Re-evaluation of Exserticlava and other genera in Chaetosphaeriaceae with chalara-, phaeostalagmus-, phialocephala- and stanjehughesia-like morphotypes

Abstract

In this study, we undertook a re-evaluation of species classified in genera Exserticlava, Phaeostalagmus, Phialocephala, and several chalara- and stanjehughesia-like fungi, whose placement has been determined within Chaetosphaeriaceae. They exhibit morphotypes that are either not exclusive to Chaetosphaeriaceae and have evolved in distantly related groups or have not been conclusively established as monophyletic within the family. Our study is based on phylogenetic reconstruction of three DNA markers and comparative morphological studies involving 21 strains, including all available ex-type strains. The non-monophyletic nature of the genus Exserticlava was elucidated and consequently, its generic concept has been emended, leading to the introduction of a segregate genus Exserticlavopsis. Chalara-like fungi occurred in three unrelated lineages, including a strongly supported clade comprising Chalarosphaeria and Fusichalara, a distinct lineage representing the newly introduced genus Chalarina gen. nov., and Sporoschisma, which produces the chalara-like synasexual morph. The genus Stanjehughesia is documented as a monophyletic, strongly supported clade. The notable similarity with other stanjehughesia-like genera is discussed. The phialocephala-like morphotype is infrequent within Chaetosphaeriaceae and is confined to two unrelated clades, specifically represented by Chloridium sect. Pseudophialocephala and Spadicocephala gen. nov., the latter being established to accommodate Phialocephala fusca. A monophyletic clade comprising members of Phaeostalagmus and Sporendocladia has been identified based on new molecular data. Since the relationship between the type species P. cyclosporus and P. tenuissimus could not be fully resolved, the clade is defined as a natural group characterized by distinct morphological patterns in conidiophore branching and aggregation of conidia. This definition is provisional, pending broader and more comprehensive taxon sampling. In this study, we introduced three new genera, two new species, and proposed six combinations. These findings emphasize the ongoing need for research to further refine the classification and enhance our understanding of the evolutionary relationships within Chaetosphaeriaceae.