Genetic variability, population structure and phylogeography of Argentinian and other Southamerican Triatoma infestans populations based on COI

PICCINALI R. V., MARCET P. L., NOIREAU F., KITRON U., GÜRTLER R. E. AND DOTSON E. M.

Atlanta, Georgia, United States of America

Congreso; 55th Annual Meeting of the American Society of Tropical Medicine and Hygiene; 2006

American Society of Tropical Medicine and Hygiene

Knowledge on the genetic variability, population structure and evolutionary history of Triatoma infestans may be useful for developing vector control strategies. A total of 222 bugs from nine Argentinian provinces, and individuals from Uruguay, Peru, and Bolivia (including domestic bugs, sylvatic bugs and one dark morph), were sequenced for a 661bp fragment of the mtDNA gene COI, and several population genetics and phylogeographic analyses were performed. High levels of nucleotide variation were found within Argentina, with 37 variable sites distributed among 30 haplotypes. Total heterozygosity ranged from 0.0097 to 0.0052 according to θW and π estimators, the highest value reported for T. infestans to date. The domestic Bolivian sample showed four haplotypes not found in Argentina, and had lower levels of nucleotide variation. Three of these haplotypes were shared with the sylvatic Andean bugs, indicating a possible domestic origin. The dark morph, in contrast, exhibited a private haplotype. Departures fromneutrality expectations suggest a recent population expansion of T. infestans in Argentina, whereas AMOVA and KST* analysis support a strong population structure, but not following an isolation by distance model as appeared to have operated in Bolivia. A haplotype network showed an Argentinian/Uruguayan clade and a Bolivian/Peruvian clade. The dark morph, however, was separated from these two clusters by seven mutational steps, suggesting that it is an ancient form, strongly isolated from the remaining populations. Interestingly, the Argentinian/Uruguayan clade had a general star-like shape but also five highly divergenthaplotypes. This unusual haplotype structure may be explained by incomplete lineage sorting or population admixture. These results arise new questions about the genetic variability of T. infestans and its potential response to selective forces such as insecticide spraying, the gene flow between sylvatic and domestic bugs, and the historical patterns of dispersal of the species.