Interspecific competition among macroparasites in a density-dependent host population

Gatto, Marino; Leo, Giulio A. De

doi:10.1007/s002850050138

Cited by 17 publications

(15 citation statements)

References 28 publications

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Section: Theoretical Mechanismsmentioning

confidence: 99%

“…It is clear that generalist parasites can overcome host density thresholds and drive a focal host species to extinction. The detailed community dynamics of multiple parasites sharing multiple hosts can be quite complex (Holt & Pickering 1985;Bowers & Turner 1997;Gatto & De Leo 1998;Bowers & Hodgkinson 2001;Holt et al 2003). However, multi-host parasites can clearly lead to apparent competition, where a host species drives a competitor to extinction by being more tolerant or encouraging reproduction of a parasite that harms its competitor (Schmitz & Nudds 1994;Holt et al 2003).…”

Section: Specialist Vs Generalist Parasites: Reservoirsmentioning

confidence: 99%

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Mechanisms of disease‐induced extinction

Castro¹,

Bolker²

2004

Ecology Letters

569

576

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Parasites are important determinants of ecological dynamics. Despite the widespread perception that parasites (in the broad sense, including microbial pathogens) threaten species with extinction, the simplest deterministic models of parasite dynamics (i.e. of specialist parasites with density-dependent transmission) predict that parasites will always go extinct before their hosts. We review the primary theoretical mechanisms that allow disease-induced extinction and compare them with the empirical literature on parasitic threats to populations to assess the importance of different mechanisms in threatening natural populations. Small pre-epidemic population size and the presence of reservoirs are the most commonly cited factors for disease-induced extinction in empirical studies. ; MacNeil et al. 2003). In conservation biology, disease is presented as a threat to population viability and a contributing factor to disease extinction (McCallum & Dobson 1995). However, the simplest disease models -which have formed the theoretical foundation for the field of disease ecologysuggest that disease alone cannot drive host populations extinct (Anderson & May 1992). More specifically, deterministic models of directly transmitted specialist parasites with density-dependent transmission predict that disease will always die out when the host population falls below a (nonzero) threshold density, before the host population can go extinct (Swinton et al. 1998;McCallum et al. 2001); stochastic models suggest that disease will often go extinct by so-called Ôfade-outÕ even above this threshold (Bartlett 1960;Black 1966;Keeling & Grenfell 1997). The first part of this paper reviews the important exceptions to these simple conclusions -the qualitative mechanisms that drive disease-induced extinction in theoretical models. The second reviews the existing empirical literature on disease-induced extinction, and makes a first attempt to assess the relative importance of the different mechanisms in natural systems.The literature search was performed in the ISI Web of Science, selecting any article containing the words [Ôextinct*Õ AND (ÔdiseaseÕ OR Ôparasit*Õ OR ÔpathogenÕ)] in the title, abstract or keywords. In total, 336 references were found. References to the coefficient of extinction of some substance (typically in the context of human physiology and medicine), articles that only vaguely mentioned disease as a possible threat for populations, and those referring to the extinction of parasites (rather than hosts) were dropped (260 in total). The remaining articles (76), which are the base of this review, were classified as either theoretical (33) or empirical (43) (some quantitative simulation models of specific hostparasite systems were included in the empirical rather than the theoretical section). We are aware that the so-called Ôgray literatureÕ, not covered by the Web of Science, contains many references on conservation subjects, but we feel confident that our reference base is representative. We have not included cases of...

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Section: Theoretical Mechanismsmentioning

confidence: 99%

Section: Specialist Vs Generalist Parasites: Reservoirsmentioning

confidence: 99%

Mechanisms of disease‐induced extinction

Castro¹,

Bolker²

2004

Ecology Letters

569

576

View full text Add to dashboard Cite

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“…The conditions for coexistence or competitive exclusion in these multi-parasite models are basic to understand how a parasite community is structured (Janovy et al . 1990; Gatto and De Leo, 1998). Purely mathematical analysis have focused on general results that apply to all possible combinations of demographic parameters, whereas interspecific comparisons for both host and parasite species demonstrate that there are constraints on the combinations of parameter values observed in nature and this constraints are often related to body size (Peters, 1983; Skorping et al .…”

Section: Introductionmentioning

confidence: 99%

“…This in turn will affect the ability of further parasite species to establish in an already infected host. In addition, optimal parasite body size was derived by Morand and Poulin (2002) as that maximizing the reproductive number R o – the expected number of adult parasites produced by a typical adult parasite during its entire period of reproductive maturity; Gatto and De Leo (1998) showed that parasite's competitive ability does not necessarily rank with respect to R o . Finally, Morand and Poulin (2002) did not investigate the range of parasite body sizes that are potentially able to establish in an uninfected host of a given body size at its carrying capacity, nor how this range may shrink in the case the host is already parasitized by one or more competing parasite species.…”

Section: Introductionmentioning

confidence: 99%

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

2016

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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.

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“…Population models or reaction-diffusion systems have attracted enormous interest both in the mathematical community and as abstract versions of real biological dynamics [8].Every year, millions of hectares of agricultural land are treated with released Trichogramma wasps [15]; for instance, to protect sugar cane from the sugar cane borer, Chilo spp., in China, or to protect corn fields from the European corn borer, OstrinianubilalisHübner, in Western Europe. Theoretical studies of host-parasitoid interactions go back to Nicholson and Bailey [3,9,13].…”

Section: Introductionmentioning

confidence: 99%