Phylogeny and Taxonomy of the Genus Amphichorda (Bionectriaceae): An Update on Beauveria-like Strains and Description of a Novel Species from Marine Sediments

Abstract

The genus Amphichorda has been recently re-erected as an independent lineage from Beauveria, circumscribed within Cordycipitaceae. However, its phylogenetic relationships with other members of this family remain obscure. In our ongoing efforts to expand the knowledge on the diversity of culturable ascomycetes from the Mediterranean Sea, we isolated several specimens of Amphichorda. Preliminary sequence analyses revealed great phylogenetic distance with accepted Amphichorda species and a close relation to Onychophora coprophila. Onychophora is a monotypic genus of enteroblastic conidiogenous cells, presumably related to Acremonium (Bionectriaceae), while Amphichorda exhibits holoblastic conidiogenesis. Here, we examine representative strains of Amphichorda species to elucidate the taxonomy of the genus and the aforementioned fungi, combining morphological, ultrastructure and multi-locus phylogenetic analyses (ITS, LSU, tef1, BenA). The results revealed Amphichorda as a member of the Bionectriaceae, where its asexual morphs represent a transition between enteroblastic and holoblastic conidiogenesis for this group of fungi. We also describe and illustrate Amphichorda littoralis sp. nov. and propose Amphichorda coprophila comb. nov. In addition, we establish key phenotypic features to distinguish Amphichorda species and demonstrate the higher salt tolerance degree of A. littoralis, consistent with its marine origin. This work provides a comprehensive framework for future studies in the genus.