Phylogenomic framework, biogeography and character evolution of the genus Campylotropis (Fabaceae, Papilionoideae)

The shrub genus Campylotropis (Fabaceae, trib. Desmodieae, subtrib. Lespedezinae) encompasses approximately 40 species, predominantly distributed across temperate and subtropical East Asia, with its diversity centered in the Hengduan Mountains and southern China. Historical constraints in sampling and methodological approaches have long obscured its evolutionary history and species relationships. This study provides the most comprehensive phylogenomic analysis of Campylotropis to date, incorporating 91 samples representing 40 taxa. Leveraging sequence data from 77 plastid genes and 1,233 single-copy nuclear genes (SCGs), we reconstructed the genus's phylogenomic framework, estimated divergence times, inferred ancestral area distributions, and traced the evolution of key morphological traits. Our results robustly confirm the monophyly of Campylotropis, distinguishing it from allied genera. We delineated six well-supported clades within the genus and resolved previously unresolved relationships. The conflicts between nuclear and chloroplast phylogenies highlight a complex evolutionary history, likely influenced by chloroplast capture and incomplete lineage sorting (ILS) during rapid radiation. We found that global climate change and tectonic activities since the late Miocene likely shaped lineage diversification, with Quaternary climate oscillations potentially triggering rapid radiation within the genus. Ancestral area reconstruction suggests that Campylotropis originated in the Hengduan Mountains and southern China before dispersing swiftly across adjacent East Asian regions. By integrating extensive sampling with nuclear genomic data, this study elucidates the evolutionary history of Campylotropis and enhances our understanding of diversification processes in biodiversity hotspots.