Herpetological assemblages of the Pilbara biogeographic region, Western Australia: ecological associations, biogeographic patterns and conservation

Abstract

-The Pilbara region has one of the most diverse reptile assemblages in the world and includes many typical arid zone species as well as many saxicoline endemics. We present the results of a four-year survey of the region during which pitfall trap lines were used to sample 297 quadrats for a total of two weeks in spring and in autumn. The quadrats were located across the region and were chosen to sample the main substrate types. Environmental variables were measured to characterise the soil as well as the geomorphic, vegetative and climatic setting of each quadrat. We used the program PATN to expose patterns in species composition among quadrats, and in relation to the environmental variables.A strong signal for community structure emerged that was linked to surface type. Broad rock, clay, sand and loam categorisations seemed to explain most assemblage composition, with climatic variables showing only weak infl uence. However, many taxa occurred across several surface types, refl ecting the close juxtaposition of habitats within the region, wide dispersion of some taxa, and perhaps the infl uence of recent environmental history including anthropogenic changes.Examination of biogeographic characteristics of the species groups indicated strong endemism for taxa that preferred rocky substrates. In addition, many saxicoline Pilbara taxa have ranges that extend south into rocky areas of the Gascoyne, western Murchison and adjacent areas. Sandy habitats similar to those found in the Pilbara are widespread across Australia's arid zone, and accordingly few endemic taxa showed a preference for sandy surface types, and taxa with such preferences have distributions extending far beyond the Pilbara. The sandy areas of the coastal plain in the Roebourne subregion contained many taxa from Dampierland and the Great Sandy Desert to the north and north-east, as well as some taxa from the rich sand-adapted fauna of the Carnarvon region to the south. Some endemic taxa are associated with clay in the region, although clay surfaces were not as extensive as the rocky, loamy and sandy surfaces. Species associated with the fi ne-textured soils of the mulga woodlands in the southern part of the region appear to be an extension of herpetofaunal communities of regions to the south.Herpetofauna composition at the regional scale appears to have persisted, and patterns discerned in our analysis appear robust, despite the changes that have accompanied European colonisation in the Pilbara, including pastoralism, changed fi re regimes, weeds, introduced animals, mining and infrastructure. However, the existing reserve system does not adequately capture the region's herpetofaunal diversity, especially the endemic taxa in the Fortescue and Roebourne subregions, and there are likely to have been changes in community composition at the local level.

Spots before the eyes: revision of the saxicoline geckos of the Gehyra punctata (Squamata: Gekkonidae) species complex in the Pilbara region of Western Australia

“…The most apparent pattern of Pilbara region Gehyra is the high species diversity for saxicoline species compared to arboreal and generalist species such as G. variegata and G. purpurascens in the arid zone (see also Pepper et al 2014;Heineke et al 2017;Ashman et al 2018). The arboreal-generalist species tend to have massive distributions across the arid zone, whereas the saxicoline species have much smaller distributions, possibly reflecting patterns of diversity related to the rocky regions such as the Pilbara and Central Ranges that serve as ancient refugia that are able to promote speciation through time (Doughty et al 2011;Pepper et al 2013;Ashman et al 2018). The lower diversity of arboreal-generalist species may be correlated with their habitat preferences for trees and shrubs because arboreal habitats are continuous through the arid zone compared to the clumped nature of rocky refugia.…”

“…nov. occurring exclusively in the northern Pilbara and G. punctata to the south. The nature of the rock outcrops within these distributions also differs with ironstones to the south and more granitoids in the north, and the species may be adapted to these different substrates (Pepper et al 2013), bearing in mind the complex matrix of habitat types in close proximity in the Pilbara (Doughty et al 2011). The Hamersley endemic species G. fenestrula sp.…”

“…of the complex were trapped at much higher frequency in pitfall traps (Doughty et al 2011). In contrast, searching for lizards with head torches at night on rocky ridges almost invariably resulted in large numbers of G. punctata seen and collected, with very few of the smallbodied G. punctata species complex members seen.…”

“…nov., this species was captured in high numbers in pitfall traps (Doughty et al 2011). PBS sites where G. micra sp.…”

“…In particular, environmental impact assessments carried out by biological consultants required for mining proposals and the WA Department of Environment & Conservation's (now Department of Biodiversity, Conservation & Attractions) Pilbara Biodiversity Survey (PBS) (McKenzie et al 2009;Doughty et al 2011) resulted in the collection of a large series of G. punctata sensu lato specimens, most of which had tissue samples taken for genetic analysis. Therefore it is timely to reassess the status of the many forms of G. punctata from the region using evidence from morphology, mtDNA, distribution and habitat preferences.…”