Meeting Abstract
Populations may evolve fixed allelic differences in response to variation in selection regimes over geographic space and time leading to quantifiable patterns of adaptive phenotypic divergence. However, establishing the link between genotypes and phenotypes remains particularly challenging in natural populations. Genome-wide association (GWA) techniques provide an indirect method of understanding local adaptation of non-model organisms to natural systems by relating observed phenotypic variation among individuals to underlying genetic variation. Here, we use GWA methods to examine the statistical association between morphology and thousands of SNPs in song sparrows (Melospiza melodia graminea) distributed along a strong climate gradient on the California Channel Islands. Specifically, we related bill surface area, a trait that differs significantly between islands with different climates, and RAD-seq generated SNPs using single-locus and multi-locus models implemented in GenABEL and GEMMA. After aligning SNPs to the annotated-reference genome of a closely-related sparrow and controlling for population structure, we identified several SNPs significantly associated with bill variation. Most SNPs were found in genes, or closely-linked to genes, responsible for metabolic function and immune response, but some genes (e.g., SLCA1 and WCNT4) are also implicated in craniofacial development and binding of calmodulin, a pathway known to influence bill morphology in Darwin’s finches. This suggests bill morphology is a complex trait controlled by multiple genes and provides further support for local adaptation to climate in Channel Island song sparrows.
