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Ecoregion Description


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Species Richness


# of Endemic Species


Threats

806: Lake Eyre Basin

Major Habitat Type:

xeric freshwaters and endorheic (closed) basins

Author:

Peter Unmack

Reviewers:

Michael Hammer, Evolutionary Biology Unit, South Australian Museum, Australia;  Helen Larson, Curator of Fishes, Museum and Art Gallery of the Northern Territory, Australia

Countries:

Australia

Boundaries:

This ecoregion is largely defined by the boundaries of the Lake Eyre Basin, although it also includes the Barkly Tableland, the Bulloo-Bancannia Basin, and the Lake Torrens Basin.

Drainages flowing into:

All drainage is endoheric (landlocked) and fails to reach the ocean.

Main rivers or other water bodies:

The major rivers are Cooper Creek, and the Diamantina, Georgina, Neales, and Finke rivers.  There are many large (usually dry or saline, and fresh when full) lakes, including Lake Eyre, Lake Frome and Lake Torrens.

Topography:

Most of the ecoregion is covered by low elevation desert and sand dunes.  However, parts of the Central and MacDonnell Ranges in the west, as well as the Torrens Ranges in the south, are included in this ecoregion.

Climate:

The ecoregion grades from semi-arid in the north to arid in the south.

Freshwater habitats:

This ecoregion encompasses one massive—and formerly interconnected—river system covering over 1,677,000 square kilometers, or 21% of Australia (Wager and Unmack 2000).  Lake Eyre is a large terminal lake that floods intermittently and is located at 15 m below sea level.  In dry years it is dominated by a large salt pan.

Several rivers flow across the desert and reach the lake in years with high water levels.  All rivers and creeks of this ecoregion are ephemeral with short periods of flow following rain and extended periods of no flow.  Braided channels, floodplains, waterholes, salt lakes, and wetlands characterize the freshwater systems of this ecoregion.  The braided watercourses that often extend across large flat floodplains in western Queensland are referred to locally as "Channel Country."  The ecoregion also overlies much of the Great Artesian Basin such that several groups of artesian springs also occur here.

Terrestrial Habitats:

Grasslands, deserts, and open woodlands are the major vegetation types found in this diverse region.  The Simpson and Tirari-Stuart Deserts cover large parts of the ecoregion.  The Simpson Desert contains dunehills and sandplains covered with sparse shrubland and grasses.  The Stuart Stony Desert has chenopod shrublands, belah and mallee open woodlands, and mulga woodlands and scrubland with extensive gibber plains (Thackway & Cresswell 1995).  In the north Mitchell Grass Downs cover undulating plains of brown and grey clays and form an extensive band of almost treeless grasslands (World Wildlife Fund 2001).

Fish Fauna:

Thirty-three freshwater fishes from 11 families are known from this ecoregion.  The family Eleotridae (gudgeons or sleepers) has seven representatives, Gobiidae (gobies) has six species, Atherinidae (silversides or hardyheads) and Plotosidae (eel-tailed catfishes) have five species while Terapontidae (grunters) has four species.  The remaining six families have single representatives. This ecoregion consists of a mix of species (many with northern origins), but several groups likely have southern or eastern origins such as Retropinna (smelt), some Craterocephalus (hardyhead), Macquaria (golden perch), and Bidyanus (silver perch).

Description of endemic fishes:

Two monotypic genera—Neosiluroides and Scaturiginichthys—are endemic, and both have particularly restricted ranges. The Finke River contains two endemic species, a hardyhead (Craterocephalus centralis) and a goby (Chlamydogobius japalpa). Nineteen species out of 33 (58%) in the ecoregion are considered endemic. Eight of those species live in small, highly restricted spring-fed environments.

Other noteworthy aquatic biotic elements:

There appear to be relatively few invertebrate groups that are endemic to the rivers in the province, but a large number of species are endemic to the numerous springs across the basin (Ponder 2004).  These include many species of hybrobiid snails, amphipods, ostracods, isopods, and others (Ponder 2004) as well as the shrimp Caridina thermophila—which is endemic to the Barcaldine spring group in Queensland (Riek 1953).

