Diatomophthoraceae – a new family of olpidiopsis-like diatom parasitoids largely unrelated to Ectrogella

摘要

The oomycete genus currently comprises a rather heterogeneous group of obligate endoparasitoids, mostly of diatoms and algae. Despite their widespread occurrence, little is known regarding the phylogenetic affinities of these bizarre organisms. Traditionally, the genus was included within the , based on zoospore diplanetism and a saprolegnia/achlya-like zoospore discharge. The genus has undergone multiple re-definitions in the past, and has often been used largely indiscriminately for oomycetes forming sausage-like thalli in diatoms. While the phylogenetic affinity of the polyphyletic genus has recently been partially resolved, taxonomic placement of the genus remained unresolved, as no sequence data were available for species of this genus. In this study, we report the phylogenetic placement of infecting the freshwater diatom . The phylogenetic reconstruction shows that is grouped among the early diverging lineages of the with high support, and is unrelated to the monophyletic diatom-infecting olpidiopsis-like species. As these species are neither related to , nor to the early diverging lineages of . and , they are placed in a new genus, , in the present study.