New insights into the phylogeny and taxonomy of Chinese Physospermopsis (Apiaceae)

Physospermopsis (Apiaceae) comprises about 10 species, but its taxonomy and phylogeny are disputed. The genus is mostly distributed in the Himalayas and Hengduan Mountains at high elevation. Earlier molecular studies involving six species of Physospermopsis indicated that this genus is not monophyletic and is nested in the East Asia Clade. Therefore, the aims of this study were to re-assess the phylogenetic position of, and interspecific relationships within, Physospermopsis based on two chloroplast loci (rpl16, rps16) and one nuclear region, the internal transcribed spacers of ribosomal DNA (ITS). Eight species involving 13 populations of Physospermopsis were collected. These were sequenced and analyzed with the sequences of 31 other Apiaceae species obtained from the NCBI to determine phylogenetic relationships using Bayesian inference (BI) and Maximum likelihood (ML). Our study found that Physospermopsis is monophyletic, nested in Pleurospermeae of Apiaceae, sister to Pleurospermum. And we propose that the Physospermopsis clade should be replaced by the East Asia Clade. However, the interspecific relationships within Physospermopsis were not well resolved and the positioning of species was unclear. Diagnostic characteristics to distinguish Physospermopsis species in the field and laboratory are provided for future Physospermopsis phylogenetic studies.