Length polymorphisms at two candidate genes explain variation of migratory behaviors in blackpoll warblers (<i>Setophaga striata</i>)

Abstract

Migratory behaviors such as the timing and duration of migration are genetically inherited and can be under strong natural selection, yet we still know very little about the specific genes or molecular pathways that control these behaviors. Studies in candidate genes <i>Clock</i> and <i>Adcyap1</i> have revealed that both of these loci can be significantly correlated with migratory behaviors in birds, though observed relationships appear to vary across species. We investigated geographic genetic structure of <i>Clock</i> and <i>Adcyap1</i> in four populations of blackpoll warblers (<i>Setophaga striata</i>), a Neotropical-Nearctic migrant that exhibits geographic variation in migratory timing and duration across its boreal breeding distribution. Further, we used data on migratory timing and duration, obtained from light-level geolocator trackers to investigate candidate genotype-phenotype relationships at the individual level. While we found no geographic structure in either candidate gene, we did find evidence that candidate gene lengths are correlated with five of the six migratory traits. Maximum <i>Clock</i> allele length was significantly and negatively associated with spring arrival date. Minimum <i>Adcyap1</i> allele length was significantly and negatively associated with spring departure date and positively associated with fall arrival date at the wintering grounds. Additionally, we found a significant interaction between <i>Clock</i> and <i>Adcyap1</i> allele lengths on both spring and fall migratory duration. <i>Adcyap1</i> heterozygotes also had significantly shorter migration duration in both spring and fall compared to homozygotes. Our results support the growing body of evidence that <i>Clock</i> and <i>Adcyap1</i> allele lengths are correlated with migratory behaviors in birds.