A multi-functional approach to assessing species interactions in human-modified tropical landscapes

Tropical land-use change via rainforest degradation and agricultural expansion is driving a global extinction crisis. Understanding community dynamics, functional diversity (FD) and species interactions in relation to these land-use changes is essential to both conservation actions and ecological theory. Landscapes are altered at multiple scales, and the changing landscape mosaic impacts biodiversity and in turn potential functional processes and ecosystem services (or dis-services). I use field data combined with functional and modelling statistical approaches, and primarily examine dung beetle communities, but also use bird and ant assemblages to compliment my investigations. I study these communities across a land-use gradient of primary rainforest, selectively logged forest, and adjacent oil palm plantations in Malaysian Borneo.

Logging caused significant shifts in community composition but FD of dung beetles and birds was at similar levels compared to primary rainforest. Along logging roads edge effects penetrated 100m into the logged forest interior, with significant declines in species richness, abundance and biomass with increasing proximity to road edges, and a marked change in species composition. Logged forest communities were predominately randomly assembled across three taxonomic groups, with a strong influence of dispersal assembly for dung beetles. The conversion of forest to oil palm, however lead to a significant reduction in FD, greater influence of habitat filtering in the assembly of dung beetle communities, and significant segregation in dung beetle and bird community assembly. The extent of forest cover and proximity to forest were not significant predictors of oil palm yield.

Understanding the stability and resilience of FD and the dominant assembly processes emphasises the high value of logged forests as refugia for biodiversity. Nevertheless, better landscape design practices for forestry, specifically road planning, and in-situ habitat conservation within plantations is strongly encouraged. Critically a functional approach to land-use change gives conservation a complete and practical focus.