A DIVERGENCE TIME ANALYSIS OF BUTTERFLIES IN THE PARADIGM OF THE PLEISTOCENE REFUGIA HYPOTHESIS

Abstract

Several hypotheses have been proposed to explain the diversity and distribution of organisms. A leading hypothesis for biodiversity in the Neotropics, the Pleistocene Refugia Hypothesis (PRH), suggests that a series of climatic oscillations during the Pleistocene Epoch (2.6 mya – 12 kya) produced glacial cycles that periodically isolated plant communities into “islands”. These islands of suitable habitat surrounded by areas of relatively inhospitable habitat became refugia for organisms that required those specific plant communities, and speciation occurred when populations were isolated. I examined whether or not diversity of extant species of butterflies can be explained by the PRH. To do so, I identified pairs of sister species from previously published phylogenies, and used a molecular clock, based on the mitochondrial DNA CO1 sequence, to infer divergence times for each sister pair. Most species (83%) I examined diverged during the Pleistocene; thus, my data complement a growing body of evidence in support of the PRH.