Phylogenetic Diversity Patterns Of Plant Communities In Different Habitats In Alpine Zone Of Hengduan Mountains

In recent years,more and more studies on plant community ecology have taken into account the evolutionary history of species,i.e.phylogenetic relationships.Hengduan Mountains is one of hotspots of biodiversity in the word.Taking Baima Snow Mountain as an example,the phylogenetic tree of 54 species in plant communities of different habitats along the elevation gradient of Baima Snow Mountain was constructed by APG III system.The richness index,species diversity index and phylogenetic relationship index(NRI and NTI)of related species were calculated and analyzed by R software.We were used to analyze the changes of phylogenetic structure and phylogenetic diversity of plant communities in different habitats in the alpine zone of Baima Snow Mountains,and to analyze the causes of the changes and the maintenance mechanism.The main conclusions are as follows:1 Phylogenetic structure of plant communities in the alpine zone of Baima Snow Mountains along the altitude gradient and change patterns in different habitatsIn this study,NTI,which is more sensitive to explaining the phylogenetic structure of alpine plant communities,was used to characterize the phylogenetic structure of alpine plant communities in Baima Snow Mountain.Phylogenetic structure of alpine plant communities in Baima Snow Mountain is aggregated at relatively low altitude(below 4500 m,alpine meadow,alpine shrub and screes bottom side).The main synergistic effect among species is shown.With the increase of altitude,the phylogenetic structure tends to be random.At relatively middle altitude(4500m-4600 m,screes,cliff),the plant communities in Baima Snow Mountain are aggregated at relatively low altitude(4500m-4600 m,screes,cliff).Phylogenetic structure is divergent and competition is dominant among species.As altitude continues to rise,the phylogenetic structure of plant communities in the alpine zone of Baima Snow Mountain tends to be random from divergence to higher altitude(more than 4600 m,the top of screes and the edge of cliff),and the phylogenetic structure of plant communities in the Alpine zone of Baima Snow Mountain tends to aggregate again,and the main relationship among species is cooperation again.In alpine meadow habitats,the phylogenetic structure gathers,the degree of aggregation increases with the increase of coastal altitude,and the relationships among species are getting closer and closer.The phylogenetic structure tends to be random in the habitat of the screes.The randomness of altitude increases,and the randomness of relationship among species increases.In cliff habitats,the phylogenetic structure tends to diverge,the degree of divergence decreases or tends to aggregate with the increase of coastal altitude,and the degree of sparseness among species decreases.2 Phylogenetic Alpha diversity patterns of plant communities in alpine zone of baima Snow Mountain in different habitatsIn this study,two phylogenetic relationship indices and two phylogenetic distance indices were used to characterize the phylogenetic Alpha diversity patterns of plant communities in different habitats in the alpine zone of Baima Snow Mountain.NRI showed a downward trend in the screes habitat along elevation gradient,and an upward trend in the alpine meadow and cliff habitat.NTI increased with altitude in all habitats.MPD and NTD decreased with altitude in all habitats.3 Phylogenetic Beta diversity patterns of plant communities in alpine zones of Baima Snow Mountain in different habitatsIn this study,two phylogenetic distance indices and Phylo Sor index of phylogenetic Beta diversity were used to characterize the variation pattern of phylogenetic Beta diversity in different habitats along vertical and horizontal directions in the alpine zone of Baima Snow Mountain.In the vertical direction,the two phylogenetic distance indices MPD,MTD and Phylo Sor index of phylogenetic Beta diversity were not significantly decreased with the increase of altitude difference in alpine meadow habitats.In the screes and cliff habitats,MPD,NTD and Phylo Sor index of phylogenetic Beta diversity increased with the increase of altitude difference,while phylogenetic Beta diversity increased with the increase of phylogenetic Beta diversity.Vertical direction showed an increasing trend.Horizontal,except Phylo Sor index of phylogenetic Beta diversity in alpine meadow habitats,MPD,NTD and Phylo Sor index of phylogenetic Beta diversity in all habitats increased with the increase of geographical distance.Habitat filtration,diffusion restriction and competitive exclusion together form the causes and maintenance mechanism of phylogenetic diversity pattern of plant communities in Baima Snow Mountain alpine zone.At relatively low altitude(below 4500m),alpine meadow,alpine shrub and bottom of screes dominate the role of habitat filtration;at relatively middle altitude(4500m-4600 m,screes and cliff)the dominant role of competitive exclusion;at higher altitude(above 4600 m,the top and edge of screes)the role of habitat filtration is stronger than that of competitive exclusion.Diffusion restriction is the cause and maintenance mechanism of phylogenetic Beta diversity pattern in different habitats.