Biology Department, Duke University, Durham, North Carolina, USA.
Evolution. 2013 Jun;67(6):1622-34. doi: 10.1111/evo.12023. Epub 2013 Jan 4.
Modernization has increased longevity and decreased fertility in many human populations, but it is not well understood how or to what extent these demographic transitions have altered patterns of natural selection. I integrate individual-based multivariate phenotypic selection approaches with evolutionary demographic methods to demonstrate how a demographic transition in 19th century female populations of Utah altered relationships between fitness and age-specific survival and fertility. Coincident with this demographic transition, natural selection for fitness, as measured by the opportunity for selection, increased by 13% to 20% over 65 years. Proportional contributions of age-specific survival to total selection (the complement to age-specific fertility) diminished from approximately one third to one seventh following a marked increase in infant survival. Despite dramatic reductions in age-specific fertility variance at all ages, the absolute magnitude of selection for fitness explained by age-specific fertility increased by approximately 45%. I show that increases in the adaptive potential of fertility traits followed directly from decreased population growth rates. These results suggest that this demographic transition has increased the adaptive potential of the Utah population, intensified selection for reproductive traits, and de-emphasized selection for survival-related traits.
现代化在许多人类群体中延长了寿命并降低了生育率，但人们并不清楚这些人口转变在何种程度上改变了自然选择的模式。我将基于个体的多维表型选择方法与进化人口学方法相结合，以展示 19 世纪犹他州女性人口的人口转变如何改变了适应度与年龄特定存活率和生育率之间的关系。与这一人口转变同时发生的是，适应度的自然选择（以选择机会衡量）在 65 年内增加了 13%至 20%。随着婴儿存活率的显著增加，年龄特定存活率对总选择（年龄特定生育率的补充）的比例贡献从大约三分之一减少到七分之一。尽管所有年龄段的年龄特定生育率方差都大幅降低，但年龄特定生育率解释的适应度选择的绝对幅度增加了约 45%。我表明，生育力特征的适应潜力的增加直接源于人口增长率的降低。这些结果表明，这种人口转变提高了犹他州人口的适应潜力，强化了对生殖特征的选择，并降低了对与生存相关特征的选择。
