New article: Invasive pathways of the Argentine ant in a Mediterranean region

From introduction to equilibrium: reconstructing the invasive pathways of the Argentine ant in a Mediterranean region.

Determining the geographical range of invasive species is an important component of formulating effective management strategies. In the absence of detailed distributional data, species’ distribution models can provide estimates of the geographic range of an invasion and also increase our understanding of the ecological processes acting at various spatial scales.

The aim of this study published in the journal of Global Change Biology together wiuth our colleagues of CIB in South Africa was to provide a better understanding of the geographic limits of a highly invasive species by combining ecological niche and dynamic spread modelling techniques. We provide new insights into the processes that influence the expansion of biological invasions, by using the Argentine ant (Linepithema humile) as a study case.

The methodological approach is composed of two major steps. Firstly, we calibrated a series of ecological niche models using occurrence and environmental data at various spatial scales (i.e. different extent and resolution), which allowed us to identify the most influential environmental factors and elucidate the status of the invasion by comparing final predictions. Secondly, we tested several hypotheses about the possible introduction of the species and its subsequent expansion at local by means of a spread model that simulated the jump dispersal of the species scales in Catalonia (NE Iberian Peninsula).

Based on the results of both modelling practices, we suggest that L. humile might have reached its maximum geographic range at regional scales in the NE Iberian Peninsula. However, the species does not appear in equilibrium with the environment at small spatial scales. The current distribution of the species seems to be mainly restricted to the major focus of introduction, coastal areas. Our simulations suggest that the species would have been introduced successfully at multiple coastal localities, although some inland localities could have also been invaded at an early stage of the invasion. Therefore, further expansions of L. humile into coastal and inland urban areas could be expected in the future.

Overall, the use of occurrence data at different spatial scales and the combination of these two modelling approaches provided new insights to the understanding of the Argentine ant invasion. It permitted us to evaluate the equilibrium status of the invasion, and infer hypotheses about the introduction of the species in the area and also to determine future patterns of spread.

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Des de la introducció a l'equilibri: reconstruïnt el procés d'invasió de la formiga argentina en una regió Mediterrània

Roura-Pascual, N., Bas, J.M., Thuiller, W., Hui, C. Krug, R.M. & Brotons, L. 2009. From introduction to equilibrium: reconstructing the invasive pathways of the Argentine ant in a Mediterranean region. Global Change Biology, 15:2101-2115.