Allee Effects in Ecology and Conservation by Franck Courchamp

By Franck Courchamp

Allee results are (broadly) outlined as a decline in person health at low inhabitants dimension or density. they could lead to severe inhabitants thresholds less than which populations crash to extinction. As such, they're very correct to many conservation programmes, the place scientists and bosses are usually operating with populations which were decreased to low densities or small numbers. there are a number of mechanisms which could create Allee results together with mating platforms, predation, environmental amendment, and social interactions. The abrupt and unexpected collapses of many exploited populations is only one representation of the necessity to convey Allee results to the leading edge of conservation and administration suggestions. Allee results in Ecology and Conservation presents a concise but authoritative evaluation of the subject, collating and integrating a extensively dispersed literature from a variety of fields - marine and terrestrial, plant and animal, theoretical and empirical, educational and utilized. This available textual content, with its transparent and easy motives of either empirical observations and theoretical predications is especially compatible for pro and educational ecologists requiring an summary of the cutting-edge in Allee influence examine, in addition to for graduate scholars in inhabitants ecology and conservation biology. it is going to even be of relevance to a large readership of pros in conservation and administration requiring a concise precis of the subject.

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Extra resources for Allee Effects in Ecology and Conservation

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In this case, predator dilution is likely to lead to a demographic Allee effect, since small colonies were declining (to extinction in some cases) due to heavy predation, while large colonies could persist (Cuthbert 2002). Likewise, in colonies of thick-billed murre (Uria lomvia, also called Brunnich's guillemot), predatory gulls could attack murres throughout small, sparse colonies, but are generally restricted to colony edges in large dense colonies (Gilchrist 1999; although in this case the small and large colonies were geographically far apart and may have differences other than size and density—the problem of confounding variables).

Some of the most striking elements of animal behaviour are adaptations for finding mates, including calls and song, displays, odour and pheromone marking, reproductive aggregations and so on. A mate-finding Allee effect may arise if these mate-finding behaviours are themselves disrupted at low density. For example, heavy fishing on spawning aggregations of reef fish results in knowledge of spawning sites and migration routes being lost from the population, as well as disruption of spawning behaviour via the removal of dominant males (Sadovy 2001), although Allee effects have not been specifically demonstrated in these populations.

2001). Spatial or temporal refuges from predation may also stabilize predator-prey dynamics (Gascoigne and Lipcius 2004a). The protective effect of high density for prey via the dilution effect is distinct from any anti-predator benefits which arise from prey behaviour such as aggregation, temporal synchrony, group vigilance and group aggression towards predators. Below we discuss examples of each, organized by prey behaviour, from straightforward dilution, through prey aggregation in space or time, to more complex prey behaviours such as group vigilance and aggression.

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