Ecological Entomology (2012), 37, 342–349 DOI: 10.1111/j.1365-2311.2012.01370.x The dominant exploiters of the fig/pollinator mutualism vary across continents, but their costs fall consistently on the male reproductive function of figs S I M O N T . S E G A R 1 and J A M E S M . C O O K 1,2 of Reading, Reading, U.K. and 2 1 School of Biological Sciences, University Hawkesbury Institute for the Environment, University of Western Sydney, Sydney, Australia Abstract. 1. Fig trees (Moraceae: Ficus) are keystone species, whose ecosystem function relies on an obligate mutualism with wasps (Chalcidoidea: Agaonidae) that enter fig syconia to pollinate. Each female flower produces one seed (fig female reproductive function), unless it also receives a wasp egg, in which case it supports a wasp. Fig male reproductive function requires both male flowers and pollinator offspring, which are the only vectors of fig pollen. 2. The mutualism is exploited by other wasps that lay eggs but provide no pollination service. Most of these non-pollinating fig wasps (NPFWs) do not enter syconia, but lay eggs through the wall with long ovipositors. Some are gall-makers, while others are parasitoids or lethal inquilines of other wasps. 3. Ficus is pan-tropical and contains >750 fig species. However, NPFW communities vary across fig lineages and continents and their effects on the mutualism may also vary. This provides a series of natural experiments to investigate how the costs to a keystone mutualism vary geographically. 4. We made the first detailed study of the costs of NPFWs in a fig (Ficus obliqua G. Forst) from the endemic Australasian section Malvanthera. In contrast to the communities associated with section Americana in the New World, wasps from the subfamily Sycoryctinae (Chalcidoidea: Pteromalidae) dominated this community. 5. These sycoryctine wasps have a negative impact on pollinator offspring numbers, but not on seed production. Consequently, while the NPFW fauna varies greatly at high taxonomic levels across continents, we show that the consistent main effect of locally dominant exploiters of the mutualism is to reduce fig male reproductive function. Key words. Conflict, costs, Ficus, mutualism, pollination, stability, wasps. Introduction Mutualisms are partnerships between members of different species, often from highly divergent taxa, that exchange resources or services (Foster & Wenseleers, 2006; Leigh, 2010). These associations underpin various ecosystem functions, such as nitrogen fixation and pollination, and are key components of global biodiversity (Wardle et al., 2004; Sachs & Simms, 2006). Mutualisms obviously involve co-operation, but also have inherent conflicts, because the fitness of partners is never perfectly aligned (Herre et al., 1999; Yu, 2001; Foster & Wenseleers, 2006). The associations often involve a Correspondence: James M. Cook, School of Biological Sciences, University of Reading, Reading, RG6 6AS, UK. E-mail: james.cook@reading.ac.uk 342 large host species and several smaller symbiont species, some of which are beneficial (i.e. mutualists) and others that are not. The non-mutualist species have been variously termed ‘parasites’, ‘cheaters’, or ‘interlopers’ (Bronstein, 2001; Yu, 2001). For simplicity, we refer to them here as exploiters to avoid potential confusion between a generalised use of the term parasite and the more precise ecological role of parasitoid. It is common for such exploiters to be ecologically and taxonomically similar to the mutualistic symbiont species (e.g. Althoff et al., 2001). The exploiters of mutualisms are generally viewed as detrimental to one or both mutualism partners (Bronstein, 1994), but their effects have rarely been quantified. Intriguingly, such exploiters might destabilise mutualisms (e.g. Lach, 2008), or alternatively help stabilise them (Dunn et al., 2008), depending on circumstances, so their roles and costs clearly require targeted study.  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society Segar and Cook exploiters decrease fig male function Ecosystem functions, such as nitrogen fixation and pollination, occur globally and those underpinned by mutualisms often involve the same lineages (higher taxa) on different continents. However, the exact species involved usually differ across continents and their little-studied exploiter assemblages are also likely to differ (Thompson, 2005). An important pantropical mutualism involves fig trees (genus Ficus) and fig-pollinating wasps (family Agaonidae). This evolved some 75 MYA (Cruaud et al., 2012) and has radiated into over 750 species pairs (Berg & Corner, 2005). Fig trees are an important constituent of tropical and subtropical forests on all continents (Harrison, 2005), as well as occurring in more open savannah habitats. They can play a key role in sustaining vertebrate frugivore populations because of their unusual phenology, which leads to year-round fruit production in most tropical species at the population level. This, in turn, is linked to their intimate symbiosis with fig wasps, in which the wasps provide pollination services to fig trees in exchange for nourishment for their larvae (Cook & Rasplus, 2003). Female wasps enter fig syconia (inflorescences or ‘figs’) during a brief period of receptivity. Once inside, they pollinate the female flowers, but also lay eggs into some of them. Each fig flower can support the development of either one seed or one pollinator