Messina Frank J, Lish Alexandra M, Springer Amy, Gompert Zachariah
Department of Biology, Utah State University, Logan, UT.
Environ Entomol. 2020 Aug 20;49(4):938-946. doi: 10.1093/ee/nvaa065.
The ability to adapt to a novel host plant may vary among insect populations with different genetic histories, and colonization of a marginal host may be facilitated by genetic admixture of disparate populations. We assembled populations of the seed beetle, Callosobruchus maculatus (F.), from four continents, and compared their ability to infest two hosts, lentil and pea. We also formed two cross-continent hybrids (Africa × N.A. and Africa × S.A.). In pre-selection assays, survival was only ~3% in lentil and ~40% in pea. For three replicate populations per line, colonization success on lentil was measured as cumulative exit holes after 75-175 d. On pea, we estimated the change in larval survival after five generations of selection. Females in all lines laid few eggs on lentil, and survival of F1 larvae was uniformly <5%. Subsequently, however, the lines diverged considerably in population growth. Performance on lentil was highest in the Africa × N.A. hybrid, which produced far more adults (mean > 11,000) than either parental line. At the other extreme, Asian populations on lentil appeared to have gone extinct. The Africa × N.A. line also exhibited the highest survival on pea, and again performed better than either parent line. However, no line displayed a rapid increase in survival on pea, as is sometimes observed on lentil. Our results demonstrate that geographic populations can vary substantially in their responses to the same novel resource. In addition, genetic admixtures (potentially caused by long-distance transport of infested seeds) may facilitate colonization of an initially poor host.
适应新宿主植物的能力在具有不同遗传历史的昆虫种群中可能有所不同，不同种群的基因混合可能有助于在边缘宿主上定殖。我们收集了来自四大洲的豆象Callosobruchus maculatus (F.)种群，并比较了它们侵染两种宿主（小扁豆和豌豆）的能力。我们还培育了两个跨洲杂交种（非洲×北美和非洲×南美）。在预筛选试验中，在小扁豆上的存活率仅约为3%，在豌豆上约为40%。对于每个品系的三个重复种群，在75 - 175天后，以累积出孔数来衡量在小扁豆上的定殖成功率。在豌豆上，我们估计了经过五代选择后幼虫存活率的变化。所有品系的雌性在小扁豆上产卵很少，F1幼虫的存活率均低于5%。然而，随后各品系在种群增长方面出现了很大差异。非洲×北美杂交种在小扁豆上的表现最佳，产生的成虫数量（平均>11,000）远远多于任何一个亲本品系。在另一个极端，亚洲种群在小扁豆上似乎已经灭绝。非洲×北美品系在豌豆上也表现出最高的存活率，并且再次比任何一个亲本品系表现更好。然而，没有一个品系在豌豆上的存活率像在小扁豆上有时观察到的那样迅速增加。我们的结果表明，地理种群对相同新资源产生的反应可能有很大差异。此外，基因混合（可能由受侵染种子的远距离运输引起）可能有助于在最初不太适宜的宿主上定殖。
