Sexual size dimorphism in Orthoptera (sens. str.) - a review
Sexual size dimorphism in Orthoptera (sens. str.) - a review
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DOI：
10.1665/1082-6467-17.2.189
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发表时间：
2008-01-01
影响因子：
0.8
通讯作者：
Groening, Julia
中科院分区：
文献类型：
--
作者：
Hcchkirch, Axel;Groening, Julia
两性大小二态性（SSD）是动物分类群中的一种普遍现象。虽然雄性在许多鸟类和哺乳动物中是较大的性别，但雌性偏向的SSD在昆虫中占主导地位，包括直翅目。通过对1503种直翅目昆虫体型差异的分析，发现长翅目昆虫的体长分布比较均匀，雌性个体平均比雄性个体大9%（-20 ~+40%）。相比之下，SSD通常在Caelifera中更强（37%），并且变化更大（范围从-20到+140%）。与较大的女性Caelifera表现出较强的大小差异比较小的物种，而在Ensifera SSD下降与男性的身体大小，但不相关的10个女性的大小。直翅目昆虫的性别大小差异通常与雌性若虫的较高龄期有关，导致雄性成虫出现较早（雄性先熟）。生长速率和龄期数似乎都受到遗传和环境线索的影响。两个主要的假说被提出来解释SSD的最终原因：间性竞争假说和差异均衡假说。第一种观点认为，两性异形是一种减少种内竞争的机制，使两性能够专注于不同的食物。差异平衡假说认为，不同的体型代表着性别特异性的最适适应值，这是由它们特定的生活史策略造成的。雌性可以通过增加卵的数量（或大小）（繁殖力选择）来最大限度地提高其繁殖成功率，而雄性可以通过更移动的和在短时间内大量繁殖雌性来最大限度地提高其繁殖成功率。两性生活史策略的这些根本差异也可能导致性选择，这有时被称为一个附加假设。对于SSD的根本原因还需要更多的实证研究。目前，有更多的支持差异均衡假说，但间性竞争假说很少被测试。我们提出了一些实验方法来测试这两个假设在微观和宏观进化的背景下。
Sexual size dimorphism (SSD) is a common phenomenon in animal taxa. While males are the larger sex in many birds and mammals, female- biased SSD predominates among insects, including Orthoptera. We analyzed size differences of 1503 Orthoptera species, Suggesting that SSD is rather uniform in Ensifera, with the females being on average 9% larger than the males (ranging from -20 to +40%). In contrast, SSD is Usually much Stronger in Caelifera (37%) and also more variable (ranging from -20 to +140%). Caelifera with larger females exhibit stronger size differences than smaller species, whereas in Ensifera SSD decreases with male body size, but is not related 10 female size. Sexual size differences in Orthoptera are usually associated with a higher number of nymphal instars in females, leading to art earlier emergence of adult males (protandry). Both growth rates and the number of instars seem to be affected by genetic and environmental Cues. Two major hypotheses have been proposed to explain the ultimate causes for SSD: the intersexual competition hypothesis and the differential equilibrium hypothesis. The first suggests that Sexual dimorphism is a mechanism to reduce intraspecific competition, enabling the sexes to specialize on different food items. The differential equilibrium hypothesis proposes that the different body sizes represent sex-specific fitness optima, which are caused by their specific life-history strategies. Females may maximize their reproductive Success by increasing the number (or size) Of eggs (fecundity selection), whereas males may maximize their reproduction by being more mobile and fertilizing many females in a short period of time. These fundamental differences in the life-history strategies of the sexes may also lead to sexual selection, which has sometimes been referred to as an additional hypothesis. There is still a need for more empirical research oil the ultimate Causes for SSD. At present, there is much more support for the differential equilibrium hypothesis, but the intersexual competition hypothesis has rarely been tested. We propose some experimental approaches to test both hypotheses in micro- and macroevolutionary contexts.