Large-scale destruction or human-induced disturbances often damage severely the aboveground plant parts. Consequently, plants may have their morphological, phenological and structural traits modified. Such changes may enhance plant susceptibility to herbivores and their natural enemies. Abiotic factors, such as nutrients, may also exert an important role in influencing the second and third trophic level. This study aims to evaluate insect community responses to changes in plant traits within a naturally occurring population of Chromolaena pungens (Asteraceae). We carried out an experiment to test the hypothesis that plant resprouting indirectly promotes bottom-up effects cascading up to higher trophic levels. In particular, we evaluate how clipping and nutrients influence: (i) the vegetative and reproductive traits of plants; (ii) the abundance of galls, leaf-chewers and sap-suckers; (iii) the incidence of their predaceous arthropods; (iv) the species composition, richness, diversity and abundance of the endophagous insects associated with flower heads; and additionally, (v) the incidence of their parasitoids.

Results/Conclusions

The results indicated that clipping promoted changes in plant morphological, phenological and physical traits. Plants that resprouted after clipping were shorter and their leaves were larger and had higher water content and specific leaf area. These plants produced fewer and larger flower heads than those produced by partially clipped and unclipped plants. Changes in plant traits modified the insect community structure associated with C. pungens. In resprouted plants, achene predation and the abundance, richness and diversity of flower head endophages increased, and herbivore species composition was altered. The number of galls decreased on resprouted plants, whereas the abundance of sap-sucking and leaf-chewing insects was not affected. Moreover, leaf consumption was almost 4 times higher on resprouted plants. The incidence of predators and parasitoids were also influenced by the treatments, but in a less pronounced way. Predaceous arthropods were more commonly recorded on resprouted plants, and the parasitism rate of flowerhead endophages was influenced by the interactions between clipping and nutrient. Our findings provide a clear experimental demonstration that plant damage, contingent on nutrient availability, can considerably affect the incidence and effects of second and third trophic level organisms, and thus contribute to understanding the effects of disturbances on insect-plant interactions.