Lindenfors P, Székely T, Reynolds J D
Department of Zoology, Stockholm University, Stockholm, Sweden.
J Evol Biol. 2003 Sep;16(5):930-8. doi: 10.1046/j.1420-9101.2003.00595.x.
The Charadrii (shorebirds, gulls and alcids) are one of the most diverse avian groups from the point of view of sexual size dimorphism, exhibiting extremes in both male-biased and female-biased dimorphism, as well as monomorphism. In this study we use phylogenetic comparative analyses to investigate how size dimorphism has changed over evolutionary time, distinguishing between changes that have occurred in females and in males. Independent contrasts analyses show that both body mass and wing length have been more variable in males than in females. Directional analyses show that male-biased dimorphism has increased after inferred transitions towards more polygynous mating systems. There have been analogous increases in female-biased dimorphism after transitions towards more socially polyandrous mating systems. Changes in dimorphism in both directions are attributable to male body size changing more than female body size. We suggest that this might be because females are under stronger natural selection constraints related to fecundity. Taken together, our results suggest that the observed variation in dimorphism of Charadrii can be best explained by male body size responding more sensitively to variable sexual selection than female body size.
从两性体型差异的角度来看，鸻形目（涉禽、鸥类和海雀类）是最多样化的鸟类群体之一，在雄性偏向型、雌性偏向型体型差异以及体型无差异方面都呈现出极端情况。在本研究中，我们运用系统发育比较分析来探究体型差异在进化过程中是如何变化的，区分在雌性和雄性中发生的变化。独立对比分析表明，雄性的体重和翅长都比雌性更具变异性。定向分析表明，在推断向更多一夫多妻制交配系统转变之后，雄性偏向型体型差异有所增加。在向更多社会型一妻多夫制交配系统转变之后，雌性偏向型体型差异也有类似的增加。两个方向上体型差异的变化都归因于雄性体型比雌性体型变化更大。我们认为这可能是因为雌性受到与繁殖力相关的更强自然选择约束。综合来看，我们的结果表明，鸻形目体型差异中观察到的变化，最好的解释是雄性体型比雌性体型对变化的性选择反应更敏感。
