Abstract
The effects of Late Quaternary climate change have been examined for many temperate New World taxa, but the impact of Pleistocene glacial cycles on Neotropical taxa is less well understood, specifically with respect to changes in population demography. Here, we examine historical demographic trends for six species of milksnake with representatives in both the temperate and tropical Americas to determine if species share responses to climate change as a taxon or by area (i.e., temperate versus tropical environments). Using a multilocus dataset, we test for the demographic signature of population expansion and decline using non-genealogical summary statistics, as well as coalescent-based methods. In addition, we determine whether range sizes are correlated with effective population sizes for milksnakes. Results indicate that there are no identifiable trends with respect to demographic response based on location, and that species responded to changing climates independently, with tropical taxa showing greater instability. There is also no correlation between range size and effective population size, with the largest population size belonging to the species with the smallest geographic distribution. Our study highlights the importance of not generalizing the demographic histories of taxa by region and further illustrates that the New World tropics may not have been a stable refuge during the Pleistocene.
Highlights
Populations of all extant species that originated prior to the Holocene have experienced cyclical climatic change
The Extended Bayesian Skyline Plots (EBSP) using all loci generally showed stable populations through time for L. triangulum and L. gentilis, but for L. elapsoides, there was an increase in population size at ~50 kya (Fig 3)
When the EBSP analyses were run using only the nuclear loci, results were similar to the full loci EBSPs for some species for the populationsizechange parameter (L. polyzona, L. micropholis), but only L. micropholis resulted in a non-zero highest posterior density (HPD)
Summary
Populations of all extant species that originated prior to the Holocene have experienced cyclical climatic change. For those found in temperate regions of North America and Europe, populations likely responded directly to climate changes induced by the glacial and interglacial cycles of the Quaternary [1]. Populations of different species occurring in areas of changing. Tecnología (SENESCYT); The City University of New York High Performance Computing Center; and for tissue samples loaned from the University of Texas at Arlington, support was granted by National Science Foundation Grant (DEB-0613802) to J.A. Campbell
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