Collaborative Research: Testing Mechanisms of Microgeographic Adaptation

进化生态学的一个目标是了解导致物种更好地适应当地环境的过程。历史上，对局部适应的研究主要集中在地理上分离的种群上，在这些种群中，个体在种群之间的有限分散维持了适应性差异。然而，越来越多的证据表明，适应性进化可以在较小的空间距离内发生。尽管在人类健康、农业和生物多样性方面得到了应用，但这种精细的规模、适应是如何产生和保持的仍未得到解决。在圣克鲁斯岛，岛丛鸦有两种形态。松树栖息地的鸟喙又长又细，而橡树栖息地的鸟喙又短又深。众所周知，这些差异有助于松果和橡子的取食，但这种适应性遗传差异是如何在很小的地理距离内保持的，目前尚不清楚。研究人员将收集来自这两种栖息地的个体的基因组数据，以测试松树和橡树种群之间是否有相同的一组基因，以及基因组的其他区域在整个岛屿上的空间变化。这些测量将与遥测研究相结合，跟踪鸟类如何移动和使用橡树和松树栖息地。此外，声音实验将测试雄性是否更喜欢来自其栖息地的雌性。从这项工作中获得的数据将用于开发通用模型，该模型可以告知可能发生适应性差异的条件。这样的模型会引起管理这种和其他独特或稀有物种的保护管理者的兴趣。此外，该项目将制作一个高中课堂使用的学习模块，并将为本科生和研究生提供研究机会。微地理适应的案例挑战了经典进化理论，该理论认为适应性差异应该受到基因流的限制，从而导致对进化过程发生的空间尺度的重新评估。研究小组最近发现，在邻近的橡树和松树栖息地，尽管基因在这些邻近的栖息地之间流动，但松鸦喙形状的适应性差异是复制的。这种模式发生在相隔不到一公里的栖息地。研究人员将测试不同选择、分散和非随机交配如何在喙形态中形成适应性差异的其他假设。在目标1中，他们开发了种群遗传模型，以测试不同空间尺度上选择、基因流动、分类交配和遗传结构的相互作用。在目标2中，他们将通过测量选择梯度、检查基因组分化模式以及识别与喙形态变异相关的候选基因来测试分化选择。在目标3中，他们将结合种群基因组学、遥测和移植实验来测试种群基因组结构，以及是否分散是非随机的。在目标4中，他们将测试喙形态的差异是否与发声有关，并促进分类交配。总的来说，建议的工作在一个可处理的研究系统中采用综合方法。这项研究对于理解适应性分化发生的空间尺度，以及允许单个种群内的个体在异质栖息地中分化的条件具有广泛的意义。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

One goal of evolutionary ecology is to understand the processes that lead to species becoming better adapted to their local environment. Studies of local adaptation have historically focused on geographically separated populations, where adaptive differences are maintained by limited dispersal of individuals between populations. Growing evidence, however, suggests that adaptive evolution can occur over small spatial distances. How this fine scale, adaptation arises and is maintained remains unresolved, despite applications for human health, agriculture, and biodiversity. On Santa Cruz Island, the Island Scrub Jay has two morphologies. Birds in pine habitat have long and thin beaks where as those in oak habitats have short and deep beaks. These differences are known to facilitate feeding on pine cones versus acorns, but how such adaptive genetic differences are maintained over very small geographic distances is unknown. The researchers will collect data on the genomes of individuals from both types of habitats to test if the same set of genes are differentiated between pine and oak populations, and how other regions of the genome change spatially across the island. These measurements will be coupled with telemetry studies that track how birds move and use oak and pine habitats. In addition, vocal experiments will test if males prefer females that originate within their habitat. The data obtained from this work will then be used to develop general models that can inform the conditions under with adaptive differences in can occur. Such models would be of interest to conservation managers that manage this and other unique or rare species. Additionally, the project will produce a learning module for high school classroom use, and will provide research opportunities for both undergraduate and graduate students. Cases of microgeographic adaptation challenge classical evolutionary theory that posits adaptive divergence should be constrained by gene flow, leading to a reassessment of the spatial scale at which evolutionary processes occur. The research team has recently discovered replicated, adaptive divergence in jay bill shape in adjacent oak and pine habitats, despite gene flow between these adjacent habitats. This pattern occurs across habitats separated by less than one kilometer. The researchers will test alternative hypotheses about how divergent selection, dispersal, and non-random mating shape adaptive divergence in bill morphology. In Aim 1, they develop population genetic models that test the interacting effects of selection, gene flow, assortative mating, and genetic architecture at different spatial scales. In Aim 2, they will test for divergent selection by measuring selection gradients, examining patterns of genomic divergence, and by identifying candidate genes associated with variation in bill morphology. In Aim 3, they will use a combination of population genomics, telemetry, and transplant experiments to test for population genomic structure and if dispersal is non-random In Aim 4, they will test if divergence in bill morphology is correlated with vocalizations and facilitates assortative mating. Collectively, the proposed work takes an integrative approach in a tractable study system. This research has broad implications for understanding both the spatial scale at which adaptive divergence occurs, and the conditions that allow individuals within a single population to diverge across heterogeneous habitats.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.