The Circumscription Of Genus Sibbaldia In China And The Phvlogeographical Study Of Sibbaldia Procumbens S.l.

Accurate species delimitation is the basis for almost all the biological research that related to biodiversity.The genus Sibbaldia belongs to Potentilleae,Rosaceae,which is mainly distributed in alpine mountains of North Hemisphere,there is a complex classification existed in the genus,especially in the broadly distributed S.procumbens and its closely related species(e.g.S.procumbens var.aphanopetala,S.cuneata,and S.parviflora).Qinghai-Tibet Plateau(QTP)and its adjacent regions is one of the biodiversity hotpots in the world,in which the genus has a biodiversity center.However,the classification of the taxa especially those mianly distributed in the QTP are relatively confused.The type species S.procumbens having a wide Eurasia-North America disjunct pattern,which providing good materials for exploring the origin and dispersal route for Alpine herbs.For the delimitation of Sibbaldia,we combined the morphological characters and molecular data.Through extensive investigation to speeimen of herbaria and extensive sampling in field,the leaf and flowers morphological characters of the genus were measured and analyzed.Seeds were also collected for observation and comparison.Meanwhile,11 pairs of SSR primers which are easily amplified with high polymorphism were selected from the Fragaria,so as to investigate the population genetic structure and genetic component.Three chloroplast fragments(trnL+trnL-F,atpI-atpH)were used to detect the phylogeographical pattern of S.procumbens and its relatives.We constructed the phylogenetic tree and made the haplotypes network.BEAST software was used to estimate the origin and diversification time of species.Ecological niche modeling was used to detect the suitable habitats of these species in different periods(including the Last maximum glacial,last interglacial,current and fifty years later).The main results as follows:In the integrated study to the taxonomy of the genus,we combined the seed surface texture and the morphological features of leaves with the SSR data.We proposed that:(1)The Chinese Sibbaldia consists of three species,namely S.procumbens,S.aphanopetala and S.cuneata.We proposed that S.parviflora may be equal to S.cuneata9 thus can be included by the latter.(2)The species S.procumbens mainly occurs in the high altitude areas.It has a disjunct pattern between Eurasia and North America.In China it is distributed in Changbai Mountains of Jilin province and few localities of Northwest of Xinjiang province.S.aphanopetala has a relatively narrow range that constricted in Hengduan Mountains of west southern China,with partial range expanding to QTR The leaves of the species are slender and its seeds are smoother without stripes compared with S.cuneata.The species S.cuneata is mainly distributed in western QTP and can extend to European Mediterranean.The leaves of S.cuneata are wider,and there are obvious stripes on the surface of seeds.(3)There is a significant stable correlation between SSR data and the morphological characters that examined.Our SSR analysis implied that weak gene flow can be detected between S.aphanopetala and S.cuneata,whereas obvious genetic differentiation existing within 5.aphanopetala.The phylogeographical analysis of S.procumbens and its allies implied that,(1)high genetic differentiation existed in the S.procumbens complex(Nst>Gst,P<0.01),and there were obvious phylogeographical structure;(2)The BEAST analysis revealed that Sibbaldia may have originated in late Miocene,with the divergence concentrated in Pleistocene of Quaternary,the origin of the taxa may have been influenced by the complicated climate and geological events.(3)The phylogeny tree and haplotype network suggested that the haplotypes in the southeast of Tibet and western Hengduan Mts.presented to be the earliest divergent clade,which has high haplotype diversity.We thus argue that the species may have originated in the location during Tertiary Miocene.During the period of global cooling,these species spread eastward,and consequently to North America via the Bering land bridge.Meanwhile,we suggested that,westward,it can migrate to North Europe along high mountains.Also,northward it can disperse to North America via the north Atlantic land bridge.Therefore,it can form a bidirectional migration route in the North hemisphere.(4)The ecological niche modeling implied that the species may have experienced expansion in the Last glacial maximum.The populations experienced shrink when climate became warmer.The predicted distribution range of the species complex in 2070 will constrict to narrow places of high mountain peaks of Qinghai-Tibet Plateau,along with the increasing global carbon dioxide concentration and the rising temperature,Alpine herbaceous are facing great challenges,which also providing suggestions and warnings for us in the field of species conservation and ecological environment protection.