Ecological phenomena:

Due to the extreme aridity of this province, many species appear to have exceptional dispersal qualities in order to be able to recolonize areas following droughts.  Several fishes within Dalhousie Springs have exceptionally high temperature tolerances, with Neosilurus gloveri, (Dalhousie catfish), Craterocephalus dalhousiensis (Dalhousie hardyhead), and Chlamydogobius gloveri (Dalhousie goby) all naturally occurring in minimum temperatures of 40oC (Glover 1989; Wager & Unmack 2000).  Chlamydogobius eremius (desert goby) can also can live at temperatures as high as 40oC (Glover 1973) as most species in this genus are able to do.  Several species also have high salinity tolerances; Glover reported Chlamydogobius eremius tolerates up to 60ppt, while Craterocephalus eyresii (Lake Eyre hardyhead) has been recorded up to 110ppt (Glover 1982).  Two species in Edgbaston Springs, Scaturiginichthys vermeilipinnis (redfinned blue-eye) and Chlamydogobius squamigenus (Edgbaston goby) likely experience extreme variations in temperature in summer.  Water temperatures have been recorded to vary over 20oC in 3-4 hours (Wager & Unmack 2000).

Evolutionary phenomena:

The endemic Neosiluroides cooperensis (Cooper Creek catfish) is an evolutionary oddity. It has the lowest fecundity per unit body size of any central Australian fish. Few (or no) individuals less than 15 cm have ever been collected. It has exceptional eye sight, yet it lives in permanent, extreme turbidity with almost no visibility (Unmack 1996). The occurrence of the pseudomugilid species, Scaturiginichtys vermeilipinnis, is unusual in that all other species in this family usually live in lowland areas close to the ocean. Some other species appear to have speciated within the province in response to isolation by aridification, especially in the genera Mogurnda and Chlamydogobius.

Justification for delineation:

The Barkly Tablelands, Lake Eyre, Bulloo-Bancannia, and Lake Torrens basins have high faunal similarity and thus have been combined into the Lake Eyre Basin ecoregion. This entire area is isolated by drainage divides.

Level of taxonomic exploration:

Overal taxonomic exploration is good, with aspects of the fauna being relatively well known.  However, a number of taxonomic problems remain in regards to the taxonomic status of Retropinna semoni, the Australian smelt (Wager & Unmack 2000; Hammer et al. 2007), one Mogurnda population (M. Adams pers. comm.), and within Hypseleotris (Thacker et al. 2007).  Populations of Macquaria ambigua (golden perch) are also considered distinct, but remain undescribed (Musyl & Keenan 1992).

References/sources:

Department of Environment and, Heritage (2005). "Australian Wetlands Database" (2005; www.deh.gov.au/water/wetlands/database/).

Glover, C. J. M. (1989)"Fishes" In Zeidler, W.;Ponder, W.F. (Ed.). Natural History of Dalhousie Springs. (pp. 89-112) Adelaide: South Australian Museum.

Glover, C. J. M. (1973). "Adaptations of a central Australian gobiid fish" Bulletin of the Australian Society for Limnology 5 8-10.

Glover, C. J. M. (1982)"Adaptations of fishes in arid Australia" In Barker, W.R.;Greenslade, P.J.M. (Ed.). Evolution of the Flora and Fauna of Arid Australia. (pp. 241-246) Adelaide: Peacock Publications.

Musyl, M. K.,Keenan, C. P. (1992). "Population genetics and zoogeography of Australian freshwater golden perch, Macquaria ambigua (Richardson 1845) (Teleostei: Percichthyidae), and electrophoretic identification of a new species from the Lake Eyre Basin" Australian Journal of Marine and Freshwater Research 43(6) 1585-1601.

Ponder, W. F. (2004). "Endemic aquatic macroinvertebrates of artesian springs of the Great Artesian Basin-progress and future directions" Records of the South Australian Museum Monograph Series 7 101-110.

Riek, E. F. (1953). "The Australian freshwater prawns of the family Atyidae" Records of the Australian Museum 23 111-121.

Thacker, C., Unmack, P. J., et al. (2007). "Comparative phylogeography of five sympatric Hypseleotris species (Teleostei: Eleotridae) in southeastern Australia reveals a complex pattern of drainage basin exchanges with little congruence across species" Journal of Biogeography 34(9) 1518-1533.

Thackway, R.,Cresswell, I. D. (1995). "An Interim Biogeographic Regionalisation for Australia: a framework for establishing the national system of reserves, Version 4.0" Canberra, Australia: Australian Nature Conservation Agency.

Unmack, P. J. (1996). "The unique Cooper Creek catfish from central Australia" Fishes of Sahul 10 460-464.

Unmack, P. J. (2001). "Biogeography of Australian freshwater fishes" Journal of Biogeography 28(9) 1053-1089.

Wager, R.,Unmack, P. J. (2000). "Fishes of the Lake Eyre Catchment of Central Australia" Brisbane: Queensland Department of Primary Industries.

World Wildlife, Fund (2001). "Mitchell Grass Downs (AA0707" 2005 (2005; www.worldwildlife.org/wildworld/profiles/terrestrial/aa/aa0707_full.html).

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