Phenotypic plasticity and cryptic generic enigma in Pleosporales: Establishing Sporidesmioidesaceae fam. nov. and Rostriconidium synnematicum sp. nov. from India

Abstract

This study reappraised the taxonomy of the genus Rostriconidium, and introduced a new species, Rostriconidium synnematicum, based on an integrated molecular and morphological taxonomic approach. This new taxon is the only synnematous species within Rostriconidium and forms a sister lineage to other Rostriconidium species in Torulaceae, as supported by phylogenetic analyses of ITS, LSU, SSU, rpb 2 and tef 1 - α sequences using Maximum Likelihood and Bayesian Inference methods.

Additionally, a new combination Rostriconidium yunnanensis is proposed under Rostriconidium. The study addresses the taxonomic complexities of four morphologically similar but phylogenetically distinct genera (Neopodoconis, Pseudohelminthosporium, Rostriconidium, and Sporidesmioides) within the Pleosporales. There are a few taxonomic challenges in resolving relationships among these genera, given their polyphyletic nature and overlapping morphologies.

In this study, advanced mycological studies were conducted to resolve the generic circumscription of Sporidesmioides. In this study, we propose a new familial lineage, Sporidesmioidesaceae, to accommodate the monotypic species S. thailandica, based on phylogenetic analyses of a multi-locus dataset (ITS, LSU, SSU, rpb 2, and tef 1 - α). The results also accommodate Pseudohelminthosporium within Neomassarinaceae, rather than accepting the synonymization of Pseudohelminthosporium clematidis under Neopodoconis ampullacea.

The conspecific nature of P. clematidis and N. ampullacea warrants a future type-based study to validate them. These findings underscore the critical importance of examining type specimens (morphological and multi-locus sequence analysis) before proposing synonymy among cryptic species and genera. This study also revalidated the placement of the recently proposed family Megacapitulaceae and provided their multigene sequence information.