Freshwater molluscs in the Australian arid zone

Abstract

Important freshwater systems found in arid areas range from springs to waterholes and rivers�� Periods of extreme aridity in the Pleistocene, especially during the last glacial period, resulted in the drying of most freshwater systems apart from a few permanent water holes and artesian springs�� The present composition of the freshwater molluscan fauna reflects this history and is a mix of recent recolonisers and relictual taxa�� A database of 5,047 records of freshwater molluscs was compiled from museum records for continental Australia and interrogated for the purposes of examining distributional trends for inland arid and semi-arid Australia�� Endemism and species richness were examined at species, genus and family level�� Of the 125 species-group taxa included in the analysis, 42 (33�� 6%) are narrow-range endemics (occupying three or fewer 10 km 2 grid squares�� Of these endemics, 33 (78�� 6% of the narrow range endemics and 26�� 4% of the remaining taxa are found only in artesian springs associated with the Great Artesian Basin�� In addition to molluscs, these springs contain many other indigenous aquatic invertebrates and fishes and several rare or indigenous plants�� A few large permanent waterholes also contain endemic taxa�� Most molluscs found in intermittent waters adopt strategies to avoid desiccation or to facilitate dispersal and are generally widely distributed�� The presence of molluscan and other (fishes, turtles) endemics in some large arid zone waterholes suggests that those habitats may have persisted through the last glacial�� The continued existence of many of these habitats, and thus their inhabitants, is under threat from human activities relating to water use and modification of habitats��

The ecology of narrow-range endemic macro-invertebrates of Great Artesian Basin springs

“…Restricted geographical distributions are the norm across the broad range of taxa endemic to GAB springs Ponder & Slatyer, 2010), and high endemic diversity is concentrated in particular regions. This has important implication for how the system is conserved.…”

“…Many species endemic to springs lack the adaptations other arid-zone aquatic flora and fauna have that tune their life-histories to the "boom and bust" cycle of water availability in the aridzone (Arthington & Balcombe, 2011). For example the diverse gastropod fauna endemic to springs are all completely aquatic and, unlike other arid zone gastropods, require permanent water with stable water chemistry and temperature (Davis et al, 2013;Ponder & Slatyer, 2010).…”

“…coms.). These points of permanent water through periods of climatic change "trapped" some of the diversity that undoubtedly persisted in the wetter, more mesic times before the aridification of the continents interior that culminated in the late Miocene (Ponder, 1985;Ponder & Slatyer, 2010). In some cases, the colonisation of springs is posited to have occurred via multiple independent events, for example from surface systems as well as from the subterranean Cumulative number of described species stygofauna (Murphy et al, 2009).…”

“…However, appraisals of the species that compose the "threatened community", their distribution, and the information available about them generally remain taxon (e.g. plants (Fensham & Price, 2004;Silcock et al, 2011), gastropods (Ponder & Slatyer, 2010)) or locality specific (De Deckker, 1979; and, to date, the extensive review that accompanied the original Recovery Plan remains the only system-wide analysis of biodiversity across the full range of taxa in the system . Some species identified as being at particularly high extinction risk are afforded additional protection through individual listing (e.g.…”

“…Unlike broadly distributed arid zone aquatic flora and fauna, species endemic to springs lack the ability to persist in the face of water impermanence (e.g. to go into diapause (Ponder & Slatyer, 2010)) and environmental fluctuations (e.g. conductivity or time out of water (Ponder et al, 1989)).…”