Ecological phylogeography and coalescent models suggest a linear population expansion of Anastrepha fraterculus (Diptera: Tephritidae) in southern South America

Abstract

This work is a first approach to an integrated view of the genetics, ecology and dispersion patterns of Anastrepha fraterculus in southern South America. We studied the association of genetic variation with geographical patterns and environmental variables to provide insight into the crucial factors that drive the structure and dynamics of fly populations. Data from a 417 bp mitochondrial COII gene fragment from seven Argentinian populations and one South Brazilian population (from five ecoregions grouped in three biomes) were used to identify population clusters using a model-based Bayesian phylogeographical and ecological clustering approach. The sequences were also analysed under a coalescent model to evaluate historical demographic changes. We identified 19 different haplotypes and two clusters differing in all the environmental covariables. The assumption of neutral evolution and constant population size was rejected, and the population growth parameters suggested a linear population expansion starting 2500 years before present. The most likely ancestral location is Posadas, from where A. fraterculus would have expanded southwards and westwards in Argentina. This result is consistent with Holocene changes and anthropic factors related to the expansion of the Tupí-Guaraní culture, 3000-1500 years before present.