How is leaf herbivory related to agriculture? Insights from the Mexican center of crop origin

Abstract

Although insect herbivory is thought to be higher in agroecosystems compared to natural ecosystems, direct evidence on how agriculture itself has impacted herbivory remains scarce. To understand the effects of agriculture, or the cultivation of domesticated crops, over higher trophic levels, it is necessary to compare cultivated crops and their wild counterparts in centers of origin. In such regions, insect herbivores have a shared history of interacting with wild host plants prior to crop domestication and cultivation. However, most studies evaluating the impacts of agriculture on herbivory have been conducted in geographic regions where crops have been introduced. Here, we studied how insect herbivory is related to agriculture in Mexico, which is part of the Mesoamerican center of origin. We focused on patterns of leaf herbivory across four Mexican crops (squash, beans, maize, and husk tomatoes). We tested if total leaf herbivory, as well as the composition and dominance of different types of damage caused by leaf-feeding insects, differed between domesticated crops and their wild counterparts. Overall, we found that the relationship between agriculture and leaf herbivory depends on the observed crop. Compared to their wild ancestors (or wild relatives), leaf herbivory was higher in squash and maize, lower in husk tomatoes, and similar in beans. We also found that, due to differences in damaged area and/or shifts in dominance, damage compositions varied in squash, maize, and husk tomatoes. Therefore, our findings reinforce the idea that crop resistance against herbivory varies depending on the plant species and herbivore under study.