Phylogenetic patterns of shrub communities along the longitudinal and latitudinal gradients on the northeastern Qinghai–Tibetan Plateau

Biodiversity distribution patterns are a basic and long-standing but crucial aspect of ecology research.These patterns form the primary source of data used to develop biodiversity protection practices,especially in mountain ecosystems.Shrubs comprise one of the main types of vegetation on the Qinghai–Tibetan Plateau,where they serve vital ecological functions.In this study,we used a community phylogenetic approach to examine the distribution patterns of shrub communities along the longitudinal and latitudinal gradients on the northeastern Qinghai–Tibetan Plateau.We observed significant latitudinal trends in both the phylogenetic diversity(PD)and net relatedness index(NRI)values of shrub communities,such that the former decreased and the latter increased with increasing latitude.However,no significant PD,NRI and nearest taxon index(NTI)distribution patterns were observed along a longitudinal gradient.A further analysis revealed that the combination of temperature-related and precipitation-related climate variables most strongly affected the PD,NRI and NTI values of shrub communities,indicating that the latitudinal patterns in the PD,NRI and NTI of a shrub community may be determined mainly by interactions with these climate factors.

Phylogenetic structure and phylogenetic diversity of angiosperm assemblages in forests along an elevational gradient in Changbaishan,

Aims Understanding what drives the variation in species composition and diversity among local communities can provide insights into the mechanisms of community assembly.Because ecological traits are often thought to be phylogenetically conserved,there should be patterns in phylogenetic structure and phylogenetic diversity in local communities along ecological gradients.We investigate potential patterns in angiosperm assemblages along an elevational gradient with a steep ecological gradient in Changbaishan,China.Methods We used 13 angiosperm assemblages in forest plots(32×32 m)distributed along an elevational gradient from 720 to 1900 m above sea level.We used Faith’s phylogenetic diversity metric to quantify the phylogenetic alpha diversity of each forest plot,used the net relatedness index to quantify the degree of phylogenetic relatedness among angiosperm species within each forest plot and used a phylogenetic dissimilarity index to quantify phylogenetic beta diversity among forest plots.We related the measures of phylogenetic structure and phylogenetic diversity to environmental(climatic and edaphic)factors.Important Findings Our study showed that angiosperm assemblages tended to be more phylogenetically clustered at higher elevations in Changbaishan.This finding is consistent with the prediction of the phylogenetic niche conservatism hypothesis,which highlights the role of niche constraints in governing the phylogenetic structure of assemblages.Our study also showed that woody assemblages differ from herbaceous assemblages in several major aspects.First,phylogenetic clustering dominated in woody assemblages,whereas phylogenetic overdispersion dominated in herbaceous assemblages;second,patterns in phylogenetic relatedness along the elevational and temperature gradients of Changbaishan were stronger for woody assemblages than for herbaceous assemblages;third,environmental variables explained much more variations in phylogenetic relatedness,phylogenetic alpha diversity and phylogenetic beta diversity for woody assemblages than for herbaceous assemblages.