offspring. When the pollinator offspring are mature, they hatch and mate in the syconium before the pollen-bearing females disperse to find receptive syconia on other trees. About half of all Ficus species are monoecious and the other half functionally dioecious (Berg & Corner, 2005). The dioecious species have male trees that produce pollen and wasps, and female trees that produce only seeds. In monoecious fig species, there is just one type of tree and male and female function occur together in the same syconia (Berg & Corner, 2005). While many aspects of the fig/pollinator interaction are similar on all tropical continents, each has one or more endemic radiations of figs from the subgenus Urostigma. These are Malvanthera in Australasia, Galoglychia in Africa, Conosycea and Urostigma in Asia, and Americana in America. Some of these Ficus sections co-occur locally, but each has been evolving independently for at least 30 million years (Rønsted et al., 2005). Fig syconia host specialist exploiters – several lineages of non-pollinating fig wasps (NPFWs) that belong to the superfamily Chalcidoidea (Hymenoptera) and develop only in Ficus syconia (see Table 1). Most NPFW species are known from only one host fig species, just like the pollinating wasps (Cook & Segar, 2010). Some NPFW lineages have been associated with Ficus for tens of millions of years and have radiated across many Ficus sections and continents [e.g. subfamily Sycophaginae (Cruaud et al., 2011a)], while others are likely to be more recent colonisers with lower diversity and geographic range (e.g. family Ormyridae). Importantly, NPFW communities can differ greatly across continents. For example, most fig wasp communities from Africa and Asia include species from several subfamilies (Table 1) (Compton et al., 1994; Chen et al., 1999; Kerdelhué et al., 2000), while those associated with the highly speciose New World section Americana figs (Bronstein & McKey, 343 Table 1. The families and subfamilies of chalcid wasps associated with Ficus. Taxa in bold are only known to occur on fig plants. (Sub)family Region Trophic role(s) Sycophaginae Epichrysomallinae Otitesellinae Sycoryctinae Sycoecinae Eurytomidae Torymidae Ormyridae Pantropical Old world Pantropical Pantropical Old world Pantropical Pantropical Old world Galling wasps and inquilines Large galling wasps Galling wasps and inquilines Parasitoids/inquilines Galling wasps and inquilines Large parasitoids/inquilines Large parasitoids/inquilines Large galling wasps and inquilines 1989; West et al., 1996) are dominated by NPFWs from one subfamily (Sycophaginae). Consequently, the impacts of exploiters on fig/pollinator mutualisms may vary considerably across continents. To date, most studies that have directly addressed the cost of exploiters in monoecious figs have involved figs from the section Americana (e.g. Bronstein, 1991; West & Herre, 1994; West et al., 1996; Pereira & Prado, 2005). Costs of exploitation can be difficult to detect, due to unmeasured variation between syconia in resource availability and pollination intensity, and the fact that NPFW numbers are often low (Bronstein, 1988, 1992; West & Herre, 1994; Bronstein & Hossaert-McKey, 1996; Cook & Power, 1996). However, where a significant cost has been found in neotropical figs, it has always been to fig male function, through reduction in numbers of pollinator offspring. In figs from other continents, some wasps from the chalcid subfamily Sycoryctinae may reduce pollinator numbers in a few Asian species (Weiblen et al., 2001; Tzeng et al., 2008). There is more equivocal evidence for costs using survey data from African fig species (Kerdelhué et al., 2000), but again any costs seem to be to fig male function, and there is further evidence for this from a manipulative study in which ant exclusion led to increased attack by Apocrypta wasps and reduced pollinator production (Compton & Robertson, 1988). Here, we provide the first detailed description of a NPFW community of an Australian fig (Ficus obliqua) from the endemic section Malvanthera and contrast this with the better studied American and African communities. We then explore the effects of the dominant NPFW subfamily on fig male and female function. Our study species, F. obliqua, is particularly suitable for identifying such costs, because two major confounding factors – pollination intensity (related to pollinator foundress number; West & Herre, 1994) and resource availability (related to fig size; Cook & Power, 1996) – show little variation within and between fruit crops. Specifically, most fruits receive just one foundress and the small fruits show little size variation compared to closely related species such as F. rubiginosa Desf. Ex Vent. (Cook & Power, 1996). Within our overall aim to assess the effects of exploiters on the mutualism, is a subsidiary aim to clarify the ecological roles and effects of certain key NPFW taxa. This community is dominated by sycoryctine wasps, the most species-rich lineage  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society, Ecological Entomology, 37, 342–349 344 Simon T. Segar and James M. Cook of parasites in figs globally (Segar et al., 2012), but one whose impacts on the mutualism remain controversial (Dunn et al., 2008; Herre et al., 2008). The costs of sycoryctines, absent from the Americana figs, are amenable to study in F. obliqua, where they prove to be the dominant exploiters of the mutualism. Methods