Invetebrate communities of Relict streams in the Arid Zone: the George Gill Range, Central Australia

Abstract

The George Gill Range (24�S,132�E) 220 km south west of Alice Springs in the Northern Territory, lies within one of the driest regions of Australia. Diel and seasonal temperature differences are extreme and the average rainfall is 250 mm per annum. The streams of the Range are the largest group within the Central Ranges and are relatively pristine. Their flow regimes are episodic but deep rock pools appear to act as reservoirs of surface runoff and may also receive groundwater from the Mereenie aquifer. The waterbodies of the Range and some nearby areas were sampled in July and December 1986 to determine the composition of the macroinvertebrate communities and biogeographical relationships with the fauna of lotic systems elsewhere in Australia. Macroinvertebrate species richness at the Range was comparable with that of other Australian streams but no Plecoptera, Isopoda or Amphipoda were collected. The almost complete absence of shredders may reflect low allochthonous inputs, because riparian vegetation in the arid zone is generally sparse. A small proportion of the fauna of the Range appears to be a relictual stream fauna. Species of low vagility such as the waterpenny, Sclerocyphon fuscus, would not be capable of dispersal across the large tracts of arid land that now separate the Range from southern Australia, where it is also found. The occurrence of new species at the Range suggests that it is also a site of allopatric speciation within some groups. The conservation values of the streams of the George Gill Range and other sites, such as Giles Springs in the Chewings Range, are extremely high. They represent unique aquatic communities of both ecological and evolutionary importance in the arid zone.

An arid zone awash with diversity: patterns in the distribution of aquatic invertebrates in the Pilbara region of Western Australia

“…In central Australia, Davis (1997), Davis et al (1993) andBrim Box et al (2008) recorded 130 macroinvertebrate species from 42 central Australian wetlands. Richness ranged from 4 to 64 per wetland but several groups likely to be speciose were not identified to species.…”

Central Australian waterbodies: The importance of permanence in a desert landscape

“…Collections of macroinvertebrates and fishes from isolated waterbodies in CA suggest that an aquatic fauna is present that is distinct from other arid Australian waterbodies (Bayly, 2001;Blackburn, 1896;Davis, 1996;Davis et al, 1993;Duguid et al, 2005;Glover and Sim, 1978;Tate, 1896b;Unmack, 2001;Zietz, 1896). For example, the fishes of CA include at least three endemic species (Unmack, 1995), and may include additional, undescribed species (Duguid et al, 2005).…”

“…A larger, more comprehensive biological survey was made during the Horn Scientific Expedition of 1894, but since then few broad-scale sampling efforts have been made. Recent collecting efforts in CA include surveys of some permanent waterbodies in the West MacDonnell and George Gill Ranges (e.g., Davis, 1995Davis, , 1996Davis et al, 1993), and an inventory of wetlands in the arid NT that included observations and limited collections of birds, fishes and invertebrates (Duguid et al, 2005). Additional, albeit disparate, collections have also been made through community outreach programs or other projects, but any data generated from these efforts are generally non-existent or unavailable.…”

“…A small rockhole near Papunya, sampled after flooding, contained an aquatic invertebrate fauna that was distinct from similar habitats in southwestern Australia and included undescribed species (Bayly, 2001). Davis et al (1993) speculated that the isolation of waterbodies in CA, as well as their unique hydrological and physio-chemical conditions, has likely contributed to allopatric speciation. Invertebrates (e.g., the dragonfly, Hemicordulia flava) and fish species endemic to CA support this assertion, as does the aquatic fauna of the George Gill Range (Davis et al, 1993), which was found to be distinct from other permanent waterbodies in Australia.…”

“…1000 km to the north of CA). However, surveys of some of the more prominent waterbodies (e.g., Davis, 1995Davis, , 1996Davis et al, 1993) suggest that these features are relatively unscathed by European settlement and that a unique aquatic fauna is present. If so, then CA waterbodies can potentially serve as model systems to investigate: (1) the ecological role of unaltered isolated wetlands in arid zones, (2) the evolutionary responses, including allopatric speciation, to long-term habitat fragmentation, (3) the importance of groundwater inputs to isolated aquatic ecosystems, and (4) the ecological responses to climate change in arid wetlands, as CA has experienced some of the strongest effects of global warming thus far recorded on the continent.…”