Abstract Theoretical models of animal contests such as the Hawk-Dove game predict that variation in fighting behavior will persist due to mixed evolutionarily stable strategies (ESS) under certain conditions. However, the genetic basis for this variation is poorly understood and a mixed ESS for fighting can be interpreted in more than one way. Specifically, we do not know whether variation in aggression within a population arises from among-individual differences in fixed strategy (determined by an individual’s genotype—direct genetic effects [DGEs]), or from within-individual variation in strategy across contests. Furthermore, as suggested by developments of the original Hawk-Dove model, within-individual variation in strategy may be dependent on the phenotype and thus genotype of the opponent (indirect genetic effects—IGEs). Here we test for the effect of DGEs and IGEs during fights in the beadlet sea anemone Actinia equina. By exploiting the unusual reproductive system of sea anemones, combined with new molecular data, we investigate the role of both additive (DGE + IGE) and non-additive (DGE × IGE) genetic effects on fighting parameters, the latter of which have been hypothesized but never tested for explicitly. We find evidence for heritable variation in fighting ability and that fight duration increases with relatedness. Fighting success is influenced additively by DGEs and IGEs but we found no evidence for non-additive IGEs. These results indicate that variation in fighting behavior is driven by additive indirect genetic effects (DGE + IGE), and support a core assumption of contest theory that strategies are fixed by DGEs.

中文翻译：

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对抗海葵的直接和间接遗传效应分析

摘要 鹰鸽博弈等动物竞赛的理论模型预测，在某些条件下，由于混合进化稳定策略（ESS），战斗行为的变化将持续存在。然而，人们对这种变异的遗传基础知之甚少，并且对战斗的混合 ESS 可以有多种解释。具体来说，我们不知道群体内攻击性的差异是否源于个体间固定策略的差异（由个体的基因型直接遗传效应[DGEs]决定），还是源于个体内部在不同比赛中策略的差异。此外，正如最初的鹰-鸽模型的发展所表明的那样，个体内策略的变化可能取决于对手的表型和基因型（间接遗传效应——IGE）。在这里，我们测试了 DGE 和 IGE 在小珠海葵马葵的战斗中的效果。通过利用海葵不寻常的繁殖系统，结合新的分子数据，我们研究了加性（DGE + IGE）和非加性（DGE × IGE）遗传效应对战斗参数的作用，后者已被假设但从未明确测试过。我们发现了战斗能力存在遗传变异的证据，并且战斗持续时间随着相关性而增加。战斗成功受到 DGE 和 IGE 的加性影响，但我们没有发现非加性 IGE 的证据。这些结果表明，战斗行为的变化是由加性间接遗传效应（DGE + IGE）驱动的，并支持竞争理论的核心假设，即策略由 DGE 决定。