![]() ![]() In North America the ice sheets were present as far as south as 40 oN with the Pacific Northwest, Northeast coast, Southwest US and Beringia serving as the major refugia for a diverse array of organisms. North America has been one of the main areas for studies on post-glacial expansion, and as such is an area where the impacts of the last glacial maximum (LGM) on organisms from a geological and biological perspective are best understood. The changing conditions following the melting of the ice sheets make this continent a natural laboratory to study patterns of colonization, geographic variation, adaptive radiation and extinction –. Most plants and animals probably survived in areas south of the ice sheets quite different from present-day North America, where ∼20,000 species of vascular plants, more than 800 species of birds, and more than 640 species of mammals dominate a diverse and complex landscape. Some areas north of the glacial maximum may have remained ice-free such as the Queen Charlotte Islands (Haida Gwaii), Alaska (Beringia) and parts of Newfoundland. ![]() Two immense ice sheets (Cordilleran and Laurentide) covered most of Canada, and the northern part of the US at the LGM (last glacial maximum). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist.Ĭontinental North America has been a climatically and biologically dynamic place during the last two million years, especially during the last part of the Quaternary ice ages, 21,000 years ago when the polar ice sheets were at their maximum extent. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: Funding was provided by NSERC Discovery Grant ( ), and Alberta Innovates Tech Futures-New Scholars Award ( ), both to Theresa M. Received: JanuAccepted: JPublished: July 9, 2012Ĭopyright: © 2012 Pulgarín-R, Burg. PLoS ONE 7(7):Įditor: Norman Johnson, University of Massachusetts, United States of America The lack of considerable geographic structure and the starburst haplotype network, combined with several population genetic tests, suggest a scenario of demographic expansion during the last part of Pleistocene and early Holocene.Ĭitation: Pulgarín-R PC, Burg TM (2012) Genetic Signals of Demographic Expansion in Downy Woodpecker ( Picoides pubescens) after the Last North American Glacial Maximum. The SDM suggested several areas in the southern US as containing suitable Downy Woodpecker habitat during the LGM. However, populations in Idaho and southeast BC contained high haplotype diversity and, in general were characterized by the absence of the most common mtDNA haplotype. Mitochondrial DNA, an important marker to detect historical patterns, recovered only one group. Microsatellites, which have higher resolution and are able to detect recent differences, revealed two geographic groups where populations along the eastern edge of the Rocky Mountains (Montana, Utah, Colorado, and southern Alberta) were genetically isolated from the rest of the sampled populations. Analyses of Downy Woodpeckers from 23 geographic areas suggested little differentiation, shallow genealogical relationships, and limited population structure across the species’ range. ![]() ![]() DNA sequences from the mitochondrial tRNA-Lys, and ATPase 6 and 8 genes, and microsatellite data from seven variable loci were combined with a species distribution model (SDM) to infer possible historical scenarios for this species after the last glacial maximum. Here we present evidence of a postglacial expansion for the Downy Woodpecker ( Picoides pubescens), a common member of the forest bird communities in North America with a continental distribution. The glacial cycles of the Pleistocene have been recognized as important, large-scale historical processes that strongly influenced the demographic patterns and genetic structure of many species. ![]()
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