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Zusammenfassung:
Evolutionary reconstruction of the natural history of an organism benefits from studies of mutational processes as the source of natural variation. The nematode Pristionchus pacificus has been established as a model system in evolutionary developmental biology for comparison to Caenorhabditis elegans. P. pacificus has a well-defined association with scarab beetles, the ecology and phylogeny are well known and recent studies on LaRéunion Island provide a case study to link population genetics with ecology and evo-devo. We assess the genome evolution of P. pacificus using the mutation accumulation (MA) lines approach to study spontaneous mutation rates in the mitochondrial genome and representative microsatellite markers. The major aim is to relate genetic variation in wild isolates to the mutation rate estimates from the MA lines in order to obtain first insight into minimal divergence times in P. pacificus. Mitochondrial DNA analysis reveals an unusual suppressor tRNA for the codon UAA that has most likely influenced the spectrum of observable mutations in the MA lines. With a mitochodrial mutation rate of 7.6×10-8 per site per generation, we calculated the minimum time to the most recent common ancestor at 105 to 106 generations between nine representative isolates of the species (Molnar et al. 2011). Similarly, microsatellite markers are used to robustly provide minimal divergence time estimates for 30 closely related strains from LaRéunion. The combination of mutation rate analysis with intra-specific divergence provides a powerful tool for the reconstruction of the natural history of P. pacificus.
