Component, group and demographic Allee effects in a cooperatively breeding bird species, the Arabian babbler (Turdoides squamiceps)
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- 作者：Oded Keynan ; Amanda R. Ridley
- 刊名：Oecologia
- 出版年：2016
- 出版时间：September 2016
- 年：2016
- 卷：182
- 期：1
- 页码：153-161
- 全文大小：715 KB
- 刊物类别：Biomedical and Life Sciences
- 刊物主题：Life Sciences
Ecology
Plant Sciences - 出版者：Springer Berlin / Heidelberg
- ISSN：1432-1939
- 卷排序：182
文摘
In population dynamics, inverse density dependence can be manifested by individual fitness traits (component Allee effects), and population-level traits (demographic Allee effects). Cooperatively breeding species are an excellent model for investigating the relative importance of Allee effects, because there is a disproportionately larger benefit to an individual of being part of a large group. As a consequence, larger groups have greater performance than small groups, known as the group Allee effect. Although small populations of cooperative breeders may be prone to all levels of Allee effects, empirical evidence for the existence of a demographic Allee effects is scarce. To determine the extent to which Allee effects are present in a cooperatively breeding species, we used a comprehensive 35-year life history database for cooperatively breeding Arabian babblers (Turdoides squamiceps). Firstly, we confirmed the existence of a component Allee effect by showing that breeding individuals in large groups receive greater benefits than those in small groups; second, we confirmed the existence of group Allee effect by showing that larger groups survive longer. And thirdly, we identified a demographic Allee effect by showing that per capita population growth rate is positively affected by population density. Finally, we found that emigration and immigration rates, although dependent on group size, do not buffer against component and group-level Allee effects becoming a demographic Allee effect. Our finding of the existence of all three levels of Allee effects in a cooperative breeder may have important implications for future research and conservation decisions.KeywordsAllee effectArabian babblersCooperationDensity dependenceGroup size population dynamics