Geographical origin determines responses to salinity of Mediterranean caddisflies

Abstract

Many freshwater ecosystems worldwide, and particularly Mediterranean ones, show increasing levels of salinity. These changes in water conditions could affect abundance and distribution of inhabiting species as well as the provision of ecosystem services. In this study we conduct laboratory experiments using the macroinvertebrate Smicridea annulicornis as a model organism. Our factorial experiments were designed to evaluate the effects of geographical origin of organisms and salinity levels on survival and behavioral responses of caddisflies. The experimental organisms were captured from rivers belonging to three hydrological basins along a 450 Km latitudinal gradient in the Mediterranean region of Chile. Animals were exposed to three conductivity levels, from 180 to 1400 μS/cm, close to the historical averages of the source rivers. We measured the behavioral responses to experimental stimuli and the survival time. Our results showed that geographical origin shaped the behavioral and survival responses to salinity. In particular, survival and activity decreased more strongly with increasing salinity in organisms coming from more dilute waters. This suggests local adaptation to be determinant for salinity responses in this benthic invertebrate species. In the current scenario of fast temporal and spatial changes in water levels and salt concentration, the conservation of geographic intra-specific variation of aquatic species is crucial for lowering the risk of salinity-driven biodiversity loss.

The acclimatory response of the mayfly Neocloeon triangulifer to dilute conditions is linked to the plasticity of sodium transport

“…Ionocytes (also known as chloride cells) are sites of ion uptake on the body surfaces (especially tracheal gills) of nymphs [41]. Little is definitively known about how salinity impacts the density of ionocytes of aquatic insects [42][43][44][45].…”

Physiological responses of freshwater insects to salinity: molecular-, cellular- and organ-level studies

“…These more severe effects on the gut can be limited with gradual acclimation to salt water (Sutcliffe, 1962). Behavioural responses to salinity appear to be determined by the salinity of the Trichoptera larvae's original habitat, suggesting that there is a degree of acclimation that can occur over multiple generations (Carter et al, 2020). Some evidence of acclimation is also seen from measurements of stress biomarkers in Trichoptera larvae collected from areas with different salinity (Sala et al, 2016).…”

Regional and fine-scale local adaptation in salinity tolerance in Daphnia inhabiting contrasting clusters of inland saline waters

“…Parallel to environmental sorting structuring metacommunities, salinity changes can also exert strong selection pressures impacting the evolution of local populations and consequently metapopulation structure [26,27]. There is evidence for local adaptation to salinity gradients in multiple taxonomic groups including fish, amphibians and insects [28][29][30]. For example, populations of the amphibian Hyla cinerea in anthropogenically salinizing coastal wetlands evolved an increased salinity tolerance compared to freshwater populations, showing a higher fecundity and increased hatching success and tadpole survival upon salt-exposure [29].…”