Aubier Thomas G, Lerch Brian A
Centre de Recherche sur la Biodiversité et l'Environnement (CRBE), Université de Toulouse, CNRS, IRD, Toulouse INP, Université Toulouse 3 - Paul Sabatier (UT3), Toulouse, France.
Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Evolution. 2025 Feb 3;79(2):176-192. doi: 10.1093/evolut/qpae147.
Several empirical examples and theoretical models suggest that the greenbeard effect may be an important mechanism in driving the evolution of altruism. However, previous theoretical models rely on assumptions such as spatial structure and specific sets of pleiotropic loci, the importance of which for the evolution of altruism has not been studied. Here, we develop a population-genetic model that clarifies the roles of extrinsic assortment (e.g., due to population structure) and pleiotropy in the maintenance of altruism through the greenbeard effect. We show that, when extrinsic assortment is too weak to promote the evolution of altruism on its own, the greenbeard effect can only promote altruism significantly if there is a pleiotropic locus controlling both altruism and signaling. Further, we show that indirect selection via genetic associations is too weak to have a noticeable impact on altruism evolution. We also highlight that, if extrinsic assortment is strong enough to promote the evolution of altruism on its own, it also favors the spread of alleles encoding the other functions of a greenbeard trait (signaling and discriminatory behavior), as well as genetic associations. This occurs despite the fact that the greenbeard effect did not favor the evolution of altruism in the first place. This calls for caution when inferring the causality between greenbeard traits and the evolution of altruism.
几个实证例子和理论模型表明，绿胡须效应可能是推动利他主义进化的一个重要机制。然而，以往的理论模型依赖于空间结构和多效基因座的特定集合等假设，而这些假设对利他主义进化的重要性尚未得到研究。在这里，我们建立了一个种群遗传模型，该模型阐明了外在分类（例如，由于种群结构）和基因多效性在通过绿胡须效应维持利他主义方面的作用。我们表明，当外在分类过于微弱，无法独自促进利他主义的进化时，只有在存在一个控制利他主义和信号传递的多效基因座时，绿胡须效应才能显著促进利他主义。此外，我们表明通过基因关联的间接选择过于微弱，对利他主义进化没有明显影响。我们还强调，如果外在分类足够强大，能够独自促进利他主义的进化，那么它也有利于编码绿胡须性状其他功能（信号传递和歧视行为）的等位基因的传播，以及基因关联的传播。尽管绿胡须效应最初并不利于利他主义的进化，但这种情况仍然会发生。这就要求在推断绿胡须性状与利他主义进化之间的因果关系时要谨慎。
