The evidence for Allee effects

  title={The evidence for Allee effects},
  author={Andrew M. Kramer and Brian A. Dennis and Andrew M. Liebhold and John M. Drake},
  journal={Population Ecology},
Allee effects are an important dynamic phenomenon believed to be manifested in several population processes, notably extinction and invasion. [] Key Result We focus on empirical signatures that are used or might be used to detect Allee effects, the types of data in which Allee effects are evident, the empirical support for the occurrence of critical densities in natural populations, and differences among taxa both in the presence of Allee effects and primary causal mechanisms.

Review: Allee effects in social species

It is shown that group size heterogeneity and intergroup interactions affect the strength of population-level demographic Allee effects, and this provides a conceptual framework that allows for the integration of differentAllee effects in social species.

Variation in Allee effects: evidence, unknowns, and directions forward

This work synthesizes evidence for variation in Allee effects and highlights potential mechanisms, and emphasizes the “Allee slope,” i.e., the magnitude of the positive effect of density on the per-capita growth rate, as a metric for demographic Allee Effects.

Detection of Allee effects in marine fishes: analytical biases generated by data availability and model selection

The present study demonstrates that there is no substantive scientific basis to support the perception that Allee effects are rare or non-existent in marine fishes, by analysing nine populations of Atlantic herring using Bayesian statistical methods.

The hidden side of the Allee effect: correlated demographic traits and extinction risk in experimental populations

These results provide the first empirical demonstration of a correlation between the presence of positive density-dependence and impaired demographic performance, which increases the extinction risk of population, especially during the establishment phase.

Interaction between Allee effects caused by organism-environment feedback and by other ecological mechanisms

The authors' simulations explicitly considering spatial structure demonstrate that local interaction among habitat patches can greatly mitigate such superimposed Allee effects as well as individual Allee effect, implying that spatially structurized habitat could play an important role in ecological conservation and management.

Undetected Allee effects in Australia’s threatened birds: implications for conservation

Traits of the Regent Honeyeater suggests this species’ decline in particular is accelerated by an undetected demographic Allee effect, and an inability to detect Allee effects need not preclude efforts to account for their potential presence through precautionary conservation management.

Allee effects and resilience in stochastic populations

Stochasticity amplifies the risks arising from Allee effects, mainly by prolonging the amount of time a population spends at low abundance levels, and a complete understanding of alternative stable states in ecological systems must include stochasticity.

Exploiting Allee effects for managing biological invasions.

It is described how tactics that strengthen an existing Allee effect or create new ones could be used to manage biological invasions more effectively, and the concept of Allee effects can be integral in risk assessments and in the prioritization of resources allocated to manage non-native species.

Allee effects and the Allee-effect zone in northwest Atlantic cod

According to the theory of compensatory dynamics, depleted populations should recover when the threat responsible for their decline is removed because per capita population growth is assumed to be

Evidence for an Allee effect in a declining fur seal population

Investigating the potential for Allee effects in an Antarctic fur seal population that is declining in response to climate change-induced reductions in food availability found the opposite, with higher pup mortality at low density and the majority of deaths attributable to predation.



Allee effects in biological invasions

Allee Effects and the Risk of Biological Invasion

  • J. Drake
  • Environmental Science
    Risk analysis : an official publication of the Society for Risk Analysis
  • 2004
A previously published model of the Allee effect for continuously sexually reproducing species is reviewed and a new model for seasonally parthenogenetic species such as Bythotrephes is developed, demonstrating the potential consequences of Allee effects.

Allee effects driven by predation

A series of simple heuristic models were used to develop a theoretical framework for understanding predation-driven Allee effects as a function of predator functional and aggregative responses.

Multiple Allee effects and population management.

The competitive dynamics of metapopulations subject to the Allee-like effect.

Dangerously few liaisons: a review of mate-finding Allee effects

Considering ‘mate-finding’ as mate searching in mobile animals, and also as the meeting of gametes for sessile animals and plants, the role of demographic stochasticity in generating mate-finding Allee effects is considered.

Allee effects in stochastic populations

The Allee effect, or inverse density dependence at low population sizes, could seriously impact preservation and management of biological populations. The mounting evidence for widespread Allee

Allee effect limits colonization success of sexually reproducing zooplankton.

In support of mate limitation as the mechanism underlying recovery failure, a significant positive relationship between mating success and density across experimental and natural H. shoshone populations is found and a mesocosm experiment provided evidence of increased per capita population growth rate with increasing population density in another diaptomid species, Skistodiaptus pallidus.

Evidence for Allee effects in an over-harvested marine gastropod: density-dependent mating and egg production

Heavily exploited populations of queen conch in the Caribbean have been slow to recover despite fishery closures, and failure to recover could result from spawning stock densities that are reduced to the point at which Allee effects begin to operate on reproductive behavior.

The Allee effect, stochastic dynamics and the eradication of alien species

A model that incorporates Allee dynamics and stochasticity to observe how these two processes contribute to the extinction of isolated populations following eradication treatments of varying strength indicates that eradication of isolated gypsy moth populations could be easily achieved following a treatment of >80% mortality.