Hybridization, ecological niche, and conservation of the threatened endemic species Limonium estevei: an integrated approach in the genus Limonium

Abstract Hybridization between widespread species and narrow endemics poses a serious conservation threat, often leading to extinction via genetic swamping. In this study, we applied an integrated approach—combining genetics, morphometrics, and functional ecology—to investigate the implications of hybridization between the widespread species Limonium cossonianum and the Critically Endangered L. estevei . We combined molecular markers (AFLPs, ITS, and chloroplast markers), morphometric analyses, and elemental profiling of leaves and soils. Elemental profiles provided a novel proxy for biogeochemical niche differentiation, while genetic markers resolved phylogenetic relationships and the direction and extent of gene flow. Crucially, our results revealed extensive and asymmetric introgression occurring exclusively from the hybrid into L. cossonianum , with no evidence of genetic swamping affecting the genetic integrity of L. estevei . Elementome analyses showed that L. cossonianum occupies a significantly distinct biogeochemical niche, whereas L. estevei and the hybrid share similar elemental composition. Furthermore, the hybrid’s elementome exhibited a mosaic inheritance pattern, suggesting a novel functional strategy that may contribute to its local persistence. We conclude that the mechanisms of niche differentiation, coupled with reproductive asymmetry, have acted as an evolutionary shield for L. estevei , protecting this species from extinction through genetic swamping. Our findings indicate that, although hybridization does not currently threaten the genetic integrity of L. estevei , its long-term persistence will depend on the conservation of the highly specific edaphic conditions on which the species relies. Given the marked soil specialization documented here, strategies focusing on the preservation of its functional and edaphic niche are likely to be essential.