIVE Non-indigenous marine Mollusca in Greece Table 2. Marine Mollusca recorded from Greece whose status as aliens is here confirmed: first sighting/collection date (DATE), establishment success/invasiveness (EST/INV), most probable primary and secondary pathway/s in Greece (PATH) (in the presence of two or more pathways, listed in alphabetical order) and live/dead status (L/D). Species for which the first Mediterranean record was in Greece are marked with an asterisk *. Species for which we report significant unpublished data are highlighted in bold. See Appendix 2 for bibliographic references and further details. Abbreviations used: C – casual; CS – corridor spread; D – dead; E – established; EC – escape from confinement; I – invasive; L – live; TC – transport-contaminant; TS – transport-stowaway; U – unknown; US – unaided spread. TAXA CLASS GASTROPODA CUVIER, 1795 *Nerita sanguinolenta Menke, 1829 Smaragdia souverbiana (Montrouzier, 1863) Cerithidium perparvulum (Watson, 1886) Cerithium scabridum Philippi, 1848 Rhinoclavis kochi (Philippi, 1848) Cerithiopsis pulvis (A. Issel, 1869) Cerithiopsis tenthrenois (Melvill, 1896) *Viriola sp. [cf. corrugata (Hinds, 1843)] Sticteulima sp. [cf. lentiginosa (A. Adams, 1861)] Conomurex persicus (Swainson, 1821) Crepidula fornicata (Linnaeus, 1758) Ergalatax junionae Houart, 2008 Rapana venosa (Valenciennes, 1846) Oscilla galilae Bogi, Karhan and Yokeş, 2012 Syrnola fasciata Jickeli, 1882 Bulla arabica Malaquias and Reid, 2008 *Haminoea cyanomarginata Heller and Thompson, 1983 Ventomnestia girardi (Audouin, 1826) Acteocina mucronata (Philippi, 1849) Pyrunculus fourierii (Audouin, 1826) Bursatella leachii (Blainville, 1817) Syphonota geographica (A. Adams and Reeve, 1850) Goniobranchus annulatus (Eliot, 1904) Hypselodoris infucata (Rüppell and Leuckart, 1830) Polycerella emertoni A.E. Verrill, 1881 *Melibe viridis (Kelaart, 1858) Flabellina rubrolineata (O' Donoghue, 1929) CLASS BIVALVIA LINNAEUS, 1758 Anadara transversa (Say, 1822) Brachidontes pharaonis (P. Fischer, 1870) Septifer cumingii Récluz, 1848 Isognomon legumen (Gmelin, 1791) Pinctada imbricata radiata (Leach, 1814) Malleus regula (Forsskål in Niebuhr, 1775) Spondylus cf. spinosus Schreibers, 1793 Crassostrea/Magallana sp./spp. Dendostrea cf. folium (Linnaeus, 1758) Chama asperella Lamarck, 1819 Chama pacifica Broderip, 1835 Fulvia fragilis (Forsskål in Niebuhr, 1775) Clementia papyracea (Gmelin, 1791) *Petricolaria pholadiformis (Lamarck, 1818) Mya arenaria Linnaeus, 1758 CLASS CEPHALOPODA CUVIER, 1795 Sepioteuthis lessoniana Férussac in Lesson, 1831 complex reported was misidentified as other alien species (Table 1; details in Appendix 2). Some species were previously rejected in other papers (e.g., Zenetos et al. 2011b), but they were re-analyzed here in the light of more current knowledge. It is the case of Pyrgulina fischeri Hornung and Mermod, 1925 and Circenita DATE PATH EST/INV L/D 1969 ≤1993 2010 2007 2016 2010 1994 2016 2015 1983 1985 2007 1986 2016 2012 1998 2001 1994 1991 2013 1975 2002 2004 2007 1995 1970 2009 U(US?) US US US US US US U(US?) TS/US TS/US TC/TS US CS/TS US US TS TS/US US US US TS/US US TS/US US TS TS/US US C E C E C C C C C E/I E E C C E E E E C C E E E E C E E D U(L?) D(L?) L D D D D(L?) D L L L L D L L L D(L?) D D L L L L L L L 1993 1975 2010 2016 1961 ≤1996 2008–13 ≤1989 2005 2007 2005 1997 1985 1985 1984 TS TS/US US US EC/TS/US US TS EC? TS/US TS/US US TS/US US TS TS E E E E E/I E C E E/I E E E/I C E E L L L L L L L L L L L L D L L 2009 US E L callipyga (Born, 1778), both confused with native taxa; Conomurex decorus (Röding, 1798), Bulla ampulla Linnaeus, 1758, Brachidontes variabilis (Krauss, 1848), and Fulvia laevigata (Linnaeus, 1758) [recorded as Fulvia papyracea (Bruguière, 1789)], confused with different alien taxa (see Appendix 2). A special 421 F. Crocetta et al. mention is needed for the Caribbean shipworm Teredothyra dominicensis (Bartsch, 1921), only known from a single specimen found in 2011 in a piece of driftwood recovered off the coast of Fourni (Shipway et al. 2014; Shipway, pers. comm.). Since then, no records have occurred, and therefore the Greek record should be ranked as an invalid locality datum (Marchini et al. 2015; Zenetos et al. 2017). Additional mentions are also needed for first records of four alien species, namely Cerithium scabridum Philippi, 1848, Rhinoclavis kochi (Philippi, 1848), Cerithiopsis tenthrenois (Melvill, 1896), and Brachidontes pharaonis (P. Fischer, 1870). First records from Greece of all these taxa were incorrect (due to misidentifications or unchecked data excluded due to unreliability of the source), but subsequent records were real, and therefore we have listed them only among accepted taxa (Table 2; details on rejections in Appendix 2). Records of 47 species are here newly rejected from the Greek species lists. The six categories of rejection were: i) misidentification/s (~ 51%); ii) records based on empty shells, or records based on material presumably imported through the souvenir trade (~ 17%); iii) unchecked data excluded due to low confidence in taxonomic identification (~ 15%); iv) possible misidentification/s due to similarities with native species and the impossibility of checking the original material (~ 10%); v) incorrect and/or invalid locality data (~ 7%); vi) misreading/s (~ 1%). Among misidentifications, some examples were notable. The case of Centrocardita akabana (Sturany, 1899), for example, applies to the whole Mediterranean (see also discussions in Zenetos et al. 2017 and detailed explanations in Appendix 2). Some species often reported from Greece, such as Trochus erithreus Brocchi, 1821, Murex forskoehlii forskoehlii Röding, 1798, and Cucurbitula cymbium (Spengler, 1783) are again listed as falsified based on mixtures of misidentifications and misreadings (detailed explanations in Appendix 2). Apart from old records, all these species are also recorded in the very recent literature, but misidentifications and problems of reliability with papers by Manousis (2012) and Manousis et al. (2012) were already highlighted and discussed for other taxonomic groups (e.g., Mienis 2013; Crocetta and Tringali 2017; Romani et al. 2017). Among unchecked data excluded due to low taxonomic confidence are those appearing in some articles by De Smit and Bába (2000, 2001, 2002). These records were published in regional journals but the material was never illustrated nor were any specimens deposited. We attempted to contact the authors, but one of them died in 2007 (Levente 2007) and the whereabouts of the first author (from 422 The Netherlands) are unknown (R.A. Bank, pers. comm.). Additional discussion is again included in Table 1 and Appendix 2. Among records based on single empty shells (and never recorded from other Mediterranean countries), or records based on material presumably imported through the souvenir trade, we highlight some reservations. The identifications are correct, yet these species were never recorded as living individuals from anywhere in the Mediterranean despite their large shell sizes and/or unmistakable morphology. They are provisionally excluded, but may re-enter the list if living specimens are eventually found. Alien, intra-Mediterranean transfer, and cryptogenic species confirmed from Greece An updated checklist of the 43 marine molluscan taxa (27 Gastropoda, 15 Bivalvia, and 1 Cephalopoda) recorded from the Greek territorial seawaters and whose status as aliens was confirmed is provided in Table 2. Taxonomic or nomenclatural problems occur with at least six taxa. Two microgastropods are herein listed as Sticteulima sp. [cf. lentiginosa (A. Adams, 1861)] and Viriola sp. [cf. corrugata (Hinds, 1843)], and may even represent undescribed species. However, both species also occur in, and are presumably native to, the Red Sea (Tringali 1994; Rusmore-Villaume 2008), and therefore their alien status is here confirmed. One taxon belonging to the genus Crassostrea Sacco, 1897 or Magallana Salvi and Mariottini, 2016 is reported as Crassostrea/Magallana sp./spp. In fact, Crassostrea virginica (Gmelin, 1791), Magallana angulata (Lamarck, 1819), and Magallana gigas (Thunberg, 1793) have been recorded from Greece based on morphological identifications (Dimitrakis 1989; Goigne 2001; Prummel 2003; Manousis and Galinou-Mitsoudi 2013), but the taxonomic status of these species is still controversial or requires evaluation using molecular tools. Two bivalve species were tentatively ascribed to a possible taxon, although their identifications may later prove to be erroneous: Dendostrea cf. folium (Linnaeus, 1758), whose molecular identification has been problematic (see Crocetta et al. 2015b); and Spondylus cf. spinosus Schreibers, 1793, recorded from Greece as Spondylus cf. multisetosus Reeve, 1856 (see Manousis and Galinou-Mitsoudi 2013). Also the only cephalopod listed here belongs to an unresolved species complex, and we included it as Sepioteuthis lessoniana Férussac in Lesson, 1831 complex. Detailed taxonomical explanations for all these taxa are reported in Appendix 2. Finally, the inclusion of Oscilla galilae Bogi, Karhan and Yokeş, Non-indigenous marine Mollusca in Greece Table 3. Marine Mollusca recorded from Greece here ascribed to cryptogenics sensu lato (including intra-Mediterranean transfer): status (ST), first sighting/collection date (DATE), establishment success/invasiveness (EST/INV), and live/dead status (L/D). Species for which we report significant unpublished data are highlighted in bold. See Appendix 2 for bibliographic references and further details. Abbreviations used: C – casual; CG – cryptogenic species; D – dead; E – established; I – invasive; IM – intra–Mediterranean