INDETERMINATE OUTCOME OF CERTAIN EXPERIMENTS ON DROSOPHILA POPULATIONS
INDETERMINATE OUTCOME OF CERTAIN EXPERIMENTS ON DROSOPHILA POPULATIONS
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DOI：
10.2307/2405731
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发表时间：
1953-01-01
期刊：
影响因子：
3.3
通讯作者：
PAVLOVSKY, O
中科院分区：
文献类型：
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作者：
DOBZHANSKY, T;PAVLOVSKY, O
实验种群的果蝇pseudobscura含有的混合物与ST和CH基因排列在他们的3D染色体。在某些种群中，所有染色体的地理起源都是一致的，它们来自于在加州某个地方收集的野生祖先。在其他种群中，基础种群的果蝇是种族杂交种，携带ST染色体的果蝇来自加州，携带CH染色体的果蝇来自墨西哥的祖先。重复试验的结果。在抽样误差的范围内，地理上同一来源的人口是相似的。杂合子ST/CH表现出杂种优势，群体最终达到平衡，ST和CH染色体继续以可预测的频率出现。地理混合起源的重复种群表现出各种各样的行为。这类群体中的ST/CH杂合体原本不具有杂种优势。但6个群体中有2个群体最终产生了杂种优势，达到了平衡。其余4个群体没有杂种优势产生，CH染色体有被完全消除的趋势。ST/ST、ST/CH和CH/CH基因型的适应值随时间变化。事实上，没有两个混合起源的人群是完全相同的。在地理上混合起源的种群中，自然选择引起的变化比在地理上统一起源的种群中发生的变化更深刻。在前者中，新的适应性一致的基因型是通过自然选择从种族间杂交的分离产物中塑造出来的。在后者中，只发生了先前存在的遗传变异频率的变化。前者可称为中进化变化，后者可称为微进化变化。有限种群中的中进化变化的可预测性和可重复性是有限的。
Experimental populations of Drosophila pseudoobscura were made which contained mixtures of flies with ST and with CH gene arrangements in their 3d chromosomes. In some populations all chromosomes were of geographically uniform origin, deriving from wild ancestors collected in a certain locality in California. In other populations the flies of the foundation stock were race hybrids, the carriers of the ST chromosomes descending from California, and those of the CH chromosomes derived from ancestors collected in Mexico. The outcomes of the replicate expts. on population of geographically uniform origin were alike, within the limits of sampling errors. The heterozygotes ST/CH exhibited heterosis and the populations eventually reached equilibria, with ST and CH chromosome continuing to occur with predictable frequencies. Replicate populations of geographically mixed origin exhibited a variety of behaviors. The ST/CH heterozygotes in such populations originally possessed no heterosis. But in 2 of the 6 populations, heterosis eventually developed, and the populations reached equilibrium. In 4 remaining populations heterosis did not develop, and CH chromosomes tended to be eliminated completely. The adaptive values of the ST/ST, ST/CH, and CH/CH genotypes changed with time. In fact, no 2 of the populations of mixed origin were quite alike. Changes induced by natural selection in populations of geographically mixed origin are more profound than those which occurred in populations of geographically uniform origin. In the former, new adaptively coherent genotypes were molded by natural selection from the segregation products of the interracial cross. In the latter, only changes in frequencies of preexisting genetic variants took place. The former can be referred to as mesoevolutionary and the latter as microevolutionary changes. The predictability and repeatability of mesoevolutionary changes in finite populations are limited.