Preliminary Phylofloristic Analysis Of Seed Plants In Yulong Snow Mountain

Traditionally,floristics attempts to explore the origin and evolutionary history of floras based on the analysis of the areal-types of taxa and their distributions,mostly without take the phylogenetic relatedness into consideration.The phylofloristics is combination of phylogeny and floristics to address the evolutionary history and distributional patterns at temporal scale based on the divergent time and evolutionary rate,and the spacial patterns of phylogenetic diversity and distribution of the flora.In this study,we investigated the floristics of Yulong Snow Mountain by using the traditional analysis of floristics and phylofloristics.First,we integrate the available data to generate a species database of Yulong Snow Mountain,and then delineated their altitude distribution in Yulong Snow Mountain based on the information from specimen records and related literatures.We then constructed the mega-phylogenetic tree of the floras using the four DNA barcodes(rbcL,matK,trnH-psbA and ITS)and Phylomatic,respectively,The divergent times of main nodes(family,genus)of the flora were estimated with 42 fossil records used for calibration in TreePL.We analyzed the origin of taxa based on the phylogenetic tree and the areal-types of flora to address the mean divergent time of main groups,patterns of species diversity(SD),phylogenetic diversity(PD),and species richness along elevation of Yulong Snow Mountain.We also compared the effect on phylogenetic diversity and structure(eg.NRI and NIT)between the two methods for mega-phylogenetic tree construction.The main results and conclusions were summarized as follows.According to the demarcation of area-types for family and genus of Wu CY,the origin of Yulong Snow Mountain flora is mainly temperate.The proportion of tropical elements is larger than temperate elements at family level.While,the origin of genera in the flora is mainly temperate with significant phylogenetic signal,out of which the genera belonging to North temperate,East Asia and Pantropic areal-types showed relative high proportion.Results of PD indicated that the taxa endemic to China diverged very early in the flora.The elevational patterns of SD and PD of elements with various origin are different.The tropical origin taxa usually occurred with the peak of SD and PD at low elevation.Whereas,the SD peak of the world widespread genera emerged at higher elevation,and the temperature genera had the highest PD.The species diversity showed a single peak distribution pattern along the elevation with the SD peak at around 3000 m above sea level.Species richness for different life-forms exhibited similar pattern,but SD peak occurred at different elevations: herb = tree > shrub > liana.Compared to the phylogenetic tree on Phylomatic,the phylogenetic tree of the flora based on four DNA barcodes built here showed consistent phylogenetic relationships of APG classification and 59% nodes with bootstrap value more than 50%,and 40% nodes above 80% support.The distributional pattern of PD and SD along the elevation gradient based on the phylogenetic tree by Phylomatic and DNA barcoding data are similar but difference.The elevation of the PD peak is less than that of the SD peak.Phylogenetic structure of species at high elevation was clustered(both NRI and NTI index are positive)and around 4000 m having the highest clustered structure,suggesting that environmental filtering at the high elevation may play the most important role on species distribution.Whereas,phylogenetic structure at low elevation is overdispersed,indicating that the competition among species plays a leading role.The phylogenetic tree based on DNA barcodes is much more resolved than that on Phylomatic.Based on the divergent time estimated,most nodes of the flora diverged within 50 Ma(million years ago),and the mean divergent time of genera above 3000 m less than 10 Ma.The age of the flora is relative young and the species divergent time deceased along the elevation of Yulong Snow Mountain which may be some taxa evolved to adapting the new habitat at high elevation with the uplift of Hengduan Mountains.The results in this study support the hypothesis of tropical niche conservative.