Background: Primulina cardaminifolia Yan Liu & W.B. Xu (Gesneriaceae), a distinct new species with imparipinnate leaves, is described and illustrated from a limestone valley in Guangxi Zhuangzu Autonomous Region, China. To assure its generic placement and phylogenetic affinity, phylogenetic analyses were performed using DNA sequences of nuclear ITS and chloroplast trnL-F intron spacer region. Additionally, somatic chromosome number was counted and pollen stainability was tested.
Results: Phylogenetic analyses support its placement in Primulina; however, two phylogenetically distinct ITS sequence types were detected, suggesting a probable hybrid origin. Its pollen stainability is 100% and its chromosome number, 2n = 36, is congruent with all known counts of diploid species of the genus.
Conclusion: All available data support the recognition of the new species Primulina cardaminifolia and suggest that it could have derived from homoploid hybrid speciation. Color plates, line drawings and a distribution map are provided to aid in identification.
Keywords: Chromosome number; Flora of China; Homoploid hybrid; Molecular taxonomy; Primulina pinnata; Sino-Vietnamese limestone karst.