Morphological diversity of Triatoma infestans across biogeographic zones of Chile.

Triatoma infestans, the primary domiciliary vector of Chagas disease in Chile, has a broad geographic distribution and is characterized by high synanthropy and strong colonization capacity. Landscape characteristics are key factors in understanding population distribution and the processes that shape morphological variation. This study aimed to characterize the structures associated with dispersal and feeding using geometric morphometrics in domiciliary adults of T. infestans (n = 353 total specimens analyzed) along a latitudinal gradient (∼1,255 km). Furthermore, the specimens' localities were classified according to the Köppen-Geiger climatic regionalization, resulting in four ecoregions. The relationship between morphology and climatic variables was evaluated using bioclimatic CHELSA data (1981-2010). Cold Desert (northern distribution) individuals exhibited more compact shapes than those of the Semi-arid and Mediterranean (southern distribution) ecoregions. Pronotum centroid size remained stable across all ecoregions (p = 0.095) and between sexes (p = 0.443). The head centroid size showed sexual dimorphism in some ecoregions, with females larger than males. Females also exhibited morphological stability, which could be associated with feeding prioritization and reproductive investment rather than dispersal. In contrast, lateral head centroid size in males varied with latitude, being smaller in the Cold Desert ecoregion than the Mediterranean ecoregion (p < 0.01). Macroclimatic factors did not explain shape variation (p > 0.05 for all traits). The results suggest a modular response between the pronotum and the head, potentially driven by the microenvironmental conditions within domestic habitats. Such patterns highlight the importance of trait-specific morphological variations, which may have implications for dispersal and feeding, and could be integrated into surveillance and vector control strategies.