transfer species; L – live. TAXA CLASS GASTROPODA CUVIER, 1795 Murchisonella mediterranea Peñas and Rolán, 2013 Atys macandrewii E.A. Smith, 1872 Aplysia dactylomela Rang, 1828 Aplysia cf. parvula Mörch, 1863 Tayuva lilacina (Gould, 1852) complex Siphonaria pectinata (Linnaeus, 1758) CLASS BIVALVIA LINNAEUS, 1758 Bankia carinata (J.E. Gray, 1827) Lyrodus pedicellatus (Quatrefages, 1849) complex Nototeredo norvagica (Spengler, 1792) Teredo navalis Linnaeus, 1758 Xylophaga dorsalis (Turton, 1819) Xylophaga praestans E.A. Smith, 1903 2012 among true aliens needs explanation. It is a minute taxon only recently described from the Mediterranean Sea and widely distributed all over it easternmost coastline, including Greece, but with no additional published records from other areas worldwide (Bogi et al. 2012; Micali et al. 2017). We traced its origin to the Indo-Pacific, where this genus is widely distributed and where specimens belonging to this speciesgroup and even possibly conspecific with Mediterranean samples are present at least in Thailand (e.g., Robba et al. 2007 as Miralda sp.). Being that native species of the genus Oscilla A. Adams, 1861 are absent from the Mediterranean, we considered those listed above as concrete evidence supporting a recent introduction. Twelve species were labelled as cryptogenics sensu lato (Table 3; Appendix 1–2), as they could not be confirmed with certainty to be aliens. Among them, Siphonaria pectinata (Linnaeus, 1758) was cautiously included as “intra-Mediterranean transfer”, pending results of a wide population genetic study (see discussions in Crocetta 2016). Three taxa were labelled as cryptogenic due to uncertainties in their taxonomic status and recent records from the Mediterranean Sea. They all belong to the Heterobranchia, a comprehensive clade of minute to large species whose taxonomy is still an “ongoing work”, and are Murchisonella mediterranea Peñas and Rolán, 2013, Aplysia cf. parvula Mörch, 1863, and specimens we labelled as belonging to the Tayuva lilacina (Gould, 1852) complex (detailed explanations in Appendix 2). Two additional taxa, Aplysia dactylomela Rang, 1828 and Atys macandrewii E.A. Smith, 1872, were only recently recorded from the Mediterranean Sea. Aplysia dactylomela was ST DATE EST/INV L/D CG CG CG CG CG IM? 2008–11 2009 2005 1970–85 2012 1973 C? E E/I E C E L D(L?) L L L L CG CG CG CG CG CG 2008–13 ≤1940 ≤1940 ≤1883 ≤1883 1987 ? ? ? ? ? ? ? ? ? ? ? ? originally considered to be a circumtropical species, but recent molecular studies have revealed that Mediterranean specimens belong to A. dactylomela from the Atlantic, rather than to its cryptic IndoPacific congeneric species Aplysia argus Rüppell and Leuckart, 1830, as often suspected in the past (see Valdés et al. 2013). Preliminary molecular analysis of Mediterranean specimens are more consistent with a natural dispersal through the Gibraltar Strait, although its distribution limited to the central and the eastern parts of the basin would suggest the hypothesis of a human-mediated introduction in the Mediterranean (Valdés et al. 2013), and therefore the question remains opened. The same holds for A. macandrewii, a taxon with an Atlantic distribution, first sighted in the Mediterranean Sea in 1990 (Cachia and Mifsud 2007). Its unmistakable shell pattern with whitish bands suggest that it could not have gone overlooked in the Mediterranean basin for centuries. However, unlike A. dactylomela, it occurs throughout the entire basin. Because A. macandrewii is also widely recorded along the Spanish Mediterranean coast (Micali et al. 2016), a natural colonization through Gibraltar seems more likely. Finally, six additional cryptogenic species from Greece included wood-boring molluscs belonging to the Teredinidae Rafinesque, 1815 (4 species) and Xylophagidae Purchon, 1941 (2 species). The taxonomy of species belonging to these two families is still widely debated, with the recent discovery of cryptic or new species even in the oversampled Mediterranean Sea using a combined molecular and morphological approach (Borges et al. 2012; Romano et al. 2014). In the case of old records, such as that of Teredo navalis Linnaeus, 423 F. Crocetta et al. Figure 3. Marine alien Mollusca from Greece: rate of sighting/collection year (as number of species per 5-years periods). 1758 (first recorded in Greece ≤ 1883: see Nieder 1883), but also for recent ones, additional anatomical or genetic work may be warranted for the six distinct species (Table 3), but this may be impractical or impossible at this stage. On the other hand, several of these wood-boring Mollusca are widespread in the Mediterranean Sea, and to avoid including them is unwise because the records were clearly based on wood-boring molluscs, and only identifications are unverified. Therefore, we included all of them, with reservations. Xylophaga praestans E.A. Smith, 1903 warrants special mention. This taxon is so far known from Greece on the basis of one record (Janssen 1989; see also review by Zenetos et al. 2005b), and even its mere presence in the Mediterranean Sea is overall doubtful (Turner 1971). Nevertheless, the species still appears in recent Mediterranean or national checklists, and general molluscan atlases (e.g., Schiaparelli 2008; Templado and Villanueva in Coll et al. 2010; Huber 2015). The article by Janssen (1989) also contains several as yet unconfirmed records of other Atlantic species for the Mediterranean Sea (Mienis 2003a; Crocetta et al. 2015c). Temporal trends We plotted the rate at which first records of marine alien molluscan species were reported for 5-year intervals (Figure 3). Careful analysis of the literature and of the unpublished material analyzed here, as well as interviews with authors, led to the correction/explanation of several first sighting/collection dates or published records, including Crepidula fornicata (Linnaeus, 1758), Malleus regula (Forsskål in Niebuhr, 1775), Fulvia fragilis (Forsskål in Niebuhr, 1775), and Brachidontes pharaonis (P. 424 Fischer, 1870) (Appendix 1–2). In particular, the first record of B. pharaonis was by Koronéos (1979) [as Brachidontes variabilis (Krauss)]. However, reexamination of the original material and the illustration revealed a misidentification for the native Mytilaster lineatus (Gmelin, 1791), which lacks the characteristic Brachidontes ribs (Appendix 2). For three species, we could not analyze the original material; therefore, we included them with the acceptance/ publication date preceded by the symbol “≤”. For Spondylus cf. spinosus Schreibers, 1793, no first record date was published. Since field studies were carried out in 2008–2013 (Manousis and GalinouMitsoudi 2013), we have assigned it as 0.5 to the period 2006–2010 and 0.5 to the period 2011–2015. The lack of confirmed historical series, as well as the general absence of molluscan studies, suggests there were few to no molluscan introductions to Greece before the 1960s. A similar situation from Italy has been explained by a lack of field research attributable to the World Wars and two postwar periods (Crocetta 2012). The subsequent periods were characterized by a variable number of introductions, ranging from 0 (1976–1980) to 9.5 (2006–2010) (Figure 3). Pathways for introduction Possible introduction pathways of 13 taxa had more than one possibility (Table 2), and data on these species were weighted when extrapolating percentages. The analysis of most probable pathway(s) of arrival in Greece suggested that unaided spread (e.g., larval drift) account for ~ 61% of the Greek introductions, followed by ~ 29% of transport-stowaway, ~ 3% of escape from confinement and ~ 1% of both corridor Non-indigenous marine Mollusca in Greece spread and transport-contaminant. Unknown pathway accounted for ~ 5%. The high value for unaided spread (32 taxa) is mostly due to the geographic origin of the alien molluscan fauna. Thirty-three alien species (~ 77%) are native to the wide Indo-Pacific area, whilst only five species [Crepidula fornicata (Linnaeus, 1758), Polycerella emertoni A.E. Verrill, 1881, Anadara transversa (Say, 1822), Petricolaria pholadiformis (Lamarck, 1818), and Mya arenaria Linnaeus, 1758] are native to the Atlantic. Three species [Bursatella leachii (Blainville, 1817), Syphonota geographica (A. Adams and Reeve, 1850) and Pinctada imbricata radiata (Leach, 1814)] have a circumtropical distribution, whilst the native area of two species [Melibe viridis (Kelaart, 1858) and Crassostrea/Magallana sp./spp.] is yet unknown (Appendix 2). Although some of the Indo-Pacific species have not yet been recorded from the Red Sea, the majority of alien species may have entered the Mediterranean Sea through the Suez Canal, and reached Greece via unaided spread when carried by the prevailing Mediterranean currents (Bergamasco and MalanotteRizzoli 2010) (Table 2; Appendix 2). Consistent with this hypothesis, many first Greek sites of easy to be detected species are from the eastern Greek islands close to Turkey [e.g., Cerithium scabridum Philippi, 1848, Chama pacifica Broderip, 1835, and Dendostrea cf. folium (Linnaeus, 1758) in Rodos (Dodekanisa); Ergalatax junionae Houart, 2008 in Kriti] (Appendix 2). Transport-stowaway was the suspected pathway for 19 taxa (Table 2; Appendix 2). This vector is likely for several species [e.g., Anadara transversa (Say, 1822), Petricolaria pholadiformis (Lamarck, 1818), and Mya arenaria Linnaeus, 1758)] that were first found in Saronikos Gulf. Arrival of two species mentioned above may also be due to escape from confinement (aquaculture/mariculture) because A. transversa is often associated with cultivated mussel beds (Lodola et al. 2011; Nerlović et al. 2012) and M. arenaria