Sexual size dimorphism is biased toward males in most mammalian species. The most common explanation is precopulatory intramale sexual selection. Large males win fights and mate more frequently. In artiodactyls, previous tests of this hypothesis consisted of interspecific correlations of sexual dimorphism with group size as a surrogate for the intensity of sexual selection (I_s). However, group size is not a proper measure of sexual selection for several reasons as is largely recognized in other mammalian taxa. I conducted an interspecific test on the role of sexual selection in the evolution of sexual dimorphism using the variance in genetic paternity as a proxy for the I_s. I reviewed the literature and found 17 studies that allowed estimating I_s= V/(W²), where V and W are the variance and mean number of offspring per male, respectively. A phylogenetic generalized least squares analysis indicated that dimorphism (W_m/W_f) showed a significant positive regression with the intensity of sexual selection but not group size (multiple r²= 0.40; F_3,17= 12.78, P = 0.002). This result suggests that sexual selection may have played a role in the evolution of sexual size dimorphism in Artiodactyla. An alternative hypothesis based on natural selection is discussed.

中文翻译：

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偶蹄动物的性大小二态性和性选择

在大多数哺乳动物中，性别大小双态偏向于男性。最常见的解释是交配前男性内部的性选择。大公赢得战斗，交往更加频繁。在偶蹄类动物，这种假设的前测试包括性别二态性的种间的相关性的与组尺寸为性选择（强度的替代我_小号）。但是，由于其他原因，在其他哺乳动物分类群中也普遍认识到，群体规模并不是正确选择性行为的标准。我使用基因亲子关系的变异作为I_的代表对性选择在性二态性进化中的作用进行了种间试验。我查阅了文献，发现有17项研究可以估计我_s = V /（ W ²），其中V和W分别是每位男性的变异数和平均后代数。系统发育广义最小二乘分析表明，双态性（ W _m / W _f）与性选择强度呈显着正相关，而与群体规模无显着正相关（ r ² = 0.40； F _3,17 = 12.78，P = 0.002）。这个结果表明，性选择可能在木偶象甲的性大小二态性的进化中起作用。讨论了基于自然选择的另一种假设。