Genomic and species diversity patterns across multiple trophic levels in riverscapes

Abstract

Testing whether intra‐ and interspecific biodiversity facets co‐vary spatially across trophic levels is of utmost importance to generalize processes driving biodiversity patterns in natural landscapes. Similar processes are expected to act on intra‐ and interspecific diversity, which should lead to positive co‐variation between genetic and species diversity. Although this prediction has been verified within trophic levels, it has rarely been tested across multiple trophic levels. To meet this challenge, we focused on a riverine freshwater ecosystem in which we sampled intra‐ (genomic diversity) and interspecific (species diversity) data across three trophic levels: riparian trees, benthic macroinvertebrates and fishes. For each trophic level, we quantified α‐ and β‐diversity at both the intra‐ (SNP diversity within populations of Alnus glutinosa, Gammarus sp. or Phoxinus dragarum) and interspecific levels (species diversity within communities). We first tested for a global spatial co‐variation of diversity across trophic levels and diversity facets. We then tested whether relevant environmental parameters similarly affected each biodiversity estimate and explained potential spatial co‐variation among biodiversity components. We did not evidence any spatial co‐variation of biodiversity across trophic levels and diversity facets, neither for α‐ nor for β‐diversity. We found that sites situated in the Western part of the sampling area had higher α‐diversities, and that highly connected sites had lower β‐diversities, which holds true for all trophic levels and diversity facets. Nonetheless, the effects of other environmental predictors were specific to each biodiversity component, likely explaining the absence of spatial co‐variation among biodiversity components. Our study demonstrates that global biodiversity patterns in rivers can be hard to generalize and are rather idiosyncratic, even though a few processes might have consistent impacts on biodiversity components across trophic levels.