Ecological drivers of body size evolution and sexual size dimorphism in short-horned grasshoppers (Orthoptera: Acrididae)
Ecological drivers of body size evolution and sexual size dimorphism in short-horned grasshoppers (Orthoptera: Acrididae)
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DOI：
10.1111/jeb.13131
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发表时间：
2017-08-01
影响因子：
2.1
通讯作者：
Ortego, J.
中科院分区：
文献类型：
--
作者：
Garcia-Navas, V.;Noguerales, V.;Ortego, J.
性大小二形症(SSD)广泛存在，性质多变。虽然偏向雌性的SSD在昆虫中占主导地位，但促进这一现象的最接近的生态和进化因素在很大程度上仍未得到研究。在这里，我们使用现代系统发育比较方法对伊比利亚蝗虫的8个亚科(85个物种)进行研究，以检验不同的体型和SSD进化模型的有效性，并探索它们是如何受到一系列生态变量(栖息地专门化、底物使用、海拔高度)和/或不同进化压力(雌性繁殖力、性选择强度、繁殖季节的长度)的制约。个体大小差异主要积累在群体历史的后期，并不遵循布朗运动模式，表明这一特征存在方向性进化。我们发现在所有分类群中支持Rensch规则的相反情况(即在大物种中雌性比雄性大)，但在两个最特殊的亚科(Gomphocerinae和Oedipodinae)中不支持，这显示出等长格局。我们的结果不支持繁殖力或性选择假说，我们也没有发现栖息地利用的显著影响的证据。与预期相反，我们发现繁殖窗口较窄的物种在大小上比繁殖周期较长的物种少，这表明雄性保护不能完全解释直翅目偏向雌性的SSD的进化。我们的研究强调了在试图解释为什么在某些昆虫群体中雄性仍然很小时，需要考虑经典进化假说的替代方案。
Sexual size dimorphism (SSD) is widespread and variable in nature. Although female-biased SSD predominates among insects, the proximate ecological and evolutionary factors promoting this phenomenon remain largely unstudied. Here, we employ modern phylogenetic comparative methods on eight subfamilies of Iberian grasshoppers (85 species) to examine the validity of different models of evolution of body size and SSD and explore how they are shaped by a suite of ecological variables (habitat specialization, substrate use, altitude) and/or constrained by different evolutionary pressures (female fecundity, strength of sexual selection, length of the breeding season). Body size disparity primarily accumulated late in the history of the group and did not follow a Brownian motion pattern, indicating the existence of directional evolution for this trait. We found support for the converse of Rensch's rule (i.e. females are proportionally bigger than males in large species) across all taxa but not within the two most speciose subfamilies (Gomphocerinae and Oedipodinae), which showed an isometric pattern. Our results do not provide support for the fecundity or sexual selection hypotheses, and we did not find evidence for significant effects of habitat use. Contrary to that expected, we found that species with narrower reproductive window are less dimorphic in size than those that exhibit a longer breeding cycle, suggesting that male protandry cannot solely account for the evolution of female-biased SSD in Orthoptera. Our study highlights the need to consider alternatives to the classical evolutionary hypotheses when trying to explain why in certain insect groups males remain small.