Studies On Phylogenetic Diversity Of Bryophytes In Zhoushan Archipelago

Zhoushan islands,the largest coastal archipelago in China,are the first prefecture-level administrative division based on archipelago.Zhoushan archipelago has a land area of 1440.2 square kilometers with a total of 1390 islands.It is located in the East China Sea,between 121°30'?123°25' East Longitude and 29°32'?31°04'North Latitude.Zhoushan archipelago has a subtropical monsoon climate,warm in winter and cool in summer,with sufficient sunlight and abundant bryophyte resources.In this research,66 islands were selected including Zhoushan island,Liuheng island,Jintang island,Daishan island as the studying area,used ecological and molecular biological methods to analyse the phylogeny of bryophytes in this area,the following results were obtained:1.The phylogenetic trees were established based on ITS2(Internal transcribed spacer),trnG(trnA(Gly)(UCC))and trnL-F(cpDNA trnL-trnF intergenic space sequence)gene sequences respectively and the phylogenetic diversity index of 66 islands in Zhoushan Archipelago was calculated.The phylogenetic diversity of bryophytes increased along with the increasing diversity of species,but the increase rate of phylogenetic diversity was different based on the different gene sequences.The growth rate of trnL-F was the slowest,while the growth rate of ITS2 and trnG were basically the same.2.The phylogenetic diversity of bryophytes increased along with the increasing elevation,coastline length,area of island and habitat diversity,the r values of linear models were all higher than 0.78.MMF model was the most suitable model for the relationship between elevation,coastline length and phylogenetic diversity of bryophytes,the formulas were PD=(5.97×105+5.725×(Ele)2.73)/(1.04×106+(Ele)2.73)and PD=(1.44+11.4×(Cos)0.6)/(4.6+(Cos)0.6)respectively.The most suitable model for the relationship between island area and phylogenetic diversity of bryophytes was the Quadratic model:PD=2.031+0.597 In(Are)+0.054 In(Are)2,and there was a clear inflection point in the figure that indicated the possibility of a small island effect.The most suitable model for the relationship between habitat diversity and phylogenetic diversity of bryophytes was the Harris model:PD=1/(10.32-8.59HD0.054).3.Single inflection point of piecewise regression function was fitted to show the relationship of the phylogenetic diversity of bryophytes based on ITS2,trnG and trnL-F gene sequences and island area respectively.The obtained AIC values were all lower than the linear regression.Applied the double inflection point of piecewise regression function to fit the relationship of bryophyte phylogenetic diversity and island area,AIC value indicated that double inflection point of piecewise regression was more fitted than single's.There were two area thresholds,before the first area of threshold,bryophytes phylogenetic diversity did not change significantly with the increasing of island area,however,increased with the increasing island area after the first threshold area,and the velocity quickened significantly after second threshold area.We continued to use single inflection point and double inflection point piecewise regression functions to fit the relationship between mosses,acrocarpous mosses,pleurocarpous mosses and island area based on ITS2 gene sequence.The results showed that there existed small island effect for mosses and acrocarpous mosses,and the fitting effect of double-inflection point piecewise regression function was better than the single-inflection point piecewise regression function.4.The relationship between the habitat diversity and phylogenetic diversity was similar to the small island effect,and the threshold of the quantity of habitats was 18.