Environmental filtering consistently shapes the functional and phylogenetic structure of species across space within diverse forests. In order to have a complete understanding of the underlying community assembly mechanisms, it is imperative to integrate traits, phylogenies, and the environment across the geological space. 

Prof. CAO Min’s team from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences analyzed the relationships between traits and environmental gradients in phylogenetic and spatial contexts in the 20-ha Xishuangbanna Forest Dynamics Plot in Yunnan province, southwest China. 

The researchers measured 11 plant functional traits (seed mass, maximum diameter at breast height, maximum height, wood resistance, leaf thickness, leaf area, leaf weight, leaf mass, specific leaf area, chlorophyll, and leaf dry matter content) and generated a molecular phylogeny for the 428 tree taxa in the plot. 

They used the ordination RLQ analysis 30 and its extended version18. They applied functional traits, phylogenetic, environmental, and spatial data to explore phylogenetically-based trait distribution patterns across an environmental gradient at four spatial scales (10 × 10 m, 20 × 20 m, 50 × 50 m, and 100 × 100 m). 

They detected environmental filtering at all spatial scales except 100 × 100 m, and the filtering considerably structured the functional strategies of lineages in a species-rich tropical rainforest. 

They also found that in general, spatial variation in soil nutrient availability determined the range of the ecological strategies of species. Species with high resource acquisition-related traits were primarily associated with the resource-rich part of the plot, whereas resource conservation functional traits were distributed in limited-resource environments. 

Furthermore, the researchers detected both phylogenetic and functional clustering at all spatial scales, implying that the observed distributions of traits and lineages in space were not the result of random assembly processes. 

Moreover, they found that both trait conservatism and trait convergence shaped the functional strategies of species, perhaps suggesting that the distribution of functional traits in space cannot necessarily be linked with the evolutionary distances of species. 

The research demonstrated that environmental filtering considerably structured the functional strategies of plants in the species-rich tropical rainforest of Xishuangbanna. 

The study entitled “Environmental filtering structures tree functional traits combination and lineages across space in tropical tree assemblages” has been published in Scientific Reports.