DISSERTATION RESEARCH: Genomic basis of convergent phenotypic evolution in island populations of boa constrictors

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Islands often contain unique ecosystems and organisms. Numerous species across the animal tree-of-life have evolved a dwarfed body size on islands, and some, including Boa constrictor, the focal species for this work, have evolved dwarfism multiple times on multiple independent islands. The drastic variation between normal, large-sized mainland boas and their closely-related dwarfed island relatives suggests that a relatively small number of genetic variants in the B. constrictor genome may underlie island dwarfism, and that this system may therefore provide new insight into the genetics of body size in vertebrates. This project also leverages the replicated evolution of dwarf populations of Boa constrictor to investigate if repeated evolution of dwarfism is driven by shared or unique genes or functional pathways across multiple independently evolved dwarf island populations. This work will therefore address fundamental topics in evolutionary biology, including the genetic basis of local adaptation in natural populations and test for connections between the genetic and morphological basis for evolutionary convergence.The ability of evolution to drive the convergent evolution of phenotypic traits provides some of the strongest and clearest evidence for selection and adaptation. More recent work has become particularly interested in whether canalized paths of genetic evolution underlie convergent phenotypic evolution, or whether instead idiosyncratic and/or diverse genetic paths and processes lead to convergent phenotypic solutions. This work will use genome-wide single nucleotide polymorphisms to first delineate the population structure and phylogenetic relationships among island and mainland populations of Boa constrictor. These same markers will also be used to find regions of the genome that are putatively under selection and that are most variable between island and mainland populations, which represent the most promising regions in which to identify genes underlying body size dwarfism. Data collected from independent island lineages will be used to test whether phenotypic convergence in body size is the product of genotypic or functional convergence at the molecular level. This work will therefore answer questions about the genetics of adaptation and about the molecular basis of convergent evolution.