Statistical Population Genomics by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9781071601990
Publisher: Springer US

3.2 Empirical Results

Several empirical results have confirmed the theoretical predictions regarding the population genetics effects of selfing. Figure 3 summarizes some empirical population genetics results from selfing and outcrossing Arabidopsis and Capsella species. First, while it is difficult to disentangle the effect of past demographic events from the effect of selfing, both C. rubella and A. thaliana present high levels of population structure [21, 22, 63]. Indeed, population structure is stronger in the selfer C. rubella than in the outcrossing C. grandiflora, consistent with theoretical expectations for selfers [22] (Fig. 3).

Fig. 3Empirical results illustrating the impact of a mating system shift in the Capsella and Arabidopsis genus. (a) Population structure: Global FST among populations is higher in the selfer C. rubella than in the outcrosser C. grandiflora [22]. Elevated values of FST are also found genome-wise among populations of Arabidopsis thaliana [70]. (b) Neutral genetic diversity: nucleotide diversity at synonymous sites is lower in selfers compared to their outcrossing relatives in both Capsella and Arabidopsis [74, 76, 126]. (c) Strength of purifying selection: a higher ratio of nonsynonymous to synonymous nucleotide diversity suggests relaxed purifying selection in the selfing C. rubella [74, 76]. In contrast, in Arabidopsis, the outcrosser A. lyrata has a higher ratio of nonsynonymous to synonymous nucleotide diversity than A. thaliana. (d) Distribution of fitness effect (DFE) in bins of Nes (the product of the effective population size and the selection coefficient) for new nonsynonymous mutations [18, 74, 83, 126]. (e) Codon usage bias: maximum likelihood estimates of selection coefficient, ϒ, for the ten amino acids with twofold degenerate codons between the selfing and outcrossing species. Whiskers are 95% confidence intervals obtained by the MCMC analysis (see Qiu et al. [50] for details, with permission from GBE)

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