The study system Ficus section Malvanthera belongs to the subgenus Urostigma and comprises 23 species (Rønsted et al., 2008). It is endemic to Australasia and has two distinct geographical radiations, with nine species restricted to Papua New Guinea (PNG) and the surrounding islands, and the remaining 14 to Australia (Rønsted et al., 2008). Most species grow as hemiepiphytic stranglers in rainforests, but some grow on rocks in dry habitats. The Malvanthera probably evolved in Australian rainforests about 45 Ma (Rønsted et al., 2005). Ficus obliqua is found along most of the eastern seaboard of Australia, from Cape York to the south coast of New South Wales (Dixon et al., 2001), which is a distance of about 2000 km, and in a few south Pacific islands (Berg & Corner, 2005). It grows on rocks in arid areas and as a freestanding tree or a hemi-epiphyte in rainforests and is pollinated by two sister species of wasps from the agaonid genus Pleistodontes (Lopez-Vaamonde et al., 2002). Dissection of syconia Wasp communities were sampled by removing, counting, and identifying all the wasps in large numbers of near-ripe, but intact, syconia. In total 149 syconia from 11 different sites in Northern Queensland were collected from 1996 to 2005 and preserved in 70–95% ethanol. Fruit crops contained from 1 to 19 syconia and most syconia were measured to the nearest 0.1 mm (diameter and length) using vernier callipers before dissection. Syconia were dissected under a 10–60× dissecting microscope and each fig ovule was removed from the syconium wall and its contents recorded. Any wasps loose in the syconium cavity were also counted. Ovules were classified as seeds, exited galls, galls containing wasps or empty. Empty ovules, referred to as bladders by some authors (Corlett et al., 1990; Anstett et al., 1996), were probably undeveloped seeds or wasps. Analysing survey data A few NPFW taxa have been manipulated on the most experimentally convenient fig species, such as F. racemosa L. (Wang & Zheng, 2008). However, due to the intricacies of fig and fig wasp natural history and problems with the abortion of manipulated figs, the vast majority of studies utilise survey data (e.g. Corlett et al., 1990; Bronstein, 1991; West & Herre, 1994; Kerdelhué & Rasplus, 1996; West et al., 1996; Kerdelhué et al., 2000; Yao et al., 2005; Lin et al., 2008; but see Compton & Robertson, 1988 for an exception that uses both approaches). When investigating the cost of exploitation, variables such as resource availability and pollination intensity should be controlled for as far as possible (West & Herre, 1994; Cook & Power, 1996). The fact that F. obliqua syconia vary little in size (resource) and that most are entered by just one pollinator foundress (pollination intensity, JMC, pers. obs.) make this an excellent study species. However, we also need to consider what correlations are feasible for exploiters with different ecological roles. Herbivorous NPFWs that gall or eat pollinated flowers should have a negative relationship with seeds. However, they may also compete with pollinators for flowers, so could also show a negative relationship with pollinator offspring (West & Herre, 1994). The observed relationship will thus depend on when parasites lay eggs, which flowers they use (pollinators use mostly inner flowers), and the intensity of competition for flowers. In contrast, exploiters that usurp the galls of pollinators, killing them directly (parasitoids) or indirectly (lethal inquilines), should impact mostly on numbers of pollinator offspring. Nevertheless, as each pollinator offspring consumes one presumptive seed, parasitoids and inquilines could also show a weaker negative relationship with seeds. Impacts of exploiters on seed and pollinator production The impact of exploiters on fig male and female function was tested using the number of either seeds or pollinators as the response variable. A square root transformation of seed number was required to satisfy the assumption of normality for all analyses (Shapiro–Wilk tests after transformation: W = 0.99, P = 0.384). Pollinator number was only square root transformed for the linear mixed model analyses, which excluded syconia that lacked size measurements (Shapiro–Wilk tests after transformation: W = 0.98, P = 0.084). We controlled for fig crop (different trees) by including it as a random explanatory variable. The fixed explanatory variables were fig size (syconium diameter, a measure of resource availability), and numbers of Sycoscapter wasps, Philotrypesis wasps, or pooled sycoryctine wasps (i.e. all wasps in the genera Sycoscapter + Philotrypesis + Watshamiella). Linear mixed models were then run using the R package ‘lme4’ in R version 2.10.1 (Bates & Maechler, 2009; R Development Core Team, 2009). A maximum likelihood model was used, rather than the default restricted maximum likelihood model, in case some fixed-effects were removed during model simplification (Crawley, 2007). P -values were then calculated using the Markov Chain Monte Carlo method in the package ‘Language R’ (Bayen, 2010) using the default settings. We also calculated Nagelkerke’s R 2 (Nagelkerke, 1991) for each fixed variable in the maximal model. This calculates an analogue to a standard R 2 value (amount of variation explained) by comparing the likelihood of a full model against that of one containing only the intercept. Finally, for illustrative purposes, we conducted simple linear regressions of the same response variables on the number of exploiters.  