Integration of genetic, taxonomic, and functional dimensions of biodiversity yields conservation insights

Species richness and population genetic diversity are fundamental components of biodiversity that are both predicted to enhance ecosystem function. However, there is a lack of understanding on how biodiversity scales across levels of biological organization. Conservation initiatives differ in scope and priorities, ranging from protection of a particular species to ecosystem function such that an integrated understanding across levels may tell us how focusing on one priority may benefit others. Unionid freshwater mussels are one of the most imperiled faunal groups making them a focus of significant conservation efforts. Here we examine how genetic, species, and functional diversity are interlinked in mussels and how protection at one level may lead to greater permanence at another. We leveraged an extensive dataset from the Mobile and Tennessee River basins, a biodiversity hotspot for mussels, to test for relationships among 1) cumulative multi-species abundance, species richness, and imperilment status; 2) population genetic diversity and species abundance and richness; 3) species richness and functional diversity; and 4) genetic diversity and functional diversity. Overall, integration across these datasets revealed positive abundance-richness relationships, a positive relationship between intraspecific abundance and genetic diversity, and positive relationships for both genetic diversity and species richness with functional richness. Our results have implications for species- or ecosystem-level conservation and management efforts as managers may be able to survey diversity at a subset of levels and make reasonable predictions about the others. Despite the dire prognosis for freshwater biodiversity, we show there are opportunities for bridging basic research and conservation actions. • Unionid freshwater mussels are among the most imperiled faunal groups in the world • Conserving freshwater biodiversity is hindered by lack of information on the connections among levels • We combined measures of mussel genetic, taxonomic, and functional diversity across seven rivers in the southeast USA • We found positive relationships between abundance and richness, genetic diversity, and functional richness • Our study has implications for conservation and management regarding whether it is species- or ecosystem-level focused