We analyzed the main karyologic changes that haveoccurred during the dispersal of Triatoma infestans, themain vector of Chagas disease. We identified two allopatricgroups, named Andean and non-Andean. The Andeanspecimens present C-heterochromatic blocks in most oftheir 22 chromosomes, whereas non-Andean specimenshave only 4–7 autosomes with C-banding. These hete-rochromatin differences are the likely cause of a strikingDNA content variation (approximately 30%) betweenAndean and non-Andean insects. Our study, together withprevious historical and genetic data, suggests that T. infes-tans was originally a sylvatic species, with large quantitiesof DNA and heterochromatin, inhabiting the Andean regionof Bolivia. However, the spread of domestic T. infestansthroughout the non-Andean regions only involved insectswith an important reduction of heterochromatin and DNAamounts. We propose that heterochromatin and DNA vari-ation mainly reflected adaptive genomic changes that con-tribute to the ability of T. infestans to survive, reproduce,and disperse in different environments
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