has a high commercial interest (Crocetta and Turolla 2011). However, this pathway is unlikely in Greek waters because musselculture is barely developed in the Saronikos Gulf (Conides and Kevrekidis 2005; Theodorou et al. 2011). Transportstowaway is also suspected for other species such as Bulla arabica Malaquias and Reid, 2008 and Fulvia fragilis (Forsskål in Niebuhr, 1775). In fact, it is unlikely that they first arrived anywhere but Saronikos Gulf (Vardala-Theodorou 1999; present paper) because they are conspicuous species unlikely to be overlooked. Goniobranchus annulatus (Eliot, 1904) and P. imbricata radiata are associated with more than one pathway/vector. Two colour forms of G. annulatus are known from Greece: i) one with few yellow spots and a median purple line between the two purple circles, which is only known from Persian Gulf, and ii) one with scattered yellow spots all over the body and lacking the medium purple line between the two purple circles, which is known from the Red Sea (Appendix 2). No taxonomic studies have been conducted on these two colour forms; therefore, we have listed both under a single species. However, the Persian Gulf colour form has been only found in Salamina Island (Saronikos Gulf) (Daskos and Zenetos 2007), suggesting its arrival via transport-stowaway route. The Red Sea colour form is currently widespread on eastern Mediterranean shores, including the Dodekanisa (Kastellorizo and Rodos) (Zenetos et al. 2011b; Kondylatos and Corsini-Foka in Tsiamis et al. 2015) and Kriti (Poursanidis in Mytilineou et al. 2016), suggesting its arrival via unaided spread from Turkey. The pearl oyster P. imbricata radiata, was first found in 1961 in the Salamina Island/Attiki area (Saronikos Gulf), where it presumably arrived via naval transportation (transport-stowaway) (Serbetis 1963). The same author imported it for aquaculture in four Greek areas [Chalkis (Evvoia), Kriti, Astypalaia (Dodekanisa), and Lemnos (North Aegean Islands)], from where it may have escaped. However, P. imbricata radiata may also have reached the Greek Aegean Islands via unaided spread from the nearby easternmost Mediterranean shores due to the long larval phase of Pinctada species (up to ~ 30 days before settlement: Gervis and Sims 1992). Despite the absence of earlier records from Turkey (first recorded in 1982: Çinar et al. 2011), its presence in Cyprus since at least 1899 (Katsanevakis et al. 2009) suggests that its spread to the west along the Levantine coasts has been overlooked. Crepidula fornicata (Linnaeus, 1758) is another species introduced through multiple pathways. It has been considered as introduced to Greece due to transport-stowaway (Zenetos et al. 2009c). Unpublished records, however, first detected it from Nea Peramos (Saronikos Gulf) (Appendix 1) where mussel culture is present, which suggests its introduction via transport-contaminant. Greek records of Crassostrea/ Magallana also may represent escape from confinement; however, there was no confirmed information even suggesting introduction into Greek waters for aquaculture purposes (A. Zenetos, unpublished data; see also Belloc 1948; Theodorou et al. 2015) apart an unconfirmed report that specimens were imported in 2007 to the Thermaikos Gulf (Katsanevakis et al. 2008). Finally, the only species with a pathway of corridor spread is Rapana venosa (Valenciennes, 1846), presumably spreading from the Black Sea where it was introduced in 1947 (Drapkin 1953) 425 F. Crocetta et al. with widespread negative effects (Snigirov et al. 2013). However, the transport stowaway pathway is hypothesized for its introduction into Italy (Crocetta 2012), and may also have acted in Greece. Of the 43 alien Mollusca listed as confirmed here, only five taxa were first recorded from Greece with respect to the whole Mediterranean basin: Nerita sanguinolenta Menke, 1829; Viriola sp. [cf. corrugata (Hinds, 1843)]; Haminoea cyanomarginata Heller and Thompson, 1983; Melibe viridis (Kelaart, 1858); and Petricolaria pholadiformis (Lamarck, 1818) (Table 2). We listed the pathway of introduction of N. sanguinolenta and Viriola sp. as “unknown”; however, having been both found only in the Dodekanisa, they may easily have arrived via unaided spread, and simply their spreading from another Mediterranean country was overlooked until their finding in Greece. Curiously, Haminoea cyanomarginata is a species described from the Red Sea and better known in its invaded area than in its native one. It was first found in Greece in 2001 in Porto Germeno (Korinthiakos Gulf) (Zenetos et al. 2004; Mollo et al. 2008) and later from Turkey, Malta, and Italy (Crocetta and Vazzana 2009). The absence of records from Egypt, Israel, Lebanon, Syria, and Cyprus suggests a local introduction by transport-stowaway. Similarly, M. viridis was first recorded from Kephalonia (Ionian Islands) in 1970 and, since 1990, is recorded from large areas of the Mediterranean (Tsiakkiros and Zenetos 2011; Crocetta and Bariche in Tsiamis et al. 2015). Finally, P. pholadiformis is only confirmed so far in Greece (Zenetos et al. 2009b). It is native of the eastern Coast of North America and may have arrived in Greece by transport-stowaway vector. In this view, it has only been found in the Saronikos Gulf, which includes the sixth most central port in the worldwide network of maritime traffic (Kaluza et al. 2010) and where about 100 alien and cryptogenic species have been detected (Zenetos et al. 2015b). Establishment success and invasiveness To date, 29 out of 43 alien taxa (~ 69%) are considered to be established. The established status of Malleus regula (Forsskål in Niebuhr, 1775) and of Isognomon legumen (Gmelin, 1791) were here updated based on the unpublished data gathered and the critical analysis of the literature. The former species was previously reported from Greece based on an empty shell from Symi (Dodekanisa) (Giannuzzi-Savelli et al. 2001), as the specimens from Astypalaia (Dodekanisa) recorded as such by Angelidis in Lipej et al. (2017) are instead I. legumen. We now report M. regula as a common presence in 426 Astypalaia (Dodekanisa), where several specimens were collected in 2011–2013 in three bays (Panormos, Micro Vai and Vai: Appendix 1). However, this taxon is also well known from nearby Turkish shores, where it colonizes most of the crevices of the infralittoral fringe (FC and LPT, personal observations); therefore, its establishment in Greece was expected. On the contrary, Isognomon legumen was so far only known on the basis of two specimens from Karpathos (Dodekanisa) (Micali et al. 2017). However, the misidentified specimens reported by Angelidis in Lipej et al. (2017) first highlighted above, as well as its records from two different Greek sites and the presence of both adults and juveniles, clearly point to its local establishment. One species, Smaragdia souverbiana (Montrouzier, 1863) was first recorded in Greece about two decades ago (Buzzurro and Greppi 1994); however, this record was originally considered as questionable due to the absence of additional records or images of specimens (Zenetos et al. 2009c). Recently, this species has experienced a considerable spread in Greece, with records from three different areas (Zenetos et al. 2013; Evagelopoulos et al. 2015), necessitating a re-evaluation of the original record. Among the species we reported as established, published and unpublished observations show that the effects of alien species on the newly colonized sites can vary according to local environmental features. Cold-water species such as the gastropod Crepidula fornicata (Linnaeus, 1758) and the bivalves Anadara transversa (Say, 1822), Crassostrea/Magallana sp./spp., Petricolaria pholadiformis (Lamarck, 1818), and Mya arenaria Linnaeus, 1758 are only able to survive and reproduce in a few locations in Greece. Conversely, A. transversa and Crassostrea/Magallana sp./spp. were able to invade the whole northern Adriatic Sea, where they are considered dominant species in soft and hard substrates, respectively (Morello et al. 2004; Crocetta 2011; Lipej et al. 2012). Populations of Crassostrea/Magallana are not exploited in Greece due to low numbers and narrow distributions. The same holds true for C. fornicata, P. pholadiformis, and M. arenaria. In contrast, the crepidulid invasion along the Atlantic European shores has led to the disruption of activities of dredging, harvesting, and oyster farming (Blanchard 1997). Petricola pholadiformis has a wide introduced distribution in northern Europe (Katsanevakis et al. 2014), and the colonization of the Black Sea by M. arenaria resulted in replacement of native species such as the small bivalve Lentidium mediterraneum (O.G. Costa, 1830) and caused a noticeable impact on benthic community structure and its biodiversity (Zaitsev and Öztürk 2001). Non-indigenous marine Mollusca in Greece Among tropical species considered as established, several have either not spread further in Greece or not reached the high densities observed along other Mediterranean shores. For example, Cerithium scabridum Philippi, 1848 and Brachidontes pharaonis (P. Fischer, 1870) have almost entirely colonized easternmost Mediterranean shores, leading to the almost complete replacement of the small native Cerithidae Fleming, 1822 and Mytilidae Rafinesque, 1815 (Mienis 2003b; Crocetta et al. 2013b), but have not caused similar problems in Greece so far. The same holds true for the Sepioteuthis lessoniana Férussac in Lesson, 1831 complex, being found so far only from the Dodekanisa area, where it is sold for human consumption but not distinguished from native squids (Corsini-Foka et al. 2010). Four species were labelled as invasive in Greek waters: