Santos E S A, Machado G
BECO do Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil.
LAGE do Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brazil.
J Evol Biol. 2016 Jul;29(7):1447-54. doi: 10.1111/jeb.12885. Epub 2016 May 27.
Many animal taxa that display sexual size dimorphism (SSD) exhibit a positive allometric relationship in which the degree of dimorphism increases with body size. This macroevolutionary pattern is known as Rensch's rule. Although sexual selection is hypothesized to be the main mechanism causing this pattern, body size is influenced by several selective forces, including natural and sexual selection. Therefore, by focusing exclusively on SSD one cannot ascertain which of these selective forces drives Rensch's rule. If sexual selection is indeed the main mechanism underlying Rensch's rule, we predict that other sexually selected traits, including coloration-based ornaments, will also exhibit interspecific allometric scaling consistent with Rensch's rule. We tested this prediction using wing pigmentation of 89 species of dragonflies. Studies show that male wing pigmentation is generally under strong intra- and intersexual selection, so that sexual dichromatism in this trait should follow Rensch's rule. Conversely, the available evidence suggests that male body size is usually not sexually selected in dragonflies, so we do not expect SSD to follow Rensch's rule. First, we found that sexual dichromatism in wing pigmentation was consistent with Rensch's rule. The phylogenetic major axis regression slope was significantly greater than one. We also showed that the allometric slope for SSD was not different from unity, providing no support for Rensch's rule. Our results provide the first evidence that a trait which appears to be under strong sexual selection exhibits a pattern consistent with Rensch's rule.
许多表现出两性体型差异（SSD）的动物类群呈现出正异速生长关系，即体型差异程度随体型大小增加。这种宏观进化模式被称为伦施法则。尽管性选择被认为是导致这种模式的主要机制，但体型受到多种选择力的影响，包括自然选择和性选择。因此，仅关注两性体型差异无法确定这些选择力中的哪一种驱动了伦施法则。如果性选择确实是伦施法则的主要潜在机制，我们预测其他性选择的性状，包括基于颜色的装饰，也将表现出与伦施法则一致的种间异速生长比例关系。我们使用89种蜻蜓的翅色素沉着来检验这一预测。研究表明，雄性翅色素沉着通常受到强烈的同性内和同性间选择，因此该性状的两性异色性应遵循伦施法则。相反，现有证据表明，蜻蜓中雄性体型通常不受性选择，因此我们预计两性体型差异不会遵循伦施法则。首先，我们发现翅色素沉着的两性异色性与伦施法则一致。系统发育主轴回归斜率显著大于1。我们还表明，两性体型差异的异速生长斜率与1没有差异，这并不支持伦施法则。我们的结果提供了首个证据，表明一个似乎受到强烈性选择的性状呈现出与伦施法则一致的模式。
