Diversification of tropical damselflies in a complex South American landscape

South America's complex geological history has driven exceptional biodiversity, yet aquatic insects remain significantly understudied compared to terrestrial groups. The damselfly genus Polythore (Polythoridae), known for its vivid wing patterns and restricted ranges, offers an ideal system to investigate diversification in dynamic landscapes. Previous work identified discordance between morphological and mitochondrial patterns, as well as strong geographic structuring and potential paraphyly within described species. However, reliance on single-locus data limited our ability to resolve species boundaries and understand the evolutionary processes shaping this diversity. We integrated mitochondrial DNA and RADseq data to test alternative species delimitation models, reconstruct species trees, and evaluate demographic history. Coalescent analyses and demographic modeling suggest that some described species may be polytypic, containing multiple geographically or genetically structured populations, rather than representing a greater number of distinct evolutionary lineages. Population genomic approaches revealed patterns of genetic structure, admixture, and drift among populations. Spatial connectivity models and demographic simulations indicate that historical landscape dynamics, including periods of connectivity and isolation, have influenced patterns of divergence. Our findings highlight the importance of combining phylogenetic, phylogeographic, and population genomic perspectives to understand diversification in understudied aquatic taxa. In Polythore, speciation may involve not only geographic isolation but also incomplete lineage sorting and historical gene flow. This integrative framework helps refine systematics in Odonata and offers a model for studying the origins of biodiversity in complex regions, emphasizing the need for nuanced interpretations of genomic data.