Understanding the mechanisms underlying community assembly and species co-occurrence is a continuing topic of debate in ecology. Ecologists are using functional and phylogenetic approaches to quantify the relative importance of stochastic, abiotic filtering and biotic filtering processes shaping the pattern of species co-occurrence. A remaining challenge in functional and phylogenetic analyses of tropical tree communities is to successfully integrate the functional and phylogenetic structure of these communities across spatial and size scales and habitats in a single analysis of an assemblage.
Prof. CAO MIN and his team of Xishuangbanna Tropical Botanical Garden (XTBG) performed a study in the 20-ha Xishuangbanna forest dynamics plot (FDP) located in Yunnan Province, southwest China (21°37′08″ N, 101°35′07″ E).They analyzed the functional and phylogenetic structure of tree assemblages in the plot. They addressed the following questions: (i) Do functional traits have phylogenetic signal in that diverse tropical tree community? (ii) Do measurements of phylogenetic signal in trait data underlie the similarity or dissimilarity in the patterns of functional and phylogenetic dispersion in that forest? (iii) Does the functional and phylogenetic structure of assemblages vary across size classes, and is that consistent across the six spatial scales and the six habitat types?
They performed their analyses across three size classes (1-5 cm, 5-15 cm, and 15 cm and above), six spatial scales (5 m× 5 m, 10 m × 10 m, 20 m × 20 m, 25 m × 25 m, 50 m × 50 m and 100 m × 100 m) and six distinct habitat types (valley, low-slope, high-slope, high-gully, high-plateau and forest gap), using 10 plant functional traits and a molecular phylogeny for the > 400 tree taxa found in the plot.
Both phylogenetic and functional dispersion across size classes, spatial scales and habitats provided strong support for a deterministic model of community assembly rather than for a neutral model. Their results demonstrated that functionally similar species co-occur across spatial and size scales and habitats in the Xishuangbanna FDP indicating the importance of abiotic filtering governing the assembly process. The results also supported the hypothesis that abiotic determinism is more important at larger scales while biotic determinism is more important on smaller scales within habitats.
The study entitled “Functional and Phylogenetic Assembly in a Chinese Tropical Tree Community across Size Classes, Spatial Scales and Habitats” has been published online in Functional Ecology.