Bottom-up effects from host plants and top-down effects from predators on herbivore abundance and distribution vary with physical environment, plant chemistry, predator and herbivore trait and diversity. Tri-trophic interactions in tropical ecosystems may follow different patterns from temperate ecosystems due to differences in above abiotic and biotic conditions. We sampled leaf-chewing larvae of Lepidoptera (caterpillars) from a dominant host tree species in a seasonal rainforest in Southwest China. We reared out parasitoids and grouped herbivores based on their diet preferences, feeding habits, and defence mechanisms. We compared caterpillar abundance with leaf numbers (‘bottom-up’ effects) and parasitoid abundance (‘top-down’ effects) between different seasons and herbivore traits. We found bottom-up effects were stronger than top-down effects. Both bottom-up and top-down effects were stronger in the dry season than in the wet season, which were driven by polyphagous rare species and host plant phenology. Contrary to our predictions, herbivore traits did not influence differences in the bottom-up or top-down effects except for stronger top-down effects for shelter-builders. Our study shows season is the main predictor of the bottom-up and top-down effects in the tropics and highlights the complexity of these interactions.

Lepidopteran herbivore data for Parashorea chinensis saplings were collected by visual in late October to November 2019 (cool season) and late April to May 2020 (hot season). Each sampling was carried out in three close sub-sites (WTS, BB, CTFS). Sampling was carried out and recorded in "sampling units" (an area within ~2 m radius of the person sampling at a given sampling point). During each sampling, caterpillars were collected and reared in the lab to adults or parasitoids, and the number of leaves in the sampling units was also recorded. More details about sampling design and methodology can be found in the associated study. 

Microsoft Excel