Successional dynamics of plant-herbivore food webs in a tropical montane forest. Yawan Plant Phylogeny

1- Food web studies along ecological gradients provide insight into community assembly and stability. Secondary succession is well understood, to the point of being predictable for plant communities, but the successional dynamics of plant-herbivore food webs remains poorly explored. This is particularly true for tropical forests, despite the increasing importance of early successional stages in tropical landscapes.2- We examine the network and phylogenetic structure of plant-herbivore food webs and their dynamics along a succession series in montane rainforest in Papua New Guinea. We present one of the most comprehensive successional comparisons of food webs, and one of the few focused on montane tropical forests. 3- We use a series of nine 0.2ha whole forest plots across young secondary, mature secondary or primary forest, sampled almost completely for woody plants and larval leaf chewers (Lepidoptera), using destructive forest felling. Plant-herbivore interactions were analysed using quantitative network parameters, traditional and phylogenetic host use measures and recently developed beta diversity approaches.4- Network structure was largely constant across all three succession stages. Contrary to expectations, specialised use of resources was similar throughout succession, even decreasing slightly in primary forest. This may be explained by host plant phylogenetic diversity, which also unexpectedly decreased in primary forest relative to earlier succession stages, with local host use analyses confirming most herbivores specialise on the level of host genus in our system. High beta diversity was found between all plots, and was driven primarily by interaction turnover.5- Secondary forest is capable of rapidly re-establishing primary-like food web properties post disturbance. Further, all succession stages can harbour diverse and unique interaction networks, with network structure remaining relatively invariant despite high turnover of its components.