The mechanistic basis of demographic Allee effects: The search for mates.

In Focus: Berec, L., Kremer, A.M., Bernhauverova, V., & Drake, J.M. (2017). Density-dependent selection on mate-finding Allee effects. Journal of Animal Ecology, 87, 24-35. https://doi.org/10.1111/1365-2656.12662 In Focus: Shaw, A.K., Kokko, H., & Neubert, M.G. (2017). Details of mate finding drive dynamics of sex structured invasions. Journal of Animal Ecology, 87, 36-46. https://doi.org/10.1111/1365-2656.12658 Lowered population growth ability at low abundances is called the demographic Allee effect. The difficulty of finding mates in a sparse population is the best documented pathway through which a demographic Allee effect might arise. The articles in focus here aim to establish the mechanistic links between mate search component Allee effects and the emergent demographic Allee effect manifested at the level of population growth rate. The authors discover that limitations in the time invested in mate searching generates demographic Allee effects and that the population level adaptations of mate search time are likely to be dependent on the prevailing population density. Trade-offs between mate search, survival and reproductive outputs are key in understanding optimal mate search strategies and their fitness consequences. The present studies provide guidelines to identify populations at risk of experiencing demographic Allee effects at low abundances.