Phylogenetic relatedness within the genus Erysiphe estimated with morphological characteristics

Abstract

The genus Erysiphe has been suggested as an ancestral form within the Erysiphaceae characterized by a set of shared, relatively primitive morphological characters and may in fact be polyphyletic. However, several groups within Erysiphe are delimited by other sets of important morphological differences, resulting in its subdivision into at least three evolutionary lines (sections) and other allied genera. Further subdivision of each section into species has been suggested on the basis of more subtle morphological differentiation as well as by host range differences. While morphology can delimit taxa within Erysiphe, the use of morphology in estimating phylogenetic relatedness within and between sections has not been tested directly. In this analysis, a direct comparison of differences within Erysiphe and among allied taxa was undertaken to determine the phylogenetic utility of these morphological differences. Cladistic analysis revealed a most parsimonious consensus network that separates Blumeria from the remaining Erysiphe taxa, and groups species from section Golvinomyces into a single clade with Brasiliomyces. Sphaerotheca and Microsphaera form distinct clades. The strict consensus fails to clearly order relationships among sections Erysiphe, Galeopsidis and Golvinomyces. Bootstrap analyses suggest that section Galeopsidis is more closely aligned with section Erysiphe, and that Microsphaera and section Erysiphe share common ancestry. Phylogenetic relationships within section Golvinomyces and of Brasiliomyces trina are not clarified by morphology. Thus, morphology does show some usefulness in phylogenetic comparisons between sections of Erysiphe, but appears to have much more limited usefulness for distinguishing among species within a section.

Key Words:

• Erysiphaceae
• Erysiphales
• Erysiphe
• morphology
• powdery mildews
• systematics
• taxonomy