Bradshaw William E, Kizziar Piper, Borowczak Rudyard J, Kirsch Ethan, Holzapfel Christina M
Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403-5289, USA.
Insects. 2022 Oct 16;13(10):939. doi: 10.3390/insects13100939.
Conventional wisdom is that selection decreases genetic variation in populations, variation that should enable and be essential for population persistence in an ever-changing world. Basically, we find the opposite. Response to selection on biting in the pitcher-plant mosquito, , increases from 20 to 80% in 19 generations, but reverts back to the original 20% after seven generations of relaxed (not reversed) selection. At the same time, biting in the control line remains at the original 20% through 30 generations without blood feeding. Imposition of selection on biting in both lines elicits a rapid response in the previously selected line, but, importantly, not in the control line. Genetic variation for biting has increased, not decreased, as a consequence of long-term directional selection, contrary to expectations. Convergent phenotypes belie the underlying difference in future adaptive potential. Selection events over time in the background of individuals or populations will determine outcomes of applied research, be it in the fields of medicine, agriculture, or conservation. In short, history matters.
传统观念认为，选择会减少种群中的遗传变异，而这种变异对于种群在不断变化的世界中持续存在应该是必不可少且能够发挥作用的。但基本上，我们发现事实恰恰相反。对捕虫草蚊叮咬行为的选择反应在19代中从20%增加到了80%，但在经过七代的宽松选择（而非反向选择）后又恢复到了最初的20%。与此同时，在30代不进行血液喂养的情况下，对照品系的叮咬率一直保持在最初的20%。对两个品系的叮咬行为施加选择会在之前经过选择的品系中引发快速反应，但重要的是，对照品系却没有。与预期相反，长期的定向选择导致叮咬行为的遗传变异增加了，而非减少。趋同的表型掩盖了未来适应潜力的潜在差异。在个体或种群背景下随着时间推移的选择事件将决定应用研究的结果，无论是在医学、农业还是保护领域。简而言之，历史很重要。
