EFFECTIVE DEME SIZES DURING LONG-TERM EVOLUTION ESTIMATED FROM RATES OF CHROMOSOMAL REARRANGEMENT
EFFECTIVE DEME SIZES DURING LONG-TERM EVOLUTION ESTIMATED FROM RATES OF CHROMOSOMAL REARRANGEMENT
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DOI：
10.2307/2407380
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发表时间：
1979-01-01
期刊：
影响因子：
3.3
通讯作者：
LANDE, R
中科院分区：
文献类型：
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作者：
LANDE, R
在大多数二倍体生物中，倒位和易位杂合性和纯合性除了降低杂合子育性外很少产生表型效应。构建了一个模型的人口细分为demes自发染色体重排发生杂合子的劣势。这种重排在同群中的最初固定只能通过随机遗传漂变发生，因为它们在少数群体中被选择为反对，但在多数群体中被选择为赞成。每一代少数个体的种群间迁移可以阻止新的重排在当地的建立，这表明成功的重排通常发生在孤立的种群中。一旦在一个种群中建立，负杂种优势基因排列就可以通过随机的局部灭绝和定殖以纯合形式在一个细分种群中传播。在这个过程中，在由许多半隔离的群落组成的物种中，固定率近似等于在它的一个群落中建立新基因排列的速率。因此，在长期进化过程中的有效deme大小的估计，可以从自发发生率的数据，选择强度对杂合子和固定率的不同种类的染色体重排在同源性。自发倒位、相互易位和罗伯逊融合在各种动物中以每代10-4和10-3/配子的速率发生。相互易位的固定通常缺乏导致杂合子半不育性和常见的固定，在同类物种之间，倒位和罗伯逊变化引起百分之几的杂合子不利。在许多动物分类群的进化过程中，有效的同群个体大小可能在几十到几百个个体的范围内。这些结果是相当不敏感的自发发生率和固定率的值中的不准确性，在胚胎发育。这里估计的有效种群大小与现有种群的繁殖结构的观察是一致的，并表明在宏观进化的随机遗传漂变的可能性相当大。
In most diploid organisms inversion and translocation heterozygosity and homozygosity rarely produce phenotypic effects, other than reducing heterozygote fertility. A model is constructed of a population subdivided into demes where spontaneous chromosomal rearrangements occur having heterozygote disadvantage. The initial fixation of such rearrangements in a deme can happen only by random genetic drift, because they are selected against when in the minority, but favored when in the majority. Interdeme migration of a few individuals per generation can prevent the local establishment of new rearrangements, suggesting that successful rearrangements generally arise in isolated populations. Once established in a deme, a negatively heterotic gene arrangement can spread in homozygous form through a subdivided population by random local extinction and colonization. For this process, the fixation rate in a species composed of many semi-isolated demes is approximately equal to the rate of establishment of new gene arrangements in a single one of its demes. Estimates of effective deme sizes during long-term evolution can thus be obtained from data on spontaneous occurrence rates, selection intensities against heterozygotes and fixation rates of different kinds of chromosomal rearrangements in phylogeny. Spontaneous inversions, reciprocal translocations and Robertsonian fusions occur at rates between 10-4 and 10-3/gamete per generation in a variety of animals. The usual absence of fixation of reciprocal translocations causes heterozygote semisterility and the common fixation, between congeneric species, of inversions and Robertsonian changes entailing several percent heterozygote disadvantage. During the evolution of many animal taxa effective deme sizes may have been in the range of a few tens to a few hundreds of individuals. These results are rather insensitive to inaccuracies in the values of the spontaneous occurrence rates and fixation rates in phylogeny. The effective deme sizes estimated here are consistent with observations on the breeding structure of existing populations, and indicate considerable possibility for random genetic drift in macroevolution.