3. Hybridization between Thick-billed and Common Murres

Thick-billed and common murres are migratory seabirds that breed in colonies in the North Pacific and North Atlantic oceans. Despite these sister species diverging 6.5 million years ago, they have been found to hybridize. In this study, hybridization between thick-billed and common murres was investigated in 15 Atlantic colonies of murres. Some colonies were single species colonies, and at other colonies both species breeds. DNA from wing samples collected from the annual murre hunt in Newfoundland and Labrador was also analyzed. Restriction-site associated DNA sequencing was performed on the samples, identifying single nucleotide polymorphisms throughout the genome. The program STACKS was used to identify and genotype loci. Software such as STRUCTURE was used to investigate admixture between the two populations. 32 of 166 common murres and 26 of 188 thick-billed murres were identified as hybrids. This totaled to 16% of the samples, a higher proportion of hybrid murres than found in previous studies of Pacific colonies. Interestingly, a significantly larger proportion of hunted than non-hunted birds were identified as hybrids. Furthermore, hybrid individuals were found at both shared colonies, and those where only one species breeds. As top predators that are threatened by human-mediated activities such as hunting and oil pollution, and that may be vulnerable to climate change, research into the hybridization of murres has numerous conservation implications. Currently, there is uncertainty of the impact hybridization will have on the murre populations, and research into the rate and trends of hybridization is of importance.