| Abstract Detail
Tuesday Morning Contributed Talks Städler, Thomas [1], Arunyawat, Uraiwan [1], Stephan, Wolfgang [1]. Population genomics of the speciation process in two closely related wild tomatoes. MULTILOCUS studies assessing patterns of nucleotide polymorphism within and among closely related species provide access to genealogical information bearing on demographic and geographic aspects of their speciation history. We present a large sequencing study concerned with assessing patterns of polymorphism and divergence in the closely related wild tomato species, Solanum peruvianum and S. chilense. The data comprise four population samples per species and nine mapped nuclear loci (about 86 alleles per locus and 11.5 kB across loci). Both tomato species are highly polymorphic at the nucleotide level, with estimates of average silent nucleotide diversity being about 1.4 times higher in S. peruvianum. Both species are characterized by modest-to-high amounts of population subdivision (average intraspecific Fst ~ 0.2). Standard tests of neutrality suggest that one of the loci deviates from neutral assumptions, while the other eight loci appear to evolve in a neutral fashion, and hence may be used to infer demographic and historical processes under appropriate coalescent models. We employ the analytical framework of divergence population genetics in testing the ‘isolation’ model of speciation, in particular the critical assumption of divergence without gene flow. While the isolation model cannot be rejected by goodness-of-fit criteria, patterns of intragenic linkage disequilibrium are indicative of historical introgression at least in some regions of the genome. These results suggest that speciation occurred under residual gene flow, implying natural selection as one of the evolutionary forces driving the divergence of these tomato lineages. Reasonable demographic parameter estimates are obtained in single (interspecific) population comparisons, but the presence of population structure within both taxa implies that using pooled samples is inappropriate. We are in the process of extending the isolation model to allow for population structure and interspecific gene flow following initial divergence; parameters of this more realistic model are estimated in a maximum likelihood framework.
Log in to add this item to your schedule
1 - University of Munich (LMU), Department Biologie II, Grosshaderner Strasse 2, Planegg-Martinsried, D-82152, Germany
Keywords:
Wild Solanum species
modes of speciation
divergence population genetics
interspecific gene flow
gene genealogies
coalescent models.
Session: SOL04-6
Location: Ballroom AB/Monona Terrace
Date: Tuesday, July 25th, 2006
Time: 9:50 AM
Abstract ID:166 |
