Salinity as a driver of aquatic invertebrate colonisation behaviour and distribution in the wheatbelt of Western Australia

Abstract

To understand how environmental change will modify community assembly and the distribution of organisms it is valuable to understand mechanisms that drive the occurrence of organisms across the landscape. Salinisation of agricultural land in southwest Western Australia, as a result of land clearing, is a widespread environmental change, which threatens numerous taxa, but provides an opportunity to elucidate such mechanisms. Although salinisation affects terrestrial fauna and flora, the greatest impacts are seen in wetlands and waterways. Many aquatic insect taxa colonise ephemeral water bodies directly as adults or by oviposition. Few empirical studies, however, evaluate the influence of abiotic factors, such as water body salinity, on the colonisation behaviour of aquatic fauna. We conducted a manipulative experiment using mesocosms to test whether colonising insect fauna select aquatic habitats based upon salinity. We found that halosensitive fauna selected less saline mesocosms for oviposition and colonisation, demonstrating that behaviour can influence the distribution of aquatic organisms. Additionally, we utilised field surveys of insects from ephemeral water bodies across a broad region of southwest Western Australia to determine if mesocosm results reflected field observation. The abundance of the same insect taxa and taxonomic groups in the field were highly variable and, with the exceptions of Culex australicus Dobrotworksy and Drummond and Anopheles annulipes Giles (Diptera: Culicidae), did not show similar patterns of distribution to those observed in the mesocosm experiment. Both mesocosm and field assemblages exhibited similar and significant trajectories associated with the salinity gradient, even though there were differences in assemblage structure between the two. Our findings give empirical support to the importance of behaviour in the spatial distribution and assembly of some aquatic insects.

Environmental drivers for Coquillettidia mosquito habitat selection: a method to highlight key field factors

“…were strongly associated with vegetated freshwater pools (Medlock et al, 2005). Several studies have demonstrated that ovipositing mosquitoes from different genera (Culiseta, Aedes, Anopheles) could tolerate a variety of salt concentrations but the larvae failed to develop correctly in salt water (Bentley & Day, 1989;Carver et al, 2009). In the case of Coquillettidia, survival of the larvae might be affected by salt water, as suggested by laboratory experiments which have shown that egg hatching and development of larvae were perturbed by salt water (EID Montpellier-France, personal communication).…”

Dryland salinity and vector-borne disease emergence in southwestern Australia

“…Studies on aquatic invertebrates in wetlands throughout inland southwest WA have demonstrated that salinity is the primary factor influencing community structure (Carver et al 2009d;Kay et al 2001;Pinder et al 2004). Secondary saline wetlands had significantly different and relatively depauperate macroinvertebrate fauna compared to remaining freshwater wetlands.…”

Influence of Meteorological Variables on Mosquitoes Breeding in Theni District, Tamilnadu, India

“…Mosquitoes are known to respond a range of environmental conditions, including disturbance, which can have their colonization (Williams, 2006;Carver et al, 2009). In India, climate change represents as additional stress on ecological and socioeconomic systems that are already facing tremendous pressures due to rapid urbanization, industrialization and economic development (Sumana et al, 2006).…”