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The farther you are, the closer you get: Environmental similarity connects aquatic invertebrate communities across large river networks via ecological convergence

Freedman, Jared1; Kennedy, Theodore2; Lytle, Dave1

Published Sep 08, 2026 on Dryad. https://doi.org/10.5061/dryad.573n5tbnp

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Abstract

In freshwater river networks, a key spatial factor affecting biodiversity is the multiple pathways of ecological connectivity and dispersal including the continuous and often sinuous river network and the three-dimensional terrestrial landscape. Differential dispersal of aquatic organisms across both pathways, in combination with environmental factors, can shape aquatic community structure through habitat filtering and dispersal dynamics.

Here, we use the high throughput capacity of environmental DNA (eDNA) metabarcoding to explore the influence of spatial relationships and environmental heterogeneity across an expansive and diverse landscape. We collected invertebrate eDNA samples from 70 lotic habitats ranging from small, free-flowing headwater tributaries to anthropogenically altered high order rivers, spanning five major drainage regions in the Colorado River watershed. Data contained in this repository include the community dataset of OTUs identified at each site, the taxonomic identification of OTUs based on the BOLD reference database, as well as the R code and metadata used for statistical analyses.

Communities displayed high alpha and beta diversity among the drainage regions, structured by a combination of spatial and environmental factors. A novel distance-decay framework adapted from population genetics indicated invertebrate dispersal along terrestrial pathways played a role in structuring communities throughout the network. Consistent with this finding, hierarchical clustering identified patterns of convergent similarity in invertebrate communities of headwater tributaries in two different regions that were geographically proximal but separated by extreme river network distances. These results indicate spatial and environmental metacommunity dynamics in general, and dispersal across the terrestrial landscape specifically, are structuring aquatic invertebrate communities in the Lower Colorado River Basin and can shape convergent patterns of biodiversity in river networks.