Evolutionary dynamics and adaptive mechanisms of <i>Impatiens</i> species in response to climate change: insights from chloroplast genomics and ecological niche modelling in Southwest China

Abstract This study integrates chloroplast genomics, phylogenetics, and ecological modelling to unravel the adaptive evolution of Impatiens, a taxonomically complex and species-rich genus endemic to Southwest China. Comparative chloroplast genome analyses of six representative species revealed conserved genomic architecture alongside signatures of adaptive divergence in key photosynthetic genes (rbcL, matK) and metabolic regulators (psbA, ndhF), particularly in subtropical monsoon and montane plateau species. Originating during the Eocene–Oligocene transition (∼40 Mya), the family Balsaminaceae diversified through the Qinghai-Tibetan Plateau uplift, enabling colonization of altitudinal gradients from subtropical lowlands to alpine ecosystems. Projections under future climate scenarios revealed contrasting habitat dynamics: under SSP1-2.6, high-altitude regions in the Hengduan Mountains and northern Yunnan may serve as climatic refugia, enabling habitat expansion (5–20%) for Impatiens arguta and Impatiens yui; however, under SSP5-8.5, species occupying subtropical monsoon zones are projected to lose a substantial proportion of suitable habitat, underscoring altitudinal migration as a key survival strategy. These findings highlight the role of plastome evolution in mediating climatic adaptability and underscore the urgent need to prioritize montane biodiversity corridors for conservation in Southwest China.