飞蝗抱对行为的进化意义及两型间相异的交配策略

飞蝗Locusta migratoriaL.不仅交配时间长,而且进行频繁的、长时间的交配前抱对。一般认为,交配前抱对行为是雄虫为了等待时机获取适时的交配。最近的研究表明,飞蝗的交配时间与P2值(最后交配雄虫子代的比例)、交配前抱对时间与交配时间存在显著的正相关关系,即飞蝗长时间的交配前抱对行为能延长其后续的交配时间,从而提高P2值。飞蝗具变型现象,散居型和群居型在形态特征、生理机能、行为及体色等方面存在明显差异。最近的研究结果显示,散居型较群居型具更高的P2值,较短的交配前抱对和较长的交配时间。冲绳和筑波种群散居型成虫的交配前抱对时间与交配时间存在显著的正相关关系,而群居型无此相关性。这些结果证实飞蝗散居型和群居型之间存在着繁殖策略的差异。

The evolutionary significance of precopulatory mounting and phase-related differences in mating strategy of Locusta migratoria

The migratory locust, Locusta migratoria L. shows frequent and prolonged mounting as well as prolonged copulation. The precopulatory mounting has been proposed to guard a female or ensure timely mating. Recent studies suggested that precopulatory mounting has a function other than guarding or just waiting in this locust: prolonged precopulatory mounting increases the length of copulation, which in turn increases the P_2 value. This locust shows phase polymorphism in which various morphological, physiological, and behavioral traits change according to population density. But mating strategy in different phase has not been investigated. The results of recent investigations showed that solitarious adults had a higher P_2 value, shorter precopulatory mounting, and longer copulation than gregarious adults. A significant positive correlation between length of precopulatory mounting and copulation was found in gregarious adults, but not in solitarious adults in the two geographic strains, Okinawa strain and Tsukuba strain of Japan. The results demonstrate phase-related differences in reproductive strategy that are likely to be adaptive for locusts facing a large variation in chance of encounters between the two sexes.