Lehmann Laurent, Perrin Nicolas, Rousset François
Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, United Kingdom.
Evolution. 2006 Jun;60(6):1137-51.
Limited dispersal may favor the evolution of helping behaviors between relatives as it increases their relatedness, and it may inhibit such evolution as it increases local competition between these relatives. Here, we explore one way out of this dilemma: if the helping behavior allows groups to expand in size, then the kin-competition pressure opposing its evolution can be greatly reduced. We explore the effects of two kinds of stochasticity allowing for such deme expansion. First, we study the evolution of helping under environmental stochasticity that may induce complete patch extinction. Helping evolves if it results in a decrease in the probability of extinction or if it enhances the rate of patch recolonization through propagules formed by fission of nonextinct groups. This mode of dispersal is indeed commonly found in social species. Second, we consider the evolution of helping in the presence of demographic stochasticity. When fecundity is below its value maximizing deme size (undersaturation), helping evolves, but under stringent conditions unless positive density dependence (Allee effect) interferes with demographic stochasticity. When fecundity is above its value maximizing deme size (oversaturation), helping may also evolve, but only if it reduces negative density-dependent competition.
有限的扩散可能有利于亲属之间利他行为的进化，因为这增加了他们的亲缘关系，但它也可能抑制这种进化，因为这增加了这些亲属之间的局部竞争。在这里，我们探索摆脱这种困境的一种方法：如果利他行为能使群体规模扩大，那么阻碍其进化的亲属竞争压力就会大大降低。我们探讨了两种允许种群扩张的随机性的影响。首先，我们研究在可能导致斑块完全灭绝的环境随机性下利他行为的进化。如果利他行为导致灭绝概率降低，或者通过未灭绝群体分裂形成的繁殖体提高斑块重新定殖的速率，那么利他行为就会进化。这种扩散模式在社会性物种中确实很常见。其次，我们考虑在存在人口统计学随机性的情况下利他行为的进化。当繁殖力低于其使种群规模最大化的值（未饱和）时，利他行为会进化，但除非正密度依赖（阿利效应）干扰人口统计学随机性，否则条件很苛刻。当繁殖力高于其使种群规模最大化的值（过饱和）时，利他行为也可能进化，但前提是它能减少负密度依赖竞争。
