Patterns of species richness and beta diversity of vascular plants along elevation gradient in Brazilian páramo

Understanding the relationships between plant diversity and the environment is an important step towards conservation of species and ecosystems.In this study,we hypothesize that community species richness decreases and species composition change along the elevation gradient,with a greater contribution of species turnover than nestedness to beta diversity.We surveyed plant species in 300 plots(1 m×1 m)in four elevational bands(2100 m,2300m,2500 m,and 2700 m)in the CaparaóNational Park,Southeastern Brazil.The samples presented a great number of species(97 spp.,59 genera,27families),however,74%of the species were considered rare with their relative abundance being<1%.Among the four bands along the gradient,we detected two distinct communities with few species in common.The transition between the two communities occurred at 2500 m,and this elevation band also had the highest species richness in total.A non-metric multidimensional scaling(NMDS)showed floristic differences between the bands even though they had similar richness.In 89%of the plot pairs,using pairwise comparison of species composition,only half of the species that occurred in one did occur in the other plot.The dissimilarity among the plots and elevational band reflects a significant contribution of spatial species turnover to the species richness and beta diversity on the Caparaómountain.Beta diversity increased with spatial scale(from plot to elevational-band).The dissimilarity(βSOR=0.907)in the area was due almost exclusively to spatial species turnover(βSIM=0.879),with very low contribution of species nestedness(βSNE=0.028).Our research showed that species richness does not decrease with elevation in the study area,but the floristic composition changes.The clear distinction of species along the gradient show that spatial species turnover is the major diversitygenerating process in the studied area.