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Title: Evolutionary history of the little fire ant Wasmannia auropunctata before global invasion: inferring dispersal patterns, niche requirements, and past and present distribution within its native range

Author
item CHIFFLET, L - Universidad De Buenos Aires
item RODRIGUERO, M - Universidad De Buenos Aires
item CALCATERRA, L - Fuedei
item DINGHI, P - Universidad De Buenos Aires
item BACCARO, F - Instituto Nacional De Pesquisas Da Amazonia (INPA)
item Follett, Peter
item CONFALONIERI, V - Universidad De Buenos Aires

Submitted to: Journal of Evolutionary Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2015
Publication Date: 2/28/2016
Citation: Chifflet, L., Rodriguero, M., Calcaterra, L., Dinghi, P., Baccaro, F., Follett, P.A., Confalonieri, V. 2016. Evolutionary history of the little fire ant Wasmannia auropunctata before global invasion: inferring dispersal patterns, niche requirements, and past and present distribution within its native range. Journal of Evolutionary Biology. doi:10.1111/JEB.12827.

Interpretive Summary: Classic and Bayesian phylogeographic tools were combined with a paleodistribution modeling approach to study the historical demographic processes that shaped the distribution of the invasive little fire ant Wasmannia auropunctata in its native South America. Results suggest that the ancestor of the two main clades within W.auropunctata was placed in central Brazil during the Pliocene, 3.92 million years ago approximately. A secondary contact process in many regions of central South America began 380 thousand years ago and might be continuing at present. Ecological niche modeling analysis indicates that Argentina constitutes a marginal region for the species, and our study supports that the little fire ant is native in this region, not having been introduced by human activity. It appears that W.auropunctata is expanding its range southward in recent times (last 50 years) and may continue expansion within the current climatic scenario.

Technical Abstract: We integrated classic and Bayesian phylogeographic tools with a paleodistribution modeling approach to study the historical demographic processes that shaped the distribution of the invasive ant Wasmannia auropunctata in its native South America. We generated mitochondrial Cytochrome Oxidase I sequences from 154 individuals belonging to two major clades (A and B) within W.auropunctata collected through a wide part of its native range. We performed a Bayesian phylogeographic analysis to determine the origin of the common ancestor of all our samples and the patterns of further expansion and diversification across the landscape. With an ecological niche modeling we detected central and marginal areas of distribution of the species for three climatic periods and we analyzed whether niche requirements of both clades differ between clades differ. We examined if the southernmost limit of its native distribution (Argentina) constitutes a marginal region of the species and if this region it was colonized through a natural expansion process or mediated by human influence. Our results suggest that the ancestor of the two main clades within W. auropunctata was placed in central Brazil during the Pliocene, 3.92 million years ago approximately. The diversification into two clades, clade A northward and clade B southward, was probably influenced by climatic oscillations driven by Milankovitch cycles, which promoted forest fragmentation and consequently speciation during the Tertiary. The most suitable habitats seem to be different between clades, suggesting that the genetic differentiation might be accompanied by a differentiation in their niche requirements, being clade A being a tropical linage and clade B being a mostly subtropical linage , that also extends into temperate regions of South America. A secondary contact process in many regions of central South America began 380 thousand years ago and might be continuing at present. Ecological niche modeling analysis indicates that Argentina constitutes a marginal region for the species, and our study supports that the LFA is native in this region, not having been introduced by human activity. It seems that W. auropunctata has expanded its range southward during the last 50 years and may continue expanding it in the future within the current climatic scenario.