Animal aggregations, a study in general sociology

Allee, W. C.

doi:10.5962/bhl.title.7313

Cited by 1,015 publications

(689 citation statements)

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“…In ecological terms, the results can be seen as the consequence of a balance between a rescue effect (Brown & Kodric-Brown 1977)-where the parasite population in one host can be rescued from extinction by immigrationand an Allee effect (Allee 1931)-where the necessity of finding a mate introduces a threshold for populations to be sustainable. These two effects have different dependences on the host population size.…”

Section: Discussionmentioning

confidence: 99%

Stochastic and spatial dynamics of nematode parasites in farmed ruminants

Cornell

Isham

Grenfell

2004

Proc. R. Soc. Lond. B

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Host-parasite systems provide powerful opportunities for the study of spatial and stochastic effects in ecology; this has been particularly so for directly transmitted microparasites. Here, we construct a fully stochastic model of the population dynamics of a macroparasite system: trichostrongylid gastrointestinal nematode parasites of farmed ruminants. The model subsumes two implicit spatial effects: the host population size (the spatial extent of the interaction between hosts) and spatial heterogeneity ('clumping') in the infection process. This enables us to investigate the roles of several different processes in generating aggregated parasite distributions. The necessity for female worms to find a mate in order to reproduce leads to an Allee effect, which interacts nonlinearly with the stochastic population dynamics and leads to the counter-intuitive result that, when rare, epidemics can be more likely and more severe in small host populations. Clumping in the infection process reduces the strength of this Allee effect, but can hamper the spread of an epidemic by making infection events too rare. Heterogeneity in the hosts' response to infection has to be included in the model to generate aggregation at the level observed empirically.

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Section: Discussionmentioning

confidence: 99%

Stochastic and spatial dynamics of nematode parasites in farmed ruminants

Cornell

Isham

Grenfell

2004

Proc. R. Soc. Lond. B

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“…Allee effect: when the per-capita birth rate increases with density but the percapita death rate does not [59]. Low population sizes are therefore vulnerable to extinction because the birth rate is less than the death rate.…”

Section: Glossarymentioning

confidence: 99%

Ecological consequences of phenotypic plasticity

Miner

Sultan

Morgan

et al. 2005

Trends in Ecology & Evolution

738

632

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“…The Allee effect refers to the observation that many populations of species do not only suffer from detrimental effects when densities are high, i.e. because of intraspecific competition, but also when densities are low [1,17]. This may result, for instance, from difficulties in finding mates or cooperative feeding [17], or a positive relationship between a component of individual fitness and the number of conspecifics [34].…”

Section: Modelmentioning

confidence: 99%

Detecting Tipping points in Ecological Models with Sensitivity Analysis

Broeke

Voorn

Kooi³

et al. 2016

Math. Model. Nat. Phenom.

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Abstract. Simulation models are commonly used to understand and predict the development of ecological systems, for instance to study the occurrence of tipping points and their possible ecological effects. Sensitivity analysis is a key tool in the study of model responses to changes in conditions. The applicability of available methodologies for sensitivity analysis can be problematic if tipping points are involved. In this paper we demonstrate that not considering these tipping points may result in misleading statistics on model behaviour. In turn, this limits the applicability of simulation models in ecological research. Tipping points are best revealed when asymptotic model behaviour is considered, i.e. by applying bifurcation analysis. Bifurcation analysis, however, is limited to deterministic dynamic models, whereas many ecological simulation models are nondeterministic and can only be analysed using sensitivity analysis methodologies. In this paper we explore the possibilities for applying methodologies of sensitivity analysis to analyse models with tipping points. The Bazykin-Berezovskaya model, a deterministic ecological model of which the structure regarding tipping points is known a priori, is used as case study. We conclude that important clues about the occurrence of tippings points can be revealed from different sensitivity analysis methodologies, if proper statistical and graphical measures are used. The results raise awareness about how tipping points affect temporal model responses in ecological simulation models, and may also be more generally applicable for nondeterministic models that cannot be analysed using bifurcation analysis.

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Animal aggregations, a study in general sociology

Cited by 1,015 publications

References 0 publications

Stochastic and spatial dynamics of nematode parasites in farmed ruminants

Stochastic and spatial dynamics of nematode parasites in farmed ruminants

Ecological consequences of phenotypic plasticity

Detecting Tipping points in Ecological Models with Sensitivity Analysis

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