Purcell Jessica, Brelsford Alan, Avilés Leticia
Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, Canada, BC V6T 1Z4; Department of Ecology and Evolution, University of Lausanne, Bâtiment Biophore, CH-1015 Lausanne, Switzerland.
Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, Canada, BC V6T 1Z4; Department of Ecology and Evolution, University of Lausanne, Bâtiment Biophore, CH-1015 Lausanne, Switzerland.
J Theor Biol. 2012 Nov 7;312:44-54. doi: 10.1016/j.jtbi.2012.07.016. Epub 2012 Jul 25.
Explaining the evolution of sociality is challenging because social individuals face disadvantages that must be balanced by intrinsic benefits of living in a group. One potential route towards the evolution of sociality may emerge from the avoidance of dispersal, which can be risky in some environments. Although early studies found that local competition may cancel the benefits of cooperation in viscous populations, subsequent studies have identified conditions, such as the presence of kin recognition or specific demographic conditions, under which altruism will still spread. Most of these studies assume that the costs of cooperating outweigh the direct benefits (strong altruism). In nature, however, many organisms gain synergistic benefits from group living, which may counterbalance even costly altruistic behaviours. Here, we use an individual based model to investigate how dispersal and social behaviour co-evolve when social behaviours result in synergistic benefits that counterbalance the relative cost of altruism to a greater extent than assumed in previous models. When the cost of cooperation is high, selection for sociality responds strongly to the cost of dispersal. In particular, cooperation can begin to spread in a population when higher cooperation levels become correlated with lower dispersal tendencies within individuals. In contrast, less costly social behaviours are less sensitive to the cost of dispersal. In line with previous studies, we find that mechanisms of global population control also affect this relationship: when whole patches (groups) go extinct each generation, selection favours a relatively high dispersal propensity, and social behaviours evolve only when they are not very costly. If random individuals within groups experience mortality each generation to maintain a global carrying capacity, on the other hand, social behaviours spread and dispersal is reduced, even when the latter is not costly.
解释社会性的演化颇具挑战性，因为群居个体面临着不利因素，而这些不利因素必须由群居生活的内在益处来平衡。社会性演化的一条潜在途径可能源于对扩散的规避，在某些环境中扩散可能存在风险。尽管早期研究发现局部竞争可能会抵消粘性种群中合作的益处，但后续研究已经确定了一些条件，比如亲缘识别的存在或特定的人口统计学条件，在这些条件下利他行为仍会传播。这些研究大多假设合作的成本超过直接益处（强利他主义）。然而，在自然界中，许多生物从群居生活中获得协同益处，这甚至可能抵消代价高昂的利他行为。在此，我们使用基于个体的模型来研究当社会行为产生协同益处，且这种协同益处比先前模型所假设的能在更大程度上抵消利他主义的相对成本时，扩散和社会行为是如何共同演化的。当合作成本很高时，对社会性的选择对扩散成本反应强烈。特别是，当更高的合作水平与个体较低的扩散倾向相关联时，合作就能在种群中开始传播。相比之下，成本较低的社会行为对扩散成本不太敏感。与先前的研究一致，我们发现全球种群控制机制也会影响这种关系：当每一代整个斑块（群体）都灭绝时，选择有利于相对较高的扩散倾向，并且只有当社会行为成本不高时才会演化。另一方面，如果群体中的随机个体每一代都经历死亡以维持全球承载能力，那么即使扩散成本不高，社会行为也会传播而扩散会减少。
