Temporal variations of fluctuating asymmetry in wing size and shape of Triatoma infestans populations from northwest Argentina

Environmentally-induced developmental instability has frequently been assessed using fluctuating asymmetry (FA) methods. For Triatoma infestans, the major vector of Chagas disease, the combined effects of host-feeding sources and habitats affected wing developmental instability depending on sex in Figueroa villages, northwest Argentina. Here we investigated whether habitat, sex, season/year and insecticide applications affected wing developmental instability in T. infestans populations from Amamá and other rural villages of northwest Argentina over a four-year period. We measured the occurrence and amount of wing size and shape FA in 423 adult triatomines collected in domiciles, goat corrals, pig corrals, storerooms and wood piles. Significant wing size and wing shape FA occurred in females and males from all habitats as determined by two-way mixed ANOVA and Procrustes ANOVA, respectively. For wing size and shape, the highest corrected indices of FA (FAI) for females occurred in wood piles, goat corrals and domiciles in late summer or early autumn, whereas for males, the largest FAIs consistently appeared in domiciles and storerooms. Wing size FAIs were significantly higher in recently infested goat corrals rather than in persistently infested goat corrals. The follow-up of four infested peridomestic sites showed that FA patterns were not stable over time or sites. Temporal variation of FA among habitats appears to be modified by the history of insecticide spraying, either through direct effects on insect development or through indirect effects related to flight dispersal and house invasion. Whether FA may provide another marker to identify the sources of reinfestant triatomines requires further investigation.