The effect of multiple natural enemies on a shared herbivore prey

1. Natural enemy diversity is thought to be important for effective suppression of herbivores in production systems. Studies investigating the importance of the diversity and composition of the natural enemy complex often use within year empirical studies or experimental exclusion set-ups. 2. However, within year population suppression might not translate in long term population regulation. Therefore, I used a combination of long-term data collection and an exclusion experiment to investigate mechanisms behind year-to-year population changes and potential effects of disturbance of the natural enemy complex. 3. Using the holly leaf miner study system in Wytham woods, I find that the dominant predator in the system does not necessarily contribute the most to the reduction in year-to-year changes in mine density or within-patch fluctuations. Using the exclusion experiment, it becomes clear that parasitism later in the prey life cycle, can to a certain level compensate for disruption of mortality in the earlier life stage of the prey. 4. Thus, for host suppression in perennial systems the mortality pressure over the whole the life-cycle is important and disturbance during one part of the life cycle might not necessarily be buffered by mortality in other parts of the life cycle, especially if the natural enemy complex consists of multiple predator guilds.