Sean B. Menke1, Robert N. Fisher2, Walter Jetz1, and David A. Holway1. (1) Ecology, Bahavior, and Evolution, UC - San Diego, Division of Biological Sciences, MC-0116, 9500 Gilman Drive, La Jolla, CA 92093-0116, (2) Western Ecological Research Center, USGS, 4165 Spruance Road, Suite 200, San Diego, CA 92101
Predicting potential range limits of introduced species has become a focal task in ecology and conservation. Studies attempting to forecast future range limits of invasive species use environmental niche, climate-envelope models or related procedures. Few attempts have been made to quantify the generality of predictive models for species invasions across space or scale. The Argentine ant system presents unique opportunities for much needed model scrutiny. It is well known that the abiotic environment is of preeminent importance for invasion success of Argentine ants in southern California. Due to scaling issues, important additional factors exist that may only be poorly addressed by simple climatic models of species range limits. For example, urban run-off, and precipitation in the upper elevations of watersheds have the potential to influence the abundance and spread of Argentine ants in nearby habitats. Here we thus establish a more general model using 15 predictor variables of climate, habitat, and human impact. Preliminary results indicate that elevation, distance to nearest highway and urban area are important predictors at the landscape-level. Based on this information, we then asses the generality of these predictors across two different regions in southern California, with 348 sampling points in one and planned 400 in the other. Using this information we build logistic regression models separately for each area and the entire region and compare the strength of predictors. Finally, we compare these models with those from previous work on Argentine ant range limits at the global level. Studies like ours will help to significantly advance models of potential range limits of introduced species by improving their generality and explicit scrutiny of regional and scale effects.
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