van Noordwijk A J
Netherlands Institute of Ecology, Heteren.
EXS. 1994;68:131-46. doi: 10.1007/978-3-0348-8510-2_12.
Current population genetic and population dynamic models are inappropriate to judge the risk of extinction of small populations due to the combined effects of inbreeding, genetic drift, demographic stochasticity, and environmental stochasticity. Instead, a model based on the aggregated fates of individuals is advocated. The unequal distribution of resources over individuals is an essential part of this model. The model allows the incorporation of the mutation-selection dynamics of alleles leading to inbreeding effects and to fixation of slightly deleterious mutations as a result of genetic drift. The slightly deleterious mutations lower the conversion of resources into offspring. Whereas lethal alleles are rapidly eliminated by selection in small populations, the selection against mild deleterious effects depends strongly on effective population size and on the social system, that is, on the division of resources among individuals. The model allows for the study of rates at which processes occur while far away from equilibrium, which is crucial in understanding the extinction risks of threatened populations. One example of the latter is illustrated in simulations in which small populations become extinct between approximately 100 and 200 generations after they became small populations, due to a gradual accumulation of mildly deleterious mutations.
由于近亲繁殖、遗传漂变、种群统计学随机性和环境随机性的综合影响，当前的种群遗传模型和种群动态模型并不适合用来判断小种群的灭绝风险。相反，有人主张采用一种基于个体总体命运的模型。个体间资源分配不均是该模型的一个重要组成部分。该模型允许纳入等位基因的突变-选择动态，从而导致近亲繁殖效应，并由于遗传漂变导致轻度有害突变的固定。轻度有害突变会降低资源向后代的转化。在小种群中，致死等位基因会通过选择迅速被淘汰，而针对轻度有害效应的选择则强烈依赖于有效种群大小和社会系统，即个体间的资源分配。该模型允许研究远离平衡状态时各种过程发生的速率，这对于理解受威胁种群的灭绝风险至关重要。后者的一个例子在模拟中得到了说明，在模拟中，小种群在变成小种群后的大约100到200代之间灭绝，原因是轻度有害突变的逐渐积累。
