State key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
PLoS One. 2012;7(2):e31562. doi: 10.1371/journal.pone.0031562. Epub 2012 Feb 9.
Identifying the reproductive consequences of insect migration is critical to understanding its ecological and evolutionary significance. However, many empirical studies are seemingly contradictory, making recognition of unifying themes elusive and controversial. The beet webworm, Loxostege sticticalis L. is a long-range migratory pest of many crops in the northern temperate zone from 36 °N to 55 °N, with larval populations often exploding in regions receiving immigrants. In laboratory experiments, we examined (i) the reproductive costs of migratory flight by tethered flight, and (ii) the reproductive traits contributing to larval outbreaks of immigrant populations. Our results suggest that the beet webworm does not initiate migratory flight until the 2nd or 3rd night after emergence. Preoviposition period, lifetime fecundity, mating capacity, and egg hatch rate for adults that experienced prolonged flight after the 2nd night did not differ significantly from unflown moths, suggesting these traits are irrelevant to the severity of beet webworm outbreaks after migration. However, the period of first oviposition, a novel parameter developed in this paper measuring synchrony of first egg-laying by cohorts of post-migratory females, for moths flown on d 3 and 5 of adulthood was shorter than that of unflown moths, indicating a tightened time-window for onset of oviposition after migration. The resulting synchrony of egg-laying will serve to increase egg and subsequent larval densities. A dense population offers potential selective advantages to the individual larvae comprising it, whereas the effect from the human standpoint is intensification of damage by an outbreak population. The strategy of synchronized oviposition may be common in other migratory insect pests, such as locust and armyworm species, and warrants further study.
确定昆虫迁徙的生殖后果对于理解其生态和进化意义至关重要。然而，许多实证研究似乎相互矛盾，使得统一主题的识别变得难以捉摸和有争议。甜菜夜蛾，Loxostege sticticalis L. 是北温带 36°N 至 55°N 许多作物的长距离迁徙害虫，幼虫种群经常在接收移民的地区爆发。在实验室实验中，我们研究了（i）用系绳飞行的迁徙飞行的生殖代价，以及（ii）导致移民种群幼虫爆发的生殖特征。我们的结果表明，甜菜夜蛾直到出现后的第 2 或第 3 晚才开始迁徙飞行。经历第 2 晚后长时间飞行的成虫的预产卵期、终生产卵量、交配能力和卵孵化率与未飞行的蛾没有显著差异，表明这些特征与迁徙后甜菜夜蛾爆发的严重程度无关。然而，第 3 天和第 5 天成年期飞行的蛾的首次产卵期，本研究中开发的一个新参数，用于测量迁徙后雌性群体首次产卵的同步性，比未飞行的蛾短，表明产卵的时间窗口在迁徙后更紧。由此产生的产卵同步性将有助于增加卵和随后的幼虫密度。一个密集的种群为其中包含的个体幼虫提供了潜在的选择优势，而从人类的角度来看，这会加剧爆发种群的破坏程度。同步产卵的策略可能在其他迁徙性昆虫害虫中很常见，如蝗虫和粘虫物种，值得进一步研究。
