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Dryad

Recent origin of a range-restricted species with subsequent introgression in its widespread congener in the Phyteuma spicatum group (Campanulaceae)

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Nov 24, 2024 version files 40.27 MB

Abstract

Understanding the causes of restricted geographic distributions is of major interest to evolutionary and conservation biologists. Inferring historical factors has often relied on ad hoc interpretations of genetic data, and hypothesis testing within a statistical framework under different demographic scenarios remains underutilized. Using coalescent modeling on RAD-sequencing data we (i) test hypotheses about the origin of Phyteuma gallicum (Campanulaceae), a range-restricted endemic of central France sympatric with its widespread congener P. spicatum, and (ii) date its origin, irrespective of its mode of origin, to test the hypothesis that the restricted range is due to a recent time of origin. The best-supported model of origin is one of a dichotomous split of P. gallicum, confirmed as a distinct species, and the Central European P. nigrum with subsequent gene flow between P. gallicum and P. spicatum. The split of Ph. gallicum and P. nigrum is estimated at 45–55,000 years ago. Coalescent modeling on genomic data not only clarified the mode of origin (dichotomous speciation instead of hybridogenic origin) but identified recency of speciation as a sufficient, though likely not the sole, factor to explain the restricted distribution range. Coalescent modeling strongly improves our understanding of the evolution of range-restricted species that are frequently of conservation concern, as is the case for P. gallicum.