Complex Food Webs: The Role of Parasites

Abstract

Parasites are vital aspects of an ecosystem, and yet have only recently begun to be included in theoretical studies of food webs. There are numerous reasons for this neglect, but recent interest has arisen in remedying the situation. Key to the addition of parasites are various structural features that ecological networks display, and the mechanisms behind them. We look at two of these features, nestedness and downward asymmetry, and describe mathematically the forces that create them. We discover from the basic reproductive ratio that population dynamics are insufficient to drive nested and anti-nested patterns in host-parasite networks, and instead we demonstrate the manner in which adaptive dynamics may be used to explain patterns through the coevolution of species interaction traits. We use the same technique in a mutualistic network in order to compare results. Following this, we use the basic reproductive ratio to demonstrate how the population dynamics of infectious systems promote the presence of trophic parasites in particular interaction motifs, and discuss the implications of the addition of parasites to the stability of ecological networks as a whole.In summary, we demonstrate that the optimal use of resources by species in order to promote population growth results in two important structural patterns of host-parasite networks. Insights gained from this motivate us to investigate the importance of parasites on models of food web dynamics, and in particular, their stability.

Date of Award	21 Jan 2014
Original language	English
Awarding Institution	University of Bath
Sponsors	Department for International Development
Supervisor	Nicholas Britton (Supervisor)