Messina F J, Peña N M
Department of Biology, Utah State University, Logan, Utah 84322-5305, USA.
Bull Entomol Res. 2012 Oct;102(5):497-503. doi: 10.1017/S0007485312000028. Epub 2012 Feb 24.
Colonization of a novel plant by herbivorous insects is frequently accompanied by genetic changes that progressively improve larval or adult performance on the new host. This study examined the genetic basis of adaptation to a marginal host (lentil) by the seed beetle Callosobruchus maculatus (F.). Quasi-natural selection in the laboratory rapidly increased the tendency to oviposit on lentil. The mode of inheritance of this increase in host acceptance was determined from crosses between three lentil-adapted lines and a line maintained on the ancestral host, mung bean. In each set of crosses, females from the lentil lines laid two to three times more eggs on lentil than did females from the mung-bean line. Hybrid females consistently displayed an intermediate level of host acceptance, which did not differ between reciprocal crosses. Alleles promoting greater oviposition on lentil thus were inherited additively, with no evidence of sex-linkage or cytoplasmic effects. In a time-course study, hybrid females initially resembled the parent from the mung-bean line, as few eggs were laid on lentil during the first 24 h. However, oviposition rates on lentil after 72 h were closer to the rate observed in the lentil-line parent. Inferences about additivity vs. dominance in genes affecting oviposition may, therefore, depend on experimental protocol. Comparison with earlier work suggests that inheritance patterns observed in crosses between recently derived selection lines (as in this study) may differ from those obtained in crosses between long-divergent geographic populations.
食草昆虫对新植物的定殖常常伴随着基因变化，这些变化会逐渐提高幼虫或成虫在新宿主上的表现。本研究调查了黄斑豆象（Callosobruchus maculatus (F.)）对边缘宿主（小扁豆）适应性的遗传基础。实验室中的准自然选择迅速增加了在小扁豆上产卵的倾向。通过三个适应小扁豆的品系与一个维持在原始宿主绿豆上的品系之间的杂交，确定了宿主接受度增加的遗传模式。在每组杂交中，来自小扁豆品系的雌虫在小扁豆上产的卵比来自绿豆品系的雌虫多两到三倍。杂种雌虫始终表现出中等水平的宿主接受度，正反交之间没有差异。因此，促进在小扁豆上更多产卵的等位基因是加性遗传的，没有性连锁或细胞质效应的证据。在一项时间进程研究中，杂种雌虫最初与来自绿豆品系的亲本相似，因为在最初的24小时内在小扁豆上产的卵很少。然而，72小时后在小扁豆上的产卵率更接近在小扁豆品系亲本中观察到的比率。因此，关于影响产卵的基因中加性与显性的推断可能取决于实验方案。与早期工作的比较表明，在最近衍生的选择品系之间的杂交中观察到的遗传模式（如本研究）可能与在长期分化的地理种群之间的杂交中获得的遗传模式不同。
