Triatoma infestans Klug, 1834

Winchuka, Triatoma infestans Klug, 1834 View in CoL is the main vector of T. cruzi in the Southern Cone of Latin American countries between the latitudes of 10° and 46°S, where it is primarily restricted to domestic and peridomestic environments. This species has been the target of control programmes as part of the Southern Cone Initiative ( Moncayo & Silveira, 2009). However, the goals of current vector control policies are compromised by several factors, including the abundance of other vector species and the extension of the areas of the disease, which hamper regularity in entomological surveillance ( Tarleton et al., 2014). In addition, resistance to pyrethroid insecticides has been reported as a fact that renders vector control strategies difficult ( Mougabure-Cueto & Picollo, 2015). The longterm effectiveness of the control campaigns is greatly dependent upon the vector population structure. Genetic analysis of populations of T. infestans provides a new basis for understanding the evolutionary history, migration patterns, genetic structure and dynamics of vector populations. It also helps to resolve questions on processes such as dispersal and recolonization of the species that directly affect the efficiency of control efforts. Knowledge of the population structure of the vector is also important for management of the resistance to pyrethroid insecticides.

Based on archaeological findings and historical reconstructions, it has been suggested that T. infestans originated from the Andean highlands in Bolivia. Mainly because only a few sylvatic populations have been found in Bolivian Andean valleys, they were traditionally believed to represent the centre of origin of T. infestans . The present distribution of the species has been interpreted as the result of dispersal from the site of origin, coupled with recent and rapid changes in the spread of T infestans related to human activities, particularly between the 19 th and 20 th centuries ( Schofield, 1988). Previous phylogeographical studies carried out with cytochrome b, ITS1 and ITS2 as genetic markers have suggested a Bolivian Andean origin of T. infestans ( Monteiro et al., 1999; Bargues et al., 2006). These studies and another performed with mitochondrially encoded cytochrome c oxidase I (COI) gene fragments ( Piccinali et al., 2009) recovered two groups of T. infestans , but Bolivian haplotypes were not basal, as would be expected for an ancestral group. Moreover, the discovery of sylvatic T. infestans in lowlands in the Bolivian Chaco challenges this hypothesis. This finding supported the alternative hypothesis that the most ancient populations would be thoseofthedrysubtropicalChacoforestinsouth-eastern Bolivia, Paraguay and northern Argentina ( Carcavallo et al., 2000). In contrast, analysis of haplotype genealogies of the mitochondrial cytochrome b gene from Bolivian sylvatic populations showed that the non-Andean (Gran Chaco) haplotypes would have been derived from the Andean ones, supporting an Andean origin of T. infestans ( Waleckx et al., 2011) . However, a non-Andean origin could not be excluded, because higher genetic variability was detected in a Chacoan population than in all the Bolivian Andean valley populations studied ( Waleckx et al., 2011). Given that in older populations, the longer period of time would allow accumulation of higher levels of genetic variation, the non-Andean region could be the centre of origin and dispersal. In concordance, analyses carried out using mitochondrial COI sequences were consistent with the presence of ancestral haplotypes in sylvatic bugs from the Argentinian Chaco ( Piccinali et al., 2011). The occurrence of lowland sylvatic basal haplotypes in phylogenetic analyses performed in that study, which included Bolivian Andean haplotypes, in addition to the higher level of genetic variability detected in sylvatic bugs than in domestic and peridomestic T. infestans populations from Argentina, support the hypothesis of the Chaco region as the area of origin of T. infestans ( Piccinali et al., 2011) .

The maternally inherited markers analysed in T. infestans , such as cytochrome b, 12S, 16S and COI genes, either exhibit low levels of variation ( Monteiro et al., 1999; García et al., 2003; Segura et al., 2009) or have not allowed hylogeographical inferences to be obtained about the Chagas disease vector in Argentina ( Piccinali et al., 2009). To this respect, Piccinali et al. (2009) stated that further studies from other independent gene regions would make it possible to determine whether phylogeographical inferences from COI data constitute distinctive features of this species. Given that the phylogenetic and phylogeographical analyses remain inconclusive, more sequences need to be examined. Fernández et al. (2013) analysed the variation in mitochondrial NADH dehydrogenase subunit 5 (ND5) and NADH dehydrogenase subunit 4 (ND4) genes in T. infestans . Based on their results, it was inferred that ND5 sequences would be useful for phylogeographical studies. However, the inclusion of nuclear DNA markers in evolutionary and population genetic studies is indispensable for a better understanding of evolutionary processes ( Zhang & Hewitt, 2003). The nuclear gene encoding elongation factor-1 alpha (EF-1α) has been well characterized and was used for several systematic and phylogeographical studies ( Broughton & Harrison, 2003; Glennon et al., 2008; Rubinoff, 2008; Ready et al., 2009; Nahavandi et al., 2012; Valderrama et al., 2014). In order to contribute to knowledge of the phylogeographical pattern of T. infestans , in the present study we analysed sequences of the mitochondrial ND5 gene and the nuclear gene EF-1α of specimens from Argentina and Bolivia.