Conomurex persicus (Swainson, 1821), Pinctada imbricata radiata (Leach, 1814), Dendostrea cf. folium (Linnaeus, 1758), and Fulvia fragilis (Forsskål in Niebuhr, 1775). Adults of C. persicus have almost entirely colonized shallow soft and hard substrates in the whole Eastern Mediterranean (Zibrowius and Bitar 2003), including Greece, whilst juveniles may be also found on rocky substrates with algal cover. Ecological impacts subsequent to its colonization have not been fully studied in the Mediterranean Sea, although Mutlu and Ergev (2006) suggested that the presence of juveniles was strongly correlated with a decrease in the density of Jania rubens (Linnaeus) J.V. Lamouroux of a magnitude consistent with the potential grazing impact of the gastropods. Empirical observations carried out by one of the authors (FC) along the Greek and Turkish soft sea bed suggested that, where adults are present, native molluscan biodiversity is reduced. Furthermore, it is speculated that adults of C. persicus feed on detritus; therefore, suggesting that the diversity and biomass of microscopic infaunal species may be locally reduced by its colonization. Due to high local densities, C. persicus has been exploited in Rodos (Dodekanisa) in recent years, and is sporadically found in restaurants in Greece (Katsanevakis et al. 2008) and consumed locally. The same also holds for the species in Israel (Mienis 1999). Pinctada imbricata radiata is also widespread around Greece, mostly attached to hard substrates. As already reported, it was imported for aquaculture in several areas of Greece, although these attempts seem to have been unsuccessful. Despite early attempts of mariculture in Kriti, the first field presence of this pearl oyster from the main Greek Island was from 2003 (Zenetos et al. 2008b). Recent field work in the island coastlines suggests successful colonization of this area, with its presence recorded in 12 of 36 sites sampled and with high abundances in at least three (F. Crocetta, unpublished data). P. imbricata radiata is also consumed locally but we have no evidence of use in restaurants. Dendostrea cf. folium (Linnaeus, 1758) was only recently recorded from Greece (2010: Zenetos et al. 2011b), although its presence was first noted in 2005 in Rodos (Dodekanisa) (Ovalis and Zenetos in Karachle et al. 2016). This species was first mistaken for the native Ostrea stentina Payraudeau, 1826 but, soon after its first record, molecular techniques confirmed its identification as an Indo-Pacific immigrant (Crocetta et al. 2015b). Its presence was subsequently reported in several Greek sites (Zenetos et al. 2013; Bianchi et al. 2014; Corsini-Foka et al. 2015; Angelidis in Karachle et al. 2016; Appendix 2), where it now dominates the infralittoral fringe. We also suspect that its distribution is wider than that currently known due to misidentifications by both marine biologists and citizen scientists (shell collectors, scuba divers), who are still not as yet aware of the presence this species. Finally, F. fragilis is again currently known from several sites (Goigne 2001; Zenetos et al. 2005b, 2008b; Young 2006; Angelidis 2013; Manousis and Galinou-Mitsoudi 2013; Angelidis in Lipej et al. 2017; Appendix 2), and has widely colonized several muddy locations since its record from Saronikos Gulf (Vardala-Theodorou 1999; present paper). With regards to the 14 species we considered as casual, nine are difficult-to-identify or -to-detect micro-species (usually < 1 cm) [Cerithidium perparvulum (Watson, 1886), Cerithiopsis pulvis (A. Issel, 1869), Cerithiopsis tenthrenois (Melvill, 1896), Viriola sp., Sticteulima sp., Oscilla galilae Bogi, Karhan and Yokeş, 2012, Acteocina mucronata (Philippi, 1849), Pyrunculus fourierii (Audouin, 1826), and Polycerella emertoni A.E. Verrill, 1881], and so their current establishment status may be biased by taxonomic impediments and the absence of field research. We hope that bringing attention to these species may lead to more records, or that non molluscan specialists may provide us with unidentified molluscan material currently stored in institutional collections. Of the remaining five species, Nerita sanguinolenta Menke, 1829 is so far known from a single record based on an empty shell (Nordsieck 1973); its identification should be straightforward due to its size and the absence of Mediterranean congeneric species. The same holds true for Rapana venosa (Valenciennes, 1846), which is among the largest known Mediterranean gastropods, and is so far only known from Greece on the basis of a single record of two living specimens and one shell (Koutsoubas and Voultsiadou-Koukoura 1991; Manousis et al. 2012). If established in Greek coastal 427 F. Crocetta et al. waters, it is unlikely to have been overlooked. Clementia papyracea (Gmelin, 1791) was only recently recorded from Greece on the basis of specimens collected in 1985 (Crocetta et al. 2016). However, the exceeding fragility of its valves makes it substantially more difficult to find than the majority of alien species, and it requires SCUBA diving procedures and molluscan taxonomic knowledge to be identified in the field. Finally, Spondylus cf. spinosus Schreibers, 1793 and Rhinoclavis kochi (Philippi, 1848) are among the most recent arrivals. The record of the former from Epanomi (Thermaikos Gulf) (Manousis and Galinou-Mitsoudi 2013) does not suggest an arrival via unaided spread, but rather an arrival of a small number of larvae via a transport-stowaway mechanism. This species is as yet not recorded from the Turkish Aegean coastline. In contrast, the record of R. kochi is based on few empty shells from Gavdos (Kriti) (Poursanidis and Zaminos in Lipej et al. 2017). However, given its common presence in Turkey, the finding of more specimens is expected. Among species we labelled as cryptogenics in Greece, four [Atys macandrewii E.A. Smith, 1872, Aplysia dactylomela Rang, 1828, Aplysia cf. parvula Mörch, 1863, and Siphonaria pectinata (Linnaeus, 1758)] are considered as established, and A. dactylomela has also been labelled as invasive, with 20 published records subsequent to its first finding in Greece in 2005 (Sterniuk-Gronek 2005; Appendix 2). The only species with more published records are P. imbricata radiata and C. persicus, with 31 and 24 published records, respectively (Appendix 2). However, both of these species have been known from Greece for several decades (1961 and 1983: Serbetis 1963; Verhecken 1984), while A. dactylomela is a relative newcomer to the country. Finally, specimens of the Tayuva lilacina (Gould, 1852) complex lack an external/internal shell, and therefore require specific SCUBA diving skills and underwater photography to be found, as well as detailed sea slug taxonomic knowledge. Regardless of which species they belong (either the native or the alien), discussions above are on the basis of the first records made in 2012 only (Crocetta et al. 2015c). Concluding remarks Out of approximately 100 records of extraMediterranean molluscan species in Greek waters, only half belonged to alien (43 species) and cryptogenic species (12) (Tables 1–3). The combined rejected records from this study plus the 50 “de facto” excluded taxa are double that of the accepted ones, a situation similar to that documented for Italy (Crocetta 428 2012). Our results highlight the necessity of reliable local ecological knowledge for compiling accurate species inventories. In fact, whilst morphological taxonomic studies on minute species or of narrow specialist’s interest may often be accepted and uncommented upon for decades, periodic reassessments are critical in alien species’ inventories that play important roles in regional policy and management decisions, thus there must be high confidence in the validity of species identifications. In our case, the inflation of “bibliographically introduced” alien records on the Mollusca is mostly attributed to local and international shell collectors and other groups among citizen scientists, such as tourists, who are eager for new findings and can publish their presumptive results in amateur journals. Publications in such nonpeer reviewed journals, but also errors in indexed ones, can lead to an artificial increase in the number of alien-species records (see also Zenetos et al. 2004), and thus emphasizes the need for periodic updates and re-evaluation. On the other hand, the contribution of citizen scientists is still crucial for our understanding of the overall distribution of the Mediterranean molluscan biota, including in Greece. In fact, it was previously stated that the first reports of 14 species of marine NIS in Greek waters (6%) were attributed to citizen scientists (Zenetos et al. 2013). On a better screening of the literature, which reports upon the 43 validated marine alien Mollusca in Greece, it appears that only 12 (~ 28%) taxa have been found during formal research projects or by institutional researchers, whilst the remaining 31 (~ 72%) Mollusca have been first found by amateurs (mostly shell collectors and SCUBA divers/photographers), although several of these findings were then published under the supervision of experts. Comparing the alien molluscan diversity of nearby Mediterranean countries, the number of true alien species ascertained for Greece was greater than in Malta (Evans et al. 2015) and Albania (Zenetos et al. 2011a; Xharahi et al. in Gerovasileiou et al. 2017) due to the limited coastline of the former and the geographic position and paucity of field studies of the latter. The numbers were roughly similar to those for Italy (~ 35 species: Crocetta 2012; Crocetta et al. 2013c) and perhaps the Turkish Aegean shores (~ 30 taxa: Çinar et al. 2011; Öztürk et