Phylogeography of a mite, Halozetes fulvus, reflects the landscape history of a young volcanic island in the sub-Antarctic

Elizabeth Mortimer,Bettine Jansen Van Vuuren,Steven L Chown,K Ian Meiklejohn

doi:10.1111/j.1095-8312.2011.01770.x

Elizabeth Mortimer, Bettine Jansen Van Vuuren + Show 2 more

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https://doi.org/10.1111/j.1095-8312.2011.01770.x

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Abstract

Previous studies of the microarthropods of Marion Island, Southern Ocean, documented high mitochondrial COI (cytochrome c oxidase subunit I) haplotype diversity and significant genetic structure, which were ascribed to landscape subdivision. In this paper we revisit these ideas in light of new geomorphological evidence indicating a major lineament orientated along N26.5°E. Using the microarthropod Halozetes fulvus, we test the hypothesis that the eastern and western sides of the island show different population genetic patterns, corresponding to the previously unrecognized geological separation of these regions, and perhaps also with differences in climates across the island and further landscape complexity. Mitochondrial COI data were collected for 291 H. fulvus individuals from 30 localities across the island. Notwithstanding our sampling effort, haplotype diversity was under-sampled as indicated by rarefaction analyses. Overall, significant genetic structure was found across the island as indicated by ΦST analyses. Nested clade phylogeographical analyses suggested that restricted gene flow (with isolation-by-distance) played a role in shaping current genetic patterns, as confirmed by Mantel tests. At the local scale, coalescent modelling revealed two different genetic patterns. The first, characterizing populations on the south-western corner of the island, was that of low effective population size and high gene flow. The converse was found on the eastern side of Marion Island. Taken together, substantial differences in spatial genetic structure characterize H. fulvus populations across Marion Island, in keeping with the hypothesis that the complex history of the island, including the N26.5°E geological lineament, has influenced population genetic structure. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 131–145.

Highlights

The complex biological and geological history of the southern hemisphere is emerging as a common biogeographical theme
Myburgh et al (2007; see McGaughran et al, 2010b) documented high mitochondrial COI haplotype diversity and significant genetic structure in two indigenous springtail species from Marion Island, and suggested that this may be a consequence of landscape subdivision by volcanic and glacial events on the island
To provide further insight into the likelihood that complex landscape evolution on Marion Island is reflected in invertebrate phylogeography, we investigate an additional species endemic to the Prince Edward Islands, namely the oribatid mite Halozetes fulvus, using a much larger sample size [the largest number of individuals studied to date is 113 for the springtail species Cryptopygus antarcticus travei (McGaughran et al, 2010b) compared with the 291 H. fulvus individuals included in the present study]

Summary

Introduction

The complex biological and geological history of the southern hemisphere is emerging as a common biogeographical theme (see, for example, Bergstrom & Chown, 1999; Chown & Convey, 2007; Convey &Stevens, 2007). Similar findings of significant genetic structure across Marion Island were reported for the prostigmatid mite Eupodes minutus (57 individuals from 11 localities; Mortimer & Jansen van Vuuren, 2007), the cushion plant Azorella selago (Mortimer et al, 2008), and for members of the Ectemnorhinus group of weevils (Grobler et al, 2006, 2011a, b) These studies suggest that landscape evolution has substantially affected the phylogeography of species on the island in a way similar to landscape effects on species of other islands such as Rapa and the Hawaiian and Canary archipelagos (Paulay, 1985; Wagner & Funk, 1995; Gillespie, 2004; Emerson et al, 2006). The ways in which population genetic structure may be affected by topography, distance, and the complexity of the environment are recognized as significant for understanding spatial patterns in diversity, as is recognized generally within landscape genetics (e.g. Storfer et al, 2010)

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