Peltigera is a genus of approximately 100 species of folioselichens in the familyPeltigeraceae.[2] Commonly known as the dog or pelt lichens, species of Peltigera are often terricolous (growing on soil), but can also occur on moss, trees, rocks, and many other substrates in many parts of the world.[3]
Most species of Peltigera have the cyanobacteriumNostoc as the dominant photobiont but some have the algae Coccomyxa. The presence of both a green alga and a cyanobacterium makes some tripartite; in this case they show cephalodium growths containing the third partner, Nostoc. Because of their ability to fix nitrogen from the atmosphere, such lichens are influential in soil composition and generation.
Description
Species of Peltigera are foliose, with broad lobed thalli. Although the size of the thalli is variable and species-dependent, in some species the thalli can grow quite large, up to 30 cm in diameter.[4] The color of the upper surface may range from drab gray, brown or greenish. Lower surfaces are typically without a cortex (unlike other foliose lichens),[5] and cottony, often with fungal hyphae fused to form a network of veins. The reproductive structures isidia, soredia or lobules may be present in some species.[6] All species of Peltigera associate with the nitrogen-fixing cyanobacteria Nostoc.[7]
Peltigera can be distinguished from the equally large and leaf-like lichen, Nephroma, by its veined lower cortex; Nephroma, by contrast, has a smooth, unveined lower cortex.[8]
Habitat
Peltigera are mainly ground-dwelling, but can also be found on mosses or dead wood.[8] Some species are used as forest succession indicators.
Taxonomy
In 1753, Linnaeus first described the species Lichen apthosus and L. caninus back when all known lichens were grouped into the genus Lichen.[9] Later, in 1787, Willdenow circumscribed the genus Peltigera, and redescribed P. aphthosa and P. canina.[10]
The generic name is derived from the Latin languagepelta (small shield), and refers to the shield-shaped thallus in these species. The common name, the dog lichen, refers to the perceived resemblance of P. caninus to a dog.[11]
Phylogeny
In a comparative analysis of both morphological and chemical characteristics as well as sequences of large subunit nuclear ribosomal DNA, it was shown that the genus Peltigera is monophyletic.[12] Several species, such as P. canina, have been changed to a group as there appears to be several species clustered under a single name.
Recent taxonomic work has led to the consolidation of three previously recognized aquatic Peltigera species (P. hydrothyria, P. gowardii, and P. aquatica) into a single species with three varieties. According to Bruce McCune and Daphne Stone (2022), while molecular analysis showed three distinct genetic clades, maintaining them as separate species proved impractical for conservation and research purposes. This was because P. gowardii and P. aquatica, which occur together in western North America, are indistinguishable without DNA sequencing. The difficulty in identifying specimens to species level effectively stalled data collection, with most specimens remaining classified only as P. hydrothyriasensu lato. To resolve this issue while preserving information about genetic diversity, the three taxa were reclassified as P. hydrothyria var. hydrothyria (eastern North America), P. hydrothyria var. gowardii (western), and P. hydrothyria var. aquatica (western). This taxonomic solution allows for practical field identification while still acknowledging the genetic differences between populations.[13]
Distribution
The Peltigera have a widespread distribution, and are found on all continents. There are 34 North American species, 30 European species, 25 species from South America, and 16 species from New Zealand.[3][4][14][15] There are 27 Peltigera species that have been recorded from China.[16]
Ecology
Peltigera lichens serve as important hosts for diverse microbial communities, functioning as miniature ecosystems rather than simply dual symbiotic partnerships. Recent research has revealed that Peltigera species harbour rich communities of basidiomycete yeasts, with some species supporting multiple distinct yeast taxa within their thalli. For example, P. rufescens has been found to host over 90 different yeast isolates representing 18 distinct taxa, demonstrating the complexity of these microbial associations. These lichens appear to acquire key microbial symbionts directly from the soils where they grow, suggesting their local environments serve as reservoirs for their microbiome diversity.[17]
