The latitudinal distribution patterns of spermatophyte floristic elements in Yuanjiang River Basin

In this study,based on the species distribution information and floristic elements information at large-scale,coupled with the bivariate correlation analysis,we probed into the overall composition of spermatophyte flora components and latitudinal patterns of the spermatophyte flora in Yuanjiang River Basin.The results showed that the study area had a total of 5149 seed plant species,belonging to 241 families,1585 genera.The study area was one of the important distribution centers of some important families and genera in Yunnan,and even in China.At family level,the Pantropical elements(T2) accounted for the largest proportion(45.4%).The secondary was the World distribution elements(T1)(22.4%).At genus level,the most important elements were Tropical Asian elements(T7)(23.2%) and the Pantropical elements(T2)(18%).Both at families and genera level,the tropical elements accounted for around 70% of the total,whereas the temperate elements accounted for about 30%,showing strong characters of tropical flora.It may be related to the geographical and biogeographical locations of the study area.The results also showed that with the increase of latitude,the tropic floristic elements presented a decreasing trend,whereas the temperate elements increased,which may be linked with the environmental gradient on latitudinal gradient.At the same time,it also may be related to the channel effectof Yuanjiang River basin in flora migration process.