Linking thermo-tolerances of the highly invasive little fire ant, Wasmannia auropunctata, to its current and potential distribution. Biological Invasions

Abstract

Species distribution models based on the correlation of bioclimatic variables and presence spatial data-points are useful for recognizing species habitat suitability. However, they have limitations in predicting the introduced ranges of invasive species that could be overcome by using species eco-physiological traits. By combining bioclimatic variables with thermal tolerance plasticity of the highly invasive little fire ant, Wasmannia auropunctata, we intend to better understand the mechanism underlying its current and future distributions. To this end, we performed: 1) laboratory physiological experiments to assess thermal tolerances (CTmin and CTmax) and evaluate the effect of acclimation (laboratory) and acclimatization (nature) on these variables, 2) behavioral foraging observations in the field, 3) a correlative and a simple mechanistic SDM. Briefly, physiological results showed a modulation of the CTmax and CTmin by different acclimation temperatures and by seasonal thermal acclimatization. In the field, worker foraging activity begins at environmental temperatures just above (less than 1°C) the lowest CTmin recorded in the laboratory. At the global scale, CTmin constitutes a key physiological trait that, when linked with the minimum temperature of the coldest month, could explain the southernmost limit of W. auropunctata native distribution and its physiological capacity to expand in the Mediterranean region. The eco-physiological approach carried out here may help explain the current distribution and predict potential spread of populations when there is no certain information about the whole distribution of the species or under a changing environment. The latter is of great importance especially when analyzing invasive insects, pests or disease vectors.