van den Berghe Eric P, Gross Mart R
Behavioral Ecology Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, V5A 1S6, CANADA.
Evolution. 1989 Jan;43(1):125-140. doi: 10.1111/j.1558-5646.1989.tb04212.x.
We studied breeding competition among wild female coho salmon (Oncorhynchus kisutch) and quantified natural selection acting on two important female characters: body size and kype size (a secondary sexual character used for fighting). We found that body size contributed to adult female fitness in three ways, through 1) an increased initial biomass of egg production, 2) the ability to acquire a high-quality territory for egg development, and 3) success in nest defense. These factors together resulted in as much as a 23-fold fitness advantage to the largest females in the population. The initial investment into egg production accounted for 50-60% of the measured intensity of natural selection on female body size. The effective investment into egg production (after female competition for territories) accounted for 40-50% of natural selection on female body size. Therefore, success in breeding competition is about as important as egg production in the current evolution of female body size. This is contrary to the expectation based on most fisheries literature. The size of a female's kype was also important to female reproductive success, although its contribution could not be separated from that of body size in our study. The strong natural selection that we have found for female competitive ability is presumably the basis for the evolution of female parental care in salmonids.
我们研究了野生银大麻哈鱼（Oncorhynchus kisutch）雌鱼之间的繁殖竞争，并对作用于雌鱼两个重要特征（体型大小和颌钩大小，一种用于争斗的第二性征）的自然选择进行了量化。我们发现，体型大小通过三种方式对成年雌鱼的适合度产生影响：一是通过增加产卵的初始生物量，二是通过获取高质量产卵区域的能力，三是通过成功进行巢穴防御。这些因素共同作用，使得种群中体型最大的雌鱼在适合度上比其他雌鱼高出多达23倍。对产卵的初始投入占测量到的对雌鱼体型自然选择强度的50%至60%。对产卵的有效投入（在雌鱼争夺领地之后）占对雌鱼体型自然选择的40%至50%。因此，在当前雌鱼体型的进化过程中，繁殖竞争的成功与产卵的重要性相当。这与大多数渔业文献的预期相反。雌鱼颌钩的大小对雌鱼的繁殖成功也很重要，尽管在我们的研究中其作用无法与体型大小的作用区分开来。我们所发现的对雌鱼竞争能力的强烈自然选择，大概是鲑科鱼类中雌鱼亲代抚育行为进化的基础。
