Mycoparasitism and the evolution of Basidiomycota

dr. Nathan Schoutteten

Promotor Mieke Verbeken

Basidiomycota are the second largest group of fungi in species numbers, and harbour a huge diversity of fungal life forms and ecological functions. For many people, most familiar are the typical mushroom forming fungi, but also crusts, bracket fungi, puffballs, coral fungi, rusts and smuts are members of Basidiomycota. This diversity is also reflected in ecological functions, various trophic strategies have evolved, with decayers, phytoparasites and mycorrhizal fungi as well-known examples. In recent decades, a number of curious genera and species have been described which derive their nutrients from other fungi, also known as basidiomycetous mycoparasites. They have some remarkable characters, such as septated basidia, secondary spore formation and a dimorphic life cycle (alternation between yeast and hyphal stage).


Basidiomycetous mycoparasites are usually very small fungi, and several of them don’t even form own basidiocarps, but rather grow inside or between the tissues of their host species. Several different types of functional interaction structures have been discovered, of which haustoria and colacosomes are the two main types. Haustoria forming fungi belong to various different genera and classes, whereas colacosomes are found in very few species only, belonging to the classes Cryptomycocolacomycetes and Microbotryomycetes (Pucciniomycotina). The latter class also comprises the enigmatic anther smuts, a lineage of highly specialized plant parasites, which probably evolved from a mycoparasitic ancestor. Most basidiomycetous mycoparasites have been described and delineated using a morphological species concept, although the little available morphological characters often confronted mycologists with serious uncertainties when assigning species to genera and higher taxa.


We aim to shed light on the diversity and evolution of mycoparasitism in Basidiomycota at two different levels, i.e. the organismic and the genomic level. Fieldwork is an important part of this project, since fresh specimens are being isolated in pure culture for subsequent molecular studies. Phylogenetic and phylogenomic reconstructions of mycoparasitic taxa allow to unravel the evolution of this trophic strategy, and to establish an integrative species concept in this group which incorporates phylogenetic evidence, detailed micromorphological analyses and ecological data. Genome sequences of selected mycoparasites will allow 1) a better phylogenomic reconstruction of Basidiomycota (especially focussing on the oldest lineages) and 2) a comparison of mycoparasites and closely related phytoparasites at the genomic level.