No abstract

As one of the big genera in Apiaceae, Bupleurum L. has received considerable attention from plant taxonomists. Nevertheless, there are still many gaps in our knowledge of this genus, especially of those species endemic to China that have often been excluded from previous studies. In spite of a few recent studies on the phylogeny and classification of the Chinese Bupleurum, the most essential problem of species delimitation still remains unresolved. We re‐evaluate the taxonomy of the Chinese Bupleurum using morphological and molecular evidence. Careful observations of living plants growing the field and herbarium specimens were made to understand the morphological variation and to ensure species identification for the molecular analysis. Phylogenetic analyses were carried out on sequence data of nuclear ribosomal internal transcribed spacer (nrITS), trnH‐psbA, and matK, using parsimony and Bayesian approaches to evaluate species relationships. Analyses of both nrITS and combined datasets of the three regions revealed the following results: (i) the Chinese Bupleurum species were divided into two major lineages; and (ii) most species were well defined, but some traditional inter‐ and infraspecific relationships were not supported. Our results, along with the results of previous works support that the Chinese Bupleurum species were derived from two different lineages and should be placed in Neves and Watson's subgenus Bupleurum. Our detailed taxonomic re‐assessment of several Chinese species resulted in new taxonomic recombinations with rank changes for three species: Bupleurum tenerum, B. amplexicaule, and B. franchetii; new combination for one variety, B. smithii var. flaviflorum; and the description of one variety and one species, B. stenophyllum var. leiocarpum and B. sikangense.

Prinsepia Royle (Rosaceae) is a genus native to China and the Himalayan region. In order to explain its current fragmented distribution pattern and to compare the impact of relatively recent climate changes on the genetic structure of Prinsepia species in different regions of China, a total of 66 populations and 617 individuals of four species of Prinsepia were genotyped, using three cpDNA markers. Meanwhile, phylogenetic reconstructions and divergence dating were conducted using the cpDNA haplotypes dataset and the nuclear ribosomal internal transcribed spacer (ITS) dataset, respectively. Ecological niche modeling (ENM) was performed to predict the potential distribution of each species of Prinsepia at present and during the Last Glacial Maximum. Both ITS and cpDNA gene trees support a north-south divergence of Prinsepia species in China. The divergence time of the northern and southern Clades occurred around the late Oligocene epoch. Combining the present distribution of Prinsepia species and their habitats, we inferred that the transition to a monsoon climate system in East Asia during the late Oligocene epoch, created a humid forest vegetation zone from central to East China, which potentially gave rise to the north-south divergence of Prinsepia species. Both regional climates and allopatric divergence may have played an important role in the speciation of P. sinensis and P. uniflora . P. sinensis had the lowest genetic diversity and a putative northward post-glacial colonization. The distribution range of P. uniflora was also extremely sensitive to interglacial-glacial cycles. P. utilis from southwestern China preserved more haplotypes than P. sinensis and P. uniflora due to its multiple and isolated refugia.

Megacodon is an ideal genus to study speciation and ecological adaptation in the Sino-Himalayan region. The genus contains two species distributed at different elevations and in two separate areas. However, studies of this genus have long been impeded by a lack of fieldwork on one of its species, Megacodon venosus. In this study, we collected specimens of two Megacodon species and found an extraordinary new species of Megacodon in Lushui county of north-west Yunnan province, which we have since named Megacodon lushuiensis . We propose new species based on both morphological and molecular evidence. The finding of this new species emphasized the importance of ecological divergence in the divergence of Megacodon stylophorus and its parapatric low-elevation Megacodon species. To identify genetic determinants that underlie adaptations to different elevations, we characterized transcriptomes of the new species M. lushuiensis , which is distributed at low elevations, and M. stylophorus, which is distributed at high elevations. Comparative transcriptome analysis identified 8926 orthogroups containing single-copy genes, and 370 orthogroups containing significantly positively selected genes. The set of positively selected genes was enriched into 25 Gene Ontology terms, including “response to water deprivation”, “response to osmotic stress”, and “cellular response to external stimulus”. Our results provide new insights into how ecological adaptation and speciation occurred in Megacodon and highlight the role of heterogeneous habitats in the speciation of plants in the Sino-Himalayan region.