No abstract

Predators kill and consume prey, but also scare living prey. Fitness of prey can be reduced by direct killing and consumption, but also by non-consumptive effects (NCEs) if prey show costly risk-induced trait responses (RITRs) to predators, which are meant to reduce predation risk. Recently, similarities between predators and parasites as natural enemies have been recognized, including their potential to cause victim RITRs and NCEs. However, plant-herbivore and animal host-parasite associations might be more comparable as victim-enemy systems in this context than either is to prey-predator systems. This is because plant herbivores and animal parasites are often invertebrate species that are typically smaller than their victims, generally cause lower lethality, and allow for further defensive responses by victims after consumption begins. Invertebrate herbivores can cause diverse RITRs in plants through various means, and animals also exhibit assorted RITRs to increased parasitism risk. This synthesis aims to broadly compare these two enemy-victim systems by highlighting the ways in which plants and animals perceive threat and respond with a range of induced victim trait responses that can provide pre-emptive defense against invertebrate enemies. We also review evidence that RITRs are costly in terms of reducing victim fitness or abundance, demonstrating how work with one victim-enemy system can inform the other with respect to the frequency and magnitude of RITRs and possible NCEs. We particularly highlight gaps in our knowledge about plant and animal host responses to their invertebrate enemies that may guide directions for future research. Comparing how potential plant and animal victims respond pre-emptively to the threat of consumption via RITRs will help to advance our understanding of natural enemy ecology and may have utility for pest and disease control.

No abstract

Characteristics of individual plants from the same species can differ significantly between habitats based on abiotic factors such as light intensity and temperature. In turn, these differences in plant quality can affect herbivores that feed on the plant. Here, we examined the effects of habitat on leaf characteristics for the invasive vine Vincetoxicum rossicum, as well as the preference and performance of its biological control agent, Hypena opulenta, on sun versus shade foliage. V. rossicum leaves grown in sunny habitats were tougher, thicker, and had lower water content than shade leaves. H. opulenta larvae consumed greater amounts of shaded foliage than sun foliage and were predominately night-active. H. opulenta larval development did not differ between sun and shade foliage diets; however, females preferred to oviposit on sun foliage. The underlying mechanisms of these results are discussed, as well as their implications for the biological control of Vincetoxicum species.iii