Pyxine subcinerea

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Pyxine subcinerea
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Lecanoromycetes
Order: Caliciales
Family: Caliciaceae
Genus: Pyxine
Species:
P. subcinerea
Binomial name
Pyxine subcinerea
Stirt. (1898)
Synonyms[1]
  • Pyxine cocoes var. caesiopruinosa Tuck. (1869)
  • Pyxine meissneri var. sorediosa Müll.Arg. (1879)
  • Physcia melanenta C.Knight (1882)
  • Pyxine sorediata f. caesiopruinosa (Tuck.) Hue (1900)
  • Pyxine chrysanthoides Vain. (1915)
  • Pyxine caesiopruinosa (Tuck.) Imshaug (1957)

Pyxine subcinerea is a species of foliose lichen in the family Caliciaceae. It has a pantropical distribution, and typically grows on bark, but less commonly on rocks. The lichen is characterised by its yellow medulla, soralia on the margins on the lobes that make up the thallus, and the presence of the chemical lichexanthone in the cortex.

Taxonomy[edit]

The lichen was first formally described by the Scottish scientist James Stirton from specimens collected in Queensland, Australia. He noted that its thallus was similar to that of Pyxine sorediata, but Stirton distinguished it from that species by the "internal organization of both the thallus and the apothecia", as well as the negative K reaction of the thallus, compared to the yellow reaction of P.  sorediata.[2]

Synonyms of Pyxine subcinerea include:[1] Physcia melanenta, described by Charles Knight in 1882;[3] Pyxine chrysanthoides, described by Edvard August Vainio in 1915 from material collected in the Antilles;[4] Pyxine meissneri var. sorediosa, described by Johannes Müller Argoviensis in 1879;[5] and Pyxine cocoes var. caesiopruinosa, described by Edward Tuckerman in 1869[6] (and later promoted to distinct species status as Pyxine caesiopruinosa by Henry Andrew Imshaug in 1957).[7]

Description[edit]

Closeup of lobes; the scale bar is 0.5 mm.

The thallus of Pyxine subcinerea is 3–8 cm (1.2–3.1 in) wide, with an upper surface ranging in colour from yellowish grey to grey to brownish grey or olive-grey. The lobes that comprise the thallus are 0.3–1.5 mm (0.01–0.06 in) wide, somewhat tightly apressed to the substrate and are more or less flat but often somewhat concave near the tips. The lobe surface are pruinose, with the pruina resembling dense points near the lobe tips.[8] These pruina contain weddellite, a mineral form of calcium oxalate.[9] There are distinct pseudocyphellae at the margins of the lobes. The soralia are near the lobe margins. The medulla is quite thin and yellow above. The lower surface is black in the centre, but becomes paler towards the margin. Rhizines are more or less dense, and divided into branches.[8] The upper cortex is paraplectenchymatous (a cell arrangement where the hyphae are oriented in all directions), while the lower cortex is prosoplectenchymatous (a cell arrangement where the hyphae are all oriented in one direction).[10] Apothecia (reproductive structures) are common in tropical and subtropical specimens; they measure 0.3–1.5 mm (0.01–0.06 in) wide and have an indistinct internal stipe.[8] In contrast, apothecia are not typically associated with European material.[10] Ascospores measure 13–22 by 6–9 μm. The conidia are bacilliform, and measure 3–4 μm by about 1 μm.[8]

The secondary chemical in Pyxine subcinerea is lichexanthone.[8] The presence of this compound results in a golden-yellow colour when illuminated with UV light.[11] All lichen spot tests are negative.[10]

Pyxine subcinerea in 365 nm ultraviolet light

Habitat and distribution[edit]

Pyxine subcinerea has a mostly pantropical distribution. Although it is generally found growing on bark, it has also been found growing on rock,[10] and, in one instance, on mortar.[11] In Europe, it has been reported from the Azores and Italy.[10] It has been reported from Africa (Ethiopia, Uganda, Kenya, Tanzania, the Seychelles, Rwanda and Angola),[12] throughout Asia (including China),[13] Australia,[8] New Zealand,[14] In the eastern United States, its geographical range covers subtropical to more temperate regions, including the states of New York, Illinois, and Ohio to Florida, Louisiana, and Texas. Pyxine subcinerea has been recorded growing on hornbeam, hickory, hibiscus, juniper, sweetgum, magnolia, oak, locust, elm, and the genus Prunus. It tends to prefer low elevations, and occurs hardwood-pine forests as well as more open areas including farms, glades, and gardens.[11]

