Environmental filtering and spatial structuring differ among body-size and reproductive-mode groups of microcrustacean zooplankton in hardwater lakes

Abstract

Local environmental factors are considered primary drivers of lake zooplankton community assembly, yet the roles of landscape factors and dispersal processes remain underexplored. We examined 78 hardwater lakes across the northern Great Plains (Canada) to evaluate how local (water chemistry, morphometric, and catchment characteristics), regional (climate and land use), and dispersal (spatial and lake isolation) factors explain microcrustacean zooplankton community composition. The region spans strong gradients in climate, water chemistry, and land use, making it well suited for disentangling multiscale influences. Taxa were grouped by body size and reproductive mode to evaluate trait-related differences in community–environment relationships. Ordination, spatial modeling, variation partitioning, and hierarchical partitioning revealed that local physicochemical variables, especially conductivity-related ions (sulfate and chloride), were the strongest predictors of community structure. Sulfate was most strongly associated with small-bodied taxa, while chloride showed opposite effects. Primary productivity and lake metabolism played secondary roles. Regional land-use and land-cover factors, indicative of terrestrial–aquatic coupling, had relatively minor importance. Climate variables did not emerge as significant predictors of species composition. Spatial structure and lake isolation suggested a role for dispersal-related processes in endorheic basins, with asexual species more strongly shaped by spatial factors than sexual ones. Compositional differences within body-size and reproductive groups were also associated with local urban and agricultural land use. These results highlight the value of trait-based groupings for interpreting ecological responses to environmental changes and emphasize the need to incorporate dispersal limitations into bioassessment and water management in lakes under increasing environmental pressures.