Abstract: Dolichopetalum is a monotypic liana genus of Apocynaceae and is restricted to subtropical montane forests in Asian subtropical karst areas. In this study, we used plastome data to examine the tribal position of Dolichopetalum within the family, and four plastid and three nuclear loci to further clarify its relationship and taxonomic status. We also estimated the time of origin of Dolichopetalum and modeled its range change by estimating the potential historic and current distributions. Our family-wide phylogenetic analysis confirms that Dolichopetalum belongs in the tribe Marsdenieae. Our subsequent analyses of Marsdenieae further suggest that Dolichopetalum is a distinct genus and has a distant relationship with Marsdenia s.str., challenging the traditional viewpoint. Dolichopetalum is probably allied to Campestigma, Cionura, Harmandiella, and Gongronema-Dischidanthus-Sarcolobus, and originated at about 11 Ma and rapidly diverged with its four allies over a period of less than three million years, which might be associated with the intensified East Asian monsoon in the early Late Miocene. The distributional range of Dolichopetalum may have undergone a dramatic contraction since the Last Glacial Maximum and will likely further shrink and undergo fragmentation in the future, possibly driven by global warming and desertification in Asian subtropical karst areas. This study provides new insights into the evolutionary history of Dolichopetalum and will have important conservation implications for the unique biodiversity of Asian subtropical karst areas under climate change scenarios.

Key words: conservation, Dolichopetalum, East Asian monsoon, endemism, karst, phylogeny