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。对当地适应的研究历来侧重于地理上分离的种群，在这些种群中，通过种群之间有限的个体分散来维持适应差异。然而，越来越多的证据表明，适应性进化可以在很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有应用，但如何产生和维持这种良好的适应仍然没有解决。在圣克鲁斯岛上，海岛丛林鸦有两种形态。松树栖息地的鸟类有细长的喙，而橡树栖息地的鸟类有短而深的喙。众所周知，这些差异有利于以松果为食，而不是橡子，但这种适应性遗传差异是如何在非常小的地理距离上保持的尚不清楚。研究人员将收集来自这两种类型栖息地的个体基因组数据，以测试松树和橡树种群之间是否存在相同的一组基因，以及基因组的其他区域在整个岛屿上如何发生空间变化。这些测量将与跟踪鸟类如何移动和使用橡树和松树栖息地的遥测研究结合在一起。此外，发声实验将测试雄性是否更喜欢起源于它们栖息地的雌性。从这项工作中获得的数据将被用来开发通用模型，该模型可以告知可能发生适应性差异的情况。这样的模型将会引起管理这种物种和其他独特或稀有物种的保护经理的兴趣。此外，该项目将制作一个供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，该理论认为适应差异应该受到基因流动的限制，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，尽管在相邻的橡树和松树栖息地之间存在基因流动，但在相邻的橡树和松树栖息地中，松鸦嘴形状存在复制的、适应性的差异。这种模式发生在相距不到一公里的栖息地。研究人员将测试关于分化选择、分散和非随机交配如何在喙形态中形成适应性分化的替代假说。在目标1中，他们开发了种群遗传模型，在不同的空间尺度上测试选择、基因流动、分类交配和遗传结构的交互作用。在目标2中，他们将通过测量选择梯度，检查基因组分歧的模式，并通过识别与票据形态变异相关的候选基因来测试分歧选择。在目标3中，他们将使用种群基因组学、遥测和移植实验的组合来测试种群基因组结构，如果在目标4中扩散是非随机的，他们将测试喙形态上的分歧是否与发声相关，并促进分类交配。总的来说，拟议的工作在一个易于处理的研究系统中采取了综合的方法。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不同的栖息地之间分化的条件都具有广泛的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.