Radiation in sexual and parthenogenetic oribatid mites (Acari, Acariformes)

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Oribatid mites (Acari: Acariformes) are among the most abundant and diverse terrestrial arthropods. Several oribatid mite groups probably radiated despite their exclusively parthenogenetic mode of reproduction (e.g. Nanhermanniidae, Camisidae, Trhypochthonidae, Nothridae, Malaconothridae) and survived long periods of time. Both findings contradict theories on the evolution and maintenance of sex. Parthenogenetic lineages are assumed to be short lived and evolutionary dead ends. To investigate the radiation and diversity of oribatid mites we intend to investigate three topics: (1) We intend to evaluate whether sexual taxa radiated faster than asexual taxa. We are therefore comparing the genetic diversity (COI and HSP82 region) between closely related asexual taxa with that of closely related sexual groups. (2) We want to evaluate the phylogenetic position of the Astigmata within the oribatid mites using the elongation factor-1-aa. The Astigmata (Acari: Acariformes) are an entirely sexual group which has recently been hypothesised to be the sister group of an entirely parthenogenetic group of oribatid mites, the Trhypochthonidae. If this is true, the Astigmata are the only taxon in the animal kingdom that re-evolved sexual reproduction and then intensively radiated (about 10000 species of Astigmata are described). (3) We want to investigate the hypothesis that generalist predators in soil reduce biotic interactions between soil arthropods (e.g. oribatid mites) and enable the coexistence of a large number of species. Furthermore, using stable isotope techniques (15-N, 13-C) the trophic position of oribatid mites is evaluated to find out if these animals inhabit different trophic positions in the soil food web thereby indicating trophic niche differentiation.