Data from: Evolution of host acceptance and its reversibility in a seed beetle

1. Adapting to a low-quality plant may require modification of an insect's digestive physiology, oviposition behaviour, or other host-use traits. If colonising a marginal host entails a cost, a decay in adaptation would be expected after selection is relaxed, i.e. if populations on a novel host are reverted to their high-quality ancestral host. 2. Replicate lines of the seed beetle Callosobruchus maculatus (F.) rapidly adapted to lentil seeds; larval survival rose from approximately 1 to ≥ 90%, and oviposition on lentil increased more than two-fold. This study compared egg-laying behaviour in lines that either remained on lentil or were reverted to the ancestral host, mung bean, for 22–62 generations. 3. Consistent with the trade-off hypothesis, females from two reverted sublines showed decreased oviposition on lentil (estimated as lifetime fecundity), but host acceptance in a third subline was unchanged. In a short-term assay, acceptance of lentil by newly emerged females was lower in each reverted subline than in the corresponding non-reverted one. Because effective population sizes (determined from genome resequencing) were large throughout the experiment, this decline in host acceptance is unlikely to be explained solely by genetic drift. 4. Variation among replicates in the magnitude of the reversion effect was also observed in a previous study of larval survival. However, the pattern of variation for survival was not congruent with the pattern of variation for host acceptance in this study. Thus, genes mediating improved performance on lentil appear to be largely independent of those responsible for increased oviposition.

1. 适应劣质寄主植物可能需要改造昆虫的消化生理、产卵行为或其他寄主利用相关性状。若定殖边缘寄主存在适合度代价，当选择压力放松后，适应性会出现衰退——即当以新型寄主饲养的种群被转回至高质量的祖先寄主时，便会发生此类适应性衰退。
2. 本研究中，绿豆象（Callosobruchus maculatus）的重复品系可快速适应扁豆种子：幼虫存活率从约1%提升至≥90%，且在扁豆上的产卵量提升两倍以上。本研究比较了两类品系的产卵行为：一类持续以扁豆饲养，另一类被转回至祖先寄主绿豆（mung bean）饲养22至62代。
3. 与权衡假说（trade-off hypothesis）的预测相符，两个转回亚品系的雌性个体在扁豆上的产卵量（以终身繁殖力估算）出现下降，但第三个亚品系的寄主接受度未发生改变。在短期行为检测中，各转回亚品系中新羽化雌虫对扁豆的接受度，均低于对应的未转回亚品系。由于实验全程的有效种群规模（通过基因组重测序测定）始终较大，因此寄主接受度的下降不太可能仅由遗传漂变导致。
4. 此前一项针对幼虫存活率的研究中，同样观察到重复品系间反转效应的程度存在差异。但本研究中，存活率的变异模式与寄主接受度的变异模式并不一致。由此可见，介导扁豆适应性提升的基因，似乎在很大程度上独立于调控产卵量提升的基因。