Cuevas Angélica, Ravinet Mark, Saetre Glenn-Peter, Eroukhmanoff Fabrice
Department of Biosciences, Centre for Ecological and Evolutionary Synthesis, University of Oslo, Oslo, Norway.
School of Life Sciences, University of Nottingham, Nottingham, UK.
Mol Ecol. 2021 Feb;30(3):791-809. doi: 10.1111/mec.15760. Epub 2021 Jan 17.
Hybridization increases genetic variation, hence hybrid species may have greater evolutionary potential once their admixed genomes have stabilized and incompatibilities have been purged. Yet, little is known about how such hybrid lineages evolve at the genomic level following their formation, in particular their adaptive potential. Here we investigate how the Italian sparrow (Passer italiae), a homoploid hybrid species, has evolved and locally adapted to its variable environment. Using restriction site-associated DNA sequencing (RAD-seq) on several populations across the Italian peninsula, we evaluate how genomic constraints and novel genetic variation have influenced population divergence and adaptation. We show that population divergence within this hybrid species has evolved in response to climatic variation, suggesting ongoing local adaptation. As found previously in other nonhybrid species, climatic differences appear to increase population differentiation. We also report strong population divergence in a gene known to affect beak morphology. Most of the strongly divergent loci among Italian sparrow populations do not seem to be differentiated between its parent species, the house and Spanish sparrows. Unlike in the hybrid, population divergence within each of the parental taxa has occurred mostly at loci with high allele frequency difference between the parental species, suggesting that novel combinations of parental alleles in the hybrid have not necessarily enhanced its evolutionary potential. Rather, our study suggests that constraints linked to incompatibilities may have restricted the evolution of this admixed genome, both during and after hybrid species formation.
杂交增加了遗传变异，因此一旦杂交物种的混合基因组稳定且不相容性被清除，它们可能具有更大的进化潜力。然而，对于这些杂交谱系在形成后如何在基因组水平上进化，尤其是它们的适应潜力，人们知之甚少。在这里，我们研究了意大利麻雀（Passer italiae），一种同倍体杂交物种，是如何进化并在当地适应其多变环境的。通过对意大利半岛多个种群进行限制性位点关联DNA测序（RAD-seq），我们评估了基因组限制和新的遗传变异如何影响种群分化和适应。我们表明，这个杂交物种内的种群分化是对气候变化的响应而进化的，这表明正在进行局部适应。正如之前在其他非杂交物种中发现的那样，气候差异似乎会增加种群分化。我们还报告了在一个已知影响喙形态的基因中存在强烈的种群分化。意大利麻雀种群之间大多数强烈分化的位点在其亲本物种家麻雀和西班牙麻雀之间似乎并没有分化。与杂交物种不同，每个亲本分类群内的种群分化大多发生在亲本物种之间等位基因频率差异较高的位点，这表明杂交物种中亲本等位基因的新组合不一定增强了其进化潜力。相反，我们的研究表明，与不相容性相关的限制可能在杂交物种形成期间和之后都限制了这个混合基因组的进化。
