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Palaeodistribution modelling does not support disjunct Pleistocene refugia in several Central American plant taxa

Authors

  • Monica F. Poelchau,

    Corresponding author
    1. Department of Genetics, University of Georgia, Athens, GA 30602, USA
      Correspondence and present address: Monica F. Poelchau, Department of Biology, Georgetown University, Washington, DC 20057, USA.
      E-mail: mfp33@georgetown.edu
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  • J. L. Hamrick

    1. Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
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Correspondence and present address: Monica F. Poelchau, Department of Biology, Georgetown University, Washington, DC 20057, USA.
E-mail: mfp33@georgetown.edu

Abstract

Aim  We combine evidence from palaeoniche modelling studies of several tree species to estimate the extent of Central American forest during the Last Glacial Maximum (LGM). In particular, we ask whether the distributions of these species are likely to have changed since the LGM, and whether LGM distributions coincide with previously proposed Pleistocene refugia in this area.

Location  Central American wet and seasonally dry forests.

Methods  We developed ecological niche models using two simulations of Pleistocene climate and occurrence data for 15 Neotropical plant species. We focused on palaeodistribution models of three ‘focal’ tree species that occur in wet and seasonally dry Central American forests, where recent phylogeographic data suggest Pleistocene differentiation coincident with previously proposed refugia. We added predictions from six wet-forest and six seasonally dry-forest obligate plant species to gauge whether Pleistocene range shifts were specific to habitat type. Correlation analyses were performed between projected LGM and present distributions, LGM distributions and previously proposed refugia. We also asked whether modelled palaeodistributions were smaller than their current extents.

Results  According to our models, the ranges of the study species were not reduced during the LGM, and did not correlate with refugial models, regardless of habitat type. Relative range sizes between present and LGM distributions did not indicate significant range changes since the LGM. However, relative range sizes differed overall between the two palaeoclimate models.

Main conclusions  Many of the modelled palaeodistributions of study species were not restricted to refugia during the LGM, regardless of forest type. While constrained from higher elevations, most species found suitable habitat at coastal margins and on newly exposed land due to lowered sea levels during the LGM. These results offer no corroboration for Pleistocene climate change as a driver of genetic differentiation in the ‘focal’ species. We offer alternative explanations for genetic differentiation found in plant species in this area.

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