Semenov Georgy, Kenyon Haley, Funk Erik, Anderson William, McQuillan Michael, Spinelli Joan, Russell Austin, Martinez Noel, Van Huynh Alex, Alexander Alana, Schweizer Rena, Linck Ethan, Cheviron Zachary, Carling Matt, Roth Timothy, Robbins Mark, Rice Amber, Taylor Scott
Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, United States.
San Diego Zoo Wildlife Alliance, Escondido, CA, United States.
Evol Lett. 2025 May 7;9(4):421-433. doi: 10.1093/evlett/qraf009. eCollection 2025 Aug.
Determining the genetic architecture of traits involved in adaptation and speciation is one of the key components of understanding the evolutionary mechanisms behind biological diversification. Hybrid zones provide a unique opportunity to use genetic admixture to identify traits and loci contributing to partial reproductive barriers between taxa. Many studies have focused on the temporal dynamics of hybrid zones, but geographical variation in hybrid zones that span distinct ecological contexts has received less attention. We address this knowledge gap by analyzing hybridization and introgression between black-capped and Carolina chickadees in two geographically remote transects across their extensive hybrid zone, one located in eastern and one in central North America. Previous studies demonstrated that this hybrid zone is moving northward as a result of climate change but is staying consistently narrow due to selection against hybrids. In addition, the hybrid zone is moving ~5× slower in central North America compared to more eastern regions, reflecting continent-wide variation in the rate of climate change. We use whole genome sequencing of 259 individuals to assess whether variation in the rate of hybrid zone movement is reflected in patterns of hybridization and introgression, and which genes and genomic regions show consistently restricted introgression in distinct ecological contexts. Our results highlight substantial similarities between geographically remote transects and reveal large Z-linked chromosomal rearrangements that generate measurable differences in the degree of gene flow between transects. We further use simulations and analyses of climatic data to examine potential factors contributing to continental-scale nuances in selection pressures. We discuss our findings in the context of speciation mechanisms and the importance of sex chromosome inversions in chickadees and other species.
确定参与适应和物种形成的性状的遗传结构是理解生物多样性背后进化机制的关键组成部分之一。杂交带提供了一个独特的机会，利用基因混合来识别导致分类群之间部分生殖隔离的性状和基因座。许多研究都集中在杂交带的时间动态上，但跨越不同生态环境的杂交带的地理变异受到的关注较少。我们通过分析黑头山雀和卡罗来纳山雀在其广泛杂交带中两个地理上遥远的样带中的杂交和基因渗入来填补这一知识空白，一个样带位于北美东部，另一个位于北美中部。先前的研究表明，由于气候变化，这个杂交带正在向北移动，但由于对杂交种的选择，它一直保持狭窄。此外，与更东部地区相比，北美中部的杂交带移动速度慢约5倍，这反映了整个大陆气候变化速率的差异。我们对259个个体进行全基因组测序，以评估杂交带移动速率的差异是否反映在杂交和基因渗入模式中，以及哪些基因和基因组区域在不同生态环境中表现出持续受限的基因渗入。我们的结果突出了地理上遥远的样带之间的显著相似性，并揭示了大型Z连锁染色体重排，这些重排在样带之间的基因流程度上产生了可测量的差异。我们进一步利用气候数据的模拟和分析来研究导致选择压力大陆尺度细微差异的潜在因素。我们在物种形成机制以及山雀和其他物种中性染色体倒位的重要性的背景下讨论我们的发现。
