OOS 16

Allee Effects: Theory and Applications

Allee effects are a density-dependent phenomenon associated with cooperative behaviors, genetic change, and sexual reproduction. Quantifying the magnitude of Allee effects has been impeded by the difficulty of monitoring low density populations, but in recent years the widespread occurrence of Allee effect has become increasingly clear. Research has documented a diversity of mechanisms ranging from mate limitation to cooperative feeding to predator satiation. As evidence from multiple systems has accumulated, the focus has begun to change from documenting the presence of Allee effects to understanding the feedbacks and interactions with other ecological and evolutionary processes. The combined effects of these interactions are important for conserving small populations, as evident in the examples of the island fox and several fisheries, and for managing non-native species, such as invasive insects. The innovative research included in this session highlights two crucial, under-explored aspects of Allee effects, namely (1) the interaction of positive density dependence and population genetics, and (2) the role that Allee effects play in forecasting and managing pest outbreaks. The link between Allee effects and population genetics is predicted to be strong due to the role of small population sizes in ecological and evolutionary dynamics. This session will explore this link from several directions, particularly how selection weakens Allee effects and how population genetic processes can increase fitness costs in small populations. New work from a more applied viewpoint considers how Allee effects influence the dynamics of spreading pests. This session will also consider the links between these seemingly separate questions, for instance the role of selection for increased dispersal in accelerating spread in species invasions. The mix of theory and empirical results reported here shows that close interaction is fueling continued advances in the understanding of Allee effects. The current relevance of these areas is underscored by the independent pursuit of these topics in several groups. This session will provide a platform to share and synthesize this work.