Department of Biological Sciences, University of Notre Dame, South Bend, IN 46556;
Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996.
Proc Natl Acad Sci U S A. 2018 Mar 6;115(10):E2284-E2291. doi: 10.1073/pnas.1714950115. Epub 2018 Feb 20.
Climate-mediated changes in hybridization will dramatically alter the genetic diversity, adaptive capacity, and evolutionary trajectory of interbreeding species. Our ability to predict the consequences of such changes will be key to future conservation and management decisions. Here we tested through simulations how recent warming (over the course of a 32-y period) is affecting the geographic extent of a climate-mediated developmental threshold implicated in maintaining a butterfly hybrid zone ( and ; Lepidoptera: Papilionidae). These simulations predict a 68-km shift of this hybrid zone. To empirically test this prediction, we assessed genetic and phenotypic changes using contemporary and museum collections and document a 40-km northward shift of this hybrid zone. Interactions between the two species appear relatively unchanged during hybrid zone movement. We found no change in the frequency of hybridization, and regions of the genome that experience little to no introgression moved largely in concert with the shifting hybrid zone. Model predictions based on climate scenarios predict this hybrid zone will continue to move northward, but with substantial spatial heterogeneity in the velocity (55-144 km/1 °C), shape, and contiguity of movement. Our findings suggest that the presence of nonclimatic barriers (e.g., genetic incompatibilities) and/or nonlinear responses to climatic gradients may preserve species boundaries as the species shift. Further, we show that variation in the geography of hybrid zone movement could result in evolutionary responses that differ for geographically distinct populations spanning hybrid zones, and thus have implications for the conservation and management of genetic diversity.
气候介导的杂交变化将极大地改变杂交物种的遗传多样性、适应能力和进化轨迹。我们预测这些变化后果的能力将是未来保护和管理决策的关键。在这里，我们通过模拟测试了最近的变暖（在 32 年的时间内）如何影响一个与维持蝴蝶杂交区（和；鳞翅目：凤蝶科）有关的气候介导的发育阈值的地理范围。这些模拟预测这个杂交区将发生 68 公里的转移。为了实证检验这一预测，我们使用当代和博物馆藏品评估了遗传和表型变化，并记录了这个杂交区向北移动了 40 公里。在杂交区移动过程中，两个物种之间的相互作用似乎相对不变。我们没有发现杂交频率的变化，而且经历很少或没有基因渐渗的基因组区域与不断变化的杂交区基本一致。基于气候情景的模型预测表明，这个杂交区将继续向北移动，但移动的速度（55-144 公里/1°C）、形状和连续性存在很大的空间异质性。我们的研究结果表明，非气候障碍（例如，遗传不相容性）的存在和/或对气候梯度的非线性反应可能会在物种转移时保护物种边界。此外，我们还表明，杂交区移动的地理差异可能导致跨越杂交区的地理上不同的种群的进化反应不同，从而对遗传多样性的保护和管理产生影响。
