Ecology of fear: ecological and evolutionary consequences of non-consumptive effects of parasites

点击翻译按钮获取中文摘要

Parasites can cause significant harm to their hosts, hence potential hosts should try to avoid coming into contact with infectious stages of the parasite. Hosts can avoid exposure to infection by avoiding infective stages, associated cues, infected individuals, or alter their habitat use to avoid encountering parasite. These indirect non-consumptive effects are known as the “ecology of fear”. The proposed project will experimentally answer the following questions: 1) Are the non-consumptive effects (NCEs) of parasites context and state-dependent? When an organism is exposed to parasites, it may change it's activity, rate of respiration, feeding behaviour, space use, and/or time allocation to various activities in order to avoid infection. Exactly how individuals respond to a perceived threat will depend on the environmental conditions and it's own internal condition (age, sex, energetic state, etc.). We will investigate the context-dependent nature of the NCE and whether the effects carry over across developmental stages and reproductive states. 2) Are there trait-mediated indirect effects of parasites? Parasites can also modify the behaviour of the host in ways that influence how it interacts with non-host species in the community (e.g., competitors, predators). The perception of infection risk could cause an increase in activity, which could in turn put an individual at greater risk of detection by predators. We will investigate the potential for conflict between anti-parasite and anti-predator defenses. 3) Are the NCEs of parasites on host metabolism context and state-dependent? The “fight or flight” response to a natural enemy often involves increased activity and respiration. We will measure the metabolic rate of flies exposed to parasites (without contact) over the short- and long-term. The metabolic rate of an organism is known to vary with sex, age, reproductive status, and external conditions (e.g., temperature, crowding). In addition to examining the state-dependent nature of the metabolic changes, measuring the reaction norm of the mean CO2 production under different conditions, including duration of exposure, types of parasite cues, and density of conspecifics. We will also measure associated changes in fly feeding behaviour. 4) What are the evolutionary consequences of NCE? Even as evidence for the ecology of fear and its fitness consequences mounts, the long-term evolutionary consequences of non-consumptive effects remains poorly understood. We will employ "laboratory natural selection" in which the environment of a laboratory-maintained population is altered (i.e., exposed to parasites) and the survivors become the parents of the next generation. The treatment populations will be compared to unaltered control populations after 10 generations. While multiple responses are possible, we will focus on changes in metabolism, feeding behaviour, body mass, anti-parasite behaviors (grooming, activity), and resistance to infection.