PACT in practice: comparative historical biogeographic patterns and species–area relationships of the Greater Antillean and Hawaiian Island terrestrial biotas

Authors

  • Mallory E. Eckstut,

    Corresponding author
    1. Department of Biological Sciences, Southeastern Louisiana University, Hammond, LA 70402, USA
    2. School of Life Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154, USA
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  • Caleb D. McMahan,

    1. Department of Biological Sciences, Southeastern Louisiana University, Hammond, LA 70402, USA
    2. Division of Ichthology, LSU Museum of Natural Science, Baton Rouge, LA 70803, USA
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  • Brian I. Crother,

    1. Department of Biological Sciences, Southeastern Louisiana University, Hammond, LA 70402, USA
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  • Justin M. Ancheta,

    1. Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada, M5S 3G5
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  • Deborah A. McLennan,

    1. Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada, M5S 3G5
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  • Daniel R. Brooks

    1. Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada, M5S 3G5
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Mallory E. Eckstut, School of Life Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154, USA. E-mail: eckstutm@unlv.nevada.edu

ABSTRACT

Aim  To compare the evolutionary and ecological patterns of two extensively studied island biotas with differing geological histories (the Hawaiian Islands and the Greater Antilles). We evaluated the results from PACT (phylogenetic analysis for comparing trees), an innovative approach that has been proposed to reveal general patterns of biotic expansion (between regions) and in situ (within a region) diversification, as well as species–area relationships (SAR) and the taxon pulse dynamic.

Location  The Hawaiian Islands and Greater Antilles.

Methods  We used the PACT algorithm to construct general area cladograms and identified biotic expansion and in situ nodes. We analysed the power-law SAR and relative contribution of biotic expansion and in situ diversification events using power-law and linear regression analyses.

Results  Both biotic expansion and in situ nodes were prevalent throughout the PACT general area cladograms (Greater Antilles, 55.9% biotic expansion, 44.1% in situ; Hawaiian Islands, 40.6% biotic expansion, 59.4% in situ). Of the biotic expansion events, both forward and backward events occurred in both regions (Greater Antilles, 85.1% forward, 14.9% backward; Hawaiian Islands, 65% forward, 35% backward). Additionally, there is a power-law SAR for the Greater Antilles but not for the Hawaiian Islands. However, exclusion of Hawai'i (the youngest, largest Hawaiian Island) produced a power-law SAR for the Hawaiian Islands.

Main conclusions  The prevalence of in situ events as well as forward and backward biotic expansion events reveals that both Hawaiian and Greater Antillean biotas have evolved through alternating episodes of biotic expansion and in situ diversification. These patterns are characteristic of the taxon pulse dynamic, for which few data have previously been recorded on islands. Additionally, our analysis revealed that historical influences on the power-law SARs are pronounced in both assemblages: old, small islands are relatively species rich and young, large islands are relatively species poor. Thus, our PACT results are consistent with hypotheses of geological influence on the evolution of island biotas and also provide greater insight into the role of the taxon pulse dynamic in the formation of island equilibria.

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