Systematics and historical biogeography of Agkistrodon contortrix and Agkistrodon piscivorus
Item
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Title
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Systematics and historical biogeography of Agkistrodon contortrix and Agkistrodon piscivorus
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Identifier
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d_2009_2013:c5c0a8c892a0:11027
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identifier
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11306
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Creator
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Guiher, Timothy James,
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Contributor
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Frank T. Burbrink
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Date
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2011
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Language
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English
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Publisher
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City University of New York.
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Subject
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Systematic biology | Evolution & development | Agkistrodon | demographics | phylogeography | species delimitation | species trees
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Abstract
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Many studies have revealed that lineages currently inhabiting formerly glaciated areas were pushed into southern glacial refugia and have expanded into their modern range since the last glacial maximum. There have been few studies that compare the effects of glacial cycles on lineage diversification, historical demography and migration rates in closely related species with overlapping ranges. In this study I compare phylogeographic structure, historical demography, approximate lineage age, potential distributions, and migration rates in two closely related and broadly co-occurring venomous snakes in eastern North America, the cottonmouth (Agkistrodon piscivorus) and copperhead (A. contortrix) using multilocus coalescent approaches. It has recently been discovered that gene flow between closely related species with adjacent distributions may be common (Nosil 2008). However, the absence of gene flow is a primary assumption of many phylogeographic methods including species tree inference and Bayesian species delimitation. I provide a framework for examining species delimitation when gene flow between species is present and provide a taxonomic revision of A. contortrix and A. piscivorus. In addition, I explore whether hybrids between adjacent species inhabit unique environmental conditions not suitable to one or both species. Finally, I reveal that species diversification was likely a direct result of Pleistocene glacial cycles and that species with the closest proximity to formerly glaciated areas experienced population expansion following the retreat of the Laurentide Ice Sheet. A combination of population expansion out of refugia and niche expansion has resulted in hybridization between adjacent species where species distributions come into contact. It is not clear whether gene flow has persisted during speciation and subsequent interglacial periods or if it has only recently occurred following the last glacial maximum.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Biology
