Abstract
More freshwater ecosystems are drying in response to global change thereby posing serious threat to freshwater biota and functions. The production of desiccation‐resistant forms is an important adaptation that helps maintain biodiversity in temporary freshwaters by buffering communities from drying, but its potential to mitigate the negative effects of drying in freshwater ecosystems could vary greatly across regions and ecosystem types. We explored this context dependency by quantifying the potential contribution of desiccation‐resistance forms to invertebrate community recovery across levels of regional drying prevalence (defined as the occurrence of drying events in freshwaters in a given region) and ecosystem types (lentic, lotic) in temporary neotropical freshwaters. We first predicted that regional drying prevalence influences the selection of species with desiccation‐resistant forms from the regional species pools and thus increases the ability of communities to recover from drying. Second, we predicted lentic freshwaters harbor higher proportions of species with desiccation‐resistant forms compared to lotic, in response to contrasted hydrologic connectivity. To test these predictions, we used natural experiments to quantify the contribution of desiccation‐resistant forms to benthic invertebrate community recovery in nine intermittent streams and six geographically isolated temporary wetlands from three Bolivian regions differing in drying prevalence. The contribution of desiccation‐resistant forms to community recovery was highest where regional drying prevalence was high, suggesting the species pool was adapted to regional disturbance regimes. The contribution of desiccation‐resistant forms to community recovery was lower in streams than in wetlands, emphasizing the importance of hydrologic connectivity and associated recolonization processes from in‐stream refuges to recovery in lotic systems. In all regions, the majority of functional traits were present in desiccation‐resistant taxa indicating this adaptation may help maintain ecosystem functions by buffering communities from the loss of functional traits. Accounting for regional context and hydrologic connectivity in community recovery processes following drying can help refine predictions of freshwater biodiversity response to global change.
Highlights
How biodiversity is produced and maintained in ecosystems is a pervasive goal of community ecology
The occurrence of drying events is becoming exacerbated by global change and shifts from permanent to intermittent water regimes in many regions are being observed (Gleick, 2003; Smol & Douglas, 2007) or predicted (Datry et al, 2014; Döll & Schmied, 2012; Pyne & Poff, 2017)
Shifts from permanent to intermittent water regimes are projected to occur in many areas as a response to global change (e.g., Datry et al, 2014; Döll & Schmied, 2012; Pyne & Poff, 2017)
Summary
How biodiversity is produced and maintained in ecosystems is a pervasive goal of community ecology. Lotic and lentic freshwater ecosystems differ in terms of hydrologic connectivity, which should in FIGURE 1 Predicted patterns of (a) the relative contributions of stochastic and deterministic community assembly processes; (b) the proportion of species in the regional species pool with desiccation- resistant forms; and (c) the contribution of desiccation-resistant forms to community recovery along a gradient of increased regional drying prevalence. We first predicted the contribution of desiccation-resistant to community recovery to increase with the regional drying prevalence, due to a predominant selection of species with desiccation-resistant forms from the regional species pool (Figure 1c) We second predicted this contribution to be higher in wetlands than in streams, at similar levels of regional drying prevalence, due to lower hydrologic connectivity and subsequently less passive or active recolonization potential from distant sources of colonists (Figure 1c). By identifying factors that lead to context dependency in the contribution of desiccation-resistant forms, our results will improve predictions of the response of freshwater fauna, which are experiencing among the strongest declines in biodiversity of any faunal group (Dudgeon et al, 2006; Jenkins, 2003), to increased drying due to global change
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