Competition between invasive and indigenous species: an insular case study of subterranean termites

An important requirement for the management of invasive species is to identify the biological and ecological factors that influence the ability of such species to become established and spread within a new environment. Although competition is one of the key interactions determining the coexistence of species and exclusion, few studies directly examine the mechanism of competitive interactions within invasive communities. This study focused on putative competition in a social insect invader, R. flavipes, an American termite introduced into France, and an indigenous European termite, R. grassei. We first characterized and mapped a zone of sympatry between these two species. We then evaluated the degree of direct and indirect competition by comparing several life-history traits: behavioral aggression, chemical recognition and dispersion modes. Interspecific competition revealed that R. flavipes was dominant over R. grassei. Intraspecific competition was not found in R. flavipes while it appeared in varying degrees in R. grassei. These findings seemed to be correlated with the remarkable chemical homogeneity found in R. flavipes in comparison with R. grassei. Genetic analyses revealed that R. flavipes foraged over a greater distance than R. grassei colonies and might suggest a difference in the capacity to produce secondary reproductives. These findings suggest that R. flavipes has a significant advantage owing to competitive asymmetry that may enable the species to become dominant. The interspecific superiority, lack of intraspecific aggression and large extensive colonies, seem to be some of the reasons for its invasive success.