A molecular reappraisal of Nimbospora (Halosphaeriaceae, Microascales) and a new genus Ebullia for N. octonae

• Nimbospora is not a monophyletic genus.
• Nimbospora effusa and N. bipolaris grouped with Naufragella spinibarbata.
• Nimbospora octonae formed a separate clade with Haligena elaterophora.

Nimbospora is a genus in the Halosphaeriaceae with three species: N. effusa (the type species), N. bipolaris and N. octonae. All species have two-celled ascospores with a prominent sheath. A second type of appendage is present in two species, a single tuft of fibrillar appendages is present in N. effusa and two occur in N. bipolaris. Nimbospora effusa and N. bipolaris are morphologically similar, but there are major morphological differences in ascomatal morphology between N. effusa/N. bipolaris and N. octonae. In this study, we investigated the morphology of N. effusa and N. octonae and the phylogenetic relationships of the three Nimbospora species based on partial sequences of 18S and 28S rRNA genes. Bayesian analysis suggested that Nimbospora is not monophyletic. Nimbospora effusa groups with N. bipolaris in a well-supported clade, with Naufragella spinibarbata forming a sister group. Nimbospora octonae, however, clusters with Haligena elaterophora in a separate, well-supported clade. The ascomata of N. octonae differ from those of N. effusa and N. bipolaris by their thick peridium, and ascospores that lack equatorial tufts of appendages but possess polar and equatorial subulate appendages after the sheath is dissolved. Based on these characters and the correlating phylogenetic distance, the new genus Ebullia is established to accommodate N. octonae.