Wagner William E, Harper Christopher J
School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588-0118, USA.
Evolution. 2003 Sep;57(9):2054-66. doi: 10.1111/j.0014-3820.2003.tb00385.x.
In animals with internal fertilization, sperm competition among males can favor the evolution of male ejaculate traits that are detrimental to females. Female mating preferences, in contrast, often favor traits in males that are beneficial to females, yet little is known about the effect of these preferences on the evolution of male ejaculates. A necessary condition for female preferences to affect the evolution of male ejaculate characteristics is that females select mates based on a trait correlated with ejaculate quality. Previous work has shown that females of the variable field cricket, Gryllus lineaticeps, prefer males that produce calling songs containing faster and longer chirps. In this study, we tested the hypothesis that females receive more beneficial ejaculates from preferred males. Females were placed on either a high- or a reduced-nutrition diet then mated twice to a male of known song phenotype. Females received only sperm and seminal fluid from males during these matings. There was no effect of male song phenotype on any fitness component for females on the high-nutrition diet. Reduced-nutrition females mated to males that produced preferred song types, however, lived longer, produced more eggs, produced more fertile eggs, and had a higher proportion of their eggs fertilized than those mated to other males. The life-span benefit was positively associated with male chirp duration, and the reproductive benefits were positively associated with male chirp rate. We explored two possible mechanisms for the life span and reproductive benefits. First, a path analysis suggested that part of the effect of male chirp duration on female life span may have been indirect; females mated to males that produced longer chirps showed delayed oviposition, and females that delayed oviposition lived longer. Males that produce longer chirps may thus transfer fewer or less potent oviposition stimulants to females in their seminal fluid. Second, there was a positive correlation between male chirp rate and the number of sperm transferred to females. The fertility benefit may thus have resulted from females receiving more sperm from males that produce faster chirps. Finally, there was a negative phenotypic correlation between male chirp rate and chirp duration, suggesting that females may have to trade off the life span and reproduction benefits when selecting a mate.
在体内受精的动物中，雄性之间的精子竞争会促使对雌性有害的雄性射精特征的进化。相比之下，雌性的交配偏好通常有利于雄性中对雌性有益的特征，但对于这些偏好对雄性射精进化的影响却知之甚少。雌性偏好影响雄性射精特征进化的一个必要条件是，雌性根据与射精质量相关的特征来选择配偶。先前的研究表明，多变田蟋（Gryllus lineaticeps）的雌性更喜欢发出包含更快、更长唧唧声的求偶鸣叫的雄性。在本研究中，我们检验了这样一个假设：雌性从偏好的雄性那里获得更有益的射精。将雌性置于高营养或低营养饮食中，然后与具有已知鸣叫表型的雄性交配两次。在这些交配过程中，雌性只从雄性那里获得精子和精液。对于高营养饮食的雌性，雄性鸣叫表型对任何适合度成分都没有影响。然而，低营养的雌性与发出偏好鸣叫类型的雄性交配后，寿命更长，产卵更多，产出的受精卵更多，并且其卵子受精的比例高于与其他雄性交配的雌性。寿命益处与雄性唧唧声持续时间呈正相关，生殖益处与雄性唧唧声速率呈正相关。我们探究了寿命和生殖益处的两种可能机制。首先，路径分析表明，雄性唧唧声持续时间对雌性寿命的部分影响可能是间接的；与发出较长唧唧声的雄性交配的雌性产卵延迟，而产卵延迟的雌性寿命更长。因此，发出较长唧唧声的雄性可能在其精液中向雌性传递更少或效力更低的产卵刺激物。其次，雄性唧唧声速率与传递给雌性的精子数量之间存在正相关。因此，生育益处可能是由于雌性从发出更快唧唧声的雄性那里获得了更多精子。最后，雄性唧唧声速率与唧唧声持续时间之间存在负表型相关性，这表明雌性在选择配偶时可能不得不权衡寿命和生殖益处。
