Spatiotemporal variance of environmental conditions in Australian artesian springs affects the distribution and abundance of six endemic snail species

Artesian springs in arid Australia house endemic species with very small geographic distributions (most <50 km 2 ). These species have limited dispersal capabilities, but little is known about environmental variance within and across these springs and how it, too, may limit their distribution and abundance. At the Pelican Creek springs complex, the full diversity of endemic gastropod fauna is found only in springs with deep pools, an area thought to provide greater environmental stability. This implies that the distributions of most snail species at this site may be restricted by their narrow environmental requirements and limits. This study monitored spatiotemporal environmental variance in a subset of the Pelican Creek springs (within Edgbaston Reserve) across one year to assess whether pool areas differ from tail areas, and how patterns of abundance of six snail species from three different families correspond to this variance. Springs fluctuated considerably in size, depth, water chemistry and temperature at daily and seasonal scales. Patterns of environmental variance differed across areas; pools were spatiotemporally stable, and tails were ephemeral and environmentally variable. The snail species occupied these areas in different ways. Species restricted to deep springs generally had significantly higher abundance in pool areas, and most had narrow environmental limits. In contrast, species found in a greater number of springs, including those with no pool, occupied pool and tail areas and generally had broader environmental limits. Environmental variance within and across springs affects the distribution of snails in a species-specific fashion. This has important implications for how we study springs and reveals that whilst the vast majority of species are restricted to areas of environmental stability, some can persist in the most environmentally variable areas.