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Deep intra-island divergence of a montane forest endemic: phylogeography of the Puerto Rican frog Eleutherodactylus portoricensis (Anura: Eleutherodactylidae)

Authors

  • Brittany S. Barker,

    Corresponding author
    1. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
      Brittany S. Barker, Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
      E-mail: barkerbr@unm.edu
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  • Robert B. Waide,

    1. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
    2. Long Term Ecological Research Network Office, University of New Mexico, Albuquerque, NM 87131, USA
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  • Joseph A. Cook

    1. Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
    2. Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM 87131, USA
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Brittany S. Barker, Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
E-mail: barkerbr@unm.edu

Abstract

Aim  Hypotheses proposed for lineage diversification of tropical montane species have rarely been tested within oceanic islands. Our goal was to understand how basin barriers and Pleistocene climatic fluctuations shaped the distribution of diversity in Eleutherodactylus portoricensis (Eleutherodactylidae), a frog endemic to the montane rain forests of Puerto Rico.

Location  The north-eastern (Luquillo) and south-eastern (Cayey) mountains of Puerto Rico.

Methods  We generated mitochondrial DNA (mtDNA) control region sequences (c. 565 bp) from 144 individuals of E. portoricensis representing 16 localities, and sequenced 646 bp of cytochrome b and 596 bp of nuclear DNA (nDNA) rhodopsin exon and intron 1 from a subset of individuals. We conducted a phylogenetic analysis on the mtDNA sequence data and explored population substructure with maximum parsimony networks, a spatial analysis of molecular variance, and pairwise FST analysis. Coalescent simulations were performed to test alternative models of population divergence in response to late Pleistocene interglacial periods. Historical demography was assessed through coalescent analyses and Bayesian skyline plots.

Results  We found: (1) two highly divergent groups associated with the disjunct Luquillo and Cayey Mountains, respectively; (2) a shallow mtDNA genetic discontinuity across the La Plata Basin within the Cayey Mountains; (3) phylogeographic congruence between nDNA and mtDNA markers; (4) divergence dates for both mtDNA and nDNA pre-dating the Holocene interglacial (c. 10 ka), and nDNA suggesting divergence in the penultimate interglacial (c. 245 ka); and (5) historical demographic stability in both lineages.

Main conclusions  The low-elevation Caguas Basin is a long-term barrier to gene flow between the two montane frog populations. Measures of genetic diversity for mtDNA were similar in both lineages, but lower nDNA diversity in the Luquillo Mountains lineage suggests infrequent dispersal between the two mountain ranges and colonization by a low-diversity founder population. Population divergence began prior to the Holocene interglacial. Stable population sizes over time indicate a lack of demonstrable demographic response to climatic changes during the last glacial period. This study highlights the importance of topographic complexity in promoting within-island vicariant speciation in the Greater Antilles, and indicates long-term persistence and lineage diversification despite late Pleistocene climatic oscillations.

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