Multi-scale biodiversity analyses identify the importance of continental watersheds in shaping lake zooplankton biogeography

Aim We examined variation in crustacean zooplankton composition and diversity across Canada, the most lake-rich country in the world. In addition to alpha-diversity patterns, we explore mechanisms behind beta-diversity spatial variation, using taxonomic and functional metrics. Our goal was to explore geographical gradients and related mechanisms shaping zooplankton distribution across different spatial scales. Location Canada. Taxon Crustacean zooplankton. Methods Pelagic zooplankton was sampled in and characterized for 624 lakes across Canada, spanning 12 ecozones (defined by climatic, vegetation and geological differences) or 6 continental drainage basins as part of the NSERC Canadian Lake Pulse Network project. We compared taxon and trait distributions, as well as spatial (longitudinal and latitudinal) patterns of community composition and diversity. We computed taxonomic and functional spatial beta-diversity indices, decomposing these into taxon replacement and richness differences. Finally, species (or traits) and lake uniqueness (contributions) to beta-diversity (SCBD and LCBD) were estimated by ecozone and continental basin. Results In all, 90 crustacean zooplankton species were identified across the country. Differences in zooplankton taxonomic and functional composition were more distinct when considered by continental basin than by ecozone. alpha-diversity varied greatly across space, with greatest diversity in eastern Canada. beta-diversity was greatest when based on taxonomy and was driven by richness differences across all spatial and biodiversity dimensions. Main conclusions Structuring factors influencing zooplankton taxon and trait assemblages vary across spatial scales, being more important at the broadest scale considering continental hydrodynamics. Our results point to the combined effects of physical barriers to longitudinal dispersal and climate change in shaping zooplankton taxonomic and functional biogeography across Canadian lakes.

Automated summary

The study examined the composition and diversity of crustacean zooplankton across different spatial scales in Canada. The results showed distinct differences in taxonomic and functional composition when considered by continental basin, with alpha-diversity varying greatly across space. Beta-diversity was mainly driven by richness differences across all spatial and biodiversity dimensions.