Mueller L D
Proc Natl Acad Sci U S A. 1987 Apr;84(7):1974-7. doi: 10.1073/pnas.84.7.1974.
Ecological theories of life history evolution predict that natural selection should favor semelparous life histories in environments where juvenile survival is high relative to adult survival and rates of population growth are high. That is, organisms should complete their entire reproductive effort in a short period of time following maturation. Direct empirical verification of this idea has been lacking. Six independent populations of Drosophila melanogaster were maintained in two different environments, called r and K, for more than 120 generations. In the r environment population size was small, larval survival and rates of population growth were high, and reproduction was limited to a few days after eclosion. In the K environment population size was large and larval survival low, but adults were allowed to reproduce indefinitely. The fecundity of females of different sizes from each environment was measured daily for 4 weeks. No differences in fecundity were seen during the first week of adult life for females from the two environments. By the fourth week, however, the fecundity of large females from the r environment was 47-83% less than that of females from the K environment. The accelerated senescence exhibited by females from the r environment appears to be due to the accumulation of deleterious alleles whose effects are expressed late in life, which is consistent with the mutation accumulation hypothesis for the evolution of senescence.
生活史进化的生态理论预测，在幼体存活率相对于成体存活率较高且种群增长率较高的环境中，自然选择应有利于单次生殖的生活史。也就是说，生物体应在成熟后的短时间内完成其全部繁殖努力。一直缺乏对这一观点的直接实证验证。六个独立的黑腹果蝇种群在两种不同的环境中（称为r和K）维持了120多代。在r环境中，种群规模较小，幼虫存活率和种群增长率较高，繁殖仅限于羽化后的几天内。在K环境中，种群规模较大，幼虫存活率较低，但成虫可无限期繁殖。对来自每个环境的不同大小雌性果蝇的繁殖力进行了为期4周的每日测量。在成虫生活的第一周，来自两种环境的雌性果蝇在繁殖力上没有差异。然而，到第四周时，来自r环境的大型雌性果蝇的繁殖力比来自K环境的雌性果蝇低47%-83%。来自r环境的雌性果蝇表现出的加速衰老似乎是由于有害等位基因的积累，其影响在生命后期才表现出来，这与衰老进化的突变积累假说一致。