al. 2014). Explanations for the relatively low number of alien species in the Aegean versus Levantine coasts of Turkey are not clear. Although the geographic position of South Turkey (vicinity to the Suez Canal) is assumed to be the key factor, hydrography of the Aegean marine environment may also play a role. Whereas most of the alien species reported from southern Turkey are of tropical origin, a large part of Non-indigenous marine Mollusca in Greece the Aegean Sea experiences wide annual fluctuations in sea surface temperatures, which are cold in winter (Nittis and Perivoliotis 2002), so as to make the area non-viable for thermophilic species—even if surface currents favor their arrival. A further reason may be an artefact due to sparse field monitoring even in the most exposed areas (the Dodekanisa and the Saronikos Gulf), but this seems to be excluded by the similarities in the numbers of species recorded from the opposite Turkish coastline. Even though the total number of species is limited, the ratio of species of Indo-Pacific origin and of species introduced from other areas through shipping and aquaculture is consistent with the position of Greece in the eastwest Mediterranean gradient (Zenetos et al. 2010), and is likely to persist even if the number of alien species increases. This therefore suggests that further attention should be aimed at searching for potential newcomers in the Dodecanese area. Interestingly, the main conclusion of this study is that most of these 43 alien mollusca have arrived in Greek waters from other parts of the Mediterranean where they were already established. This may have been achieved both by natural spread and by smallscale (fishing, recreational boats) to medium/largescale transport (shipping). However, despite the fact that the Mollusca globally are among the first biological invaders (Molnar et al. 2008), and that colonization of the Mediterranean basin by non-native species started but a few centuries ago (Por 1978), the lack of reliable time series, as well as the general absence of molluscan studies, seems to indicate the only Greek molluscan introductions before the 1960s were by shipworms. An increasing trend of new introductions was observed after the 1980s, peaking in the 2006–2010 period. Indeed the peak in records from 1991 to 2016 is not only due to an increase in local introductions, but also due to an increased research effort by local scientists supported by Greek institutions and by wide collaboration with citizen scientists. Moreover, it is also documented that, at a global scale, climate change amplifies the entry and spread of tropical alien species (Raitsos et al. 2010). Shipping only played a secondary role as a potential pathway in Greece and is mostly evident in selected hot spots (Saronikos and Thermaikos Gulfs) where there is heavy shipping traffic. Strangely, the role of the Saronikos area is low to medium in elevating molluscan species counts, when this could be a major hub of introduction due to the amount of maritime traffic and sites where dismantled ships are moored for long periods. As already stated for Lessepsian species, even ship-transferred alien Mollusca records in the area are only reported considerably after their first records in other Mediterranean seaports such as Iskenderun, Izmir and Tunis. Nevertheless, as for other taxonomic groups such as macroalgae and polychaetes (Katsanevakis et al. 2013; Tsiamis et al. 2013), Saronikos Gulf remains a hot spot for alien molluscan species. The present update, established by a joint contribution from Mediterranean molluscan taxonomic knowledge and local expertise, provides a key estimate of the current numbers of alien molluscan species in Greece and an analysis of their temporal trends, pathways, establishment success, and invasiveness. Nevertheless, it is expected that due to progress in taxonomic studies (including use of molecular techniques), better biogeographic knowledge, and new invasions, reassessments will be needed periodically. Acknowledgements The study of the alien species from Greece was partially funded by the East and South European Network for Invasive Alien Species - a tool to support the management of alien species in Bulgaria (ESENIAS-TOOLS) (EEA funded - Contract No. Д-3351/30.06.2015) (FC and AZ), the DEVOTES (DEVelopment Of innovative Tools for understanding marine biodiversity and assessing Good Environmental Status, funded by the European Union under the seventh Framework Programme, ‘The Ocean of Tomorrow’ Theme - grant agreement no. 308392; http://www.devotes-project.eu) (AZ) and the COST (European Cooperation in Science and Technology) Action TD1209 Alien Challenge (FC) projects. John Mark Hanson and Brian Morton kindly proofread the present article and offered insight and support. This work could not have been done without the help of the following people, who kindly offered bibliographic help, scientific support, and unpublished data: Paolo Giulio Albano, Massimiliano Alesi, Kostas Apostolou, Patrice Bail, Nicolas Bailly, Manos Bakalis, Stefano Bartolini, George Bazios, Primo Bellucci, Giuseppe Bonomolo, Luisa Borges, Dimitris Boukouras, Christos Efthymiou, Giuseppe Fasulo, Alfio Germanà, Riccardo Giannuzzi-Savelli, Eleni Gliati, Hector Giourgis, Yiannis Issaris, George Karelas, Kostas Karpadakis, Stelios Katsanevakis, Stefanos Kavadas, Gerasimos Kondylatos, Stavros Kritsotakis, Luca Magliaro, Christos Maroulis, Laura Meletopoulou, Alexia MetzakisBeckmann, Dan Minchin, Andrea Nappo, Elias Papadopoulos, Christos Petrakis, Raffaele Petrone, Anastasios Porfyris, Christian Potelle, Dimitrios Poursanidis, Francesco Pusateri, Ermanno Quaggiotto, Nikolas Reissis, Mikes Reissis, Walter Renda, Alain Robin, Luigi Romani, Paolo Russo, Bruno Sabelli, Maria Salomidi, George Sangioulouglou, Korina Sangiouloglou, Vicky Sangiouloglou, Elena Sarropoulou, Carlo Sbrana, Reuben Shipway, Gianni Spada, Michele Stefanile, Loukia Triantafylli, Ángel Valdés, Thomas van Walstijn, Evi Vardala-Theodorou and the Goulandris Natural History Museum, Raimondo Villa, Dionyssis Vitsendzatos, and Christos Zeimbekis. References Angelidis A (2013) Fulvia fragilis (Forsskal in Niebuhr, 1775) (Bivalvia: Cardiidae), first record of an alien mollusk in the Gulf of Thessaloniki (Inner Thermaikos Gulf, North Aegean Sea, Greece). Journal of Biological Research-Thessaloniki 20: 228–232 Athanassopoulos GD (1917) Quelques éléments de recherches hydrobiologiques en Grèce. Bulletin. Station Hydrobiologique. Marine Grèce 2: 1–40 Azzurro E, Bariche M, Broglio E, Maynou F (2013) Seawatchers: an interactive website to monitor the occurrences of exotic fishes in the Mediterranean Sea. Rapport de la Commission Internationale pour l’Exploration Scientifique de la Mer Méditerranée 40: 599 429 F. Crocetta et al. Belloc G (1948) Inventory of the fishery resources of Greek waters. Appendix B, Catalogue of the resources of Greek waters. UNRRA-FAO, pp 65–79 Bergamasco A, Malanotte-Rizzoli P (2010) The circulation of the Mediterranean Sea: a historical review of experimental investigations. Advances in Oceanography and Limnology 1: 11–28, https://doi.org/10.4081/aiol.2010.5293 Bianchi CN, Corsini-Foka M, Morri C, Zenetos A (2014) Thirty years after: dramatic change in the coastal marine ecosystems of Kos Island (Greece), 1981–2013. Mediterranean Marine Science 15: 482–497, https://doi.org/10.12681/mms.678 Bitar G (2014) Les mollusques exotiques de la côte libanaise. Bulletin de la Société Zoologique de France 139: 37–45 Blanchard M (1997) Spread of the slipper limpet Crepidula fornicata (L. 1758) in Europe. Current state and consequences. Scientia Marina 61: 109–118 Bogi C, Karhan SÜ, Yokes MB (2012) Oscilla galilae, a new species of Pyramidellidae (Mollusca, Gastropoda, Heterobranchia) from the Eastern Mediterranean. Iberus 30(2): 1–6 Borges LMS, Sivrikaya H, le Roux A, Shipway JR, Cragg SM, Costa FO (2012) Investigating the taxonomy and systematics of marinewood borers (Bivalvia: Teredinidae) combining evidence from morphology, DNA barcodes and nuclear locus sequences. Invertebrate Systematics 26: 572–582, https://doi.org/10.1071/ IS12028 Buzzurro G, Greppi E (1994) Presenza di Smaragdia (Smaragdella) souverbiana (Montrouzier, 1863) nel Mediterraneo orientale. Bolletino Malacologico 29: 319–321 Cachia C, Mifsud C (2007) On the occurrence of Atys macandrewii E.A. Smith, 1872 (Gastropoda: Haminoeidae) in the Mediterranean. Iberus 25: 43–48 Carlton JT (1996) Biological invasions and cryptogenic species. Ecology 77: 1653–1655, https://doi.org/10.2307/2265767 Çinar ME, Bilecenoğlu M, Öztürk B Katağan T, Yokeş M.B, Aysel V, Dağli E, Açik S, Özcan T, Erdoğan H (2011) An updated review of alien species on the coasts of Turkey. Mediterranean Marine Science 12: 257–315, https://doi.org/10.12681/mms.34 Coll M, Piroddi C, Steenbeek J, Kaschner K, Lasram FBR, Aguzzi J, Ballesteros E, Bianchi CN, Corbera J, Dailianis T, Danovaro R, Estrada M, Froglia C, Galil B, Gasol JM, Gertwagen J, Gil J, Guilhaumon F, Kesner-Reyes K, Kitsos MS, Koukouras A, Lampadariou N, Laxamana E, de la Cuadra CML, Lotze HK, Martin D, Mouillot D, Oro D, Raicevich S, Rius- Barile J, SaizSalinas JI, San Vicente C, Somot S, Templado J, Turon X, Vafidis D, Villanueva R, Voultsiadou E (2010) The biodiversity of the Mediterranean Sea: estimates, patterns, and threats. PLoS ONE 5: e11842, https://doi.org/10.1371/journal.pone.0011842 Conides A, Kevrekidis K (2005) VII.3 Marine Aquaculture sector of Hellas 1985–2002. In: Papathanassiou E, Zenetos A (eds), State of the Hellenic marine environment. HCMR, Athens, Greece, pp 285–294 Convention on Biological Diversity (2000) Interim Guiding Principles. Conference of the Parties Decision V/8 