父方投资与性角色逆转现象:螽斯类昆虫的婚礼食物及对性选择方向的影响

Parental investment and sex role reversal:nuptial gift and its effects on sexual selection in katydids

大多数动物在繁殖过程中 ,雌性在繁殖过程中要比雄性付出更大投资 ,如相对于精子较大的卵子细胞 ,较长的育幼时间等 ,因而在交配过程中 ,雌性具有选择权 ,而雄性之间相互竞争以取得与雌性的交配权。然而自然世界中并不总是竞争的雄性 (competitivemale)—选择的雌性 (selectivefemale)这种婚配形式。在螽斯类昆虫中 ,雄性同样具有较大的父方投资。在繁殖期间 ,雄性螽斯争相鸣叫 ,求偶 ,且在交配后要给予雌性特殊的营养物质———精包 ,供雌性取食。因此在特定情况下 ,雌性之间将进行竞争以获取雄性配偶 ,雄性变得更具有选择性。影响这种性角色逆转的主要因素是可获得资源的紧缺。父方投资理论和性选择理论预测雄性显著地对后代投资时 ,雌性将表现出典型的雄性特征 ,她们竞争追求性活跃的雄性 ,而雄性将表现出典型的雌性特征 ,对配偶具有选择性。螽斯类昆虫中这种特殊的性角色逆转现象符合性选择理论和父方投资理论的预测。

Parental investment theory and sexual selection theory suggests that investment by males through courtship feeding of their mates may represent an important source of nutrition and ultimately influences patterns of sexual selection. In certain insects males provide nutritional products from reproductive accessory glands during mating; these are either eaten by the female or are absorbed in her genital tract. Male bushcrickets (Orthoptera: Tettigoniidae) feed their mates with an elaborate spermatophore consisting of a spermatophylax, which is eaten by the female after mating, and a sperm ampulla, eaten after the ejaculate has emptied. Studies of the species with very large spermatophores have revealed a role-reversal in reproductive behaviour, with females aggressively competing for males capable of producing spermatophores. Population density, nutritional condition and operational sex ratio are the three main affecting factors.