DISSERTATION RESEARCH: Hybridization, selection, and adaptive divergence between two bird species distributed along an environmental gradient

这两种被研究的沼泽鸟生活在沿着墨西哥湾和大西洋海岸。王轨在淡水沼泽中繁殖，而非常相似的克拉珀轨在盐沼中繁殖，两者在中间的半咸水沼泽中杂交。研究人员收集并遗传分析了分布在路易斯安那州从淡水到咸水过渡沿着的鸟类，发现了对环境的适应可能阻止这两个物种融合成一个物种的证据。美国国家科学基金会资助的项目的目标是找到这种适应背后的基因，并分析它们在过渡期间收集的样本。研究人员将使用下一代测序技术来收集已经收集的样本的大量遗传数据，并试图了解这种混合区背景下的适应性。这项研究的总体目标是更好地了解物种形成的过程。研究人员感兴趣的是使用密切相关的物种杂交，以了解维持不同物种的力量。他们对铁轨的长期目标是了解两个物种之间的遗传差异，这些差异是适应不同盐度的基础。这项研究的结果将提供迄今为止两种密切相关的杂交鸟类的最详细的种群遗传分析。此外，这将是鸟类盐腺的第一个遗传特征，盐腺是在一些鸟类中发现的一种专门的排盐器官。最后，研究结果将为该系统的后续研究奠定基础。

The two species of marsh birds being studied live along the Gulf and Atlantic coasts. King Rails breed in freshwater marshes, while the very similar Clapper Rail breeds in saltmarshes, and the two hybridize in intermediate brackish marshes. The researchers collected and genetically analyzed birds distributed along the transition from freshwater to saltwater in Louisiana, and found evidence that adaptation to the environment may be keeping the two species from fusing into one. The goal of the funded NSF project is to find the genes underlying this adaptation and analyze them for the samples collected across the transition. The researchers will use next-generation sequencing technologies to gather large amounts of genetic data on samples already collected, and try to understand adaptation in the context of this hybrid zone. The overall goal of the research is to better understand the process of speciation. The researchers are interested in using closely related species that are hybridizing to understand the forces maintaining the distinct species. Their long-term goal with the rails is to understand genetic differences between the two species that underlie adaptations to different salinities. The results of this study will provide the most detailed population genetic analysis of two closely related, hybridizing species of birds to date. Additionally, this will be the first genetic characterization of the avian salt gland, a specialized salt-excreting organ found in some birds. Finally, the results will provide a foundation for a multitude of future research studies of this system.