Study On The Phylogenetic Diversity Pattern And Assembling Mechanism Of The Plant Communities In Limestone Cave Habitats In Guangxi

Community assembling or the formation and maintenance of species diversity in a community,has always been making the core issue of community ecology research.As a special habitat,cave is an ideal natural experimental field for studying plant communities.In this study,methods from community phylogenetics were used to explore the diversity patterns and species coexistence mechanisms of the plant communities in the limestone caves in Guangxi.All vascular plant species were sampled in and out of 23 karst caves in Guangxi and one karst cave in Guizhou,and then the phylogenetic diversity patterns of these communities were studied using DNA barcode sequences.At the same time,the differences of the results between by using Phylomatic method and by DNA barcoding method were compared.Finally,the correlations between the phylogenetic structure of the communities and rainfall,temperature and altitude,respectively,were explored.The results are as follows:(1)The species richness of the community inside the cave is lower than that outside the cave,and the phylogenetic diversities are positively correlated with the species richness regardless of inside or outside the caves.(2)The phylogenetic indices(NRI)of the cave communities in the large-scale species pool showed a random phylogenetic structure,and NTI showed an aggregation of the phylogenetic structure of the cave communities.The phylogenetic indices NRI and NTI of the cave communities were random in the small-scale species pool.(3)DNA barcoding could obtain more accurate and precise community phylogenetic relationships,furthermore,the selection of rbcL+matK+trnH-psbA super matrix is more advantageous than the single-gene matrix or two-site combined matrix for species identification and differentiation of closely-related species.Moreover the Phylomatic method was less accurate and precise,which seemed to be only suitable for being as the approximation in rough studies.(4)From the perspective of ecological and environmental factors,the influence of rainfall on the community structure inside and outside the caves is consistent.With the increase of rainfall,the phylogenetic structure of the communities inside and outside the caves showed a variation trend from phylogenetic clustering to overdispersing or thedegree of phylogenetic clusering decreased.Both temperature and altitude have different effects on the phylogenetic structure of the communities inside and outside the caves.Temperature had no significant effect on the phylogenetic structure of the plant communities inside the caves,and the phylogenetic structure of the communities outside the caves showed a trend from phylogenetic oversdispersing to clustering with the increase of temperature.The effect of altitude on the community structure inside and outside the caves is opposite to that of temperature,the phylogenetic structure of the community inside the caves showed a trend from phylogenetic oversdispersing to clustering with the increase of altitude,while the phylogenetic structure of the community outside the caves showed a trend fromphylogenetic clustering to overdispersing with the increase of altitude.