Hedrick Philip
School of Life Sciences, Arizona State University, Tempe, Arizona 85287-4501, USA.
Evolution. 2005 Jul;59(7):1596-9.
The ratio of the effective population size to adult (or census) population size (Ne/N) is an indicator of the extent of genetic variation expected in a population. It has been suggested that this ratio may be quite low for highly fecund species in which there is a sweepstakes-like chance of reproductive success, known as the Hedgecock effect. Here I show theoretically how the ratio may be quite small when there are only a few successful breeders (Nb) and that in this case, the Ne/N ratio is approximately Nb/N. In other words, high variance in reproductive success within a generation can result in a very low effective population size in an organism with large numbers of adults and consequently a very low Ne/N ratio. This finding appears robust when there is a large proportion of families with exactly two progeny or when there is random variation in progeny numbers among these families.
有效种群大小与成年（或普查）种群大小的比率（Ne/N）是一个种群中预期遗传变异程度的指标。有人提出，对于繁殖力高的物种，这种比率可能相当低，在这类物种中，繁殖成功存在类似抽奖的机会，即所谓的赫奇科克效应。在此我从理论上表明，当只有少数成功繁殖者（Nb）时，该比率可能相当小，并且在这种情况下，Ne/N比率约为Nb/N。换句话说，一代内繁殖成功的高方差会导致成年个体数量众多的生物体的有效种群大小非常低，从而导致Ne/N比率非常低。当有很大比例的家庭恰好有两个后代，或者这些家庭的后代数量存在随机变异时，这一发现似乎很可靠。
