Pilbara stygofauna: deep groundwater of an arid landscape contains globally significant radiation of biodiversity

Abstract

-The Pilbara region was surveyed for stygofauna between 2002 and 2005 with the aims of setting nature conservation priorities in relation to stygofauna, improving the understanding of factors affecting invertebrate stygofauna distribution and sampling yields, and providing a framework for assessing stygofauna species and community signifi cance in the environmental impact assessment process.Approximately 350 species of stygofauna were collected during the survey and extrapolation suggests that 500-550 actually occur in the Pilbara, although taxonomic resolution among some groups of stygofauna is poor and species richness is likely to have been substantially underestimated. More than 50 species were found in a single bore. Even though species richness was underestimated, it is clear that the Pilbara is a globally important region for stygofauna, supporting species densities greater than anywhere other than the Dinaric karst of Europe. This is in part because of a remarkable radiation of candonid ostracods in the Pilbara. Ostracods are the dominant stygofaunal group in terms of both species richness and animal abundance. Together, ostracods, copepods, amphipods and oligochates comprised 77% of species and 96% of animals collected.Stygofauna were found in 72% of samples collected and 81% of wells sampled. The average sample (including those without stygofauna) contained 3.2 ± 0.1 species. A feature of the Pilbara is that stygofauna occur across most of the landscape, often where the depth to groundwater is considerable, although yields were low where depth to groundwater was >30 m. Another feature is high endemicity: on the basis of current taxonomy 98% of the stygobites and 83% of the other groundwater species occur only within the region. Few factors affecting stygofauna occurrence could be identifi ed, however. Numbers of specimens and species collected were positively related to well diameter and negatively related to depth to groundwater. Numbers of species declined in inland sub-regions, although variability within sub-regions was high.While a range of freshwater chemistries occurred, 79% of water samples were weakly saline and NaCl dominated. Profi ling and purging of wells suggested that water quality measurements refl ected aquifer conditions in most situations. Water chemistry appeared to have limited infl uence on stygofauna occurrence in the Pilbara. Geology also appeared to have little effect on stygofauna occurrence but this may have been the result of non-random siting of wells; there was a bias towards wells being in transmissive locations that were not necessarily typical of the geology in which each well occurred.No potential reserves for stygofauna are recommended in this paper but nine areas of high stygofauna richness were identifi ed, including the listed Ethel Gorge stygofauna community. Theoretical analysis of species ranges suggested that half of the species found only in the vicinity of development projects will have ranges less than 680 km 2 . Consequently, projects involving ext...

Troglofauna in the vadose zone: comparison of scraping and trapping results and sampling adequacy

“…While the main purpose of this paper is to highlight the value of scraping as a technique for collecting troglofauna from the vadose zone, the results of the sampling reported here also show that the Pilbara region of Western Australia supports a significant troglofauna community and complements the results of other subterranean surveys showing the Pilbara is rich in stygofauna (Eberhard et al 2009, Halse et al 2014. Sampling of 59 mostly small areas in the Pilbara collected 549 species and morphospecies considered to be troglofauna.…”

Biodiversity and biogeography of groundwater invertebrates in Queensland, Australia

“…17%, 12% cf. 16% respectively; Eberhard et al 2005) and copepod proportions comparable to experiences in eastern Australia and the Pilbara (Eberhard et al 2005, Halse et al 2014). However, Queensland stygofauna communities differ due to the dominance of oligochaetes (16% cf.…”

“…Western Australia) provide the most appropriate baseline for comparison given the higher survey effort employed in these regions , Halse et al 2014. While research has identified that eastern Queensland supports moderate richness stygofauna communities , Cook et al 2012, Halse et al 2014, our analysis highlights that this estimate is too low due to the low sampling effort and limited sampling coverage that largely excludes arid regions and low taxonomic resolution.…”

“…Groundwater fauna from the 5 remaining tax onomic groups yet to be identified in Queensland groundwater ecosystems include Decapoda, Polychaeta, Remipedia, Spelaeogriphacea, and Thermosbaenacea. Knowl edge of groundwater ecosystem composition in Queensland is in its infancy mirroring other Australian experiences and more broadly experiences in Africa, Asia and South America (Eberhard et al 2005, Halse et al 2014. As further survey and taxonomic research is completed it is likely that the range of taxonomic groups represented and their relative richness will change.…”

“…Many stygofauna communities around the world are dominated by amphipods, co pepods, and isopods , Halse et al 2014. Queensland stygofauna communities comprise copepods and isopods in proportions comparable with world averages (20% cf.…”