the genomic basis of local adaptation with gene flow
Atlantic silversides (Menidia menidia) are distributed along the world's steepest thermal cline along the east coast of North America. In response to this thermal gradient, silverside populations have evolved physiological and morphological traits that allow them to deal with their respective environments. Interestingly, these adaptations are maintained despite homogenizing connectivity between populations.
To characterize the genomic basis and architecture underlying local adaptation in silversides, I am building comparative linkage maps to identify structural variation between populations and quantitative trait loci maps to identify the genomic basis of key physiological traits linked to local adaptation. I am also studying how dispersal-selection dynamics play out over seasonal time scales by collecting a time series of samples from several locations to infer how selection against migrants and their offspring maintains local adaptation.
genetic and phenotypic variation in
The Neotropical red-eyed treefrog (Agalychnis callidryas) exhibits substantial phenotypic variation across a broad, primarily central American range, as well as microgeographic variation across Costa Rica and Panama populations in color pattern and body size, skin peptides, and courtship behavior.
Geographic variation in reproductive behavior
For the first component of my thesis, I examined sexual selection as a possible mechanism of divergence in red-eyed treefrogs. I conducted mate-choice trials in the field and found population-level differences in both male and female courtship behaviors of red- eyed treefrogs, and that females preferred to mate with local males. My results demonstrate that female mating displays and the role of males as signal receivers may be widely overlooked, challenging the paradigm of unidirectional courtship signaling in frogs. This study sheds light on the complexity and sex specificity of mating-signal evolution, and can be applied broadly to sexually reproducing organisms: mutual courtship is elaborate, nuanced, and comprised of geographic behavioral variants. This study has been accepted for publication in Ethology.
Genetic and phenotypic evidence of a contact zone
The second chapter of my thesis compares patterns of genetic and phenotypic diversity among hybridizing red-eyed treefrog populations. I found population genetic evidence of a recently discovered contact zone in the wild and provide evidence of phenotypic novelty in leg color - a trait expected to mediate assortative mating in this species. Analysis of hybrid ancestry reveals an abundance of later-generation Fn individuals, suggesting persistence of hybrids in the contact zone. Collectively, the evidence shows that hybridization can lead to the evolution of phenotypic novelty, which depending on the selection regime experienced by parental and hybrid populations, could promote further divergence and ultimately lead to speciation.