Genomic mechanisms underlying migration timing and population differentiation across North America in a long-distance migratory songbird
Loading...
Date
2020-08-26
Authors
de Greef, Evelien
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Understanding adaptive potential in migratory animals is important for anticipating population responses to rapid environmental changes. Because shifts in spring phenology can disrupt synchrony between individuals’ movements and seasonal resources, it is crucial to examine mechanisms underlying migration timing and population genomics in vulnerable migratory species. In this thesis, I used the purple martin (Progne subis), a long-distance migratory songbird, as a model species to address the following objectives: 1) identify genomic regions underlying migration timing and corresponding to spring phenology, and 2) examine population structure across four North American breeding colonies and relate patterns of differentiation to natal dispersal. Using next-generation sequencing, I assembled a new draft reference genome and whole-genome data for 93 individuals. I then integrated genomic variation, direct migration timing data, first bloom dates, and continent-wide band encounter records. I recorded a high heritability in migration timing, demonstrating a strong genetic basis in this trait. I also identified loci associated with spring and fall migration near multiple genes, such as MEF2D and CRY1, which could play an important role in photoreception and circadian rhythms. Additionally, I found that timing of first bloom was associated with a high proportion of genomic variance and loci of polygenic effect. Although overall population differentiation was low, I documented isolation-by-distance and greatest distinction between the most northern (Alberta) and more southern colonies. Patterns of differentiation were consistent with observations of greater longitudinal than latitudinal movement in natal dispersal. Overall, my results advance our understanding of migration genomics by demonstrating a novel connection between genomic variation and direct migration timing phenotypes in a long-distance migratory songbird, while the new reference genome provides a foundation for purple martin genomic research. The population structure and latitudinal patterns of differentiation I identified can inform conservation management of this species through delineation of distinct groups between northern and more southern breeding populations. Together, the strong genomic influences on migration timing and spatial limitations on latitudinal gene flow in the purple martin can be used as a framework to describe potential constraints on adaptability in changing climates.
Description
Keywords
migration timing, bird, genomics, population