Diverse effects of parasites in ecosystems: linking interdependent processes

Abstract

Community ecologists generally recognize the importance of species – such as pollinators – that have clear positive effects within ecosystems. However, parasites – usually regarded in terms of their detrimental effects on the individuals they infect – can also have positive impacts on other species in the community. We now recognize that parasites influence species coexistence and extirpation by altering competition, predation, and herbivory, and that these effects can, in turn, influence ecosystem properties. Parasites and pathogens act as ecosystem engineers, alter energy budgets and nutrient cycling, and influence biodiversity. Equally, because ecosystem properties – such as biodiversity – affect parasite populations, there is the potential for feedback between parasitism and ecosystem states. Using examples from animal and plant systems, we examine this potential bidirectional interdependence and challenge the conventional wisdom that parasites have only negative or inconsequential impacts on ecological communities.

Population biology of infectious diseases shared by wild and farmed fish

“…An example of a negative indirect interaction involving hosts is apparent competition in which a parasite that is shared by two host populations creates a negative correlation between the demographies of the two host populations, creating a false impression that the two hosts are competitors (Hatcher et al 2012). Two examples of parasites with multihost dynamics that also involve domesticated fish are Infectious hematopoietic necrosis virus (IHNv) and the sea louse Caligus clemensi, both of which infect salmonids, herring, and other species.…”

Multidimensionality in parasite-induced phenotypic alterations: ultimateversusproximate aspects

“…by releasing the prey community from predation pressure (Sato et al, 2012) or by affecting the availability of trophic resources to plant and animal communities (Hernandez and Sukhdeo, 2008;Boze et al, 2012). However, although the influence of PIPAs on ecosystem functioning is widely acknowledged (Thomas et al, 1997;Hatcher et al, 2012), we do not know to what extent the ecological impact of a parasite is related to the number of phenotypic alterations it brings about in its host.…”

Lessons from sea louse and salmon epidemiology

“…Interactions between parasites and host communities are numerous [63] and poorly understood for many marine pathogens. Multi-host models are underutilized and could help to improve our understanding of feedback between disease and communities.…”