Molecular Phylogeny And Speciation Of Rosa Section Microphyllae (Rosaceae)

Section Microphyllae Crep. (Rosaceae, Rosa L.) includes four species, Rosa praelucens, R. roxburghii, R. kweichowensis and R.×sterilis, and two forms, R. roxburghii f. candida and R. roxburghii f. inermis. These species are endemic to China especially in southwest region except R. roxburghii, which is also distributed in Japan. The previous studies about section Microphyllae mainly focused on biological characteristics, natural products, physiology and biochemistry. However, we have barely found related researches in sect. Microphyllae on molecular phylogeny、discrimination、speciation and divergence time. For resolving above scientific questions, we choose southwest region in China as sampling center, and widely collect materials of genus Rosa. the internal transcribed spacer (ITS) region of nuclear ribosomal DNA, the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) nuclear gene and five chloroplast gene regions(the intergenic spaces psbA-trnH, trnL-trnF, trnK-matk, psbI-psbK and rpoCl) were used to achieve useful molecular datasets for phylogenetic reconstruction. Phylogenetic method analysis of these sequences performed with Bayesian inference (BI) and Maximum likelihood (ML). And divergence times were estimated in BEASTv 1.7.4 with BI method. Our main results as follow:Section Microphyllae is not a monophyletic group. R. praelucens is sister to R. macrophylla and R. moyesii, which come from sect. Cinnamomeae DC. R. ×sterilis consists of a clade with R. longicuspis, wbich is belong to sect. Synstglae DC.. R. roxburghii constitutes a clade with its forms, but barely get a distinct discrimination with each other base on molecular data. Our nuclear gene trees are inconsistent with chloroplast genes tree for topological structure infers that hybridazation and gene introgression exist in genus Rosa.R. ×sterilis is a natural hybrid species. During its speciation, Anshun and Xingren in guizhou province is the hybrid zone, the hybridization event took place about 2.75Ma, Furthermore, R. longicuspis and R. roxburghii played role in maternal parent and paternal parent respectively during the hybrid speciation. R. praelucens has a complicated speciation, probably happened one or more hybridization event(s) with polyploidization during its evolutionary history, those genetic ingredient come from cect. Cinnamomeae, sect. Pimpinellifoliae DC. and sect. Microphyllaetake part in its speciation. R. praelucens has as a same maternal lineage with R. moyesii and R. macrophylla, and R. roxburghii is one of its parents. The origin time of R. roxburghii is about 12.25 Ma, and had occurred intraspecific differentiation event about 5.19Ma. For 3.07 Ma, R. praelucens and R. roxburghii were isolated by the rapidly uplift of Tibet plateau, distributed in high altitude area and law altitude area respectively, and occupied difference ecological niches finally.