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society, Ecological Entomology, 37, 342–349 Segar and Cook exploiters decrease fig male function ± ± ± ± ± ± ± ± ± ± ± ± 4.9 3.3 5.1 6.6 13.6 22.3 30.0 20.2 5.1 1.8 3.7 10.85 55.8 ± 6.0 58.3 ± 9.1 75.7 ± 7.5 112.6 ± 5.3 185.4 ± 14.2 122.4 ± 7.3 48.4 ± 9.1 95.9 ± 5.4 118.6 ± 8.1 98.3 ± 9.6 92.0 ± 13.9 100.5 1 ± 4.1 ± 0.02 ± 0.1 ± 0.1 ± 0.1 0 0 0 0.1 ± 0.07 0 0 0 0 0 0 0 0.01 ± 0.01 ± 0.2 ± 0.06 ± 0.08 ± 0.4 ± 0.2 0 0.2 0 0.2 0.1 0 0 0 0.1 0 0 0.08 0.08 0.4 0.2 0.1 0.2 ± ± ± ± ± ± 0.4 ± 1.7 ± 0.2 ± 0.07 ± 3.3 ± 0.1 ± 0.2 ± 0.7 ± 0.2 ± 0.3 ± 0.07 ± 0.1 0.05 1.4 2.6 0.5 0.4 0.9 0.5 2.4 0.4 ± ± ± ± ± ± ± ± ± 0 0.05 7.5 6.7 0.5 1.2 1.1 0.8 3.5 2.7  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society, Ecological Entomology, 37, 342–349 0.3 0.3 0.4 0.2 *These wasps are considerably larger than the pollinating wasps and develop in proportionately larger galls. Total means are derived from the full data set (n = 149). ± 0.07 ± 0.3 ± 0.05 0.08 0.6 0.2 0.2 0.3 0 0.08 0.6 0.2 0 0 0.2 ± 0.5 ± 0.2 0 0.9 0.2 0 0.07 0.3 0 0 0 0 0 0.1 ± 0.5 0 0.7 0 0.1 9.8 0 0 0 2.6 0.2 0 1.4 ± 0.3 ± 0.5 0.5 0.7 0 0.4 0.07 0.1 0 0.2 1.0 0.2 0 0.3 6.2 ± 1.6 4.6 ± 1.5 2.2 3.2 1.9 1.2 3.6 3.5 4.1 0.7 0.9 1.4 2.0 0.7 ± ± ± ± ± ± ± ± ± ± ± ± 9.4 9.4 3.3 4.9 11.0 4.1 11.7 1.3 2.4 3.7 4.2 6.4 4.7 4.4 6.6 3.7 4.2 12.2 4.7 5.6 5.3 5.5 3.9 2.2 There was a significant negative relationship between pooled sycoryctines and pollinator numbers that explained from 8 to 14% of the variance (Tables 4 and 5). In contrast, there was no trade-off with seed numbers, with less than 1% of the variance in seed number being explained by sycoryctines in mixed models or simple regressions (Tables 4 and 5 and Fig. 1). Sycoscapter alone also displayed a negative relationship with pollinators, but the less numerous Philotrypesis did not (Table 4). Neither Sycoscapter nor Philotrypesis showed a significant negative relationship with seeds in the mixed models (Table 4). 0.2 0.1 0.2 0.2 The impact of sycoryctine wasps on Ficus obliqua 7.0 ± 6.2 ± 7.0 ± 7.8 ± NA NA NA NA 6.7 ± 3.4 ± 7.3 ± 6.4 ± Nine genera and 10 species of wasps were found in 18 crops of F. obliqua syconia (Table 2). The numbers of seeds and wasps varied considerably between syconia and crops (Table 3), but all crops contained some NPFWs. Only 17% of individual syconia lacked NPFWs, and only 23% did not contain sycoryctines. Overall, the NPFW fauna was dominated by wasps from the subfamily Sycoryctinae (1441 individuals, 84% of all NPFWs), which was represented by three species from different genera. Sycoscapter sp. (920; 54%) was the most abundant, followed by Philotrypesis sp. (384; 22%) and the much rarer Watshamiella sp. wasps (49; 3%). In six figs (5%) the sycoryctines were not identified to genus level. Most remaining NPFWs belonged to the subfamily Sycophaginae (Table 2). Eukobelea sp. was present in only a few crops (six of 18), but quite abundant in these. In contrast, there were rarely more than four Pseudidarnes sp. wasps in a syconium (Table 2). A few species of much larger wasps that develop in large galls were also found (Table 2). These were all rare with patchy distributions and very low numbers (usually just one or two individuals) per syconium. Table 3. Mean syconium contents for 11 crops (all those with n > 5 syconia) of Ficus obliqua given with 1 SE. Wasp community composition 12 10 6 19 14 7 13 13 16 16 6 132 Results ± ± ± ± ± ± ± ± ± ± ± ± Heredotia* Sycophila* There was one species in each genus apart from Pleistodontes, which had two. Mean abundances per syconium are given with 1 SE. Prevalence refers to the percentage of syconia in which the genus was found. 45.6 34.3 65.3 63.6 24.2 52.3 54.8 76.9 51.6 85.8 93.8 57.5 Empty Seeds Megastigmus* 66 42 10 10 5 11 7 1 Pseudidarnes* 0.7 0.4 0.1 0.4 0.05 0.06 0.02 0.01 Eukobelea Sycoscapter 6.4 ± Philotrypesis 2.7 ± Watshamiella 0.3 ± Eukobelea 1.4 ± Pseudidarnes 0.1 ± Heredotia 0.2 ± Sycophila 0.08 ± Megastigmus 0.01 ± Pollinator/ galler Parasitoid Parasitoid Parasitoid Galler Galler Galler Parasitoid Parasitoid Watshamiella Sycoryctinae Sycoryctinae Sycoryctinae Sycophaginae Sycophaginae Epichrysomallinae Eurytomidae Torymidae 100 Philotrypesis 57.5 ± 2.2 Sycoscapter Pleistodontes Poll. wasps Agaonidae Diam. (mm) Genus Prevalence (%) Ecology n (Sub)family Mean abundance 1.6 1.5 2.0 2.1 2.2 3.2 4.5 2.0 1.4 0.7 2.1 1.0 Table 2. Wasp taxa sampled from Ficus obliqua. 345 346 Simon T. Segar and James M. Cook Table 4. Results of linear mixed models testing for effects of exploiters on the mutualism. Response Explanatory Figs/crops t P R2 Pollinators Sycoscapter Diameter Philotrypesis Diameter Sycoryctines Diameter Sycoscapter Diameter Philotrypesis Diameter Sycoryctines Diameter 93/11 −3.508 2.854 −0.146 3.056 −3.659 2.793 −1.320 2.462 0.057 2.564 0.062 2.447 <0.001 0.005 0.884 0.003 <0.001 0.006 0.190 0.016 0.955 0.012 0.951 0.016 11 4 4 6 8 4 7 4 6 5 <1 5 Pollinators Pollinators Seeds Seeds Seeds 93/11 96/12 87/11 87/11 90/12 Models contained the fixed explanatory variables exploiters (Sycoscapter, or Philotrypesis, or pooled sycoryctines) and fig diameter, as well as the random explanatory variable fig crop. Nagelkerke’s R 2 is given for each variable. Table 5. Results of simple regressions of seed and pollinator numbers on the number of exploiters. Response Explanatory d.f. t P % var. Pollinators Pollinators Pollinators Seeds Seeds Seeds Sycoscapter Philotrypesis Sycoryctines Sycoscapter Philotrypesis Sycoryctines 141,1 141,1 147,1 134,1 134,1 140,1 −3.887 −3.200 −5.068 −3.054 1.343 −1.344 <0.001 0.002 <0.001 0.003 0.181 0.181 9 6 14 7 1 1 Discussion The fig/pollinator symbiosis has a pantropical distribution, but both plant and pollinator species differ across continents. The associated exploiter (NPFW) communities also differ (Cook (a) & Rasplus, 2003). We conducted the first dedicated study of NPFW community composition for a fig from Ficus section Malvanthera, an Australasian radiation of figs. We found that the NPFW community differed greatly from those in studies on other continents, but that, as on other continents, the main impact of exploiters was to reduce fig male reproductive function by decreasing pollinator offspring production. Our focal species, F. obliqua, has a community dominated by NPFWs from just a single subfamily of fig wasps, the Sycoryctinae (see Tables 1 and 3). The situation appears similar in F. rubiginosa, the only other malvantheran fig in which parasites have been studied to date (Cook & Power, 1996; Dunn et al., 2008), although its parasite community composition has yet to be described in detail (but see Segar, 2011). Overall, our well-sampled F. obliqua NPFW community differs substantially from NPFW communities on New World section Americana figs, which belong to the same Ficus subgenus (Urostigma). The Americana communities are dominated in terms of numbers of both species and individuals by wasps from subfamily Sycophaginae (West et al., 1996; Pereira et al., 2000) and have no sycoryctines. In contrast, F. obliqua is dominated by sycoryctines and has only two species (Eukobelea sp. and Pseudidarnes sp.) of sycophagines, which make up only 13% of all NPFW individuals. The subfamilial composition of the F. obliqua NPFW community is more similar to communities from African and Asian Urostigma figs (Compton et al., 1994; Chen et al., 1999; Xiao et al., 2010). However, these communities include another subfamily, Otitesellinae, which is absent from malvantheran figs (Bouček, 1988). Detailed regional fig wasp surveys show that sycoryctines also account for a significant component of NPFW species diversity in Africa (van Noort & Compton, 1999; van Noort, 2004). In a survey of nine African fig species, van Noort and Compton (1999) found that 37% of all fig wasp species were sycoryctines (with 3.6 species per host fig), while the next most common subfamily represented only 18% of all species (b) Fig. 1. Scatter plots of model fitted values against the number of sycoryctines per syconium for Ficus obliqua. Fitted values result from linear mixed models with the fixed explanatory variables, sycoryctine numbers and syconium diameter, and the random explanatory variable crop. (a) The negative association between pollinators and sycoryctines (figs: 96, crops: 12, t = −3.659, P < 0.001) remained after controlling for the fig diameter and crop. (b) Sycoryctine number did not explain a significant amount of the variance in pollinator number (figs: 90, crops: 12, t = 0.062, P = 0.951) after controlling for diameter and crop. See Table 4 for further details of these relationships.  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society, Ecological Entomology, 37, 342–349 Segar and Cook exploiters decrease fig male function (1.7 species per host). Consequently, the subfamily Sycoryctinae is likely an important component of Old World fig wasp communities in general. Indeed, many Ficus species host multiple sycoryctine species, with recent reports of an average of 2.7 species per Ficus host in Africa (McLeish et al., 2010) and a conservative average of 1.9 in Asia and Australasia (Segar et al., 2012). Although sycoryctine abundance can vary dramatically both within and between crops (Cook & Power, 1996; Dunn et al., 2008), in a given crop sycoryctines can account for up to 50% of all fig wasps reared (S. van Noort, pers. comm). This high abundance means they are an important source of pollinator mortality in some syconia. Sycoryctine wasps accounted for 84% of all NPFWs sampled from F. obliqua and we explored their effects on pollinator and seed production, which represent fig tree male and female reproductive function. These wasps, especially Sycoscapter, have a significant negative effect on pollinator numbers, but little or no significant effect on seeds (Table 4). The statistical effects also decrease across species (Sycoscapter > Philotrypesis) in line with their decreasing abundance. It is largely wasps from the genus Sycoscapter driving the negative impact of sycoryctines on pollinators. Previous authors (e.g. Bronstein, 1991; Cook & Power, 1996) have also noted the difficulties of detecting statistical effects of NPFWs with low abundance, especially when there are other uncontrolled variables. We interpret this correlation to mean that at least Sycoscapter, and probably also Philotrypesis, wasps are parasitoids or lethal inquilines of pollinating wasps, i.e. they usurp the galls of pollinator larvae and kill them in the process. Nevertheless, we cannot entirely rule out alternative explanations, such as intense competition for flowers between sycoryctines and pollinators (see West & Herre, 1994). However, we support the widely accepted view of the larval biology of wasps in these genera and there is direct evidence for the parasitoid