Joint species distribution models quantify potential biotic interactions between lotic fish
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Quantifying the influence of environmental factors on species distributions can elucidate their ecological requirements and potential response to anthropogenic disturbance. Single species distribution models are commonly used to quantify taxon-environment relationships but do not account for biotic interactions (e.g. competition, predation, mutualism). Joint species distribution models (JDSMs) are a multivariate extension that overcome this challenge by modeling all taxa in an assemblage simultaneously and explicitly account for associations between species. We compiled occurrence data for ~200 fish species at 3,865 sites surveyed by U.S. Environmental Protection Agency’s National Rivers and Streams Assessment. We then used JDSMs to quantify taxon-environment relationships and pairwise associations. These models accurately characterized fish assemblages (AUC > 0.7). Gradients of specific conductance, average maximum air temperature, discharge and substrate diameter were important variables for explaining species occurrences. In addition, we found several significant associations indicating that certain species co-occur more or less than expected from environmental conditions. Leveraging these associations, we used conditional prediction to assess the potential effects of removing non-native fishes. Interestingly, removing non-native fish could either increase or decrease native taxa richness, depending on the site and region. We demonstrate that data collected for monitoring purposes provide unparalleled opportunities to quantifying species’ relationships with key environmental factors and assessing potential biotic interactions across a large spatial extent. The views expressed in this presentation are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.