Adams Nicole, Dias Tiffany, Skeen Heather R, Pegan Teresa, Willard David E, Winger Ben, Ruegg Kristen, Weeks Brian C, Bay Rachael
Department of Evolution and Ecology, University of California Davis, Davis, CA, 95616, USA.
Department of Ecology and Evolutionary Biology and Museum of Zoology, University of Michigan, Ann Arbor, MI, 48109, USA.
BMC Biol. 2025 Jan 7;23(1):3. doi: 10.1186/s12915-024-02107-5.
Rapid morphological change is emerging as a consequence of climate change in many systems. It is intuitive to hypothesize that temporal morphological trends are driven by the same selective pressures that have established well-known ecogeographic patterns over spatial environmental gradients (e.g., Bergman's and Allen's rules). However, mechanistic understanding of contemporary morphological shifts is lacking.
We combine morphological data and whole genome sequencing from a four-decade dataset in the migratory bird hermit thrush (Catharus guttatus) to test whether morphological shifts over time are accompanied by genetic change. Using genome-wide association, we identify alleles associated with body size, bill length, and wing length. Shifts in morphology and concordant shifts in morphology-associated alleles over time would support a genetic basis for the observed changes in morphology over recent decades, potentially an adaptive response to climate change. In our data, bill size decreases were paralleled by genetic shifts in bill size-associated alleles. On the other hand, alleles associated with body size showed no shift in frequency over time.
Together, our results show mixed support for evolutionary explanations of morphological response to climate change. Temporal shifts in alleles associated with bill size support the hypothesis that selection is driving temporal morphological trends. The lack of evidence for genetic shifts in body size alleles could be explained by a large role of plasticity or technical limitations associated with the likely polygenic architecture of body size, or both. Disentangling the mechanisms responsible for observed morphological response to changing environments will be vital for predicting future organismal and population responses to climate change.
在许多系统中，快速的形态变化正作为气候变化的一个结果而出现。直观地推测，时间上的形态趋势是由那些在空间环境梯度上建立了著名的生态地理模式（如伯格曼法则和艾伦法则）的相同选择压力所驱动的。然而，目前缺乏对当代形态变化的机制性理解。
我们结合了来自一个四十年数据集的形态学数据和全基因组测序，该数据集来自候鸟隐士夜鸫（Catharus guttatus），以测试随着时间推移的形态变化是否伴随着基因变化。通过全基因组关联分析，我们识别出了与体型、喙长和翅长相关的等位基因。形态上的变化以及形态相关等位基因随时间的一致变化将支持近几十年来观察到的形态变化存在遗传基础，这可能是对气候变化的一种适应性反应。在我们的数据中，喙大小的减小伴随着喙大小相关等位基因的基因变化。另一方面，与体型相关的等位基因频率随时间没有变化。
总体而言，我们的结果对气候变化导致形态反应的进化解释提供了混合支持。与喙大小相关的等位基因随时间的变化支持了选择正在驱动时间上的形态趋势这一假设。体型等位基因缺乏基因变化的证据，可能是由于可塑性的巨大作用，或者与体型可能的多基因结构相关的技术限制，或者两者兼而有之。弄清楚导致观察到的对变化环境的形态反应的机制，对于预测未来生物体和种群对气候变化的反应至关重要。
