Molecular phylogeography of the Chagas' disease vector Triatoma infestans in Argentina

Abstract

Triatoma infestans is the main vector of Chagas' disease in South America between latitudes 10°S and 46°S. A multilocus microsatellite data set of 836 individuals from 27 populations of T. infestans, from all its range of distribution in Argentina, was analyzed. Our results favor the hypothesis of two independent migration events of colonization in Argentina and secondary contacts. The majority of the populations of the western provinces of Catamarca, La Rioja, San Juan and the west of Cordoba province, had almost no shared ancestry with the rest of the populations analyzed. Probably those populations, belonging to localities close to the Andean region, could have been established by the dispersal line of T. infestans that would have arrived to Argentina through the Andes, whereas most of the rest of the populations analyzed may have derived from the dispersal line of T. infestans in non-Andean lowlands. Among them, those from the provinces of Formosa, Chaco, Santiago del Estero and Santa Fe shared different percentages of ancestry and presented lower degree of genetic differentiation. The migratory movement linked to regional economies and possibly associated with passive dispersal, would allow a higher genetic exchange among these populations of T. infestans. This study, using microsatellite markers, provides a new approach for evaluating the validity of the different hypotheses concerning the evolutionary history of this species. Two major lineages of T. infestans, an Andean and non-Andean, are suggested.

Figure 1

Isolation by distance among sampling sites. Pairwise estimates of θ/(1−θ) are plotted against the corresponding natural logharitm of the geographical distances between sites (Rousset, 1997). (a) All sampling site pairs considered (Mantel r=0.405, P=0.0005). (b) Sampling site pairs at distances ranging from 0–150 km (Mantel r=0.163, P=0.51).

Figure 2

Positions of 27 populations of Triatoma infestans in multivariate space defined by factorial correspondence analysis axes 1 and 2. Numerical code for populations corresponds to Table 1.

Figure 3

Pie chart of combined genetic ancestries of all individuals sampled in each population, as obtained by STRUCTURE (Pritchard et al., 2000). The seven different colors correspond to seven different genetic clusters, which are indicated with A, B, C, D, E, F and G. In italic the capital of Argentina as point of reference. Numerical code for populations corresponds to Table 1. A full color version of this figure is available at the Heredity journal online.