Wiegmann Daniel D, Baylis Jeffrey R, Hoff Michael H
Department of Zoology, University of Wisconsin, Madison, WI, 53706, USA.
Department of Natural Resources, Woodruff, WI, 54568, USA.
Evolution. 1992 Dec;46(6):1740-1753. doi: 10.1111/j.1558-5646.1992.tb01166.x.
Monogamy is often presumed to constrain mating variance and restrict the action of sexual selection. We examined the reproductive patterns of a monogamous population of smallmouth bass (Micropterus dolomieui), and attempted to identify sources of within-season fitness variation among females and known-age males. Many males did not acquire a nest site, and many territorial males were unsuccessful in acquiring a mate. The likelihood that territorial males mated depended on several aspects of nest sites. Mated males of age three were larger than the average size of age-three males in the population. The mean sizes of age-four and age-five mated males were not different from the average of same-age males in the population. Thus, selection resulting from the acquisition of a mate favored large size among only age-three males. Timing of nest construction and breeding among territorial males was negatively related to male size and did not depend on male age after taking male size into account. Indirect evidence (numbers of eggs deposited in nests) suggests that the timing of spawning among females was also negatively related to female size. Fertility selection favored early reproduction within the season by males of all ages, but large male size was favored among only age-four males. The combined early breeding of fecund females and female mate choice of large males may explain the positive correlation between the size of age-four males and the number of eggs acquired. Despite large differences of female fecundity, however, the variance of relative mate number contributed about two times more than the variance of relative fertility among females to the total variance of relative fitness within each sex.
人们通常认为一夫一妻制会限制交配差异并限制性选择的作用。我们研究了小口黑鲈（Micropterus dolomieui）一夫一妻制种群的繁殖模式，并试图确定雌性和已知年龄雄性在季节内适合度变化的来源。许多雄性没有获得巢穴，许多有领地的雄性也未能成功获得配偶。有领地的雄性交配的可能性取决于巢穴的几个方面。三岁的交配雄性比种群中三岁雄性的平均体型更大。四岁和五岁交配雄性的平均体型与种群中同龄雄性的平均体型没有差异。因此，获得配偶所导致的选择仅在三岁雄性中有利于大体型。在考虑雄性体型后，有领地的雄性筑巢和繁殖的时间与雄性体型呈负相关，且不取决于雄性年龄。间接证据（巢穴中产卵的数量）表明，雌性产卵的时间也与雌性体型呈负相关。生育选择有利于所有年龄段的雄性在季节内尽早繁殖，但仅在四岁雄性中有利于大体型。繁殖力强的雌性的早期繁殖与雌性对大体型雄性的配偶选择相结合，可能解释了四岁雄性体型与获得的卵数量之间的正相关关系。然而，尽管雌性繁殖力差异很大，但在每个性别中，相对配偶数量的方差对相对适合度总方差的贡献比相对生育力的方差多约两倍。
