Abstract
Recent studies exploring the molecular genetic basis for migratory variation in animals have identified polymorphisms in two genes ( CLOCK and ADCYAP1) that are linked to circadian rhythms and correlate with migratory propensity and phenology among individuals and populations. Results from these initial studies are mixed, however, and additional data are needed to assess the generality and diversity of the molecular mechanisms that regulate the biology of migration. We sequenced CLOCK and ADCYAP1 in 15 populations across the two species of the avian genus Junco, a North American lineage in which multiple recently diverged subspecies and populations range from sedentary to long-distance migrants. We found no consistent associations between allele length and migratory status across the genus for either CLOCK or ADCYAP1. However, within two subspecies groups, populations that migrate longer distances have longer CLOCK alleles on average. Additionally, there was a positive relationship between ADCYAP1 allele length and migratory restlessness (zugunruhe) among individuals within one of two captive populations studied—a result similar to those reported previously within captive blackcaps ( Sylvia atricapilla). We conclude that, while both ADCYAP1 and CLOCK may correlate with migratory propensity within or among certain populations or species, previously identified relationships between migratory behavior and sequence variants cannot be easily generalized across taxa.
Highlights
Every year billions of birds make round-trip flights from their breeding grounds to suitable winter climes and back again[1]
Together these findings suggest that allelic variation in both CLOCK and adenylate cyclase-activating polypeptide 1 (ADCYAP1) may contribute to differences in migratory behavior at some levels of analysis but not reliably across the genus
We consider how each of these three explanations for variation in relationship applies to migratory behavior and CLOCK or ADCYAP1, and we suggest that population differences in genetic background are the most likely explanation
Summary
Every year billions of birds make round-trip flights from their breeding grounds to suitable winter climes and back again[1]. This seasonal migration requires immense coordination of different systems including fattening, locomotion, orientation, and activity[2]. Understanding the molecular genetic mechanisms that regulate migration biology is imperative both for 1) understanding the evolutionary processes of behavioral adaptation and diversification, and 2) conserving and managing the phenomenon of animal migrations in the face of ongoing environmental change. Our goal in this study was to build upon previous candidate gene studies to determine whether or not similar genetic mechanisms explain variation in migratory propensity at the level of individuals, populations, and species across taxa
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