Broad-scale patterns of invertebrate richness and community composition in temporary rivers: effects of flow intermittence

Datry T, Larned S T, Fritz KM, Bogan MT, Wood PJ, Meyer EI, Santos AN

Abstract

Temporary rivers are increasingly common freshwater ecosystems, but there have been no global syntheses of theircommunity patterns. In this study, we examined the responses of aquatic invertebrate communities to fl ow intermittencein 14 rivers from multiple biogeographic regions covering a wide range of fl ow intermittence and spatial arrangements ofperennial and temporary reaches. Hydrological data were used to describe fl ow intermittence (FI, the proportion of theyear without surface water) gradients. Linear mixed-eff ects models were used to examine the relationships between FI andcommunity structure and composition. We also tested if communities at the most temporary sites were nested subsetsof communities at the least temporary and perennial sites. Taxon richness decreased as FI increased and invertebratecommunities became dominated by ubiquitous taxa. Th e number of resilient taxa (with high dispersal capacities) decreasedwith increased FI, whereas the number of resistant taxa (with adaptations to desiccation) was not related to FI. Riverspecific and river-averaged model comparisons indicated most FI-community relationships did not diff er statisticallyamong rivers. Community nestedness along FI gradients was detected in most rivers and there was little or no infl uenceof the spatial arrangement of perennial and temporary reaches. Th ese results indicate that FI is a primary driver of aquaticcommunities in temporary rivers, regardless of the biogeographic species pool. Community responses are largely due toresilience rather than resistance mechanisms. However, contrary to our expectations, resilience was not strongly infl uencedby spatial fragmentation patterns, suggesting that colonist sources other than adjacent perennial reaches were important.