Intercropping functionally similar species reduces yield losses due to herbivory: A meta-analytical approach

Abstract

Agroecosystem diversification is often implemented to diminish herbivory and reduce yield losses. However, increasing plant richness does not always reduce herbivory levels, so there is a need for better understanding which polyculture characteristics are effective in deterring herbivores. Here, we evaluated the hypothesis that functional and phylogenetic distances between intercropped species reduce herbivory pressure and enhance natural enemy response. Diminishing herbivory would be brought about by the complementarity and synergy of traits that deter herbivores and benefit herbivore natural enemies, and as a result of a decrease in the availability of host plants for specialized herbivores. Using a meta-analytical approach, we observed lower herbivore abundance and herbivory damage in focal plants when they grew in polycultures. In addition, polycultures showed increased levels of herbivore parasitism and greater abundance of predators and parasitoids, although the effect of the latter two was negligible. Interestingly, the functional distance between crops affected herbivore abundance and herbivory damage in opposite ways, but had no effect on herbivore natural enemy response. Contrary to our expectations, neither herbivory pressure nor natural enemy response appeared to be influenced by phylogenetic distance between intercropped species. Overall, our study provides valuable insights for agroecosystem design aimed at reducing yield loss by strategically intercropping functionally similar species.