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Discordant phylogeographic patterns in ecologically similar sympatric sister species: Revisiting the null hypothesis of comparative phylogeography

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Dec 22, 2025 version files 438.37 MB

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Abstract

Unravelling the complex factors underlying the current geographic patterns of biodiversity is a fundamental goal of biogeography and phylogeography. Comparative phylogeographic studies of co-distributed species have often addressed this issue by attributing observed differences in population structures to differences in interpretable traits between species. However, this approach implicitly relies on the largely untested assumption that species sharing similar ecological, spatial, and phylogenetic contexts should exhibit similar population structures. Herein, we revisited this null hypothesis of phylogeography by comparing the population structures of two sympatric sister species with high ecological similarity using high-throughput genomic data. With extensive sampling and advanced genomic analyses, we revealed the fine-scale population structure of Chaenogobius gulosus, enabling a direct comparison with the well-documented phylogeography of C. annularis. Our findings indicate that the origin of intraspecific lineages in C. gulosus is estimated to be four to five times younger than in C. annularis, with a distinct number of intraspecific lineages. These findings demonstrate that the phylogeographic origin can differ even between sympatric sister species with high ecological similarity, providing a counterexample to the null phylogeographic hypothesis. Our results highlight the role of subtle ecological differences or stochasticity in shaping geographical patterns of biodiversity.