SummaryThe interplay of orographic uplift and climatic changes in the Himalaya-Hengduan Mountains region (HHM) have had a key role in speciation and population demography. To gain further insight into these processes, we investigated their effects on Taxus wallichiana by combining molecular phylogeography and species distribution modeling.Molecular data were obtained from 43 populations of T. wallichiana. Nineteen climatic variables were analyzed alongside genetic discontinuities. Species distribution modeling was carried out to predict potential past distribution ranges.Two distinct lineages were identified, which diverged c. 4.2 (2.0-6.5) million years ago (Ma), a timescale that corresponds well with the recent uplift of the Qinghai-Tibet Plateau and subsequent climatic changes of the region. Correlations with climatic variables also suggest that ecological factors may have further reinforced the separation of the two lineages. Both lineages experienced population expansion during the last glaciation.The high genetic divergence, long-term isolation and ecological differentiation suggest a scenario of cryptic speciation in T. wallichiana associated with geological and climatic changes in the HHM. Our findings also challenge the notion of general population 'contraction' during the last glaciation in the HHM.

We studied the phylogeography of Chinese yew (Taxus wallichiana), a tree species distributed over most of southern China and adjacent regions. A total of 1235 individuals from 50 populations from China and North Vietnam were analysed for chloroplast DNA variation using polymerase chain reaction-restriction fragment length polymorphism of the trnL-F intron-spacer region. A total of 19 different haplotypes were distinguished. We found a very high level of population differentiation and a strong phylogeographic pattern, suggesting low levels of recurrent gene flow among populations. Haplotype differentiation was most marked along the boundary between the Sino-Himalayan and Sino-Japanese Forest floristic subkingdoms, with only one haplotype being shared among these two subkingdoms. The Malesian and Sino-Himalayan Forest subkingdoms had five and 10 haplotypes, respectively, while the relatively large Sino-Japanese Forest subkingdom had only eight. The strong geography-haplotype correlation persisted at the regional floristic level, with most regions possessing a unique set of haplotypes, except for the central China region. Strong landscape effects were observed in the Hengduan and Dabashan mountains, where steep mountains and valleys might have been natural dispersal barriers. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest the existence of several localized refugia during the last glaciation from which the present-day distribution may be derived. The pattern of haplotype distribution across China and North Vietnam corresponded well with the current taxonomic delineation of the three intraspecific varieties of T. wallichiana.

The polyphyletic genus Chirita is remodelled after an extensive molecular phylogenetic study of species assigned to it and to other associated genera. Most of Chirita sect. Chirita and the monotypic Hemiboeopsis are amalgamated with Henckelia sect. Henckelia, resulting in a very differently circumscribed genus Henckelia and the synonymisation of Chirita. The remaining species of Chirita sect. Chirita are accommodated in the revived genus Damrongia. Chirita sect. Liebigia is recognised as the genus Liebigia. Chirita sect. Microchirita is recognised as the genus Microchirita. Chirita sect. Gibbosaccus is, together with Chiritopsis and Wentsaiboea, included in the originally monotypic and now enormously expanded genus Primulina. The necessary combinations are made and a general list showing the present accommodation of the species previously described under Chirita, Chiritopsis, Hemiboeopsis, Primulina and Wentsaiboea is provided.