En route to resources: Foraging strategies of plant-associated insects to identify resources in complex dynamic environments

In plant-associated communities, foraging insects aim to find different resources of interest. Herbivores look for the most nutritious plant tissues, pollinators for sweet nectar and protein-rich pollen, and carnivores for their preferred prey. Although these foragers look for different resources, they face similar problems: resource cues are often highly variable and need to be detected in complex environments among non-resources. Search templates—a subset of stimuli that is likely correlated with the occurrence of a particular resource—help foragers across trophic levels to find their resources. However, search-template-based foraging can also cause perception errors. Here, we synthesize knowledge on foraging by insects from functional groups belonging to different trophic levels to reveal common problems experienced by foragers and strategies to solve such problems. We focus mostly on volatile-based foraging because this searching strategy is best studied across functional groups. We argue that search templates are both multimodal (including multiple trait types, e.g. odour and visual) and hierarchical (including multiple foraging steps). Search templates are plastic and updated by experience to match the dynamic foraging environment over time. By comparing insects from different functional groups spanning multiple trophic levels, we have identified important missing gaps on cue use and foraging strategies which should be addressed in the future in order to reduce knowledge asymmetries among functional groups about search-template-based foraging. We propose a way to achieve this goal arguing that studies on less well investigated functional groups can advance rapidly by borrowing, testing and adjusting already available hypotheses and theories formulated for other insect groups. Knowledge of search-template-based foraging across functional groups will give new insights into the evolution of foraging behaviour in complex ecological communities, help predict ecological consequences of large-scale human-made disturbances and help optimize insect-delivered ecosystem services (pollination and biological control) in cropping systems. Read the free Plain Language Summary for this article on the Journal blog.