Department of Zoology, University of Oxford, Oxford OX1 3PS, UK.
J Evol Biol. 2013 Sep;26(9):1854-65. doi: 10.1111/jeb.12195. Epub 2013 Jul 13.
Darwin suggested that the discovery of altruism between species would annihilate his theory of natural selection. However, it has not been formally shown whether between-species altruism can evolve by natural selection, or why this could never happen. Here, we develop a spatial population genetic model of two interacting species, showing that indiscriminate between species helping can be favoured by natural selection. We then ask if this helping behaviour constitutes altruism between species, using a linear-regression analysis to separate the total action of natural selection into its direct and indirect (kin selected) components. We show that our model can be interpreted in two ways, as either altruism within species, or altruism between species. This ambiguity arises depending on whether or not we treat genes in the other species as predictors of an individual's fitness, which is equivalent to treating these individuals as agents (actors or recipients). Our formal analysis, which focuses upon evolutionary dynamics rather than agents and their agendas, cannot resolve which is the better approach. Nonetheless, because a within-species altruism interpretation is always possible, our analysis supports Darwin's suggestion that natural selection does not favour traits that provide benefits exclusively to individuals of other species.
达尔文曾表示，物种间利他行为的发现将彻底推翻他的自然选择理论。然而，目前还没有正式表明物种间的利他行为是否可以通过自然选择进化，或者为什么这种情况永远不会发生。在这里，我们建立了一个关于两种相互作用物种的空间种群遗传模型，表明无差别物种间帮助可以被自然选择所青睐。然后，我们使用线性回归分析将自然选择的总作用分解为直接作用和间接作用（亲缘选择），从而询问这种帮助行为是否构成物种间的利他主义。我们表明，我们的模型可以有两种解释，既可以解释为种内利他主义，也可以解释为种间利他主义。这种歧义的出现取决于我们是否将另一个物种中的基因视为个体适应度的预测因子，这相当于将这些个体视为代理人（行为者或接受者）。我们的正式分析侧重于进化动态，而不是代理人及其议程，因此无法确定哪种方法更好。尽管如此，由于种内利他主义的解释总是可能的，因此我们的分析支持达尔文的观点，即自然选择不倾向于仅为其他物种的个体提供利益的特征。
