Hydroperiod length, not pond age, determines zooplankton taxonomic and functional diversity in temporary ponds

Mediterranean Temporary ponds (MTPs) are suffering severe alterations in their hydrological and salinity regime through global change, and restoration or conservation of these habitats is a priority. However, there is little information that can be used as a scientific basis for restoration. We studied the taxonomic and functional diversity of zooplankton communities in a set of 96 ponds in Don similar to ana, Spain during four consecutive hydroperiods after their creation. We examined the differences across hydroperiods in alpha and beta diversity (and its turnover and nestedness components) of the rotifer, cladoceran and copepod community, as well as the influence of local environmental variables including the proximity to natural wetlands. There was no general increase in diversity indices after the first two hydroperiods. We found that shorter hydroperiods significantly reduced taxonomic diversity, but increased the contribution to functional beta diversity through turnover. Shorter hydroperiods also reduced community complexity, with long-term effects. Conductivity was the most important predictor of zooplankton alpha and beta diversity, but the direction of its effects changed between hydroperiods. The distance from a natural source of colonists, and pond depth, were key during the early stage of community assembly and after a hydrological perturbation. Our results suggest that new restoration projects for MTPs should focus on increasing local environmental heterogeneity and on reducing vulnerability to salinization. The use of functional approaches in monitoring studies can improve our understanding of mechanisms and processes affecting zooplankton community assembly under dynamic hydrological regimes. This in turn can help us predict the consequences of management and restoration policies for biodiversity conservation in MTPs.