Catastrophic Floods May Pave the Way for Increased Genetic Diversity in Endemic Artesian Spring Snail Populations

The role of disturbance in the promotion of biological heterogeneity is widely recognised and occurs at a variety of ecological and evolutionary scales. However, within species, the impact of disturbances that decimate populations are neither predicted nor known to result in conditions that promote genetic diversity. Directly examining the population genetic consequences of catastrophic disturbances however, is rarely possible, as it requires both longitudinal genetic data sets and serendipitous timing. Our long-term study of the endemic aquatic invertebrates of the artesian spring ecosystem of arid central Australia has presented such an opportunity. Here we show a catastrophic flood event, which caused a near total population crash in an aquatic snail species (Fonscochlea accepta) endemic to this ecosystem, may have led to enhanced levels of within species genetic diversity. Analyses of individuals sampled and genotyped from the same springs sampled both pre (1988–1990) and post (1995, 2002–2006) a devastating flood event in 1992, revealed significantly higher allelic richness, reduced temporal population structuring and greater effective population sizes in nearly all post flood populations. Our results suggest that the response of individual species to disturbance and severe population bottlenecks is likely to be highly idiosyncratic and may depend on both their ecology (whether they are resilient or resistant to disturbance) and the stability of the environmental conditions (i.e. frequency and intensity of disturbances) in which they have evolved

Barunga, Bulman, Lajamanu, Ngukurr DLH-580 Investigations for Water and Sewerage Services DLH-587 1985.

Made available by the Northern Territory Library via the Publications (Legal Deposit) Act 2004 (NT).Date:198

Prehistoric mining at Olympic Dam in arid South Australia

A site in the Olympic Dam area, recorded during archaeological surveying as a silcrete quarry, was investigated. Hand-excavated squares and subsequent machine-excavated trenches revealed an ancient “mine” rather than a simple surface quarry. Blocks of high-quality silcrete were levered from below the ground surface and many were knapped in the immediate area. Rubble in the pit backfills included large numbers of flakes. Single-grain optical dates from sediments in the backfilled pits demonstrate that the silcrete “mining” occurred during a short period in the late Holocene.Marjorie Sullivan, Philip Hughes, Amy Mosig Way and Nigel Spoone