Indirect facilitation by leaf-rolling caterpillars on arthropod communities in different scales

Background/Question/Methods

Ecosystem engineering is a process by which some organisms change the distribution of resources, creating new habitats for other species via non-trophic interactions. Leaf-rolling caterpillars can act as forest ecosystem engineers because they may modulate interactions in arthropod-plant communities by providing shelter secondary users, which can indirectly influence the distribution pattern, abundance, and diversity of arthropods. In this study we reported the influence of leaf-rolling catterpillars on speciose communities of tropical arthropods along both spatial (i.e., leaf-level and plant-level effects) and temporal scales (i.e., dry and rainy seasons). We predict that rolled leaves can amplify arthropod diversity in both leaf and plant levels, and the strength of this effect is stronger in the dry season, in which the arthropods are more prone to desiccation. Moreover, shelter architecture (funnel and cylinder of different diameters) can affect arthropod abundance, richness and composition. In addition, plants bearing rolled leaves can intensify top-down trophic cascade by providing shelter for predators (e.g., spiders).

Results/Conclusions

Our results show that the abundance, richness and total biomass of arthropods within several guilds (i.e., predators, herbivores, parasites, detritivorous and omnivorous) were higher on naturally and artificially created leaf shelters than unaltered leaves. These effects were observed in both leaf and plant scales, in similar magnitudes. Overall, variation in shelter architecture did not influence arthropod biomass, abundance and richness. However, shelter shape affected community composition at leaf- and plant levels. As expected, arthropod abundance and biomass on plants bearing curled leaves were higher in the dry season, suggesting that these structures can be suitable shelter for arthopods during harsh environmental conditions. This study is the first to examine the extended effects of engineering caterpillars as diversity amplifiers in different temporal and spatial scales. Since shelter-building caterpillars are ubiquitous organisms in tropical forests, their effects may be more common than previously thought. Thus, they can be considered as fundamental elements in community structure of arthropods on plants in the tropics.

Financial Support: FAPESP, Process 2008/52380-3