Population genetic structure in Atlantic and Pacific Ocean common murres (Uria aalge): natural replicate tests of post‐Pleistocene evolution

Abstract

Understanding the factors that influence population differentiation in temperate taxa can be difficult because the signatures of both historic and contemporary demographics are often reflected in population genetic patterns. Fortunately, analyses based on coalescent theory can help untangle the relative influence of these historic and contemporary factors. Common murres (Uria aalge) are vagile seabirds that breed in the boreal and low arctic waters of the Northern Hemisphere. Previous analyses revealed that Atlantic and Pacific populations are genetically distinct; however, less is known about population genetic structure within ocean basins. We employed the mitochondrial control region, four microsatellite loci and four intron loci to investigate population genetic structure throughout the range of common murres. As in previous studies, we found that Atlantic and Pacific populations diverged during the Pleistocene and do not currently exchange migrants. Therefore, Atlantic and Pacific murre populations can be used as natural replicates to test mechanisms of population differentiation. While we found little population genetic structure within the Pacific, we detected significant east-west structuring among Atlantic colonies. The degree that population genetic structure reflected contemporary population demographics also differed between ocean basins. Specifically, while the low levels of population differentiation in the Pacific are at least partially due to high levels of contemporary gene flow, the east-west structuring of populations within the Atlantic appears to be the result of historic fragmentation of populations rather than restricted contemporary gene flow. The contrasting results in the Atlantic and Pacific Oceans highlight the necessity of carefully considering multilocus nonequilibrium population genetic approaches when reconstructing the demographic history of temperate Northern Hemisphere taxa.

mtDNA haplotypes differ in their probability of being eliminated by a mass die-off in an abundant seabird

“…Recent multi-locus studies of the Common Murre phylogeography showed lack of geographical structuring and low mtDNA diversity across the North Pacific (Friesen and Piatt, 2003;Morris-Pocock et al, 2008). Our results are consistent with these findings.…”

“…Mantel's test showed no correlation between genetic and geographical distances among the seven breeding colonies sampled (r 2 ¼0.08; P¼0.127). These data, as well as the results of two multi-locus studies (Friesen and Piatt, 2003;Morris-Pocock et al, 2008), justify grouping all live birds into a single unit for the following analysis of mtDNA diversity and haplotype frequencies. The MK test identified an excess of non-synonymous substitutions among polymorphic sites within species (Fisher's exact P¼0.004) suggesting purifying selection.…”

Weak population genetic differentiation in the most numerous Arctic seabird, the little auk

“…In particular, little or no genetic differentiation between populations has been reported for other alcids inhabiting the Arctic, e.g., Atlantic puffin (Fratercula arctica, Moen 1991), Atlantic subspecies of Brünnich's guillemot (Birt-Friesen et al 1992;Morris-Pocock et al 2008), common guillemot (Moum et al 1991; 1996; Moum and Arnason 2001;Riffaut et al 2005), and marbled murrelet (Brachyramphus marmoratus, Congdon et al 2000;Friesen et al 2005).…”

Use of molecular genetics for understanding seabird evolution, ecology and conservation

“…Pereira & Baker 2008, Jesus et al 2009, Patterson et al 2011, population differentiation (e.g. Morris-Pocock et al 2008, Gómez-Díaz et al 2009, Hailer et al 2011; see review by Friesen et al 2007b) and hybridization (e.g. Pacheco et al 2002, Gay et al 2007, 2008b, Taylor et al 2010b, and to estimate population parameters such as migration rates or population sizes (e.g.…”

“…However, as in phylogenetic studies, the genetic basis of morphological and behavioural characters is not usually known (but see Baião et al 2007): even if individuals or populations are morphologically similar, they may differ genetically (e.g. Friesen et al 1996a, Morris-Pocock et al 2008, Hailer et al 2011.…”