Coalescence with Background and Balancing Selection in Systems with Bi- and Uniparental Reproduction: Contrasting Partial Asexuality and Selfing
Coalescence with Background and Balancing Selection in Systems with Bi- and Uniparental Reproduction: Contrasting Partial Asexuality and Selfing
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DOI：
10.1534/genetics.115.181024
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发表时间：
2016-01-01
期刊：
影响因子：
3.3
通讯作者：
Hartfield, Matthew
中科院分区：
文献类型：
--
作者：
Agrawal, Aneil F.;Hartfield, Matthew
在二倍体中，通过无性繁殖或自交的单亲繁殖降低了独立基因座跨代传递的独立性。预计这将增加中性标记受基因组其他地方选择影响的程度。这种影响以前已经量化的聚结模型涉及自交。在这里，我们研究了背景选择和平衡选择在能够有性和无性繁殖的二倍体中的作用（即，部分无性恋）。我们发现，背景选择减少结合时间（和有效的人口规模）的影响，可以是数量级更大的时候，性别率低比性别是常见的。这是因为无性生殖通过重组效应和分离效应增强了背景选择的效果。我们发现，有几个原因，背景选择的强度不同的系统与部分无性生殖和那些具有可比水平的单亲繁殖通过自交。已经使用随机模拟验证了通过背景选择减少N-e的期望。与背景选择相反，平衡选择增加了连接的中性位点的聚结时间。对于部分无性恋，平衡选择的效果在某种程度上取决于选择的模式（例如，杂合子优势相对于负频率依赖性选择）。这是因为杂合子的频率，这是重组到替代的遗传背景，是更依赖于选择的模式与部分无性比自交。
Uniparental reproduction in diploids, via asexual reproduction or selfing, reduces the independence with which separate loci are transmitted across generations. This is expected to increase the extent to which a neutral marker is affected by selection elsewhere in the genome. Such effects have previously been quantified in coalescent models involving selfing. Here we examine the effects of background selection and balancing selection in diploids capable of both sexual and asexual reproduction (i.e., partial asexuality). We find that the effect of background selection on reducing coalescent time (and effective population size) can be orders of magnitude greater when rates of sex are low than when sex is common. This is because asexuality enhances the effects of background selection through both a recombination effect and a segregation effect. We show that there are several reasons that the strength of background selection differs between systems with partial asexuality and those with comparable levels of uniparental reproduction via selfing. Expectations for reductions in N-e via background selection have been verified using stochastic simulations. In contrast to background selection, balancing selection increases the coalescence time for a linked neutral site. With partial asexuality, the effect of balancing selection is somewhat dependent upon the mode of selection (e.g., heterozygote advantage vs. negative frequency-dependent selection) in a manner that does not apply to selfing. This is because the frequency of heterozygotes, which are required for recombination onto alternative genetic backgrounds, is more dependent on the pattern of selection with partial asexuality than with selfing.