Alien species that threaten ecosystems, habitats or species. http://www.cbd.int/ decision/cop/default.shtml?id=7150 Corsini-Foka M, Pancucci-Papadopoulou MA, Kalogirou S (2010) Is the Lessepsian Province in expansion? The Aegean Sea experience. In: EastMed. Report of the Sub-Regional Technical meeting on the Lessepsian migration and its impact on Eastern Mediterranean fishery. GCP/INT/041/EC – GRE – ITA/TD-04, pp 50–59 Corsini-Foka M, Zenetos A, Crocetta F, Çinar ME, Koçak F, Golani D, Katsanevakis S, Tsiamis K, Cook E, Froglia C, Triandaphyllou M, Lakkis S, Kondylatos G, Tricarico E, Zuljevic A, Almeida M, Cardigos F, Çağlar S, Durucan F, Fernandes AMD, Ferrario J, Haberle I, Louizidou P, Makris J, Marić M, Micu D, Mifsud C, Nall C, Kytinou E, Poursanidis D, Spigoli D, Stasolla G, Yapici S, Roy HE (2015) Inventory of alien and cryptogenic species of the Dodecanese (Aegean Sea, Greece): collaboration 430 through COST Action training school. Management of Biological Invasions 6: 351–366, https://doi.org/10.3391/mbi.2015.6.4.04 Crocetta F (2011) Marine alien Mollusca in the Gulf of Trieste and neighbouring areas: a critical review and state of knowledge (updated in 2011). Acta Adriatica 52: 247–260 Crocetta F (2012) Marine alien Mollusca in Italy: a critical review and state of the knowledge. Journal of the Marine Biological Association of the UK 92: 1357–1365, https://doi.org/10.1017/ S002531541100186X Crocetta F (2016) Backdating the confirmed presence of Siphonaria pectinata (Gastropoda: Siphonariidae) along the northern Mediterranean shores and a discussion on its status in the basin. Marine Biodiversity Records 9: 55, https://doi.org/10.1186/s41200016-0034-5 Crocetta F, Russo P (2013) The alien spreading of Chama pacifica Broderip, 1835 (Mollusca: Bivalvia: Chamidae) in the Mediterranean Sea. Turkish Journal of Zoology 37: 92–96 Crocetta F, Tringali LP (2017) Remarks on Philine striatula Monterosato, 1874 ex Jeffreys ms., with a survey on Philinidae J.E. Gray, 1850 (1815) sensu lato (Gastropoda: Cephalaspidea) recently ascribed to the Mediterranean fauna. Marine Biodiversity, https://doi.org/10.1007/s12526-017-0652-0 Crocetta F, Turolla E (2011) Mya arenaria Linné, 1758 (Mollusca: Bivalvia) in the Mediterranean: its distribution revisited. Journal of Biological Research-Thessaloniki 16: 188–193 Crocetta F, Vazzana A (2009) First record of Haminoea cyanomarginata (Gastropoda: Haminoeidae) in the Italian Seas. Marine Biodiversity Records 2: e11, https://doi.org/10.1017/S1755267208000110 Crocetta F, Zibrowius H, Bitar G, Templado J, Oliverio M (2013a) Biogeographical homogeneity in the eastern Mediterranean Sea - I: the opisthobranchs (Mollusca: Gastropoda) from Lebanon. Mediterranean Marine Science 14: 403–408, https://doi.org/10.126 81/mms.404 Crocetta F, Bitar G, Zibrowius H, Oliverio M (2013b) Biogeographical homogeneity in the eastern Mediterranean Sea. II. Temporal variation in Lebanese bivalve biota. Aquatic Biology 19: 75–84, https://doi.org/10.3354/ab00521 Crocetta F, Macali A, Furfaro G, Cooke S, Villani G, Valdés Á (2013c) Alien molluscan species established along the Italian shores: an update, with discussions on some Mediterranean alien species categories. ZooKeys 277: 91–108, https://doi.org/10.3897/ zookeys.277.4362 Crocetta F, Bitar G, Zibrowius H, Capua D, Dell’Angelo B, Oliverio M (2014) Biogeographical homogeneity in the eastern Mediterranean Sea - III: new records and a state of the art of Polyplacophora, Scaphopoda and Cephalopoda (Mollusca) from Lebanon. Spixiana 37: 183–206 Crocetta F, Zenetos A (2015) Mollusca. In: Zenetos A (ed), Illustrated Guide of Marine Alien species in the Mediterranean for Students and Citizen Scientists. COST1209 Action: Alien Challenge, 22 pp Crocetta F, Agius D, Balistreri P, Bariche M, Bayhan YK, Çakir M, Ciriaco S, Corsini-Foka M, Deidun A, El Zrelli R, Ergüden D, Evans J, Ghelia M, Giavasi M, Kleitou P, Kondylatos G, Lipej L, Mifsud C, Özvarol Y, Pagano A, Portelli P, Poursanidis D, Rabaoui L, Schembri PJ, Taşkin E, Tiralongo F, Zenetos A (2015a) New Mediterranean Biodiversity Records (October 2015). Mediterranean Marine Science 16: 682–702, https://doi. org/10.12681/mms.1477 Crocetta F, Mariottini P, Salvi D, Oliverio M (2015b) Does GenBank provide a reliable DNA barcode reference to identify small alien oysters invading the Mediterranean Sea? Journal of the Marine Biological Association of the UK 95: 111–122, https://doi.org/10. 1017/S0025315414001027 Crocetta F, Poursanidis D, Tringali LP (2015c) Biodiversity of sea slugs and shelled relatives (Mollusca: Gastropoda) of the Cretan Archipelago (Greece), with taxonomic remarks on selected species Quaternary International 390: 56–68, https://doi.org/10. 1016/j.quaint.2015.02.061 Non-indigenous marine Mollusca in Greece Crocetta F, Tringali LP, Mienis HK, Zenetos A (2016) Clementia papyracea (Gmelin, 1791) (Mollusca: Bivalvia: Veneridae): its established status in the Mediterranean Sea and the first record from Greece. Cahiers de Biologie Marine 57(3): 271–275 Daskos A, Zenetos A (2007) Additions to the knowledge of alien Opisthobranchia of Greece. Aquatic Invasions 2: 258–260, https://doi.org/10.3391/ai.2007.2.3.10 Delaney DG, Sperling CD, Adams CS, Leung B (2008) Marine invasive species: validation of citizen science and implications for national monitoring networks. Biological Invasions 10: 117– 128, https://doi.org/10.1007/s10530-007-9114-0 De Smit E, Bába K (2000) Data on the marine mollusc fauna of Cephalonia (Ionian Islands, Greece). Nachrichtenblatt der Ersten Vorarlberger Malakologischen Gesellschaft 8: 47–52 De Smit E, Bába K (2001) Data to the malacofauna of Katavothres (Kefallinia, Greece). Malacological Newsletter 19: 95–101 De Smit E, Bába K (2002) New data to the marine malacofauna from Euboea Island (Greece). Malacological Newsletter 20: 83–91 Dimitrakis KG (1989) Shells from the Greek Seas (in Greek). Orfanides Press, Athens, Greece, 67 pp Dimitriadis C, Koutsoubas D (2008) Community properties of benthic molluscs as indicators of environmental stress induced by organic enrichment. Journal of Natural History 42: 559–574, https://doi.org/10.1080/00222930701835530 Drapkin E (1953) A new mollusc in the Black Sea [in Russian]. Priroda 9: 92–95 European Commission (2008) Developing an EU Framework for Invasive Alien Species Discussion Paper, final. http://ec.europa.eu/ environment/nature/invasivealien/docs/ias_discussion_paper.pdf European Commission (2015) Review of the Commission Decision 2010/477/EU concerning MSFD criteria for assessing good environmental status. Descriptor 2. Non-indigenous species introduced by human activities are at levels that do not adversely alter the ecosystem. European Commission - Joint Research Centre, 30 pp, https://circabc.europa.eu/sd/a/cd4bbd6a-454a-40dbb805-52fb195d4e56/COMDEC_Review_D2_V6.pdf Evagelopoulos A, Poursanidis D, Papazisi E, Gerovasileiou V, Katsiaras N, Koutsoubas D (2015) Records of alien marine species of Indo-Pacific origin at Sigri Bay (Lesvos Island, northeastern Aegean Sea). Marine Biodiversity Records 8: e35, https://doi.org/10.1017/S1755267215000123 Evans J, Barbara J, Schembri PJ (2015) Updated review of marine alien species and other 'newcomers' recorded fromthe Maltese Islands (Central Mediterranean). Mediterranean Marine Science 16: 225–244, https://doi.org/10.12681/mms.1064 Galil BS (2007) Seeing Red: alien species along the Mediterranean coast of Israel. Aquatic Invasions 2: 281–312, https://doi.org/10. 3391/ai.2007.2.4.2 Gerovasileiou V, Akel EHKh, Akyol O, Alongi G, Azevedo F, Babali N, Bakiu R, Bariche M, Bennoui A, Castriota L, Chintiroglou CC, Crocetta F, Deidun A, Galinou-Mitsoudi S, Giovos I, Gökoğlu M, Golemaj A, Hadjioannou L, Hartingerova J, Insacco G, Katsanevakis S, Kleitou P, Korun J, Lipej L, Malegue M, Michailidis N, Mouzai Tifoura A, Ovalis P, Petović S, Piraino S, Rizkalla SI, Rousou M, Savva I, Şen H, Spinelli A, Vougioukalou KG, Xharahi E, Zava B, Zenetos A (2017) New Mediterranean Biodiversity Records (July, 2017). Mediterranean Marine Science 18: 355–384, https://doi.org/10.12681/mms.13771 Gervis MH, Sims NA (1992) The biology and culture of pearl oysters (Bivalvia: Pteriidae). The WorldFish Center, London, United Kingdom, 50 pp Giannuzzi-Savelli R, Pusateri F, Palmeri A, Ebreo C (2001) Atlante delle conchiglie marine del Mediterraneo. Vol. 7 (Bivalvia: Protobranchia - Pteriomorpha). Evolver, Roma, Italy, 246 pp Gofas S, Zenetos A (2003) Exotic molluscs in the Mediterranean Basin: current status and perspectives. Oceanography and Marine Biology: An Annual Review 41: 237–277 Goigne D (2001) Pêcheur a la Grecque. Xenophora 94: 12–15 Huber M (2015) Compendium of bivalves 2. ConchBooks, Harxheim, Germany, 907 pp Hulme PE (2009) Trade, transport and trouble: managing invasive species pathways in an era of globalization. Journal of Applied Ecology 46: 10–18, https://doi.org/10.1111/j.1365-2664.2008.01600.x Janssen R (1989) Benthos-Mollusken aus dem Tiefwasser des ostlichen Mittelmeeres, gesammelt wahrend der 'METEOR'Fahrt 5 (1987). Senckenbergiana maritima 20: 265–276 Kaluza P, Kölzsch A, Gastner MT, Blasius B (2010) The complex network of global cargo ship movements. Journal of the Royal Society Interface 7: 1093–1103, https://doi.org/10.1098/rsif.2009.0495 Karachle PK, Angelidis A, Apostolopoulos G, Ayas D, Ballesteros M, Bonnici C, Brodersen MM, Castriota L, Chalari N, Cottalorda JM, Crocetta F, Deidun A, Đođo AZ, Dogrammatzi A, Dulčić J, Fiorentino F, Gönülal O, Harmelin JG, Insacco G, Izquierdo-Gómez D, Izquierdo-Muñoz A, Joksimović A, Kavadas S, Malaquias MAE, Madrenas E, Massi D, Micarelli P, Minchin D, Önal U, Ovalis P, Poursanidis D, Siapatis A, Sperone E, Spinelli A, Stamouli C, Tiralongo F, Tunçer S, Yaglioglu D, Zava B, Zenetos A (2016) New Mediterranean Biodiversity Records (March 2016). Mediterranean Marine Science 17: 230–252, https://doi.org/10.12681/mms.1684 Katsanevakis S, Lefkaditou E, Galinou-Mitsoudi S, Koutsoubas D, Zenetos A (2008) Molluscan species of minor commercial interest in Hellenic seas: distribution, exploitation and conservation status. Mediterranean Marine Science 9: 77–118, https://doi.org/10.12681/mms.145 Katsanevakis S, Tsiamis K, Ioannou G, Michailidis N, Zenetos A (2009) Inventory of alien marine species of Cyprus (2009). Mediterranean Marine Science 10: 109–133, https://doi.org/10. 