Indirect effects of ecosystem engineering by insects in a tropical liana

Insects might impact communities and ecosystems through processes that are not trophic, via ecosystem engineering. In this study, we experimentally evaluated the role of the caterpillars Pandemis sp. as habitat modifiers in the tropical liana Trigonia rotundifolia. Specifically, we examined their effects on the abundance and richness of arthropods that secondarily colonize leaf-rolls (shelters) built by the caterpillars, as well as indirect effects that influence plant herbivory. Two experiments were conducted in the field to evaluate the role of natural and artificial rolls on community structure and plant damage. Plants with artificial leaf-rolls hosted 2.2 times more arthropods than plants without shelters and they had 1.5 times higher richness compared to control plants. Plants with natural shelters exhibited significantly lower arthropod richness than plants with artificial shelters or control plants, but arthropod abundance did not differ among treatments. Although plants with leaf-rolls hosted significantly more arthropods, arthropod species composition did not differ amongst treatments, as Formicidae was the most frequent group in all treatments. Herbivory was almost 3 times higher in plants with leaf-rolls compared to plants with no rolled leaves, indicating that the effect of increased arthropod abundance, and especially herbivore abundance, might influence leaf damage in plants with leaf-rolls. We demonstrate the strong impact of Pandemis as a habitat modifier on community structure as well as on community processes through indirect effects.