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.
Intellectual Merit: Two peer-reviewed publications (Brackett et al. 2013; Maley and Brumfield 2013) and Maleyâ€™s dissertation (Maley 2012) resulted from this doctoral dissertation improvement grant. This has contributed significantly to our understanding of evolution and hybridization in this system. One publication described the first phylogenetic hypothesis in the group (Maley and Brumfield 2013); the other provided microsatellite markers that can be used to understand population genetics in King Rails (Brackett et al. 2013). These markers were developed from 454 data generated using these funds.Two additional publications stemming from data collected on this grant are being prepared to elucidate adaptive divergence, speciation, and hybridization in this system. Broader Impacts: Maley and Brumfield (2013) led to a revision of the species limits in large rails, with the consequence that there are now five species instead of two. This has generated excitement in the non-scientist "birding" public and facilitated more interaction between Maley and the USFWS endangered species recovery program. Most importantly, we found that California Clapper Rails are actually a distinct species, a result that has elevated the conservation profile of this threatened species. Two undergraduate researchers were involved in this research, one of which is now a Collections Manager in the Bird Division of the Smithsonian. This work was also presented to National Wildlife Refuge managers in Louisiana who manage the marshes that these rails live in. It was also presented to the Laramie Audubon Society, Jackson Hole Bird & Nature Club, and the San Diego Field Ornithologists.