12681/mms.113 Katsanevakis S, Wallentinus I, Zenetos A, Leppäkoski E, Çinar ME, Oztürk B, Grabowski M, Golani D, Cardoso AC (2014) Impacts of invasive alien marine species on ecosystem services and biodiversity: a pan-European review. Aquatic Invasions 9: 391– 423, https://doi.org/10.3391/ai.2014.9.4.01 Katsanevakis S, Zenetos A, Poursanidis D, Nunes AL, Deriu I, Bogucarskis K, Cardoso AC (2013) ELNAIS meets EASIN: distribution of marine alien species in Greece using EASIN mapping services and ELNAIS spatial data. Mediterranean Marine Science 14: 95–98, https://doi.org/10.12681/mms.362 Koronéos J (1979) Les mollusques de la Grèce (in French). Papadakis E, Athens, Greece, 36 pp, 48 pl Koutsoubas D, Voultsiadou-Koukoura E (1991) The occurrence of Rapana venosa (Valenciennes, 1846) (Gastropoda, Thaididae) in the Aegean Sea. Bolletino Malacologico 26: 201–204 Levente F (2007) In memoriam Dr. Bába Károly (1935–2007). Malacological Newsletter 25: 5–20 Lipej L, Acevedo I, Akel EHK, Anastasopoulou A, Angelidis A, Azzurro A, Castriota L, Çelik M, Cilenti L, Crocetta F, Deidun A, Dogrammatzi A, Falautano M, Fernández-Álvarez FÁ, Gennaio R, Insacco G, Katsanevakis S, Langeneck J, Lombardo BM, Mancinelli G, Mytilineou Ch, Papa L, Pitacco V, Pontes M, Poursanidis D, Prato E, Rizkalla SI, Rodríguez-Flores PC, Stamouli C, Tempesti J, Tiralongo F, Tirnetta S, Tsirintanis K, Turan C, Yaglioglu D, Zaminos G, Zava B (2017) New Mediterranean Biodiversity Records (March 2017). Mediterranean Marine Science 18: 179–201, https://doi.org/10.12681/mms.2068 Lipej L, Mavrič B, Orlando-Bonaca M, Malej A (2012) State of the Art of the Marine Non-Indigenous Flora and Fauna in Slovenia. Mediterranean Marine Science 13: 243–249, https://doi.org/10. 12681/mms.304 Lodola A, Savini D, Mazziotti C, Occhipinti-Ambrogi A (2011) First record of Anadara transversa (Say, 1822) (Bivalvia: Arcidae) in Sardinian waters (NW Tyrrhenian Sea). Biologia Marina Mediterranea 18: 256–257 Manousis T (2012) The sea shells of Greece. Kyriakidis Brothers s.a., Thessaloniki, Greece, 381 pp 431 F. Crocetta et al. Manousis T, Galinou-Mitsoudi S (2013) New and uncommon Bivalvia Mollusca of Thermaikos Gulf (NW Aegean Sea). Journal of Biological Research-Thessaloniki 20: 339–366 Manousis T, Galinou-Mitsoudi S (2014) New gastropod records for the Eastern Mediterranean Sea and one new alien (Emarginula decorata Deshayes, 1863) for the Mediterranean Sea from NW Aegean Sea, Greece. Journal of Biological ResearchThessaloniki 21: 1–20, https://doi.org/10.1186/2241-5793-21-20 Manousis T, Mpardakis G, Paraskevopoulos C, Galinou-Mitsoudi S (2010) The Bivalvia Mollusca of Thessaloniki & Thermaikos Gulfs (North Aegean Sea, Greece) with emphasis on new species for Hellenic waters. Journal of Biological ResearchThessaloniki 14: 161–179 Manousis T, Mpardakis G, Zamora Silva A, Paraskevopoulos K, Manios D, Galinou-Mitsoudi S (2012) New findings of Gastropods in the Hellenic seas with emphasis on their origin and distribution status. Journal of Biological ResearchThessaloniki 18: 249–264 Marchini A, Galil BS, Occhipinti-Ambrogi A (2015) Recommendations on standardizing lists of marine alien species: lessons from the Mediterranean Sea. Marine Pollution Bullettin 101: 267– 273, https://doi.org/10.1016/j.marpolbul.2015.09.054 Micali P, Bogi C, Galil BS (2016) On the occurrence of Atys angustatus E. A. Smith, 1872 and Atys macandrewii E. A. Smith, 1872 (Cephalaspidea: Haminoeidae) in the Mediterranen Sea. Iberus 34: 49–53 Micali P, Siragusa F, Agamennone F, Germanà A, Sbrana C (2017) Karpathos Island (Greece) and its Indo-Pacific alien species. Part 1. Bollettino Malacologico 53: 40–49 Mienis HK (1999) Strombus persicus on the fishmarket of Yafo, Israel. De Kreukel 35: 112 Mienis HK (2003a) Woodboring bivalves from shipwrecks in the Eastern Mediterranean 2. Xylophaga from the wreck of the submarine “Dakar”. Triton 8: 5–6 Mienis HK (2003b) Native marine mollusks replaced by Lessepsian migrants. Tentacle 11: 15−16 Mienis HK (2013) Nogmaals vreemde vermeldingen van exotische Strombidae uit de Middellandse Zee. Spirula 395: 166 Mytilineou Ch, Akel EHK, Babali N, Balistreri P, Bariche M, Boyaci YÖ, Cilenti L, Constantinou C, Crocetta F, Çelik M, Dereli H, Dounas C, Durucan F, Garrido A, Gerovasileiou V, Kapiris K, Kebapcioglu T, Kleitou P, Krystalas A, Lipej L, Maina I, Marakas P, Mavrič B, Moussa R, Pe-a-Rivas L, Poursanidis D, Renda W, Rizkalla SI, Rosso A, Scirocco T, Sciuto F, Servello G, Tiralongo F, Yapici S, Zenetos A (2016) New Mediterranean Biodiversity Records (November, 2016). Mediterranean Marine Science 17: 794–821, https://doi.org/10.12681/mms.1976 Mollo E, Gavagnin M, Carbone M, Castelluccio F, Pozone F, Roussis V, Templado J, Ghiselin MT, Cimino G (2008) Factors promoting marine invasions: a chemoecological approach. Proceedings of the National Academy of Sciences U.S.A. 105: 4582–4586, https://doi.org/10.1073/pnas.0709355105 Molnar JL, Gamboa RL, Revenga C, Spalding MD (2008) Assessing the global threat of invasive species to marine biodiversity. Frontiers in Ecology and the Environment 6: 485–492, https://doi.org/10.1890/070064 Morello EB Solustri C, Froglia C (2004) The alien bivalve Anadara demiri (Arcidae): a new invader of the Adriatic Sea, Italy. Journal of the Marine Biological Association of the UK 84: 1057–1064, https://doi.org/10.1017/S0025315404010410h Mutlu E, Ergev MB (2006) Dynamics and ecology of an Indo-Pacific gastropod, Conomurex persicus in southeastern Turkey. Revista de biología tropical 54: 117–129, https://doi.org/10.15517/rbt. v54i1.13980 Nekhaev IO (2013) Distributional notes on Gibbula cineraria (Linnaeus, 1758), Pseudosetia turgida (Jeffreys, 1870) and Haliella stenostoma (Jeffreys, 1858) in Russian part of the Barents Sea (Gastropoda). Ruthenica 23: 35–39 432 Nerlović V, Doğan A, Perić L (2012) First record of Anadara transversa (Mollusca: Bivalvia: Arcidae) in Croatian waters (Adriatic Sea). Acta Adriatica 53: 139–144 Nieder X (1883) Drei Beobachtungen au Missolunghi. I. Teredo navalis. Kosmos 12: 304–305 Nittis K, Perivoliotis L (2002) Circulation and hydrological characteristics of the North Aegean Sea: a contribution from real-time buoy measurements. Mediterranean Marine Science 31: 21–31, https://doi.org/10.12681/mms.255 Nordsieck F (1973) A new Neritidae in the Mediterranean. La Conchiglia 5: 4 Ojaveer H, Galil BS, Minchin D, Olenin S, Amorim A, CanningClode J, Chainho P, Copp GH, Gollasch S, Jelmert A, Lehtiniemi M, McKenzie C, Mikuš J, Miossec L, OcchipintiAmbrogi A, Pećarević M, Pederson J, Quilez-Badia G, Wijsman JWM, Zenetos A (2014) Ten recommendations for advancing the assessment and management of non-indigenous species in marine ecosystems. Marine Policy 44: 160–165, https://doi.org/ 10.1016/j.marpol.2013.08.019 Öztürk B, Doğan A, Bitlis-Bakir B, Salman A (2014) Marine molluscs of the Turkish coasts: an updated checklist. Turkish Journal of Zoology 38: 832–879, https://doi.org/10.3906/zoo-1405-78 Perna E (2013) La collezione Perna Atlanto-Mediterranea Gastropoda. I Quaderni di Malachia 7: 1–271 Por FD (1978) Lessepsian migration: the influx of Red Sea biota into the Mediterranean by way of the Suez Canal. Ecological studies 23. Springer-Verlag, Berlin, Germany, 228 pp, https://doi.org/10. 1007/978-3-642-66728-2 Prummel W (2003) Animal husbandry and mollusc gathering. In: H.R. Reinders & W. Prummel (eds), Housing in New Halos, a Hellenistic town in Thessaly, Greece. A.A. Balkema Publishers, Lisse, pp 175–223 Raitsos DE, Beaugrand G, Georgopoulos D, Zenetos A, PancucciPapadopoulou AM, Theocharis A, Papathanassiou E (2010) Global climate change amplifies the entry of tropical species into the Eastern Mediterranean Sea. Limnology and Oceanography 55: 1478–1484, https://doi.org/10.4319/lo.2010.55.4.1478 Robba E, Di Geronimo I, Chaimanee N, Negri MP, Sanfilippo R (2007) Holocene and Recent shallow soft-bottom mollusks from the Western Gulf of Thailand: Pak Phanang Bay and additions to Phetchaburi fauna. Bollettino Malacologico 43(special issue): 1–98 Romani L, Raveggi A, Scaperrotta M, Bartolini S (2017) Nota sui micromolluschi marini conchiferi rinvenuti nei dintorni di Paleokastritsa (Corfù [Kerkyra] Grecia, Mar Ionio NordOrientale). Alleryana 35: 24–46 Romano C, Voight JR, Pérez-Portela R, Martin D (2014) Morphological and genetic diversity of the wood-boring Xylophaga (Mollusca, Bivalvia): new species and records from deep-sea Iberian canyons. PLoS ONE 9: e102887, https://doi.org/ 10.1371/journal.pone.0102887 Rusmore-Villaume ML (2008) Seashells of the Egyptian Red Sea The Illustrated Handbook. The America University in Cairo Press, Cairo and New York, 310 pp Sabelli B, Taviani M (2014) The making of the Mediterranean molluscan biodiversity. In: Goffredo S, Dubinsky Z (eds), The Mediterranean Sea: its history and present challenges. Springer, Dordrecht, Holland, pp 285–396, https://doi.org/10.1007/978-94007-6704-1_16 Schiaparelli S (2008) Bivalvia. In: Relini G (ed), Checklist della flora e della fauna dei mari italiani. Parte I. Biologia Marina Mediterranea 15 (Suppl. 