Abstract
<jats:title>Abstract</jats:title> <jats:p> Chemosensory systems play a central role in host detection, feeding behavior, and habitat selection in hematophagous insects. Here, we performed a comparative evolutionary analysis of chemosensory gene repertoires across 13 species of the Chagas disease vector genus <jats:italic>Rhodnius</jats:italic> . </jats:p> <jats:p> While gustatory receptors (GRs), ionotropic receptors (IRs), odorant-binding proteins (OBPs), and chemosensory proteins (CSPs) remained globally conserved, odorant receptors (ORs) displayed extensive lineage-specific expansions, tandem duplications, dynamic transcriptomic regulation, and recurrent signatures of positive selection. Major OR expansions were observed in <jats:italic>Rhodnius robustus</jats:italic> and <jats:italic>Rhodnius colombiensis</jats:italic> , suggesting increased sensory diversification in ecologically heterogeneous lineages. In contrast, conserved GR1 expression supports the maintenance of ancestral sugar-detection pathways despite hematophagy lifestyle. We further found no evidence of the canonical insect CO₂-associated GRs, suggesting alternative molecular mechanisms for CO₂ perception in Triatominae. Several receptors, including Orco, also displayed shifts in selective constraints between sylvatic and domiciliary species, consistent with sensory remodeling associated with adaptation to domestic habitats. </jats:p> <jats:p> Together, our results identify ORs as the most evolutionarily dynamic component of the <jats:italic>Rhodnius</jats:italic> chemosensory repertoire and highlight contrasting evolutionary trajectories among chemosensory gene families during ecological diversification and vector adaptation. </jats:p>