Effect of defoliation on leaf growth, sexual expression and reproductive success of Cnidoscolus aconitifolius (Euphorbiaceae)

Several studies on herbivory have shown that plants may have different responses to foliar damage. Most studies have been done using hermaphroditic species, here we present, using a defoliation experiment, different types of response to foliar damage by the monoecious Cnidosculus acontifolius. We evaluated four treatments: natural herbivory (control), and 25%, 50% and 100% artificial defoliation. The results suggest that this species is capable of showing the following compensatory responses: (a) undercompensation in total production of flowers and in fruit set (damage > 25%); (b) full compensation in seed weight (all levels of damage); and (c) overcompensation in leaf growth and in the proportion of female flower production (damage greater than or equal to25%). The results show that C. aconitifolius can exhibit a very fast and plastic response depending on the intensity of damage and the time since defoliation. The increase in foliar growth suggests a long-term tolerance response to hervibory, whereas the change in the proportion of female flowers produced does not appear to have a long-term effect due to the decrease of fruit production in all levels of damage. We suggest that the response in foliar growth and the change in sexual expression by C. aconitifolius, are associated with the high resource availability conditions prevalent in the population studied.