Swaegers J, Mergeay J, Van Geystelen A, Therry L, Larmuseau M H D, Stoks R
Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Deberiotstraat 32, 3000, Leuven, Belgium.
Research Institute for Nature and Forest, Gaverstraat 4, B-9500, Geraardsbergen, Belgium.
Mol Ecol. 2015 Dec;24(24):6163-76. doi: 10.1111/mec.13462.
Many species are expanding their range polewards, and this has been associated with rapid phenotypic change. Yet, it is unclear to what extent this reflects rapid genetic adaptation or neutral processes associated with range expansion, or selection linked to the new thermal conditions encountered. To disentangle these alternatives, we studied the genomic signature of range expansion in the damselfly Coenagrion scitulum using 4950 newly developed genomic SNPs and linked this to the rapidly evolved phenotypic differences between core and (newly established) edge populations. Most edge populations were genetically clearly differentiated from the core populations and all were differentiated from each other indicating independent range expansion events. In addition, evidence for genetic drift in the edge populations, and strong evidence for adaptive genetic variation in association with the range expansion was detected. We identified one SNP under consistent selection in four of the five edge populations and showed that the allele increasing in frequency is associated with increased flight performance. This indicates collateral, non-neutral evolutionary changes in independent edge populations driven by the range expansion process. We also detected a genomic signature of adaptation to the newly encountered thermal regimes, reflecting a pattern of countergradient variation. The latter signature was identified at a single SNP as well as in a set of covarying SNPs using a polygenic multilocus approach to detect selection. Overall, this study highlights how a strategic geographic sampling design and the integration of genomic, phenotypic and environmental data can identify and disentangle the neutral and adaptive processes that are simultaneously operating during range expansions.
许多物种正在向极地扩展其分布范围，这与快速的表型变化有关。然而，目前尚不清楚这在多大程度上反映了快速的基因适应或与分布范围扩展相关的中性过程，还是与新遇到的热条件相关的选择。为了厘清这些可能性，我们利用4950个新开发的基因组单核苷酸多态性（SNP）研究了豆娘细纹晏蜓（Coenagrion scitulum）分布范围扩展的基因组特征，并将其与核心种群和（新建立的）边缘种群之间快速进化的表型差异联系起来。大多数边缘种群在基因上与核心种群明显不同，且所有边缘种群之间也相互不同，这表明存在独立的分布范围扩展事件。此外，我们检测到边缘种群中存在基因漂变的证据，以及与分布范围扩展相关的适应性遗传变异的有力证据。我们在五个边缘种群中的四个中发现了一个处于持续选择下的SNP，并表明频率增加的等位基因与飞行性能的提高有关。这表明分布范围扩展过程驱动了独立边缘种群中附带的、非中性的进化变化。我们还检测到了适应新遇到的热环境的基因组特征，反映出一种反梯度变异模式。后一种特征是通过一个单核苷酸多态性以及使用多基因多位点方法检测选择的一组协变单核苷酸多态性确定的。总体而言，这项研究凸显了战略性的地理采样设计以及基因组、表型和环境数据的整合如何能够识别和厘清在分布范围扩展过程中同时发生的中性和适应性过程。
