Background Triatoma guasayana is considered an emerging vector of Chagas disease in the Southern Cone of South America. The presence of a triatomine population with brachypterous individuals, in which both wings are reduced, has recently been reported for this species. The aim of the present study was to determine if flight-related traits varied across populations, if these traits could explain differences in flight capacity across populations and if flight-related traits are associated with geographic and/or climatic variation. Methods The study involved 66 male T. guasayana specimens from 10 triatomine populations. Digital images of wing, head and pronotum were used to estimate linear and geometric morphometric variables. Variations in size and shape were analysed using one-way analysis of variance and canonical variate analysis (CVA), respectively. Mantel tests were applied to analyse the relationship between morphometric and geographic distances, and the association between size measurements was analysed using Pearson’s correlation. We explored covariation between size and shape variables using partial least square analyses (PLS). The association of geographic and climatic variables with size measurements was tested using linear regression analyses. We performed PLS analyses for shape measurements. Results Wing size differed significantly across triatomine populations. The CVA showed that wing shape of the brachypterous population is well discriminated from that of the other populations. The Mantel test showed a positive and significant association between wing shape and geographic distances. The heads of the brachypterous population were significantly larger than those of the other populations. Similar to wing shape, the head shape of the brachypterous population was well discriminated from those of the other populations. Pronotum width did not show significant differences across populations. Geographic and climatic factors were associated with size and shape of both the wing and head, but not with pronotum width. Conclusions Most of the traits related to flight dispersal varied across populations. Wing shape and head shape were found to be better markers for differentiated morphological variation across populations. Head measurements also varied in accordance with this condition. Geographic and climatic variables were associated with most of the flight-related traits. Graphical Abstract

La enfermedad de Chagas es hasta hoy día endémica en el Chaco paraguayo, perjudicando principalmente a las poblaciones rurales o de menores recursos económicos, representando así las comunidades indígenas algunas de las poblaciones más vulnerables. El objetivo de este trabajo fue determinar la presencia de triatominos vectores de Trypanosoma cruzi en las comunidades indígenas Ayoreo Totobiegosode Chaidi y Aocojadi del Alto Paraguay. Se evaluaron características de las viviendas y su relación con la permanencia de vectores. La búsqueda de vectores se realizó en el intradomicilio y peridomicilio de las viviendas, y mediante la instalación de una trampa de luz en un ambiente silvestre adyacente a una de las comunidades. Para la búsqueda de flagelados fueron examinadas al microscopio óptico las heces de los triatominos colectados. Se realizó la técnica de xenocultivo para los insectos positivos. Fueron encontrados e identificados triatominos tanto en los ambientes domésticos como en el ambiente silvestre en la zona de las comunidades del Pueblo Ayoreo Totobiegosode del Alto Paraguay: Chaidi y Aocojadi, durante el periodo de colecta del 2016. Los triatominos identificados en este estudio, Triatoma sordida y Triatoma guasayana, son propios de ambientes silvestres, aunque durante ciertas épocas del año actúan como especies intrusivas invadiendo las áreas domésticas. Se detectó la infección natural con T. cruzi-like en un ejemplar proveniente de la comunidad Chaidi, sin descartar la posibilidad de que el parásito se encuentre circulando en Aocojadi. La investigación contribuye a considerar el riesgo de exposición a la enfermedad que tiene la población local, debido a que hasta el momento de este estudio no se cuenta con información sobre la presencia o ausencia de circulación de T. cruzi en estas comunidades.