Ecological and evolutionary drivers of plant community assembly in a Bornean rain forest

The aim of this thesis was to examine the ecological and evolutionary drivers of plant community assembly in three floristic associations of tropical lowland rain forest that co-vary with a localised gradient of resource availability. I described the diversification of taxa into three communities, and assessed the evolutionary lability and functional significance of the traits of shade-tolerant habitat specialists. The three communities are structured by divergence events that occurred approximately 100 Mya, with taxa at all taxonomic levels expressing distinct habitat preferences. The communities exhibited different patterns of phylogenetic structure: random in the alluvial forest, clustered in the sandstone forest, and overdispersed in the heath forest. Analyses of community niche use confirmed that competitive interactions were prominent in the heath forest, and ecological filtering in the sandstone and alluvial forests. By investigating the mechanisms of ecological filtering in the alluvial and sandstone communities, a functional reinterpretation of the ‘worldwide leaf economics spectrum’ (WLES) was offered. Mean leaf trait values varied between habitat specialists as predicted by the WLES, with divergent resource-use strategies evident. However, the relative importance of traits clearly differed between the local and global WLES datasets, as growth rate was maximised by species growing in light, whereas light capture was prioritised by shade-tolerant species. Habitat-mediation of traits revealed different strategies of resource capture and use. Taller stature species were associated with a higher investment in woody plant components, and a greater plasticity in physiological traits, that may convey a competitive advantage in the lighter upper-canopy layers. Overall, these results substantiate the importance of ecological filtering in influencing species coexistence and community assembly in tropical forests.EThOS - Electronic Theses Online ServiceGBUnited Kingdo