Multiple Allee effects and Population Management

Department of Theoretical Ecology, Institute of Entomology, Biology Centre ASCR, Branisovská 31, 37005 Ceské Budejovice, Czech Republic.
Trends in Ecology & Evolution (Impact Factor: 16.2). 05/2007; 22(4):185-91. DOI: 10.1016/j.tree.2006.12.002
Source: PubMed


Allee effects, strongly related to the extinction vulnerability of populations and gradually becoming acknowledged by both theoretically oriented and applied ecologists, have already been shown to have important roles in the dynamics of many populations. Although not yet widely recognized, two or more Allee effects can occur simultaneously in the same population. Here, we review the evidence for multiple Allee effects and show that their interactions can take several forms, many of which are far from inconsequential. We suggest that more research is needed to assess the prevalence and interactions of multiple Allee effects, as failing to take them into account could have adverse consequences for the management of threatened or exploited populations.

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    • "The latter includes alarm networks, which may produce group mobbing (Krams et al. 2006) or anticipatory antipredatory behavior (Lima 2009). In addition, multiple Allee effects are known to operate within individual systems and are beginning to receive greater attention (Berec et al. 2006). Cues used by individuals to select breeding sites within a spatially heterogeneous environment may interact with other density-dependent processes that may modify coexisting component or demographic Allee effects produced through other mechanisms. "
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    ABSTRACT: Social information is used widely in breeding habitat se- lection and provides an efficient means for individuals to select hab- itat, but the population-level consequences of this process are not well explored. At low population densities, efficiencies may be reduced be- cause there are insufficient information providers to cue high-quality habitat. This constitutes what we call an information-mediated Allee effect. We present the first general model for an information-mediated Allee effect applied to breeding habitat selection and unify personal and social information, Allee effects, and ecological traps into a com- mon framework. In a second model, we consider an explicit mech- anism of social information gathering through prospecting on con- specific breeding performance. In each model, we independently vary personal and social information use to demonstrate how dependency on social information may result in either weak or strong Allee ef- fects that, in turn, affect population extinction risk. Abrupt transitions between outcomes can occur through reduced information transfer or small changes in habitat composition. Overall, information-mediated Allee effects may produce positive feedbacks that amplify population declines in species that are already experiencing environmentally driven stressors, such as habitat loss and degradation. Alternatively, social in- formation has the capacity to rescue populations from ecological traps.
    The American Naturalist 12/2015; 186(6):E000. DOI:10.1086/683659 · 3.83 Impact Factor
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    • "In many cases, an Allee effect might even lead to a negative population growth rate, creating an extinction threshold so that the population has to fight in order to grow [15] [17] [18]. This is also well-known as strong Allee effect [14] or critical depensation [17]. In this case, that implies the species may have a bigger tendency to be less able to overcome these additional mortality causes, to have a slower recovery, and to be prone to extinction than any other species [12]. "

    • "Other important drivers of positive interactions in subtidal communities include demographic constraints, (i.e. Allee effects), whereby population fitness displays positive density dependence (Berec et al. 2007) and resource availability, whereby benefactors can increase the nutrient availability for beneficiary species (Peterson & Heck 2001). "
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    ABSTRACT: Species interactions are integral drivers of community structure and can change from competitive to facilitative with increasing environmental stress. In subtidal marine ecosystems, however, interactions along physical stress gradients have seldom been tested. We observed seaweed canopy interactions across depth and latitudinal gradients to test whether light and temperature stress structured interaction patterns. We also quantified interspecific and intraspecific interactions among nine subtidal canopy seaweed species across three continents to examine the general nature of interactions in subtidal systems under low consumer pressure. We reveal that positive and neutral interactions are widespread throughout global seaweed communities and the nature of interactions can change from competitive to facilitative with increasing light stress in shallow marine systems. These findings provide support for the stress gradient hypothesis within subtidal seaweed communities and highlight the importance of canopy interactions for the maintenance of subtidal marine habitats experiencing environmental stress. © 2015 John Wiley & Sons Ltd/CNRS.
    Ecology Letters 05/2015; 18(7). DOI:10.1111/ele.12446 · 10.69 Impact Factor
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