Different Species Requirements within a Heterogeneous Spring Complex Affects Patch Occupancy of Threatened Snails in Australian Desert Springs

Abstract

(1) The distribution of organisms that inhabit patchy systems is dictated by their ability to move between patches, and the suitability of environmental conditions at patches to which they disperse. Understanding whether the species involved are identical to one another in their environmental requirements and their responses to variance in their environment is essential to understanding ecological processes in these systems, and to the management of species whose patchy and limited distributions present conservation risks. (2) Artesian springs in Australia’s arid interior are “islands” of hospitable wetland in uninhabitable “oceans” of dry land and are home to diverse and threatened assemblages of endemic species with severely restricted distributions. Many have strict environmental requirements, but the role of environmental heterogeneity amongst springs has rarely been considered alongside conventional patch characteristics (isolation and patch geometry). (3) We quantified environmental heterogeneity across springs, and the relationship between spring size, isolation (distances to neighbours) and environmental quality (depth, water chemistry), and patterns of occupancy and population persistence of six endemic spring snail species, all from different families, and with all restricted to a single <8000 ha system of springs in Australia. To do so, a survey was conducted for comparison against survey results of almost a decade before, and environmental variables of the springs were measured. Many of the snail species occupied few sites, and environmental variables strongly covaried, so an ordination-based approach was adopted to assess the relationship between environmental measures and the distribution of each species, and also whether springs that held a higher diversity of snails had specific characteristics. (4) Each snail species occupied a subset of springs (between 5% and 36% of the 85 sampled) and was associated with a particular set of conditions. Of the six species considered in further detail, most were restricted to the few springs that were large and deep. Species in family Tateidae were distinct in having colonised highly isolated springs (with >300 m to nearest neighbour). Springs with highest diversity were significantly larger, deeper and had more numerous neighbours within 300 m than those devoid of endemic snails, or those with low diversity. (5) Although spring size and isolation affect patterns of occupancy, the six snail species had significantly different environmental requirements from one another and these correlated with the distribution pattern of each. Approaches that ignore the role of environmental quality—and particularly depth in springs—are overlooking important processes outside of patch geometry that influence diversity. These organisms are highly susceptible to extinction, as most occupy less than 3 ha of habitat spread across few springs, and habitat degradation continues to compromise what little wetland area is needed for their persistence.

Parasites of Selected Freshwater Snails in the Eastern Murray Darling Basin, Australia

“…Additionally, due to their sensitivity to certain chemicals, aquatic snails can be used as environmental and water quality indicators. Unfortunately, several native freshwater snails in Australia are threatened [ 4 ], which is worrisome, considering the important role freshwater snails play in aquatic food webs.…”

Time capsules of biodiversity: Future research directions for groundwater-dependent ecosystems of the Great Artesian Basin

“…Clear issues and gaps in knowledge have been identified, primarily in relation to management directives, awareness, and conservation of the system as a whole or endemic species therein. However, most reviews on spring biodiversity have primarily concentrated on Queensland wetlands, in stark contrast to the fact that approximately 80% of GAB springs are found in South Australia (Rossini et al, 2017(Rossini et al, , 2018(Rossini et al, , 2020Pointon and Rossini, 2020). The ecological communities reliant on GAB springs in South Australia are some of the best-characterized in the system from a taxonomic and genetic standpoint.…”

Genetic approaches reveal a healthy population and an unexpectedly recent origin for an isolated desert spring fish

“…The origin, persistence and conservation of endemic snails, amphipods, plants and even planarians in desert springs has also attracted considerable attention (Inoue et al, 2020;Murphy et al, 2013;Murphy, King, et al, 2015;Robertson et al, 2014;Rossini et al, 2018;Rossini et al, 2020). These taxonomically disparate studies have confirmed that recent speciation and divergence contribute to the high endemism of desert waters (Campbell et al, 2022;Seidel et al, 2009;Witt et al, 2008), but also revealed that isolated springs can harbor relictual populations of ancient, formerly widespread lineages.…”