Body size and meta-community structure: the allometric scaling of parasitic worm communities in their mammalian hosts

Abstract

In this paper we derive from first principles the expected body sizes of the parasite communities that can coexist in a mammal of given body size. We use a mixture of mathematical models and known allometric relationships to examine whether host and parasite life histories constrain the diversity of parasite species that can coexist in the population of any host species. The model consists of one differential equation for each parasite species and a single density-dependent nonlinear equation for the affected host under the assumption of exploitation competition. We derive threshold conditions for the coexistence and competitive exclusion of parasite species using invasion criteria and stability analysis of the resulting equilibria. These results are then used to evaluate the range of parasites species that can invade and establish in a target host and identify the 'optimal' size of a parasite species for a host of a given body size; 'optimal' is defined as the body size of a parasite species that cannot be outcompeted by any other parasite species. The expected distributions of parasites body sizes in hosts of different sizes are then compared with those observed in empirical studies. Our analysis predicts the relative abundance of parasites of different size that establish in the host and suggests that increasing the ratio of parasite body size to host body size above a minimum threshold increases the persistence of the parasite population.

Host allometry influences the evolution of parasite host-generalism: theory and meta-analysis

“…In fact, strong positive relationships between host and parasite body size are often noted [24,25,52–54]. Because our dataset did not include any information on parasite body size, we did not incorporate such relationships into the model, but doing so would be relatively straightforward (though the analysis of such a model may not).…”

Editorial: Mathematical modelling of infectious diseases

“…Of the 10 papers in this Special Issue, eight were broadly ecological (de Leo et al 2016; Garnier et al 2016; Magpantay et al 2016; McCallum, 2016; Norman et al 2016; Park et al 2016; Viana et al 2016; Wearing et al 2016) with two focusing primarily on evolutionary aspects (Cressler et al 2016; Greischar et al 2016). These papers covered a range of topics, from highly conceptual (e.g.…”

“…These papers covered a range of topics, from highly conceptual (e.g. de Leo et al 2016) to applied work on various specific systems, covering human diseases (Magpantay et al 2016), livestock (Garnier et al 2016) and wildlife conservation (McCallum, 2016). McCallum (2016) reviews the practical application of models to guide alternative management strategies (e.g.…”

“…Relating to community effects, de Leo et al (2016) extend classical one-host-one-parasite models to incorporate multiple macroparasites (helminths), and use these to assess the rules of parasite community assembly; under what conditions can one parasite invade and persist in presence of another? Specifically they argue that bioenergetic scaling laws provide a ‘quantitative unifying theory of biological organization’, and assess this by assuming parasite functional traits (fecundity, developmental rate, pathogenicity, etc.)…”

“…scale with parasite body size. de Leo et al (2016) show how host body size constrains the range of viable body sizes, mediated by a trade-off between the fecundity benefits to parasites of large size and the costs, due to the increased likelihood of host mortality. Garnier et al (2016) also explore host–helminth interactions, seeking an appropriate level of model complexity to describe, in a data-friendly way, within-host helminth–immune system interaction dynamics.…”