Baltensweiler Werner
Institute of Plant Sciences, Phytomedicine/Applied Entomology, ETH Zürich/CLS, CH-8092, Zürich, Switzerland.
Oecologia. 1993 Mar;93(2):251-255. doi: 10.1007/BF00317678.
Studies of fluctuating insect populations generally discuss the regulating processes at high insect numbers, but very rarely why a cycling population at low densities switches immediately from the declining phase to the increasing phase of the cycle. A long-term study of the larch bud moth (Zeiraphera diniana Gn) has suggested that the key to recovery is assortative mating of specific phenotypes. Z. diniana exhibits distinct host races living either on the deciduous larch or evergreen pines and spruces. As an adaptation to its hosts Z. diniana is necessarily rather polymorphic in its life history parameters, i.e. developmental rate, fertility and survival. Apart from the direct association of the larva with the host tree, the colouration of the mature larva provides the only readily apparent trait by which the host race can be recognised; the larch form is black and the pine or spruce form has a light orange head capsule, anal plate and body colour. Evidence that frequencies of the colour morphs on larch regularly change from an intermediate colour type to black during the increasing phase of the cycle suggests that the combination of traits, such as earliest larval emergence, largest body size and homozygosity, characteristic of the black morph, constitutes the inherent driving force of population increase.
对昆虫种群数量波动的研究通常讨论昆虫数量较多时的调节过程，但很少探讨为什么处于低密度周期波动的种群会立即从下降阶段转向上升阶段。一项对落叶松芽蛾（Zeiraphera diniana Gn）的长期研究表明，种群恢复的关键在于特定表型的选型交配。落叶松芽蛾表现出明显的寄主种群，分别生活在落叶松或常绿的松树和云杉上。作为对寄主的一种适应，落叶松芽蛾在其生活史参数，即发育速率、繁殖力和存活率方面必然具有相当的多态性。除了幼虫与寄主树的直接关联外，成熟幼虫的体色是唯一能轻易区分寄主种群的明显特征；落叶松型幼虫是黑色的，而松或云杉型幼虫的头壳、肛板和体色为浅橙色。有证据表明，在种群数量上升阶段，落叶松上黑色体色形态的频率会从中间颜色类型有规律地变为黑色，这表明诸如最早羽化、体型最大和纯合性等黑色体色形态所特有的性状组合，构成了种群增长的内在驱动力。
