Insect communities in saline waters consist of realized but not fundamental niche specialists

Abstract

Considering how organisms adapt to stress is essential if we are to anticipatebiological responses to global change in ecosystems. Communities in stressfulenvironments can potentially be assembled by specialists (i.e. species thatonly occur in a limited range of environmental conditions) and/or generalistspecies with wider environmental tolerances. We review the existing literatureon the salinity tolerance of aquatic insects previously identified assaline specialists because they were exclusively found in saline habitats,and explore if these saline realized niche specialists are also specialists intheir fundamental niches or on the contrary are fundamental niche generalistspecies confined to the highest salinities they can tolerate. The resultssuggest that species inhabiting saline waters are generalists in their fundamentalniches, with a predominant pattern of high survival in freshwaterlowsalinity conditions, where their fitness tends to be similar or evenhigher than in saline waters. Additionally, their performance in freshwatertends to be similar to related strictly freshwater species, so no apparenttrade-off of generalization is shown. These results are discussed in the frameworkof the ecological and evolutionary processes driving communityassembly across the osmotic stress gradient, and their potential implicationsfor predicting impacts from saline dilution and freshwater salinization.This article is part of the theme issue ‘Salt in freshwaters: causes, ecologicalconsequences and future prospects’.