Updated Occurrence Data And Species Distribution Modeling Of The Invasive Amphipod Apocorophium Lacustre In North America

Freshwater ecosystems in North America have been greatly affected by invasive species, including invasive amphipods, which has motivated the development of predictive models to inform where invaders are likely to establish. Here, we provide the first predictive model using freshwater-specific habitat layers for the non-native amphipod Apocorophium lacustre (Vanhoffen, 1911) in the Mississippi, Laurentian Great Lakes, and Upper Saint Lawrence river basins, USA, and evaluate its current distribution in the Chicago Area Waterway System (CAWS), Illinois, USA. In the summers of 2017, 2018, and 2019, we sampled for A. lacustre at 45 sites in the CAWS. Next, we used boosted regression trees to develop an ensembled species distribution model combining A. lacustre occurrence data with the EarthEnv GIS layers to model habitats suitable for this species. We did not find A. lacustre at any of our sampling sites in the CAWS in 2017 nor 2018, but we did find the species at 7 sites in 2019. Our ensemble species distribution model evaluated habitat associations and predicted the potential distribution of A. lacustre with an average area-under-the-curve value of 0.996 and an average true skills statistic of 0.956. The model predicts that A. lacustre could establish throughout much of the Mississsippi River basin and in the Upper Saint Lawrence River basin. These predictions of habitat suitability for A. lacustre can guide management efforts by facilitating monitoring and early detection to prevent further spread and establishment of this species.