The yeasts associated with Peltigera belong to several major taxonomic groups, including members of the classes Tremellomycetes, Cystobasidiomycetes, and other basidiomycetes. Many of these yeasts are psychrotolerant, showing adaptations to cold environments, which may enhance the lichens' ability to survive in harsh conditions. This characteristic likely contributes to the successful colonisation of various habitats by Peltigera species, particularly in temperate and cold regions where they are commonly found. Studies have shown that these yeasts can maintain metabolic activity even at low temperatures, potentially supporting the lichen's overall survival and ecological functionality.[17]
The relationship between Peltigera and its microbial communities appears to vary across different environments and species. Research in southern Chile has demonstrated that Peltigera lichens can significantly enhance gamma diversity across landscapes by functioning as island-like habitats that support specialised bacteria and yeasts. This suggests that Peltigera species play a broader ecological role beyond their own survival, contributing to local microbial biodiversity patterns and ecosystem processes. While the specific functions of many associated microorganisms remain under investigation, this complex microbial diversity likely contributes to the ecological resilience of Peltigera species across different environments and may help explain their successful colonisation of diverse habitats worldwide.[17]
Peltigera species have been used historically to treat wounds, urinary disorders, thrush, tuberculosis, and rabies.[11][40][41]P. apthosa was used as a remedy for cough[42] and infantile aphthae.[43]P. furfuracea has shown potent antioxidant activity and reducing power.[44] Similarly, Peltigera specimens from Hawaii and Iceland have also been reported to show pronounced antioxidant activity.[45]
Food source
Although a few reports have described caribou and reindeer feeding on the thalli of Peltigera,[46] in general, species of Peltigera are not commonly used as a food source by mammals.[47][48] A study of the grazing habits of the land snails Cantareus aspersa and Limax species revealed that these snails prefer to eat Peltigera species (such as P. praetextata) that are lacking in secondary metabolites.[49]
^ abMartinez I, Burgaz AR, Vitikainen O, Escudero A (2003). "Distribution patterns in the genus Peltigera Willd". The Lichenologist. 35 (4): 301–323. doi:10.1016/S0024-2829(03)00041-0.
^ abVitikainen O. (1994). (1998). Taxonomic notes on neotropical species of Pelitgera. In: Lichenology in Latin America: history, current knowledge and applications. Edited by M. P. Marcelli, and M.R.D. Seaward. CETESB, Companhia de Tecnologia de Saneamento Ambiental, Estado de Sao Paulo. pp. 135-139.
^Geiser, Linda; McCune, Bruce (1997). Macrolichens of the Pacific Northwest. Corvallis: Oregon State University Press. p. 198. ISBN0-87071-394-9.
^O'Brien, Heath E.; Miadlikowska, Jolanta; Lutzoni, François (2005). "Assessing host specialization in symbiotic cyanobacteria associated with four closely related species of the lichen fungus Peltigera". European Journal of Phycology. 40 (4): 363–378. doi:10.1080/09670260500342647.
^ abSharnoff, Stephen; Brodo, Irwin M.; Sharnoff, Sylvia Duran (2001). Lichens of North America. New Haven, Conn: Yale University Press. ISBN0-300-08249-5.
^McCune, Bruce; Stone, Daphne F. (2022). "Eight new combinations of North American macrolichens". Evansia. 39 (3): 123–128. doi:10.1639/0747-9859-39.3.123.
^Goward T, Goffinet B, Vitikainen O (1995). "Synopsis of the genus Peltigera (lichenized Ascomycetes) in British Columbia, with a key to the North American species". Canadian Journal of Botany. 73: 91–111. doi:10.1139/b95-012.
^Galloway DJ (2000). "The lichen genus Peltigera (Peltigerales:Ascomycota) in New Zealand". Tuhinga. 11: 1–45.
^ abHan, Liu-Fu; Zheng, Tian-Xin; Guo, Shou-Yu (2015). "A new species in the lichen genus Peltigera from northern China based on morphology and DNA sequence data". The Bryologist. 118 (1): 46–53. doi:10.1639/0007-2745-118.1.046.
^Goffinet, Bernard; Miadlikowska, Jolanta; Goward, Trevor (2003). "Phylogenetic inferences based on nrDNA sequences support five morphospecies within the Peltigera didactyla complex (lichenized Ascomycota)". The Bryologist. 106 (3): 349–364. doi:10.1639/01.
