Stearns S C
Q Rev Biol. 1976 Mar;51(1):3-47. doi: 10.1086/409052.
This review organizes ideas on the evolution of life histories. The key life-history traits are brood size, size of young, the age distribution of reproductive effort, the interaction of reproductive effort with adult mortality, and the variation in these traits among an individual's progeny. The general theoretical problem is to predict which combinations of traits will evolve in organisms living in specified circumstances. First consider single traits. Theorists have made the following predictions: (1) Where adult exceeds juvenile mortality, the organism should reproduce only once in its lifetime. Where juvenile exceeds adult mortality, the organism should reproduce several times. (2) Brood size should macimize the number of young surviving to maturity, summed over the lifetime of the parent. But when optimum brood-size unpredictably in time, smaller broods should be favored because they decrease the chances of total failure on a given attempt. (3) In expanding populations, selection should minimize age at maturity. In stable populations, when reproductive success depends on size, age, or social status, or when adult exceeds juvenile mortality, then maturation should be delayed, as it should be in declining populations. (4) Young should increase in size at birth with increased predation risk, and decrease in size with increased resource availability. Theorists have also predicted that only particular combinations of traits should occur in specified circumstances. (5) In growing populations, age at maturity should be minimized, reproductive effort concentrated early in life, and brood size increased. (6) One view holds that in stable environments, late maturity, broods, a few, large young, parental care, and small reproductive efforts should be favored (K-selection). In fluctuating environments, early maturity, many small young, reduced parental care, and large reproductive efforts should be favored (r-selection). (7) But another view holds that when juvenile mortality fluctuates more than adult mortality, the traits associated with stable and fluctuating environments should be reversed. We need experiments that test the assumptions and predictions reviewed here, more comprehensive theory that makes more readily falsifiable predictions, and examination of different definitions of fitness.
本综述梳理了有关生活史演化的观点。关键的生活史特征包括窝卵数、幼体大小、繁殖投入的年龄分布、繁殖投入与成年个体死亡率的相互作用，以及这些特征在个体后代中的变异。一般的理论问题是预测在特定环境中生活的生物会演化出哪些特征组合。首先考虑单一特征。理论家们做出了以下预测：（1）当成年个体死亡率超过幼年个体死亡率时，生物应该在其一生中只繁殖一次。当幼年个体死亡率超过成年个体死亡率时，生物应该繁殖多次。（2）窝卵数应该使存活到成熟的幼体数量最大化，这是在亲代的整个生命周期内进行累加的。但是当最佳窝卵数在时间上不可预测时，较小的窝卵数应该更受青睐，因为它们降低了在给定尝试中完全失败的几率。（3）在种群扩张时，选择应该使成熟年龄最小化。在稳定种群中，当繁殖成功率取决于大小、年龄或社会地位时，或者当成年个体死亡率超过幼年个体死亡率时，那么成熟应该延迟，在种群数量下降时也应该如此。（4）随着被捕食风险增加，幼体出生时的大小应该增加，而随着资源可用性增加，幼体大小应该减小。理论家们还预测，在特定环境中应该只出现特定的特征组合。（5）在增长的种群中，成熟年龄应该最小化，繁殖投入集中在生命早期，窝卵数增加。（6）一种观点认为，在稳定环境中，晚成熟、少窝卵、少数大幼体、亲代抚育和小繁殖投入应该更受青睐（K选择）。在波动环境中，早成熟、许多小幼体、减少亲代抚育和大繁殖投入应该更受青睐（r选择）。（7）但另一种观点认为，当幼年个体死亡率的波动大于成年个体死亡率时，与稳定和波动环境相关的特征应该相反。我们需要进行实验来检验这里所综述的假设和预测，需要更全面的理论来做出更容易被证伪的预测，还需要审视适合度的不同定义。
