Context‐dependent resistance of freshwater invertebrate communities to drying

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.

An unexpected source of invertebrate community recovery in intermittent streams from a humid continental climate

“…and Chironomidae‐ Chaetocladius piger ‐Gr, Smittia sp.) which are mostly semi‐terrestrial forms and common inhabitants of intermittent rivers worldwide and are also considered as desiccation resistant (Arscott, Larned, Scarsbrook, & Lambert, ; Bogan et al., , ; Datry, Bonada, & Boulton, ; Datry, Vander Vorste, et al., ). Our results confirm these previous findings but suggest that this be due to the tolerance of dry conditions, without necessarily requiring the use of desiccation‐resistant stages such as eggs, dormant, or quiescent stages (Strachan et al., ; Stubbington et al., ).…”

“…Third, we quantified the similarities among the three phases and particularly explored that of post‐drying samples with during‐drying samples using presence–absence data to quantify the potential contribution of communities of the dry period to the recovery of benthic communities (both from taxonomic and functional perspectives) upon rewetting. This design was based on (Datry, Corti, & Philippe, ; Datry, Bonada, & Boulton, ; Datry, Vander Vorste, et al., ).…”

“…Others may to persist in moist interstices in dry streambeds (Boulton, Stanley, Fisher, & Lake, ; Strachan et al., ), although the importance of this pool of taxa to contribute to community recovery upon rewetting has not been quantified to date. Invertebrate resistance strategies to drying have been well quantified in naturally intermittent streams from Mediterranean and arid regions (Bogan et al., ; Boulton et al., ; Robson, Chester, & Austin, ; Stubbington & Datry, ), whereas the capacity of aquatic communities to persist under novel intermittent flow regimes is underexplored (Datry, Bonada, & Boulton, ; Datry, Vander Vorste, et al., ). In humid areas where most rivers and streams have been historically perennial, the resilience of aquatic communities to on‐going drying trends is unclear.…”

“…Secondly, we predicted a dominance of nestedness for functional β‐diversity and a dominance of turnover for the taxonomic β‐diversity of dry streambed sediments. This is due to the functional redundancy of intermittent stream communities, in which different taxa share identical functional trait combinations (Datry, Bonada, & Boulton, ; Datry, Vander Vorste, et al., ; Schriever et al., ; Vander Vorste et al., ). Thirdly, we predicted that a substantial proportion of river communities will be supported upon rewetting by the pool of tolerant species, both structurally and functionally, indicating that this species pool could promote the recovery of communities upon rewetting.…”

Structural and functional responses of macroinvertebrate assemblages to long‐term flow variability at perennial and nonperennial sites

“…As global recognition of the biodiversity value and ecosystem service provision of temporary streams increases (Acuña, Hunter, & Ruhí, 2017;Datry et al, 2017), so does their extent, in response to interacting climate change and water resource pressures. Ecologically robust conservation and management strategies are therefore required and will be most effective if informed by analyses that interpret both taxonomic and functional responses to flow permanence in the context of long-term intraannual and interannual hydrological variability (Döll & Schmied, 2012;Watts et al, 2015).…”