^Manoharan-Basil, Sheeba S.; Miadlikowska, Jolanta; Goward, Trevor; Andrésson, Ólafur S.; Miao, Vivian P.W. (2016). "Peltigera islandica, a new cyanolichen species in section Peltigera ('P. canina group')". The Lichenologist. 48 (5): 451–467. doi:10.1017/S0024282916000414.
^ abcVitikainen, O. (1985). "Three new species of Peltigera (lichenized Ascomycetes)". Annales Botanici Fennici. 22 (4): 291–298.
^Dodge, C.W.; Rudolph, E.D. (1955). "Lichenological notes on the flora of the Antarctic Continent and the subantarctic islands. I-IV". Annals of the Missouri Botanical Garden. 42 (2): 131–149.
^Holtan-Hartwig, J. (2005). "Peltigera latiloba, a new lichen species from Norway and USA (Alaska)". Graphis Scripta. 17 (2): 34–34.
^Han, Liu-Fu; Xu, X.M.; Yang, J.Y.; Guo, SY. (2018). "Peltigera neodegenii sp. nov. from Central China". Mycotaxon. 133 (2): 323–332.
^Goffinet, B.; Miadlikowska, J. (1999). "Peltigera phyllidiosa (Peltigeraceae, Ascomycotina), a new species from the Southern Appalachians corroborated by ITS sequences". The Lichenologist. 31 (3): 247–256.
^Magain, Nicolas; Sérusiaux, Emmanuël; Zhurbenko, Mikhail P.; Lutzoni, François; Miądlikowska, Jolanta (2016). "Disentangling the Peltigera polydactylon species complex by recognizing two new taxa, P. polydactylon subsp. udeghe and P. seneca". Herzogia. 29 (2): 514–528. doi:10.13158/heia.29.2.2016.514.
^Han, Liu-Fu; Yang, Jing-Yuan; Beu, Shu-Qing; Guo, Shou-Yu (2019). "Peltigera shennongjiana, a new cyanolichen from Central China". The Lichenologist. 51 (6): 561–574. doi:10.1017/s0024282919000355.
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^Han, Liu-Fu; Zhang, Ya-Ya; Guo, Shou-Yu (2013). "Peltigera wulingensis, a new lichen (Ascomycota) from north China". The Lichenologist. 45 (3): 329–336. doi:10.1017/s0024282912000837.
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^Odabasoglu F, Aslan A, Cakir A, et al. (March 2005). "Antioxidant activity, reducing power and total phenolic content of some lichen species". Fitoterapia. 76 (2): 216–9. doi:10.1016/j.fitote.2004.05.012. PMID15752633.
^Hagiwara K, Wright PR, et al. (March 2015). "Comparative analysis of the antioxidant properties of Icelandic and Hawaiian lichens". Environmental Microbiology. 18 (8): 2319–25. doi:10.1111/1462-2920.12850. PMID25808912.
^Maser Z, Maser C, Trapper JM (1985). "Food habits of the northern flying squirrel (Glaucomys sabrinus) in Oregon". Canadian Journal of Zoology. 63 (5): 1084–1088. doi:10.1139/z85-162.
^Kallman S (1992). "Wild plants as food during survival situations". Sven Bot Tidsk. 86 (2): 49–52.
^Benesperi R, Tretiach M (2004). "Differential land snail damage to selected species of the lichen genus Peltigera". Biochemical Systematics and Ecology. 32 (2): 127–138. doi:10.1016/S0305-1978(03)00141-8.
^Ingólfsdóttir K, Gudmundsdóttir GF, Ogmundsdóttir HM, Paulus K, Haraldsdóttir S, Kristinsson H, Bauer R (2002). "Effects of tenuiorin and methyl orsellinate from the lichen Peltigera leucophlebia on 5-/15-lipoxygenases and proliferation of malignant cell lines in vitro". Phytomedicine. 9 (7): 654–658. doi:10.1078/094471102321616481. PMID12487331.
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