Abstract:

Background & Aim: Species represent fundamental entities in biological research. In recent years, the Integrative Species Concept has gained increasing popularity. It emphasizes that the delimitation of closely related species should be based on multiple lines of evidence. J. coxii, initially described as a variety of J. recurva, was subsequently elevated to species rank by Adams et al. Nevertheless, population-level evidence supporting this taxonomic classification remains scarce. 

Methods: To clarify the boundaries between two taxa within the J. recurva complex from the eastern Hengduan-Himalayan region, chloroplast DNA sequences were obtained from 197 individuals across 26 populations for lineage delimitation. While the molecular data delineated the phylogenetic framework, statistical morphological analyses and niche differentiation assessments were further conducted on representative populations. Additionally, ecological niche modeling was performed by integrating environmental climatic factors from both our sampling sites and previously published occurrence records. 

Results: Chloroplast haplotype network analysis has divided the J. recurva complex into two lineages: eastern and western. Geographically, these lineages have been roughly separated by Cona County. No significant statistical discontinuity has been observed in their morphology, although morphological variation has been found among individuals. The ecological niches of the eastern and western lineages have shown significant differentiation, but some overlap has remained. 

Conclusion: The above evidence supports classifying populations west of Cona County as J. recurva, while eastern populations represent J. coxii. However, as this study relies exclusively on chloroplast DNA data, further research employing nuclear genome-derived molecular markers is warranted.

Key words: Juniperus recurva, Juniperus coxii, species delimitation, integrative species concept