Pfister C A
Department of Ecology and Evolution, 1101 E. 57th Street, University of Chicago, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 1998 Jan 6;95(1):213-8. doi: 10.1073/pnas.95.1.213.
Variability in population growth rate is thought to have negative consequences for organism fitness. Theory for matrix population models predicts that variance in population growth rate should be the sum of the variance in each matrix entry times the squared sensitivity term for that matrix entry. I analyzed the stage-specific demography of 30 field populations from 17 published studies for pattern between the variance of a demographic term and its contribution to population growth. There were no instances in which a matrix entry both was highly variable and had a large effect on population growth rate; instead, correlations between estimates of temporal variance in a term and contribution to population growth (sensitivity or elasticity) were overwhelmingly negative. In addition, survivorship or growth sensitivities or elasticities always exceeded those of fecundity, implying that the former two terms always contributed more to population growth rate. These results suggest that variable life history stages tend to contribute relatively little to population growth rates because natural selection may alter life histories to minimize stages with both high sensitivity and high variation.
种群增长率的变异性被认为会对生物体的适应性产生负面影响。矩阵种群模型理论预测，种群增长率的方差应该是每个矩阵元素的方差乘以该矩阵元素的平方敏感度项之和。我分析了来自17项已发表研究的30个野外种群的特定阶段种群统计学，以研究一个种群统计学项的方差与其对种群增长的贡献之间的模式。没有任何一个矩阵元素既具有高度变异性又对种群增长率有很大影响的情况；相反，一个项的时间方差估计值与对种群增长的贡献（敏感度或弹性）之间的相关性绝大多数为负。此外，存活率或生长敏感度或弹性总是超过繁殖力的敏感度或弹性，这意味着前两个项对种群增长率的贡献总是更大。这些结果表明，可变的生活史阶段对种群增长率的贡献往往相对较小，因为自然选择可能会改变生活史，以使具有高敏感度和高变异性的阶段最小化。
