By Franck Courchamp
Allee results are (broadly) outlined as a decline in person health at low inhabitants measurement or density. they could lead to serious inhabitants thresholds less than which populations crash to extinction. As such, they're very appropriate to many conservation programmes, the place scientists and bosses are frequently operating with populations which were diminished to low densities or small numbers. there are a selection of mechanisms which may create Allee results together with mating structures, predation, environmental amendment, and social interactions. The abrupt and unexpected collapses of many exploited populations is only one representation of the necessity to carry Allee results to the leading edge of conservation and administration thoughts. Allee results in Ecology and Conservation offers a concise but authoritative review of the subject, collating and integrating a greatly dispersed literature from quite a few fields - marine and terrestrial, plant and animal, theoretical and empirical, educational and utilized. This obtainable textual content, with its transparent and straightforward factors of either empirical observations and theoretical predications is especially appropriate for pro and educational ecologists requiring an summary of the state of the art in Allee impact examine, in addition to for graduate scholars in inhabitants ecology and conservation biology. it's going to even be of relevance to a large readership of execs in conservation and administration requiring a concise precis of the subject.
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Allee results are (broadly) outlined as a decline in person health at low inhabitants measurement or density. they could lead to severe inhabitants thresholds under which populations crash to extinction. As such, they're very proper to many conservation programmes, the place scientists and executives are frequently operating with populations which were decreased to low densities or small numbers.
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Additional info for Allee Effects in Ecology and Conservation
This is common where prey use a predation-avoidance mechanism, such as crypsis, which is more effective at low density (Seitz el al. 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.
More importantly, pollination of plants via an animal vector provides a highly evolved and sophisticated mechanism to facilitate reproduction and outcrossing even at low density which has never evolved in invertebrates, despite the fact that these invertebrate taxa have an evolutionary history which is many times longer than that of flowering plants. The answer to this apparent paradox may lie in the physics of air vs. water. Wind speeds are higher than currents (1 ms"1 is a light breeze but a very strong current); this faster flow in air dilutes gametes faster and makes gamete capture more difficult.
2005). Pollen limitation could also in theory trade off with reduced intraspecific competition at low density, but we have not come across a study which has addressed this hypothesis in plants. In sea urchins, however, this hypothesis has been tested. Echinoderms can pull off a variety of neat physiological tricks, including the ability to shrink their body mass when times get hard (Levitan 1991). Individuals in sparse populations are thus generally larger, because competition for resources is lower.