1): 296–314 Serbetis CD (1963) L’acclimatation de la Meleagrina (Pinctada) margaritifera (Lam.) en Grèce (in French). Rapport de la Commission Internationale pour l’Exploration Scientifique de la Mer Méditerranée 17: 271–272 Shipway JR, Borges LMS, Müller J, Cragg SM (2014) The broadcast spawning Caribbean shipworm, Teredothyra dominicensis (Bivalvia, Teredinidae), has invaded and become established in Non-indigenous marine Mollusca in Greece the eastern Mediterranean Sea. Biological Invasions 16: 2037– 2048, https://doi.org/10.1007/s10530-014-0646-9 Snigirov S, Medinets V, Chichkin V, Sylantyev S (2013) Rapa whelk controls demersal community structure off Zmiinyi Island, Black Sea. Aquatic Invasions 8: 289–297, https://doi.org/10.3391/ ai.2013.8.3.05 Stachowicz JJ, Whitlatch RB, Osman RW (1999) Species diversity and invasion resistance in a marine ecosystem. Science 286: 1577–1579, https://doi.org/10.1126/science.286.5444.1577 Sterniuk-Gronek L (2005) Aplysia dactylomela from Greece. [Message in] Sea Slug Forum. Australian Museum, Sydney. http://www.seaslugforum.net/find/14287 Templado J (2011) Familia Trochidae. In: Gofas S, Moreno D, Salas C (coords), Moluscos marinos de Andalucía. Volumen I. Servicio de Publicaciones e Intercambio Científico, Universidad de Málaga, Malaga, Spain, pp 104–117 Tenekides NS (1989) On a collection of shells from the Greek Seas (in Greek). Afoi Protopapa E.P.E., Athens, Greece, 187 pp Theodorou JA, Perdikaris C, Filippopoulos NG (2015) Evolution through innovation in aquaculture: a critical review of the Greek mariculture industry. Journal of Applied Aquaculture 27: 160– 181, https://doi.org/10.1080/10454438.2015.1049473 Theodorou JA, Viaene J, Sorgelos P, Tzovenis I (2011) Production and marketing trends of the cultured Mediterranean mussel Mytilus galloprovincialis Lamarck 1819, in Greece. Journal of Shellfish Research 30: 859–874, https://doi.org/10.2983/035.030.0327 Thiel M, Penna-Díaz MA, Luna-Jorquera G, Salas S, Sellanes J, Stotz W (2014) Citizen scientists and marine research: volunteer participants, their contributions, and projection for the future. Oceanography and Marine Biology: An Annual Review 52: 257–314, https://doi.org/10.1201/b17143-6 Tringali L (1994) Levant Sea: A new Lessepsian host of the genus Sticteulima F.C. Laseron, 1955. La Conchiglia 273: 57–58 Tsiakkiros L, Zenetos A (2011) Further additions to the alien mollusc fauna along the Cypriot coast: new opisthobranchia species. Acta Adriatica 52: 115–125 Tsiamis K, Aydogan Ö, Bailly N, Bariche M, Carden-Noad S, Corsini-Foka M, Crocetta F, Davidov B, Dimitriadis C, Dragičević B, Drakulić M, Dulčić J, Escánez A, FernándezÁlvarez FA, Gerakaris V, Gerovasileiou V, Hoffman R, Izquierdo-Gómez D, Izquierdo-Muñoz A, Kondylatos G, Latsoudis P, Lipej L, Madiraca F, Mavrič B, Parasporo M, Sourbès L, Taşkin E, Türker A, Yapici S (2015) New Mediterranean Biodiversity Records (July 2015). Mediterranean Marine Science 16: 472–488, https://doi.org/10.12681/mms.1440 Tsiamis K, Panayiotidis P, Salomidi M, Pavlidou A, Kleinteich J, Balanika K, Kuepper F (2013) Macroalgal community response to re-oligotrophication in Saronikos Gulf. Marine Ecology Progress Series 472: 73–85, https://doi.org/10.3354/meps10060 Turner RD (1971) Identification of marine wood boring molluscs. In: Jones EBG, Eltringham SK (eds), Marine borers and fouling organisms of wood. OECD, Paris, France, pp 17–64 Valdés A, Alexander J, Crocetta F, Yokes¸ B, Giacobbe S, Poursanidis D, Zenetos A, Cervera JL, Caballer M, Galil B, Schembri P (2013) The origin and dispersal pathway of the spotted sea hare Aplysia dactylomela (Mollusca: Opisthobranchia) in the Mediterranean Sea. Aquatic Invasions 8: 427–436, https://doi.org/10.3391/ai.2013.8.4.06 Vardala-Theodorou E (1999) The occurrence of the Indo-Pacific molluscan species Fulvia fragilis (Forsskal, 1775) and Bulla ampulla L., 1758 in Elefsis Bay. Newsletter of the Hellenic Zoological Society - February 31: 10–11 Verhecken A (1984) Strombus decorus raybaudii in de Middellandse Zee. Gloria Maris 23: 79–88 Vilà M, Basnou C, Pysvek P, Josefsson M, Genovesi P, Gollasch S, Nentwig W, Olenin S, Roques A, Roy D, Hulme PE, DAISIE partners (2010) How well do we understand the impacts of alien species on ecosystem services? A pan-European, cross-taxa assessment. Frontiers in Ecology and the Environment 8: 135– 144, https://doi.org/10.1890/080083 WoRMS Editorial Board (2017) World Register of Marine Species. http://www.marinespecies.org (accessed 26 May 2017) Young L (2006) Lessepsian Species in the Greek Seas. Pallidula 36: 12 Zaitsev Y, Öztürk B (2001) Exotic Species in the Aegean, Marmara, Black, Azov and Caspian Seas. Turkish Marine Research Foundation, Istanbul, Turkey, 265 pp Zenetos A, Gofas S, Russo G, Templado J (2004) CIESM Atlas of Exotic Species in the Mediterranean. Vol. 3 Molluscs. CIESM, Monaco, 376 pp Zenetos A, Koutsoubas D, Vardala-Theodorou E (2005a) Origin and vectors of introduction of exotic molluscs in greek waters. Belgian Journal of Zoology 135: 279–286 Zenetos A, Vardala-Theodorou E, Alexandrakis C (2005b) Update of the marine Bivalvia Mollusca checklist in Greek waters. Journal of the Marine Biological Association of the UK 85: 993–998, https://doi.org/10.1017/S0025315405012014 Zenetos A, Ovalis P, Houart R (2008a) Eastward spread of Ergalatax junionae Houart, 2008 (Gastropoda, Mollusca), a recent alien species in the Mediterranean. Journal of Biological ResearchThessaloniki 10: 221–223 Zenetos A, Vassilopoulou V, Salomidi M, Poursanidis D (2008b) Additions to the marine alien fauna of Greek waters (2007 update). Marine Biodiversity Records 1: e91, https://doi.org/10. 1017/S1755267207009281 Zenetos A, Ovalis P, Kalogirou S (2009a) Closing the gap: Cerithium scabridum Philippi, 1848 found in the South Aegean (Greece, Mediterranean Sea). Journal of Biological ResearchThessaloniki 11: 107–110 Zenetos A, Ovalis P, Vardala-Theodorou E (2009b) The American piddock Petricola pholadiformis Lamarck, 1818 spreading in the Mediterranean Sea. Aquatic Invasions 4: 385–387, https://doi.org/ 10.3391/ai.2009.4.2.15 Zenetos A, Pancucci-Papadopoulou M-A, Zogaris S, Papastergiadou E, Vardakas L, Aligizaki K, Economou AN (2009c) Aquatic alien species in Greece (2009): tracking sources, patterns and effects on the ecosystem. Journal of Biological ResearchThessaloniki 12: 135–172 Zenetos A, Gofas S, Verlaque M, Çinar ME, García Raso JE, Azzurro E, Bilecenoğlu M, Froglia C, Siokou I, Bianchi CN, Morri C, Sfriso A, San Martín G, Giangrande A, Katağan T, Ballesteros E, Ramos-Esplá A, Mastrototaro F, Ocaña O, Zingone A, Gambi MC, Streftaris N (2010) Alien species in the Mediterranean Sea by 2010. A contribution to the application of European Union’s Marine Strategy Framework Directive (MSFD). Part I. Spatial distribution. Mediterranean Marine Science 11: 381–493, https://doi.org/10.12681/mms.87 Zenetos A, Katsanevakis S, Beqiraj S, Macic V, Poursanidis D, Kashta L (2011a) Rapid assessment survey of marine alien species in the Albanian and Montenegrin coast. Technical report. RAC/SPA, N° 37/38/39/2010, 54 pp Zenetos A, Katsanevakis S, Poursanidis D, Crocetta F, Damalas D, Apostolopoulos G, Gravili C, Vardala-Theodorou E, Malaquias M (2011b) Marine alien species in Greek Seas: Additions and amendments by 2010. Mediterranean Marine Science 12: 95– 120, https://doi.org/10.12681/mms.55 Zenetos Α, Gofas S, Morri C, Rosso A, Violanti D, García Raso JE, Çinar ME, Almogi-Labin A, Ateş AS, Azzurro E, Ballesteros E, Bianchi CN, Bilecenoğlu M, Gambi MC, Giangrande A, Gravili C, Hyams-Kaphzan O, Karachle V, Katsanevakis S, Lipej L, Mastrototaro F, Mineur F, Pancucci-Papadopoulou MA, RamosEsplá A, Salas C, San Martín G, Sfriso A, Streftaris N, Verlaque M (2012) Alien species in the Mediterranean Sea by 2012. A contribution to the application of European Union’s Marine Strategy Framework Directive (MSFD). Part 2. Introduction trends and pathways. Mediterranean Marine Science 13: 328– 352, https://doi.org/10.12681/mms.327 433 F. Crocetta et al. Zenetos A, Koutsogiannopoulos D, Ovalis P, Poursanidis D (2013) The role played by citizen scientists in monitoring marine alien species in Greece. Cahiers de Biologie Marine 54: 419–426 Zenetos A, Arianoutsou M, Bazos I, Balopoulou S, Corsini-Foka M, Dimiza M, Drakopoulou P, Katsanevakis S, Kondylatos G, Koutsikos N, Kytinou E, Lefkaditou E, Pancucci-Papadopoulou MA, Salomidi M, Simboura N, Skoufas G, Trachalakis P, Triantaphyllou M, Tsiamis K, Xentidis NJ, Poursanidis D (2015a) ELNAIS: A collaborative network on Aquatic Alien Species in Hellas (Greece). Management of Biological Invasions 6: 185–196, https://doi.org/10.3391/mbi.2015.6.2.09 Zenetos A, Arashkevich E, Boicenco L, Dumitrache C, Gana S, Oros A, Öztürk B, Rilov G, Souissi K, Chikina M, Nikishina A (2015b) NIS in PERSEUS hotspot areas: Testing trends in introduction as an indicator of GES. PERSEUS Scientific Conference, Brussels 7–9 December 2015 Zenetos A, Çinar ME, Crocetta F, Golani D, Rosso A, Servello G, Shenkar N, Turon X, Verlaque M (2017) Uncertainties and validation of alien species catalogues: the Mediterranean as an example. Estuarine, Coastal and Shelf Science 191: 171–187, https://doi.org/10.1016/j.ecss.2017.03.031 Zibrowius H, Bitar G (2003) Invertébrés marins exotiques sur la côte du Liban. Lebanese Science Journal 4: 67–74 Supplementary material The following supplementary material is available for this article: Appendix 1. Unpublished data. Appendix 2. Bibliographic data. This material is available as part of online article from: http://www.aquaticinvasions.net/2017/Supplements/AI_2017_Crocetta_etal_Appendix1.xlsx http://www.aquaticinvasions.net/2017/Supplements/AI_2017_Crocetta_etal_Appendix2.xlsx 434