The phylogeny and phylogenetically based classification of myxomycetes

Abstract Within the myxomycetes, phylogenetic research is still at a relatively early stage, and available phylogenies are often based on only a single or a few marker genes. According to the available data, the “true” myxomycetes (exosporous, myxogastric) form a monophyletic clade within the phylum Eumycetozoa with two basal subclades, a dark-spored (treated as the Columellomycetidae) and a bright-spored (the subclass Lucisporomycetidae). Within the first subclade the main evolutionary branches are recognized as the orders Echinosteliales, Echinosteliopsidales, Clastodermatales, Meridermatales, Stemonitidales, and Physarales; for the bright-spored subclade, these are the orders Cribrariales, Reticulariales, Liceales, and Trichiales. In the light of molecular data the traditional criteria used in myxomycete taxonomy have to be reevaluated. The morphology of capillitia and peridia, and especially how these two structures are connected to each other in a particular taxon, seems to be highly informative, whereas their presence or absence is not. Similarly, single versus compound fruiting bodies, a character often used to delimit genera, seems to deserve a lower weight, as these structures have evolved several times in parallel. Many, especially species rich, genera seem not to represent monophyletic units, and further research will most likely change their delimitation.