Tropical forest loss and its multitrophic effects on insect herbivory

Area of Science:

• Ecology
• Tropical Ecology
• Conservation Biology

Background:

• Forest loss impacts biodiversity and ecological interactions, particularly insect herbivory.
• Determinants of insect herbivory in altered tropical landscapes remain unclear.
• Insect herbivory is influenced by bottom-up (resource availability, plant defenses) and top-down (predator-prey) forces.

Purpose of the Study:

• To assess the direct and indirect effects of forest loss on insect herbivory.
• To investigate the role of forest structure, predator abundance, and herbivore abundance in mediating these effects.
• To understand multitrophic interactions in human-altered tropical ecosystems.

Main Methods:

• Utilized structural equation models to analyze data from 40 landscapes in the Brazilian Atlantic rainforest.
• Examined forest cover as an exogenous predictor and forest structure, predator abundance, and herbivore abundance as endogenous predictors.
• Quantified insect leaf damage as the primary response variable.

Main Results:

• Leaf damage significantly increased with forest loss, both directly and indirectly through vegetation simplification and increased herbivore dominance.
• Eleven out of twelve predicted pathways were significant, highlighting complex relationships.
• Demonstrated a lack of effective top-down control of herbivores by predators (birds and arthropods).

Conclusions:

• Forest loss favors insect herbivory by weakening bottom-up control, likely due to reduced plant defenses in pioneer species.
• Altered forest structure and increased herbivore proliferation contribute to enhanced herbivory.
• Findings underscore the vulnerability of tropical ecosystems to habitat alteration and its consequences for ecological interactions.