Fine-scale comparative phylogeography of a sympatric sister species triplet of subterranean diving beetles from a single calcrete aquifer in Western Australia

Authors

  • M. T. GUZIK,

    1. Australian Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
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  • S. J. B. COOPER,

    1. Australian Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
    2. Evolutionary Biology Unit, South Australian Museum, North Terrace, Adelaide, SA 5000, Australia
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  • W. F. HUMPHREYS,

    1. Australian Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
    2. Western Australian Museum, Locked Bag 49, Welshpool DC, WA 6986, Australia
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  • A. D. AUSTIN

    1. Australian Centre for Evolutionary Biology and Biodiversity, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
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  • Michelle Guzik is an early career researcher whose interests are based in evolutionary biology. Her research is currently focused on the evolution of invertebrates in isolated aquatic habitats in Austrialia’s arid region. Steve Cooper is a Senior Research Scientist who specializes in the application of molecular techniques to investigate the systematics, evolution and ecology of Australian fauna. Andy Austin is deputy director of the Australian Centre for Evolutionary Biology and Biodiversity and is interested in the systematics and evolution of Australian arthropods. Bill Humphreys is a Senior Curator with an interest in the diversity, ecology and evolution of subterranean animals.

M. T. Guzik, Fax: +61 8 8303 4364; E-mail: michelle.guzik@adelaide.edu.au

Abstract

Calcrete aquifers in the arid Yilgarn region of central Western Australia are a biodiversity hotspot for stygofauna. A distinct pattern of interspecific size class variation among subterranean dytiscid beetle species has been observed in 29 of these aquifers where either two or three small, medium and/or large sympatric species are found that are in some cases sister species. We used a 3.5 km2 grid of bores to sample dytiscids on a fine-scale and employed a comparative phylogeographical and population genetic approach to investigate the origins of a sympatric sister species triplet of diving beetles from a single aquifer. Mitochondrial DNA sequence data from the Cytochrome oxidase c subunit I gene revealed that all three species have high levels of haplotype diversity with ancient (∼1 million years ago) intra-specific coalescence of haplotypes, but low levels of nucleotide diversity. Population analyses provide evidence for multiple expansion events within each species. There was spatial heterogeneity in the distribution of genetic variation and abundance both within and among the three taxa. Population analyses revealed significant fine-scale differentiation with isolation by distance for Paroster macrosturtensis and P. mesosturtensis, but not the smallest species P. microsturtensis. Haplotype network analyses provided limited or no evidence for past population fragmentation within the large and small species, but substantial historical divergence was observed in P. mesosturtensis that was not spatially structured. A patchy population structure with contemporaneous and historical isolation by distance in the three species is likely to have been a significant isolating and diversifying force, preventing us from ruling out a potential role for allopatric divergence during speciation of this beetle sister triplet.

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