The obligate nature of many plant-insect interactions has shaped the evolutionary history of many insects and their hosts. With this shared evolutionary history comes preferences for a specific host species or family, and ideally this preference is matched by favorable performance metrics in the insect’s larvae. Due to changing environments and an increase in the mobility of organisms through hitchhiking on consumer goods the close evolutionary ties between species of plant and insect are being broken and expanded. Species are coming into contact with each other that previously had no possible means of interaction. Understanding novel insect-host interactions can shed light on the generalized outcomes of species introductions on native insects and/or plants. I performed a meta-analysis of papers that conducted controlled, no-choice, larval performance experiments on ancestral hosts versus novel hosts. Analysis of these data serves to determine how a novel host effects fitness measures in herbivorous insects.
The results of these studies show that when a host shift occurs, the outcomes of the interaction can be categorized based on the generalized impacts on the fitness of the insect. The insects can have a negative fitness reaction due to the novel host being less suitable, they can have a positive fitness reaction due to being able to take advantage of naïve plant species or that host providing access to better resources than an ancestral host. Alternatively, host shifts may result in a net neutral fitness outcome. The phylogenetic distance between the ancestral and novel host could also potentially impact the sign and level of the fitness responses in the insects. As the environment continues to warm and increasing global connection continues to expand the potential ranges of plants and insects, we can expect to see more novel interactions form, and shape both the current ecological space and future evolutionary trajectories of species.