Howard Richard D, Kluge Arnold G
Department of Biological Sciences, Purdue University, West Lafayette, IN, 47907.
Museum of Zoology, and Division of Biological Sciences, University of Michigan, Ann Arbor, MI, 48109.
Evolution. 1985 Mar;39(2):260-277. doi: 10.1111/j.1558-5646.1985.tb05665.x.
Observations and several types of field experiments on the mating behavior of wood frogs have revealed the proximate mechanisms for a size-related reproductive advantage in both males and females. For females, larger individuals produce larger clutches; for males, larger individuals can better remain clasped to females when contested by rival males and can better depose males clasped to other females. No results obtained support of the existence of mate choice in either males or females. Males were estimated to be 4.74 times as variable as females in the number of zygotes produced per individual per season; however, much of the variation in male RS resulted from a male-biased sex ratio at the breeding site rather than from sexual selection. After taking sex ratio effects into consideration, males were estimated to be only 1.63 times as variable as females. Patterns of variation in RS in males and females are associated with numerous sex-specific differences in life history and morphology. Life history differences include differential growth rates, ages at sexual maturity, and rates of mortality. Interpretation of how the body size dimorphism (females larger than males) in this species relates to sexual selection is consistent with information on how similar variations in body size influence RS for each sex, and how males and females differ in the functional relationship between body size and RS. Average RS increases more with body size in females than in males. Although body size directly influences RS for females, the possibility exists that, for males, other anatomical features correlated with body size more directly affect RS. Preliminary evidence suggests that sexual selection influences male arm length and that the male body size : RS relationship results as an incidental correlation.
对林蛙交配行为的观察和几种类型的野外实验揭示了雄性和雌性与体型相关的生殖优势的近因机制。对于雌性来说，体型较大的个体能产出更大的卵块；对于雄性来说，体型较大的个体在与竞争对手争夺雌性时，能更好地抱紧雌性，并且能更好地将抱紧其他雌性的雄性推开。没有获得任何结果支持雄性或雌性存在配偶选择。据估计，雄性每个季节每个个体产生的受精卵数量的变异性是雌性的4.74倍；然而，雄性生殖成功率的大部分变异是由于繁殖地雄性偏向的性别比例，而非性选择。在考虑性别比例影响后，据估计雄性的变异性仅是雌性的1.63倍。雄性和雌性生殖成功率的变异模式与生活史和形态学上众多特定性别的差异相关。生活史差异包括不同的生长速率、性成熟年龄和死亡率。对该物种体型二态性（雌性比雄性大）如何与性选择相关的解释，与关于体型的相似变异如何影响每种性别的生殖成功率，以及雄性和雌性在体型与生殖成功率之间的功能关系上如何不同的信息是一致的。雌性的平均生殖成功率随体型增加的幅度比雄性大。虽然体型直接影响雌性的生殖成功率，但对于雄性来说，存在其他与体型相关的解剖特征更直接影响生殖成功率这种可能性。初步证据表明性选择影响雄性的臂长，并且雄性体型与生殖成功率的关系是一种偶然的相关性。
