Myriostoma herrerae sp. nov. (Geastrales: Basidiomycota) and a new record of M. calongei from Mexico

Myriostoma Desv. was considered a monotypic genus until five species were delimited with molecular evidence. Specimens in Mexico have been recorded under the name M. coliforme but according to the literature, this is a species complex. Therefore, the objective of this work was to determine the Myriostoma species present in Mexico based on morphological and phylogenetic studies. A bibliographic review of the genus in Mexico was carried out, and six herbaria were reviewed. Microscopic characteristics of the dried material were observed. ITS and partial LSU nuc rDNA from Mexican specimens were amplified and sequenced. Furthermore, sequences were obtained from GenBank. ITS sequence data was analysed alone and then in a concatenated ITS and LSU dataset. Analyses were performed with Maximum Parsimony, Bayesian inference, and Maximum Likelihood. The results showed that at least two species have been recorded as M. coliforme and although the morphology of this complex is highly variable, few characters help to distinguish them. Nevertheless, there are some features that would allow us to separate them. In Mexico, there is no M. coliforme or M. capillisporum, instead we find M. calongei, previously only known from Argentina, Brazil, and the USA, and M. herrerae, here described as a new species. These species differ in their endoperidial ornamentation and habitat. This is the first record of M. calongei in Mexico and there are probably two other new species, but more data are needed.