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Demographic Expansion and Contraction in a Neotropical Fish during the Late Pleistocene-Holocene

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Document pages: 14 pages

Abstract: Demographicchanges during the late Pleistocene-Holocene left signatures in the DNA ofcontemporary populations. These signatures reveal demographic phenomena likethe increase or decrease in effective population size. In this paper wesearched for signatures of demographic change in the DNA of the Neotropicalfreshwater fish Poecilia vivipara.Also, we investigated whether demographic changes are correlated withpalaeoclimatic events of the late Pleistocene-Holocene, inparticular, if changes in effective population size are correlated withexpansion and contraction of available habitats, induced by global ice-volumechanges and sea-level fluctuations. We used Bayesian Skyline Plot (BSP)analysis with sequences from the mitochondrial gene cytochrome b to estimate the ancestral demographyof the Neotropical freshwater fish P.vivipara. To test the assumptions of neutrality and absence of populationstructure we used Tajima’s D andSpatial Analysis of Molecular Variance (SAMOVA), respectively. Effectivepopulation size of P. vivipara remainedstable until 75,000 years ago, increased by 10-fold reaching a maximum atapproximately 25,000 years ago, then suddenly declined at the Pleistocene-Holoceneboundary. Variation in effective population size in P. vivipara correlates with expansion and contraction of habitatsinduced by sea-level fluctuations, caused by the advance and retreat of icesheets during the Last Glacial Maximum (LGM).

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