A revision of the genera Cordana and Exserticlava, with descriptions of new species from Taiwan

Several species of Cordana and Exserticlava were collected from submerged wood in freshwater streams of Taiwan. The two genera were reviewed, with a brief discussion on their conidiogenesis, aided by studies under the scanning electron microscope. The phylogenetic relationships of Exserticlava and Cordana were sought by comparing the concatenated sequences of their nuc ITS1-5.8S-ITS2 rDNA (ITS barcode), partial nuc 28S rDNA (LSU), and partial translation elongation factor 1-α (TEF1) gene segments. The present phylogenetic analysis supports the placement of Cordana in the Cordanaceae (Cordanales) and Exserticlava in the Chaetosphaeriaceae (Chaetosphaeriales); both are distinct taxa in the lineages of freshwater Sordariomycetes. This paper describes and illustrates seven taxa from Taiwan, including Cordana globosa comb. nov., C. oblonga, sp. nov., C. taiwanensis sp. nov., Exserticlava angustata sp. nov., E. asymmetrica sp. nov, E. variabilis sp. nov., and E. vasiformis. The present study contributed several new sequences of Exserticlava and Cordana. The morphology of six Exserticlava species lacking DNA data was reviewed, and three species (i.e., E. manglietiae, E. uniseptata, and E. yunnanensis) were transferred to the genus Cordana. The holotype materials of Cylindroconidius aquaticus and Uvarisporella aquatica were examined, and the two taxa were transferred to the genus Cordana based on morphological evidence. Cordana confusa nom. nov. is proposed in place of Cylindroconidius aquaticus, whereas Uvarisporella aquatica is synonymized with Cordana globosa.