Selection plateau during long-term selection in experimental Drosophila populations
1991
Savchenko, V.K. | Tananko, M.V. | Dobina, A.I.
As a result of long-term selection for abdominal bristle number and thorax length Drosophila populations were obtained which did not respond further to the action of artificial selection at an intensity of 10%. A study of the subpopulations which emerged on to the selection plateau showed that they did not totally lose genetic variability. Genetic variability and its selectionally significant additive component have a complex time-course and may not only decrease during the selection process but may also increase during certain time intervals. It has been shown that the subpopulations have the ability to undergo evolution to the side of the original value of the selection characters in the original population as a result of free crossing and selection in the opposite direction. This indicates that, when the selection plateau is attained, most of the alleles, which control the quantitative character, are not fixed. It was found that selection for quantitative characters leads to a change in fertility, which is an important adaptation parameter. In this case the negative consequences of artificial selection are expressed to a greater extent during selection for a decrease in the size of the quantitative character. This evidently results from the accumulation of the homozygotization of recessive alleles in the genes, which control the quantitative character and which have a pleiotropic effect on fertility.
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