Bauce Éric, Carisey Nathalie
Centre de Recherche en Biologie Forestière, Université Laval, G1K 7P4, Sainte-Foy, Québec, Canada.
Oecologia. 1996 Jan;105(1):126-131. doi: 10.1007/BF00328800.
Laboratory rearing of spruce budworm, Choristoneura fumiferana, in conjunction with field rearing indicated that the feeding behaviour of the larvae, which is affected by the insect population density, significantly influenced the impact of balsam fir, Abies balsamea, staminate flowering on spruce budworm biology. At low budworm density, the production of pollen in the midcrown of host trees reduced the insect development time by 5 days without affecting pupal weight, fecundity and survival. However, at high budworm density, the small amount of current-year foliage produced by flowering branches forced old larvae (sixth instar) either to feed on 1-year-old foliage (backfeeding) or to move from the midcrown to the lower crown section where staminate flowers are absent and more current-year foliage is available. When old larvae fed on old foliage, they exhibited reduced pupal weight and fecundity without losing the advange in development time that they obtained from feeding on pollen during their early stages of development. On the other hand, when old larvae moved to the lower crown section, they avoided the negative effects of backfeeding but lost the advantage in development time that was gained from feeding on pollen. Results from this study indicated that the production of staminate flowers by balsam fir trees could have opposite effects on spruce budworm population dynamics depending upon the insect population density when flowering occurs.
对云杉芽卷叶蛾（Choristoneura fumiferana）进行室内饲养，并结合野外饲养，结果表明，受昆虫种群密度影响的幼虫取食行为，对香脂冷杉（Abies balsamea）雄花开花对云杉芽卷叶蛾生物学特性的影响有着显著作用。在芽卷叶蛾密度较低时，寄主树中冠层产生的花粉使昆虫发育时间缩短了5天，而对蛹重、繁殖力和存活率没有影响。然而，在芽卷叶蛾密度较高时，开花枝条产生的当年生叶片较少，迫使老龄幼虫（六龄）要么取食一年生叶片（回食），要么从中冠层转移到没有雄花且当年生叶片较多的下冠层。当老龄幼虫取食老叶片时，它们的蛹重和繁殖力降低，但在发育早期取食花粉所获得的发育时间优势并未丧失。另一方面，当老龄幼虫转移到下冠层时，它们避免了回食的负面影响，但失去了取食花粉所获得的发育时间优势。这项研究的结果表明，香脂冷杉树产生雄花，在开花时，根据昆虫种群密度的不同，可能对云杉芽卷叶蛾的种群动态产生相反的影响。
