Trans-Beringia Comparisons of Mitochondrial DNA Differentiation in Birds

Abstract

We compared mitochondrial DNA (mtDNA) restriction fragment profiles from samples of 13 bird species that occur on both sides of Beringia. All but two species, Lapland Longspur (Calcarius lapponicus) and Green-winged Teal (Anas crecca), exhibited evidence of genetic differentiation, albeit at varying degrees. Several species exhibited mtDNA differentiation consistent with species-level distinctness: Marbled Murrelet (Brachyramphus marmoratus), Three-toed Woodpecker (Picoides tridactylus), Whimbrel (Numenius phaeopus), Mew Gull (Larus canus), Black-billed Magpie (Pica pica), American Pipit (Anthus rubescens), and Rosy Finch (Leucosticte arctoa). Other species exhibited levels of mtDNA differentiation intermediate between populations and species: Barn Swallow (Hirundo rustica), Common Tern (Sterna hirundo), Common Snipe (Gallinago gallinago), and Pelagic Cormorant (Phalacrocorax pelagicus). Because of small sample sizes, we do not recommend formal taxonomic changes, although our data could be combined with other data to raise several taxa to species level. Our data do not indicate a consistent level of mtDNA differentiation between putatively conspecific populations on different sides of Beringia, suggesting different times of colonization or cessation of gene exchange. Most comparisons of birds within continents exhibit less mtDNA differentiation than our trans-Beringia comparisons, suggesting limited gene flow between continents.