Alter, Phylogenie und genetische Diversität von parthenogenetischen Oribatiden-Arten
Zusammenfassung der Projektergebnisse
The project investigated evolutionary patterns of sexual and parthenogenetic reproduction in oribatid mites using molecular phylogenetics and micro- and mesocosm experiments. Parthenogenesis is rare in nature but occurs comparatively frequent in oribatid mites. Among oribatid mites, parthenogenetic taxa are not randomly distributed but lumped in phylogenetic clusters. In natural populations sexual and parthenogenetic species co-exist in the same habitat. These two aspects make oribatid mites ideal model organisms to investigate function and maintenance of sex and were studied using two methodological approaches. Knowledge on the phylogenetic relationship of sexual and parthenogenetic taxa is necessary to infer evolutionary constraints and significance of either reproductive mode for the success of oribatid mites. The phylogenetic relationships of sexual Astigmata relative to oribatid mites is widely disputed and this study provides a large molecular dataset showing that Astigmata did not evolve within the parthenogenetic clade Desmonomata. The relationship of sexual Crotoniidae among parthenogenetic Desmonomata, however, reveal that the re-establishment of a lost character, sexual reproduction, from parthenogenetic ancestors is possible. This refutes Dollo's law and demonstrates extreme adaptabiliy of oribatid mites to evolutionary pressures, which partly explains their remarkable evolutionary success. Exceptions to Dollo's law are rare in nature and have only been demonstrated in very few cases. Further, this work provided new markers for deep phylogenetic analyses by sequencing the first mitochondrial genomes of Sarcoptiformes. The complete mitochondrial genomes revealed unusual genearrangements in the sexual species Steganacarus magnus as the complete loss of tRNAs and excluded heteroplasmy and gene duplications as source of the extraordinary high genetic variance in the barcoding gene COI. Ecological microcosm experiments showed that sexual and parthenogenetic species reacted differently to resource availability and resource quality and that communities of parthenogenetic species are not static. One initial parthenogenetic community can be replaced by other parthenogenetic species, dividing parthenogenetic oribatid mites into two groups: exploiters of easily available resources and consumers of leaf litter associated resources that are not easily accessible. Further, the microcosm experiments demonstrated that females in parthenogenetic oribatid mites carry less eggs than females in sexual species and that they are not faster colonizers of empty habitats. Both traits, faster reproduction and colonizing ability, have been proposed as fundamental advantages of parthenogenetic reproduction but these traits presumably do not hold in oribatid mites. Results of these studies can be incorporated into theories on function and maintenance of sex as they provided new insights into phylogenetic and ecological constraints regarding sexual and parthenogenetic reproduction and how natural populations react to changing environments. We started to develop such models. This work also provides fundamental data to establish oribatid mites as model organisms for evolutionary and ecological questions on sex and parthenogenesis.
Projektbezogene Publikationen (Auswahl)
- (2007) Re-evolution of sexuality breaks Dollo’s law. Proceedings of the National Academy of Science USA 104, 7139-7144
Domes K, Norton RA, Maraun M, Scheu S
- (2007) Resources and sex: soil re-colonization by sexual and parthenogenetic oribatid mite species. Pedobiologia 51, 1-11
Domes K, Scheu S, Maraun M
- (2007) The phylogenetic relationship between Astigmata and Oribatida (Acari) as indicated by molecular markers. Experimental and Applied Acarology 42, 159-171
Domes K, Althammer M, Norton RA, Scheu S, Maraun M
- (2008) Molekulare Phylogenie von Oribatiden (Hornmilben). In: Theorie in der Ökologie Band 12. Bodenzoologie und Ökologie: 30 Jahre Umweltforschung an der Freien Universität Berlin. Jopp F, Pieper S (Hrsg.). Peter Lang Internationaler Verlag der Wissenschaften, Frankfurt/Main
Maraun M, Domes K, Schaefer I, Scheu S
- (2008) The complete mitochondrial genome of the sexual oribatid mite Steganacarus magnus: genome rearrangement and loss of tRNAs. BMC Genomics 9, 532
Domes K, Maraun M, Scheu S, Cameron SL
- (2009) Multiple convergent evolution of arboreal life in oribatid mites indicates the primacy of ecology. Proceedings of the Royal Society B 276, 3219-3227
Maraun M, Erdman G, Schulz G, Norton RA, Scheu S, Domes K
- (2009) Parthenogenesis and sexuality in oribatid mites. Phylogeny, mitochondrial genome structure and resource dependence. PhD Dissertation, TU Darmstadt
Domes-Wehner K
- (2009) Resource depletion and colonization: a comparison between parthenogenetic and sexual Collembola species. Pedobiologia 52, 181-189
Chahartaghi M, Maraun M, Scheu S, Domes K