habit in one Sycoscapter species (Tzeng et al., 2008), the lethal inquiline habit in two Philotrypesis species (Kuttamathiathu, 1959; Abdurahiman & Joseph, 1978; Bouček, 1988) and indirect evidence for the hyper-parasitoid habit in Watshamiella (Compton et al., 2009) from other figs. Evidence from manipulation experiments further shows that the sycoryctine wasp Apocrypta guineesis Grandi has a strong negative impact on pollinator numbers in Ficus sur Forsk (Compton & Robertson, 1988). There is also considerable indirect evidence supporting the idea that most Sycoscapter and Philotrypesis species are parasitoids or inquilines in the galls of other fig wasps, rather than making their own galls. For example, to our knowledge they are only found in the pollinated male syconia of dioecious fig species (Henderson, 1982; Abdurahiman, 1986; Bouček, 1988) and not the seed-producing female syconia, which contain no pollinator larvae. This is also consistent with our observations that wasps of both species lay their eggs a considerable time after the pollinators have laid their eggs, while known gallmakers tend to attack very young fig fruits before, or about the same time, as the pollinators (Cruaud et al., 2011b). In our study, sycoryctines and pollinators were the only wasp occupants in over 50% of all F. obliqua syconia, but 347 sycoryctines were never found without pollinators, and appear to use pollinator galls as their primary or only hosts. Our new results therefore provide evidence that the sycoryctines associated with F. obliqua are indeed likely to be inquilines or parasitoids of the pollinators. They have limited impact on seed production, even though far more seeds than pollinators are accessible to sycoryctine wasps laying eggs through the syconium wall in the closely related fig F. rubiginosa (AlBeidh et al., 2012). The weak, negative statistical association of Sycoscapter with seeds may even be a by-product of their preferential attack of pollinators in the outer seed layer rather than inner ovules (Dunn et al., 2008). Some studies on African and neotropical sycoryctines have also detected a negative trade-off with pollinator offspring, but not with seeds (West et al., 1996; Kerdelhué et al., 2000; Weiblen et al., 2001), again stressing that the costs fall on fig male function. West et al. (1996) concluded that this pattern was due to competition between pollinators and wasps from the neotropical genus Critogaster for ovule space in figs from the section Pharmacosycea. The authors observed Critogaster wasps ovipositing at the same time as pollinators and therefore concluded that they were galling wasps. However, recent phylogenetic work suggests that Critogaster may not be a true member of the sycoryctine clade and could represent a separate colonisation of figs in South America (Segar et al., 2012). More detailed ecological and phylogenetic studies are now required to confirm the role of Critogaster and the evolutionary history of the subfamily Sycoryctinae. Above, we have shown how the dominant subfamily of exploiters impacts upon pollinators and seeds in an endemic Australasian fig species. However, we also found wasps from several other taxa (Table 2). Apart from Eukobelea, sycophagine wasps occurring in low numbers, these other wasps are all much larger than the pollinators or the common parasite taxa. They develop in large galls emanating from syconium wall tissue and are all relatively rare (Table 3). Even when they do occur, there are usually only a few individuals per syconium. Large wasps like these seem to occur as rare members of most fig wasp communities and can sometimes prevent abortion of unpollinated syconia or decrease seed or pollinator production by draining resources (Compton, 1993; West & Herre, 1994; Peng et al., 2010). However, their effects could be more complex at the syconium level if the presence of large galls leads to the plant directing extra resources to these syconia. This phenomenon is known for cynipid wasp galls on dandelions (Bagatto et al., 1995) and would be a valuable line of future study on figs. However, these are only rare species and, overall, we find that while the dominant exploiter taxa differ greatly across continents, the main cost is consistently to fig male function (pollinator offspring production). Acknowledgements We would like to thank Teresa Bradley, Susie Joslin, Karl Davey, Sarah West and Laura Chamberlain for assistance with field sampling and dissection of syconia. We are grateful to Derek Dunn, Lizzie Jones, Simon van Noort, and an  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society, Ecological Entomology, 37, 342–349 348 Simon T. Segar and James M. Cook anonymous referee for comments on an earlier version of this manuscript. We thank NERC and the University of Reading for supporting this research. References Abdurahiman, U.C. (1986) Biology and behaviour of Philotrypesis pilosa Mayr (Torymidae: Hymenoptera). Bulletin of Entomology, 27, 121–127. Abdurahiman, U.C. & Joseph, K.J. (1978) Cleptoparasitism of the fig wasps (Torymidae: Chalcidoidea) in Ficus Hispida L. Entomon, 3, 181–186. Al-Beidh, S., Dunn, D.W., Power, S.A. & Cook, J.M. (2012) Parasites and mutualism function: measuring enemy-free space in a fig/pollinator symbiosis. Oikos, in press. Althoff, D.M., Groman, J.D., Segraves, K.A. & Pellmyr, O. (2001) Phylogeographic structure in the bogus yucca moth Prodoxus quinquepunctellus (Prodoxidae): comparisons