Ecological and demographic correlates of helping behaviour in a cooperatively breeding bird.
Ecological and demographic correlates of helping behaviour in a cooperatively breeding bird.
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DOI：
10.1111/1365-2656.12017
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发表时间：
2013-03
期刊：
影响因子：
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通讯作者：
B. Hatchwell;S. P. Sharp;A. Beckerman;J. Meade
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文献类型：
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作者：
B. Hatchwell;S. P. Sharp;A. Beckerman;J. Meade
合作的演化对于进化生物学家来说是一个持续存在的问题。特别是，对于促进合作繁殖物种中帮助行为表达的因素的理解仍然薄弱，这可能是因为促进社会性的生态和种群统计学驱动因素具有多样性。在这项研究中，我们利用对一种兼性合作繁殖者——长尾山雀（Aegithalos caudatus）的长期研究数据，来调查影响帮助行为年度变化的因素。长尾山雀表现出转向帮助行为，即繁殖失败的个体可能会成为帮助者，通常是在亲属的巢穴中；因此，据推测帮助行为与巢穴失败的原因以及重新筑巢或提供帮助的机会有关。我们测试了关于合作行为的年度指标与四个解释变量之间关系的预测：巢穴捕食率、繁殖季节长度、种群层面的亲缘关系以及种群密度。我们发现帮助的程度主要由限制成功独立繁殖的两个因素决定。首先，正如所预测的那样，当既有繁殖失败的个体（即潜在的帮助者）又有活跃的巢穴（即潜在的接受者）时，合作行为在巢穴捕食处于中等水平时达到峰值。其次，在繁殖季节较短时，当繁殖失败的个体重新筑巢的机会更有限时，会有更多的帮助者。这些是鸟类合作繁殖系统中帮助行为的新驱动因素，并且这项研究说明了确定此类系统演化背后的常见生态或种群统计学因素的困难。
The evolution of cooperation is a persistent problem for evolutionary biologists. In particular, understanding of the factors that promote the expression of helping behaviour in cooperatively breeding species remains weak, presumably because of the diverse nature of ecological and demographic drivers that promote sociality. In this study, we use data from a long-term study of a facultative cooperative breeder, the long-tailed tit Aegithalos caudatus, to investigate the factors influencing annual variation in helping behaviour. Long-tailed tits exhibit redirected helping in which failed breeders may become helpers, usually at a relative's nest; thus, helping is hypothesised to be associated with causes of nest failure and opportunities to renest or help. We tested predictions regarding the relationship between annual measures of cooperative behaviour and four explanatory variables: nest predation rate, length of the breeding season, population-level relatedness and population density. We found that the degree of helping was determined principally by two factors that constrain successful independent reproduction. First, as predicted, cooperative behaviour peaked at intermediate levels of nest predation, when there are both failed breeders (i.e. potential helpers) and active nests (i.e. potential recipients) available. Second, there were more helpers in shorter breeding seasons when opportunities for renesting by failed breeders are more limited. These are novel drivers of helping behaviour in avian cooperative breeding systems, and this study illustrates the difficulty of identifying common ecological or demographic factors underlying the evolution of such systems.