Botryandromyces, a morphology-based genus concept scrutinized by molecular data

Abstract

Laboulbeniales (Ascomycota) are an order of understudied, biotrophic microfungi uniquely associated with arthropods. More than 2300 species are described but only a fraction of those have been sequenced. Molecular studies have shown that cryptic diversity and phenotypic plasticity are present within the Laboulbeniales. Thus far, all of the 146 genera described in Laboulbeniales have been based on morphological characteristics; features commonly used to delineate genera are the organization of receptacle cells and the number of perithecial outer wall cells. The genus Botryandromyces was erected to accommodate two species, B. heteroceri and B. ornatus (type), which share similar morphological characteristics and are different from other genera in their number of perithecial outer wall cells. Here, we generated sequences of multiple loci (18S, ITS, and 28S) of B. heteroceri and several Laboulbenia species. Our phylogenetic analyses retrieved Botryandromyces within Laboulbenia with high support. The two Botryandromyces species are similar to related Laboulbenia species in their upper receptacle (i.e., cells IV and V). We propose to transfer Botryandromyces ornatus and B. heteroceri to Laboulbenia as L. heteroceri and L. mairei nom. nov., respectively, due to a complicated taxonomic history. These results advocate the use of molecular data and the necessity of an integrative taxonomy approach in the study of Laboulbeniales not only to delineate species, but also to investigate relationships among species, genera, and higher taxa as well as to understand the evolution of morphology in this group of fungi.