Department of Plant Biology, University of Vermont.
J Hered. 2017 Dec 21;109(1):38-46. doi: 10.1093/jhered/esx079.
Admixture can break up divergent genetic architectures between populations, resulting in phenotypic novelty and generating raw material for environmental selection. The contribution of admixture to progeny trait variation and fitness varies based on the degree of genetic isolation between the parental populations, for which most studies have used geographic distance as a proxy. A novel approach is to estimate optimal crossing distance using the adaptive genetic distance between mates estimated from loci that contribute directly to local adaptation. Here, we aim to understand the effect of admixture on disrupting local adaptation of ecotypes of Arabidopsis thaliana separated along gradients of geographic, background, and locally adaptive genetic distances. We created experimental F1 hybrids between ecotypes that vary in geographic distance and used SNP data to estimate background (putatively neutral) and adaptive genetic distance. Hybrids were grown under controlled conditions, and fitness, growth, and phenology traits were measured. The different traits measured showed a clear effect of adaptive genetic distance, but not geographic distance. The earliest bolting hybrids were intermediate in the adaptive genetic distance between their parents, and also had higher biomass and fitness in terms of fruit and seed production. Our results suggest that disruption of locally adaptive genomic loci decreases the performance of offspring between distantly related parents, but that crosses between very closely related parents also reduce performance, likely through the expression of deleterious recessive alleles. We conclude that during admixture, selection may have to balance the consequences of disrupting local adaption while also avoiding inbreeding depression.
杂种形成可以打破种群间的分化遗传结构，导致表型新颖，并为环境选择提供原材料。杂种形成对后代性状变异和适应性的贡献取决于亲种群之间遗传隔离的程度，大多数研究都使用地理距离作为代理。一种新的方法是使用直接影响本地适应性的基因座估计的配偶之间的适应性遗传距离来估计最佳杂交距离。在这里，我们旨在了解杂种形成对沿着地理、背景和本地适应性遗传距离梯度分离的拟南芥生态型的本地适应性的破坏的影响。我们在地理距离不同的生态型之间创建了实验性 F1 杂种，并使用 SNP 数据来估计背景（假定为中性）和适应性遗传距离。杂种在受控条件下生长，并测量适应性、生长和物候性状。所测量的不同性状清楚地显示了适应性遗传距离的影响，但与地理距离无关。最早抽薹的杂种在其父母之间的适应性遗传距离中处于中间位置，并且在果实和种子产量方面也具有更高的生物量和适应性。我们的结果表明，破坏本地适应性基因组位点会降低来自远缘亲本的后代的表现，但来自非常近缘亲本的杂交也会降低表现，可能是由于有害隐性等位基因的表达。我们得出的结论是，在杂种形成过程中，选择可能必须平衡破坏本地适应的后果，同时避免近交衰退。
