Gene flow improves fitness at a range edge under climate change

Populations at the margins of a species' geographic range are often thought to be poorly adapted to their environment. According to theoretical predictions, gene flow can inhibit these range edge populations if it disrupts adaptation to local conditions. Alternatively, if range edge populations are small or isolated, gene flow can provide beneficial genetic variation, and may facilitate adaptation to environmental change. We tested these competing predictions in the annual wildflower Clarkia pulchella using greenhouse crosses to simulate gene flow from sources across the geographic range into two populations at the northern range margin. We planted these between-population hybrids in common gardens at the range edge, and evaluated how genetic differentiation and climatic differences between edge populations and gene flow sources affected lifetime fitness. During an anomalously warm study year, gene flow from populations occupying historically warm sites improved fitness at the range edg...

物种地理分布边缘的种群通常被认为对其环境的适应性较差。根据理论预测，如果基因流（gene flow）干扰了对本地条件的适应，则会抑制这些边缘种群的生存。反之，若边缘种群规模较小或处于隔离状态，基因流则可提供有益的遗传变异，进而促进其对环境变化的适应。我们以一年生野花Clarkia pulchella为研究对象，通过温室杂交模拟来自地理分布范围内不同来源的基因流向北部边缘的两个种群，对上述相互矛盾的预测进行了验证。我们将这些种群间杂交后代种植于边缘区域的同质园（common gardens）中，评估了边缘种群与基因流来源种群之间的遗传分化及气候差异对终生适合度（lifetime fitness）的影响。在异常温暖的研究年份中，来自历史上气候温暖区域种群的基因流提升了边缘种群的适合度……