Evidence for population fragmentation within a subterranean aquatic habitat in the Western Australian desert

Abstract

The evolution of subterranean animals following multiple colonisation events from the surface has been well documented, but few studies have investigated the potential for species diversification within cavernicolous habitats. Isolated calcrete (carbonate) aquifers in central Western Australia have been shown to contain diverse assemblages of aquatic subterranean invertebrate species (stygofauna) and to offer a unique model system for exploring the mechanisms of speciation in subterranean ecosystems. In this paper, we investigated the hypothesis that microallopatric speciation processes (fragmentation and isolation by distance (IBD)) occur within calcretes using a comparative phylogeographic study of three stygobiontic diving beetle species, one amphipod species and a lineage of isopods. Specimens were sequenced for the mitochondrial cytochrome c oxidase 1 gene from three main sites: Quandong Well, Shady Well (SW) and Mt. Windarra (MW), spanning a 15 km region of the Laverton Downs Calcrete. Phylogenetic and haplotype network analyses revealed that each species possessed a single divergent clade of haplotypes that were present only at the southern MW site, despite the existence of other haplotypes at MW that were shared with SW. IBD between MW and SW was evident, but the common phylogeographic pattern most likely resulted from fragmentation, possibly by a salt lake adjacent to MW. These findings suggest that microallopatric speciation within calcretes may be a significant diversifying force, although the proportion of stygofauna species that may have resulted from in situ speciation in this system remains to be determined.

Evolutionary refugia and ecological refuges: key concepts for conserving Australian arid zone freshwater biodiversity under climate change

“…A subsequent comparative study of the genetic diversity and population genetic structure of these dytiscid beetle species, one chiltoniid amphipod species and a lineage of Haloniscus isopods by Guzik et al . () revealed a shared evolutionary history among these subteranean species. They considered it likely that multiple isolation and expansion events had occurred at different times within the study aquifer.…”

Protecting the innocent: studying short-range endemic taxa enhances conservation outcomes

“…Molecular systematic and population genetic methods are crucial to unearthing cryptic taxa (Cook et al 2010), owing at least, in some taxonomic groups, to their morphological constancy. This has been recently documented among the Western Australian subterranean fauna by Bradford et al (2010) and Guzik et al (2011b).…”

Fine‐scale genetics of subterranean syncarids

“…Furthermore, existing boreholes are generally not specifically designed for biological studies (Hancock & Boulton, 2009;Guzik et al, 2011). Furthermore, existing boreholes are generally not specifically designed for biological studies (Hancock & Boulton, 2009;Guzik et al, 2011).…”

“…A major challenge when studying stygofauna is that sampling is restricted to pre-drilled bores because the cost of drilling holes is often prohibitive. Furthermore, existing boreholes are generally not specifically designed for biological studies (Hancock & Boulton, 2009;Guzik et al, 2011). As a result, sampling is patchy and provides incomplete coverage of an aquifer.…”