Pyxine subcinerea is relatively resistant to air pollution, and has been investigated for use as a candidate for biomonitoring. It bioaccumulates toxic heavy metals that it acquires from the air and retains the pollutants in the thallus, which can then be sampled and assayed to determine their concentration.[15][16]

References[edit]

  1. ^ a b "Synonymy: Pyxine subcinerea Stirt". Species Fungorum. Retrieved 21 February 2021.
  2. ^ Stirton, J. (1897). "A new classification of the genus Pyxine". Transactions of the New Zealand Institute. 30: 393–398.
  3. ^ Knight, C. (1882). "Contributions to the Lichenographia of New South Wales". Transactions of the Linnean Society of London. 2nd Series. 2: 37–51.
  4. ^ Vainio, E.A. (1915). "Additamenta ad lichenographiam Antillarum illustrandum". Annales Academiae Scientiarum Fennicae (in Latin). 6 (7): 71.
  5. ^ Müller, J. (1879). "Lichenologische Beiträge IX". Flora (Regensburg) (in Latin). 62 (19): 289–298.
  6. ^ Nylander, W. (1869). Synopsis Methodica Lichenum Omnium hucusque Cognitorum, Praemissa Introductione Lingua Gallica (in Latin). Vol. 2. p. 2.
  7. ^ Imshaug, H.A. (1957). "The lichen genus Pyxine in North and Middle America". Transactions of the American Microscopical Society. 76 (3): 246–269. doi:10.2307/3223889. JSTOR 3223889.
  8. ^ a b c d e f Elix, John Alan (2009). "Physciaceae". Flora of Australia. Vol. 57. Canberra & Melbourne: CSIRO Publishing. p. 532. ISBN 978-0-643-09664-6.
  9. ^ Modenesi, P.; Bombardi, V.; Giordani, P.; Brunialti, G.; Corallo, A. (2007). "Dissolution of weddellite, calcium oxalate dihydrate, in Pyxine subcinerea". The Lichenologist. 33 (3): 261–266. doi:10.1006/lich.2001.0321. S2CID 83716323.
  10. ^ a b c d e Moberg, R. (1983). "Studies on Physciaceae (Lichens) II. The genus Pyxine in Europe". The Lichenologist. 15 (2): 161–167. doi:10.1017/S0024282983000250.
  11. ^ a b c Amtoft, Anja (2002). "Pyxine subcinerea in the Eastern United States" (PDF). The Bryologist. 105 (2): 270–272. doi:10.1639/0007-2745(2002)105[0270:PSITEU]2.0.CO;2.
  12. ^ Bock, Christina; Hauck, Markus; Fischer, Eberhard (2007). "The lichen flora of Rwanda: an annotated checklist". Willdenowia. 37 (2): 563–575. doi:10.3372/wi.37.37216. S2CID 84822147.
  13. ^ Yang, Mei-Xia; Wang, Xin-Yu; Liu, Dong; Zhang, Yan-Yun; Li, Li-Juan; Yin, An-Cheng; Scheidegger, Christoph; Wang, Li-Song (2019). "New species and records of Pyxine (Caliciaceae) in China". MycoKeys. 45 (45): 93–109. doi:10.3897/mycokeys.45.29374. PMC 6363720. PMID 30733639.
  14. ^ Hayward, Bruce W.; Hayward, Glenys C. (1990). "Lichens of Whale (Motuhora) and Rurima Islands, Bay of Plenty, New Zealand" (PDF). Tane. 32: 61–71.
  15. ^ Shukla, Vertika; Upreti, Dalip K. (2007). "Effect of metallic pollutants on the physiology of lichen, Pyxine subcinerea Stirton in Garhwal Himalayas". Environmental Monitoring and Assessment. 141 (1–3): 237–243. doi:10.1007/s10661-007-9891-z. PMID 17879139. S2CID 1325600.
  16. ^ Shukla, Vertika; Upreti, Dalip K. (2010). "Changing lichen diversity in and around urban settlements of Garhwal Himalayas due to increasing anthropogenic activities". Environmental Monitoring and Assessment. 174 (1–4): 439–444. doi:10.1007/s10661-010-1468-6. PMID 20440642. S2CID 33101795.
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