Phylogenetics, Phylogeography, Historical Demography, and Morphology of Milksnakes (Genus Lampropeltis)
Item
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Title
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Phylogenetics, Phylogeography, Historical Demography, and Morphology of Milksnakes (Genus Lampropeltis)
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Identifier
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d_2009_2013:2c9f7f839691:11684
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identifier
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12246
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Creator
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Ruane, Sara,
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Contributor
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Frank T. Burbrink
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Date
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2013
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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 | Biology | geometric morphometrics | historical demography | kingsnake | Lampropeltis | milksnake | species tree
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Abstract
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A primary goal for systematists is the discovery and identification of Earth's biodiversity. To meet these goals, coalescent-based phylogenetic and phylogeographic methods have been developed that help quantify diversity and provide a better understanding of processes generating species. Here, I use these methods to examine milksnakes (genus Lampropeltis). Milksnakes are among the widest ranging of New World squamates and are frequently used as model organisms in Batesian mimicry studies. Despite this, there has been no research detailing their systematics within a molecular phylogenetic framework. Furthermore, previous molecular studies that include milksnakes have shown they do not form a monophyletic group within the genus and that color pattern, which has been the basis for their previous classification may not be informative with respect to evolutionary history. The study detailed here examines milksnakes across their intercontinental range to determine whether there is unrecognized diversity in this group. To meet this goal, I have developed a multi-locus dataset consisting of 11 nuclear genes and one mitochondrial gene. I use a molecular delimitation method to determine support for putative species, assess migration between species, and, within a species-tree framework, infer a phylogeny for the genus Lampropeltis, including all newly elevated milksnakes and all other recognized taxa within the genus. This dataset also provides the opportunity to examine how the inclusion of cryptic taxa and species tree methods provide a more accurate assessment of timing, rates and process of species diversification. After delimiting species, I use both non-genealogical and coalescent-based models to infer the historical demographic patterns of milksnakes. As the milksnake species identified here have representatives in both the temperate and tropical Americas, I am able compare demographic responses with respect to changes in effective population size between the Nearctic and Neotropical taxa. Specifically, I ask, do closely related milksnake species have similar demographic patterns resulting from Pleistocene glacial cycles despite their origination in the Neotropics or Nearctic. Results indicate that milksnakes do not share similar demographic patterns as a taxonomic group or by area and I conclude that authors should use caution in generalizing historical demographic trends based on geography. In addition to examining milksnakes using molecular data, I determine if there are detectable morphological differences independent of color pattern using geometric morphometrics. By taking photographs of 487 specimens, digitizing landmarks on their heads, and using geometric morphometric analyses, I determine that these types of analyses are useful in snake systematics for detecting distinct morphological shape variation among genetically delimited species, although they may not be powerful enough to use as an a priori species discovery tool.
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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
