The Phylogeny and Genome Size in Myxomycetes

Myxomycete is a group of eukaryotic organisms with special life cycle living as animals and fungi. They have myxamoebae, swarm cells, and plasmodia like protozoa and also produce spores like fungi in life-cycle. Origin of Myxomycetes is still unclear though it belongs to protozoa . Ontogenetic and phylogenetic analyses will provide the information to discuss a the origin and evolution of myxomycetes.

Phylogenetic analysis of myxomycetes was investigated with the sequences of COI, SSU rDNA, ITS rDNA, 16S rDNA and EF1-αgene and their morphology and ontogeny were examined. Combined phylogenetic trees with the morphological characteristics and phylogeny showed that Ceratiomyxales which has external spores located at the base of these trees, and Physarales and Stemonitales which have dark spores were sister group of the trees. Trichiales which has no columellium were separated before Physarales and Stemonitales. The mutation rate of ITS rDNA sequences of Physarales were higher than that of Trichiales and Liceales.Meanwhile, Relationships among the types of habitats, phylogenetic groups and morphological characteristics were recognized.

Genome size is also an important biological information to discuss evolution. Genome size of Trichiales can be divided into two groups. Among them, most species of Perichaena, Trichia and Metatrichia have a higher C-value than those of Arcyria and Hemitrichia. It was suggested that genome size was related with the differentiation of these genera.