Genus of lichen
Micarea is a genus of lichen-forming fungi in the family Pilocarpaceae. The widely distributed genus contains 142 species and new species are described actively. Species in the genus are crustose lichens and their photobiont (the non-fungal organism) is a single-celled green alga.
Taxonomy.
"Micarea" was circumscribed by Elias Magnus Fries in his 1825 work "Systema Orbis Vegetabilis". There have been some taxonomic disputes about the genus. Nowadays, the genus is accepted, although it is paraphyletic and in need of further research. "Micarea prasina" is the type species of the genus.
Reproduction.
Lichenized fungi have developed diverse reproduction strategies. The microlichen genus "Micarea" is an excellent model for studying the effects of reproductive traits and environmental factors on speciation because it shows intricate variation in substrate requirements and reproduction modes. Certain "Micarea" species are generalists and able to grow on various substrata, while some are specialized and live in strict microhabitats. Some of the "Micarea" species are predominately sexual, while some frequently lack sexual structures but bear numerous pycnidia where asexual conidia are produced. The actual roles of the three types of conidia present are not thoroughly understood, but mesoconidia are likely asexual propagules based on, for example, the observation that many of the species are frequently found with only mesopycnidia and no apothecia. Recent phylogenetic analyses together with ancestral state reconstruction among "Micarea" species showed that the shift in reproduction mode has evolved independently several times within the group and that facultative and obligate lignicoles are sister species. This supports the assumption that the ancestor of these species was a facultative lignicole. It is presumed that a shift in substrate requirement from bark to wood leads to differentiation in reproduction mode and becomes a driver of speciation in "Micarea" microlichens. The case of "Micarea" is the first observation that among lichenized fungi reproduction mode is connected to substrate requirement. It is also the first example where such an association is demonstrated to lead to lichen speciation. The main hypothesis behind this phenomenon is that obligate species on dead wood need to colonize new suitable substrata relatively fast and asexual reproduction is a more effective strategy for successful colonisation.
Species.
As of October 2024[ [update]], Species Fungorum accepts 142 species of "Micarea".
References.
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