An overview on the biology and phylogeny of the early-diverging oomycetes

Abstract

Holocarpic oomycetes are ubiquitous especially in marine and freshwater environments. These organisms are mostly obligate biotrophic parasites and members of the deep-branching, early-diverging clades of the Oomycota, comprising of several genera that had their phylogenetic position only recently investigated (Miracula, Olpidiopsis, Eurychasma, Haptoglossa, Anisolpidium, Diatomophthora, Pontisma, Haliphthoros) as well as some unresolved genera (Ducellieria, Petersenia, Sirolpidium, Eurychasmidium, Pseudosphaerita, Rozellopsis). Despite their widespread occurrence and importance for understanding the evolution of the oomycetes, knowledge on the biology and ecology of these bizarre organisms is still fragmentary for temperate regions and almost absent for the tropics. Here, an overview on the current state of knowledge on early-diverging oomycetes is presented, with emphasis on the general biology, systematics and ecology.