with coexisting pollinator yucca moths. Molecular Phylogenetics and Evolution, 21, 117–127. Anstett, M.C., Bronstein, J.L. & Hossaert-McKey, M. (1996) Resource allocation: a conflict in the fig/fig wasp mutualism? Journal of Evolutionary Biology, 9, 417–428. Bagatto, G., Paquette, L.C. & Shorthouse, J.D. (1995) Influence of galls of Phanacis taraxaci on carbon partitioning within common dandelion, Taraxacum officinale. Entomologia Experimentalis et Applicata, 79, 111–117. Bates, D. & Maechler, M. (2009) lme4: linear mixed-effects models using S4 classes, R package version 0999375-32. Bayen, R.H. (2010) languageR: data sets and functions with ‘Analyzing Linguistic Data: a practical introduction to statistics’, R package version 1.0. Berg, C.C. & Corner, E.J.H. (2005) Flora Malesiana, Series I – Seed Plants. National Herbarium Nederland, University of Leiden, Leiden, The Netherlands. Bouček, Z. (ed.) (1988) Australasian Chalcidoidea (Hymenoptera). C.A.B. International, Wallingford, U.K. Bronstein, J.L. (1988) Mutualism, antagonism, and the fig-pollinator interaction. Ecology, 69, 1298–1302. Bronstein, J.L. (1991) The non-pollinating wasp fauna of Ficus pertusa: exploitation of a mutualism. Oikos, 61, 175–186. Bronstein, J.L. (1992) Seed predators as mutualists: ecology and evolution of the fig-pollinator interaction. Insect-Plant Interactions (ed. by E. Bernays), pp. 1–44. CRC Press, Boca Raton, Florida. Bronstein, J.L. (1994) Conditional outcomes in mutualistic interactions. Trends in Ecology & Evolution, 9, 214–217. Bronstein, J.L. (2001) The exploitation of mutualisms. Ecology Letters, 4, 277–287. Bronstein, J.L. & Hossaert-McKey, M. (1996) Variation in reproductive success within a subtropical fig pollinator mutualism. Journal of Biogeography, 23, 433–446. Bronstein, J.L. & McKey, D. (1989) The fig-pollinator mutualism – a model system for comparative biology. Experientia, 45, 601–604. Chen, Y.-R., Chuang, W.-C. & Wu, W.-J. (1999) Chalcid wasps on Ficus microcarpa L. in Taiwan (Hymenoptera: Chalcidoidea). Journal of Taiwan Museum, 52, 39–79. Compton, S.G. (1993) An association between epichrysomallines and eurytomids (Hymenoptera: Chalcidoidea) in southern African fig wasp communities. African Entomology, 1, 123–125. Compton, S.G. & Robertson, H.G. (1988) Complex interactions between mutualisms – ants tending homopterans protect fig seeds and pollinators. Ecology, 69, 1302–1305. Compton, S.G., Rasplus, J.-Y. & Ware, A.B. (1994) African fig wasp parasitoid communities. Parasitoid Community Ecology (ed. by B. Hawkins and W. Sheehan), pp. 323–348. Oxford University Press, Oxford, U.K. Compton, S.G., van Noort, S., McLeish, M., Deeble, M. & Stone, V. (2009) Sneaky African fig wasps that oviposit through holes drilled by other species. African Natural History, 9, 9–15. Cook, J.M. & Power, S.A. (1996) Effects of within-tree flowering asynchrony on the dynamics of seed and wasp production in an Australian fig species. Journal of Biogeography, 23, 487–493. Cook, J.M. & Rasplus, J.-Y. (2003) Mutualists with attitude: coevolving fig wasps and figs. Trends in Ecology and Evolution, 18, 241–248. Cook, J.M. & Segar, S.T. (2010) Speciation in fig wasps. Ecological Entomology, 35, 54–66. Corlett, R.T., Boudville, V. & Seet, K. (1990) Seed and wasp production in five fig species (Ficus, Moraceae). Malayan Nature Journal, 44, 97–102. Crawley, M.J. (2007) The R Book, 5th edn. John Wiley and Sons Ltd, Chichester, U.K. Cruaud, A., Jabbour-Zahab, R., Genson, G., Couloux, A., Yan-Qiong, P., Da Rong, Y. et al. (2011a) Out of Australia and back again: the world-wide historical biogeography of non-pollinating fig wasps (Hymenoptera: Sycophaginae). Journal of Biogeography, 38, 209–225. Cruaud, A., Jabbour-Zahab, R., Genson, G., Kjellberg, F., Kobmoo, N., van Noort, S. et al. (2011b) Phylogeny and evolution of lifehistory strategies in the Sycophaginae non-pollinating fig wasps (Hymenoptera, Chalcidoidea). BMC Evolutionary Biology, 11, 178. Cruaud, A., Rønsted, N., Chantarasuwan, B., Chou, L.S., Clement, W.l., Couloux, A. et al. (2012) An extreme case of plant-insect codiversification: figs and pollinating wasps. Systematic Biology, in press. Dixon, D.J., Jackes, B.R. & Bielig, L.M. (2001) Figuring out the figs: the Ficus obliqua-Ficus rubiginosa complex (Moraceae: Urostigma sect. Malvanthera). Australian Systematic Botany, 14, 133–154. Dunn, D.W., Segar, S.T., Ridley, J., Chan, R., Crozier, R.H., Yu, D.W. et al. (2008) A role for parasites in stabilising the fig-pollinator mutualism. PLoS Biology, 6, 490–496. Foster, K.R. & Wenseleers, T. (2006) A general model for the evolution of mutualisms. Journal of Evolutionary Biology, 19, 1283–1293. Harrison, R.D. (2005) Figs and the diversity of tropical rainforests. Bioscience, 55, 1053–1064. Henderson, L.J. (1982) Fig wasps of Heron Island, Great Barrier Reef. Proceedings of the Royal Society of Queensland, 93, 21–29. Herre, E.A., Knowlton, N., Mueller, U.G. & Rehner, S.A. (1999) The evolution of mutualisms: exploring the paths between conflict and cooperation. Trends in Ecology & Evolution, 14, 49–53. Herre, E.A., Jander, K.C. & Machado, C.A. (2008) Evolutionary ecology of figs and their associates: recent progress and outstanding puzzles. Annual Review of Ecology Evolution and Systematics, 39, 439–458. Kerdelhué, C. & Rasplus, J.-Y. (1996) Non-pollinating afrotropical fig wasps affect the fig- pollinator mutualism in Ficus within the subgenus Sycomorus. Oikos, 75, 3–14. Kerdelhué, C., Rossi, J.P. & Rasplus, J.