Title: Effects of resource availability on tolerance of herbivory in the invasive Alternanthera philoxeroides and the native Alternanthera sessilis
Abstract: Resource availability is known to affect herbivore selectivity and the ability of plants to respond to herbivores. However, little information is available for the performance of invasive plants subject to insect herbivory and limited resources availability. We conducted a glasshouse experiment using both the invasive Alternanthera philoxeroides and its native congener Alternanthera sessilis, to compare the effects of resource availability on plant tolerance to herbivory. The results suggest that water availability affects plant tolerance to herbivory, such that stressful water conditions promoted greater herbivore tolerance for A. philoxeroides and decreased herbivore tolerance for A. sessilis. The addition of fertiliser also affected the plant’s ability to respond to herbivory. Fertilised plants of both species generated more biomass and had greater tolerance to herbivory than unfertilised plants. Adding fertiliser appeared to increase the compensation capacity to herbivory for A. philoxeroides. In unfertilised conditions, moisture had no effect on A. philoxeroides tolerance to herbivory, and plants performed better under drought conditions. The results of this study may help to further our understanding of why biological control efforts against A. philoxeroides have been successful in some aquatic environments, but not others. Our study suggests that control of A. philoxeroides in high-moisture and nutrient poor environments should be more effective than control under nutrient rich and low-moisture soils. Understanding the mechanism of invasive plant compensation under different environmental conditions will be important for improving and predicting management efficiency. [SUN, Y., DING, J. and FRYE, M. J. , Effects of resource availability on tolerance of herbivory in the invasive Alternanthera philoxeroides and the native Alternanthera sessilis. Weed Research, no. doi: 10.1111/j.1365-3180.2010.00822.x]