Understanding the relative importance of sexual and natural selection in shaping morphological traits is a long-standing goal of evolutionary ecology. Male-biased sexual size dimorphism (SSD) is typically associated with male-male competition. Similarly, male polymorphisms are considered a consequence of competitive social interactions. This classic paradigm overlooks the fact that environmental factors mediate social interactions and can lead to ecological adaptations. Common side-blotched lizards, Uta stansburiana, are a model system for this paradigm due to well-known rock-paper-scissors social dynamics between male morphs. SSD in this species has been considered primarily a consequence of social interactions, with male size resulting from the number of morphs in each population and female size being constrained through fecundity benefits. We test if the environment explains intraspecific variation in SSD and number of male morphs in U. stansburiana. By compiling data from 49 populations, we show that environmental variables are stronger predictors of SSD than the number of male morphs. Similarly, we show that the environment mediates SSD and potentially contributes to morph loss in colder environments. We propose that the environment favours smaller males in areas of high seasonality. Our results demonstrate the importance of the environment as a mediator of SSD.

中文翻译：

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具有替代交配策略的蜥蜴性别二态性的环境驱动因素。

了解性选择和自然选择在塑造形态特征方面的相对重要性是进化生态学的一个长期目标。男性偏向性大小二态性 (SSD) 通常与男性-男性竞争有关。同样，男性多态性被认为是竞争性社会互动的结果。这种经典范式忽视了这样一个事实，即环境因素介导社会互动并可能导致生态适应。由于雄性变种之间众所周知的石头剪刀布社会动态，常见的侧斑蜥蜴 Uta stansburiana 是这种范式的模型系统。该物种的 SSD 主要被认为是社会互动的结果，雄性体型由每个种群的变体数量产生，雌性体型受到生育优势的限制。我们测试环境是否解释了 SSD 的种内变异和 U. stansburiana 中雄性变体的数量。通过汇编来自 49 个种群的数据，我们表明环境变量比男性变体的数量更能预测 SSD。同样，我们表明环境会调节 SSD，并可能导致较冷环境中的变形损失。我们建议在季节性强的地区，环境有利于体型较小的雄性。我们的结果证明了环境作为 SSD 中介的重要性。我们表明环境会调节 SSD，并可能导致较冷环境中的变形损失。我们建议在季节性强的地区，环境有利于体型较小的雄性。我们的结果证明了环境作为 SSD 中介的重要性。我们表明环境会调节 SSD，并可能导致较冷环境中的变形损失。我们建议在季节性强的地区，环境有利于体型较小的雄性。我们的结果证明了环境作为 SSD 中介的重要性。