-Y. (2000) Comparative community ecology studies on old world figs and fig wasps. Ecology, 81, 2832–2849. Kuttamathiathu, J.J. (1959) The biology of Phylotrypesis caricae (L.), parasite of Blastophaga psenes (L.) (Chalcidoidae: parasitic Hymenoptera). Proceedings of the XVth International Congress of Zoology, pp. 662–664. London. Lach, L. (2008) Argentine ants displace floral arthropods in a biodiversity hotspot. Diversity and Distributions, 14, 281–290.  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society, Ecological Entomology, 37, 342–349 Segar and Cook exploiters decrease fig male function Leigh, E.G. Jr. (2010) The evolution of mutualism. Journal of Evolutionary Biology, 23, 2507–2528. Lin, S.L., Zhao, N.X. & Chen, Y.Z. (2008) Phenology and the production of seeds and wasps in Ficus microcarpa in Guangzhou, China. Symbiosis, 45, 101–105. Lopez-Vaamonde, C., Dixon, D.J., Cook, J.M. & Rasplus, J.-Y. (2002) Revision of the Australian species of Pleistodontes (Hymenoptera: Agaonidae) fig-pollinating wasps and their host- plant associations. Zoological Journal of the Linnean Society, 136, 637–683. McLeish, M.J., van Noort, S. & Tolley, K.A. (2010) Parasitoid fig-wasp evolutionary diversification and variation in ecological opportunity. Molecular Ecology, 19, 1483–1496. Nagelkerke, N.J.D. (1991) A note on a general definition of the coefficient of determination. Biometrika, 78, 691–692. van Noort, S. (2004) Fig Wasp (Hymenoptera: Chalcidoidea: Agaonidae, Pteromalidae, Eurytomidae & Ormyridae) and Ficus (Moraceae) species richness and biogeography of Monts Doudou in South-Western Gabon. California Academy of Sciences Memoir, 28, 217–233. van Noort, S. & Compton, S.G. (1999) Fig wasps (Agaonidae, Hymenoptera) and fig trees (Moraceae) of Mkomazi. Mkomazi: The Ecology, Biodiversity and Conservation of a Tanzanian Savanna (ed. by M. J. Coe, M. C. McWilliam, G. N. Stone and M. Packer), pp. 299–320. Royal Geographical Society (with The Institute of British Geographers), London, U.K. Peng, Y.-Q., Zhao, J.-B., Harrison, R.-D. & Yang, D.-R. (2010) Ecology of parasite Sycophilomorpha sp. on Ficus altissima and its effect on the fig-fig wasp mutualism. Parasitology, 137, 1913–1919. Pereira, R.A. & Prado, A.P. (2005) Non-pollinating wasps distort the sex ratio of pollinating fig wasps. Oikos, 110, 613–619. Pereira, R.A., Semir, J. & Menezes Junior, A.-O. (2000) Pollination and other biotic interactions in figs of Ficus eximia Schott (Moraceae). Revista Brasileira de Botânica, 23, 217–224. R Development Core Team (2009) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. Rønsted, N., Weiblen, G.D., Cook, J.M., Salamin, N., Machado, C.A. & Savolainen, V. (2005) 60 million years of co-divergence in the fig-wasp symbiosis. Proceedings of the Royal Society B: Biological Sciences, 272, 2593–2599. Rønsted, N., Weiblen, G.D., Savolainen, V. & Cook, J.M. (2008) Phylogeny, biogeography, and ecology of Ficus section Malvanthera (Moraceae). Molecular Phylogenetics and Evolution, 48, 12–22. 349 Sachs, J.L. & Simms, E.L. (2006) Pathways to mutualism breakdown. Trends in Ecology & Evolution, 21, 585–592. Segar, S.T. (2011) The ecology and evolution of fig wasp communities. PhD thesis, University of Reading, Reading, UK. Segar, S.T., Lopez-Vaamonde, C., Rasplus, J.Y. & Cook., J.M. (2012) The global phylogency of the subfamily sycoryctinae (pteromalidae): Parasites of an obligate mutualism. Molecular Phylogenetics and Evolution, 65, 116–125. Thompson, J.N. (2005) The Geographic Mosaic of Coevolution. The University of Chicago Press, Chicago, Illinois. Tzeng, H.-Y., Tseng, L.-J., Ou, C.-H., Lu, K.-C., Lu, F.-Y. & Chou, L.-S. (2008) Confirmation of the parasitoid feeding habit in Sycoscapter, and their impact on pollinator abundance in Ficus formosana. Symbiosis, 45, 129–134. Wang, R.-W. & Zheng, Q. (2008) Structure of a fig wasp community: temporal segregation of oviposition and larval diets. Symbiosis, 45, 113–116. Wardle, D.A., Bardgett, R.D., Kilironomos, J.N., Setala, H. & van der Putten, W.H. (2004) Ecological linkages between aboveground and belowground biota. Science, 304, 1629–1633. Weiblen, G.D., Yu, D.W. & West, S.A. (2001) Pollination and parasitism in functionally dioecious figs. Proceedings of the Royal Society of London Series B: Biological Sciences, 268, 651–659. West, S.A. & Herre, E.A. (1994) The ecology of the New World figparasitizing wasps Idarnes and implications for the evolution of the fig-pollinator mutualism. Proceedings of the Royal Society of London Series B: Biological Sciences, 258, 67–72. West, S.A., Herre, E.A., Windsor, D.M. & Green, P.R.S. (1996) The ecology and evolution of the New World non-pollinating fig wasp communities. Journal of Biogeography, 23, 447–458. Xiao, J.-H., Wang, N.-X., Li, Y.-W., Murphy, R.W., Wan, D.-G., Niu, L.-M. et al. (2010) Molecular approaches to identify cryptic species and polymorphic species within a complex community of fig wasps. PLoS ONE, 5, e15067. Yao, J., Zhao, N., Chen, Y., Jia, X., Deng, Y. & Yu, H. (2005) Resource allocation for coevolved figs and fig wasps in monoecious figs: where and how are seeds and wasps produced? Symbiosis, 39, 143–149. Yu, D.W. (2001) Parasites of mutualisms. Biological Journal of the Linnean Society, 72, 529–546. Accepted 30 May 2012  2012 The Authors Ecological Entomology  2012 The Royal Entomological Society, Ecological Entomology, 37, 342–349