Topographic Barriers and Lowland Corridors Structure Gene Flow in the Chagas Vector Rhodnius pallescens Across the Isthmian Forests

Abstract

Aim Biogeographic processes can profoundly shape the connectivity and evolutionary potential of arthropod disease vectors. We investigated how Panama's ecological and topographic transitions structure populations of the kissing bug Rhodnius pallescens , the primary vector of the Chagas disease agent Trypanosoma cruzi in the region. Location Central America. Period Present. Methods Using 3RAD sequencing, we analysed genome‐wide Single Nucleotide Polymorphisms (SNPs) from 101 individual kissing bugs collected at 11 sites spanning three ecoregions: the Isthmian‐Pacific Moist Forests, the Isthmian‐Atlantic Moist Forests and the Panamanian Dry Forests. We evaluated genetic diversity and divergence, directional migration, and spatially explicit gene‐flow models to map genetic connectivity onto landscape features. Results Across analyses, R. pallescens samples segregated into two well‐supported genetic lineages corresponding to Isthmian‐Pacific Moist Forests versus Isthmian‐Atlantic Moist Forests/Dry Forests regions, with little evidence of admixture. Migration networks revealed asymmetric, spatially structured exchange within ecoregions, but no detectable gene flow between them. Effective Migration Surfaces identified three robust biogeographic breaks: (i) the mountainous corridor around El Valle de Antón along the continental divide, (ii) the ecotone between Pacific moist and dry forests and (iii) a barrier associated with the Panama Canal/Soberanía forest corridor. Parasite SNPs showed weak spatial structure, indicating dispersal decoupled from vector populations. Main Conclusions Together, these patterns indicate that elevation gradients and ecoregional transitions, rather than geographic distance alone, are determinants of gene flow. This observed structure is consistent with short‐range dispersal and strong habitat association with Attalea palms, the primary habitat of R. pallescens . Our results position the Cordillera Central and adjacent ecotones as enduring filters to R. pallescens gene flow, generating long‐standing regional lineages and shaping the landscape over which adaptive alleles can spread. This study provides a biogeographic framework to inform the design of ecoregion‐tailored Chagas vector surveillance and control across the Isthmian divide, anticipating regional reinfestation pathways.

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