Published 22 August 2023
Among the myriad little-known fungi inhabiting the world are members of the family Patellariaceae. These are saprobes or weak parasites, typically found growing on dead wood or bark. Among the reasons for their obscurity is their size: Patellariaceae are minute, their fruiting bodies largely looking like a dusting of black spots across their substrate. Nevertheless, Patellariaceae are distinctive enough that the family was first recognised as far back as 1838 (Yacharoen et al. 2015).
Like other members of the diverse fungal class Dothideomycetes, Patellariaceae have bitunicate (that is, double-walled) asci from which spores are released when the inflexible outer wall is split open by the swelling of the inner wall. More specific to Patellariaceae is the production of apothecia, fruiting bodies forming a more or less flat disc against the substrate. The ascospores arise from an underlying layer called the hypothecium, and are protected from the elements by an overlying epithecium. In a small number of genera, the fruiting body forms a hysterothecium, with the sides folded up to form a structure resembling a pair of lips or a boat. In the majority of species, the fruiting bodies are superficial, lying on the surface of the substrate, but they are more rarely immersed or erumpent. The combination of bitunicate asci and apothecia is found in few taxa outside the Patellariaceae (one notable exception being the genus Rhytidhysteron, long included among the Patellariaceae but recently transferred to the distantly related Hysteriaceae on the basis of molecular data).
Asexual morphs are little known, remaining unidentified for most species. Pem et al. (2018) did find molecular evidence to associate the asexual taxon Yuccamyces with Patellariaceae (the name of this genus refers not to being found growing on yuccas, but to the conidiomata in culture resembling yucca bushes).
Most studies of Patellariaceae to date have remained at the taxonomic level. Many species seem particular about their substrates. For instance, species of Holmiella are found on the bark of junipers, with particular fungi associated with particular juniper species. Hysteropatella prostii is found on the bark of apples and pears, more rarely on that of Prunus species. A few species have been found growing on lichens or other fungi. If most Patellariaceae are restricted to wood coming from a limited range of trees, and relatively few but disparate trees have been recorded as hosts to Patellariaceae, it is possible that many species of this family remain to be discovered. It just requires someone to go out and look for them.
Pem, D., Y. Gafforov, R. Jeewon, S. Hongsanan, I. Promputtha, M. Doilom & K. D. Hyde. 2018. Multigene phylogeny coupled with morphological characterization reveal two new species of Holmiella and taxonomic insights within Patellariaceae. Cryptogamie Mycologie 39 (2): 193–209.
Yacharoen, S., Q. Tian, P. Chomnunti, S. Boonmee, E. Chukeatirote, J. D. Bhat & K. D. Hyde. 2015. Patellariaceae revisited. Mycosphere 6 (3): 290–326.