

Author: Arunyawat Uraiwan Stephan Wolfgang Stdler Thomas
Publisher: Oxford University Press
ISSN: 0737-4038
Source: Molecular Biology and Evolution, Vol.24, Iss.10, 2007-10, pp. : 2310-2322
Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.
Abstract
We employed a multilocus approach to examine the effects of population subdivision and natural selection on DNA polymorphism in 2 closely related wild tomato species (Solanum peruvianum and Solanum chilense), using sequence data for 8 nuclear loci from populations across much of the species range. Both species exhibit substantial levels of nucleotide variation. The species-wide level of silent nucleotide diversity is 18% higher in S. peruvianum (sil 2.50%) than in S. chilense (sil 2.12%). One of the loci deviates from neutral expectations, showing a clinal pattern of nucleotide diversity and haplotype structure in S. chilense. This geographic pattern of variation is suggestive of an incomplete (ongoing) selective sweep, but neutral explanations cannot be entirely dismissed. Both wild tomato species exhibit moderate levels of population differentiation (average FST 0.20). Interestingly, the pooled samples (across different demes) exhibit more negative Tajimas D and Fu and Li's D values; this marked excess of low-frequency polymorphism can only be explained by population (or range) expansion and is unlikely to be due to population structure per se. We thus propose that population structure and population/range expansion are among the most important evolutionary forces shaping patterns of nucleotide diversity within and among demes in these wild tomatoes. Patterns of population differentiation may also be impacted by soil seed banks and historical associations mediated by climatic cycles. Intragenic linkage disequilibrium (LD) decays very rapidly with physical distance, suggesting high recombination rates and effective population sizes in both species. The rapid decline of LD seems very promising for future association studies with the purpose of mapping functional variation in wild tomatoes.
Related content








Exploring linkage disequilibrium
MOLECULAR ECOLOGY RESOURCES, Vol. 15, Iss. 5, 2015-09 ,pp. :


The Structure of Evolution by Natural Selection
By Campbell Richmond Robert Jason Scott
Biology and Philosophy, Vol. 20, Iss. 4, 2005-09 ,pp. :