Watson Marcus J O, Hoffmann Ary A
School of Genetics and Human Variation, La Trobe University, Bundoora, Victoria 3083, Australia.
Evolution. 1996 Jun;50(3):1182-1192. doi: 10.1111/j.1558-5646.1996.tb02359.x.
The way populations respond to selection can be altered when populations are acclimated prior to selection. To examine this possibility, the responses of replicate lines of Drosophila melanogaster and D. simulans to selection for increased resistance to cold were compared. Flies were selected without hardening or after they had been hardened by holding them at 4°C for one hour. The selection response in both species was much greater when flies were not cold-hardened. Cold resistance in both sets of selected lines reached a plateau after a few generations. Surprisingly, continued selection for increased resistance resulted in decreasing levels of resistance. This decrease was no longer evident after selection had been relaxed for a generation, suggesting cross-generation effects. The magnitude of the cross-generation effects increased with additional generations of selection. Cross-generation effects were also detected for fitness components. Relaxing selection for a generation increased fecundity, weight, viability, and development time. Comparisons of relaxed lines and control lines indicated that only fecundity was influenced by selection. Both sets of selected lines had a lower fecundity than control lines. Crosses between control and selected lines and among replicate selected lines indicated that this decrease in fecundity was not associated with inbreeding. The direct and correlated responses to selection for cold resistance can therefore be influenced by acclimation and cross-generation effects.
当种群在选择前进行驯化时，种群对选择的反应方式可能会改变。为了检验这种可能性，比较了黑腹果蝇和拟果蝇的重复品系对增加抗寒能力选择的反应。果蝇在未进行硬化处理时或在4°C下放置一小时进行硬化处理后进行选择。当果蝇未进行冷硬化处理时，两个物种的选择反应都要大得多。两组选择品系的抗寒能力在几代后都达到了平稳状态。令人惊讶的是，持续选择增加抗寒能力导致抗寒水平下降。在选择放松一代后，这种下降不再明显，表明存在跨代效应。跨代效应的大小随着选择代数的增加而增加。还检测到了适合度成分的跨代效应。选择放松一代会增加繁殖力、体重、活力和发育时间。放松选择品系与对照品系的比较表明，只有繁殖力受选择影响。两组选择品系的繁殖力都低于对照品系。对照品系与选择品系之间以及重复选择品系之间的杂交表明，这种繁殖力的下降与近亲繁殖无关。因此，对冷抗性选择的直接和相关反应可能会受到驯化和跨代效应的影响。
