CSIRO Ecosystem Sciences, GPO Box 1700, Canberra, Australian Capital Territory 2601, Australia.
J Chem Ecol. 2011 Mar;37(3):286-300. doi: 10.1007/s10886-011-9916-5. Epub 2011 Feb 19.
Individual Eucalyptus trees in south-eastern Australia vary considerably in susceptibility to herbivores. On the one hand, studies with insect herbivores have suggested that variation in the concentrations of foliar monoterpenes is related to variation in susceptibility. On the other, studies with marsupial folivores have suggested that variation in the concentrations of sideroxylonals (a group of formylated phloroglucinol compounds) is responsible for variation in susceptibility. We examined relative importance of sideroxylonals and 1,8-cineole (a dominant monoterpene) in host tree selection by Christmas beetles (Anoplognathus species: Coleoptera: Scarabaeidae) by using no-choice experiments, choice/no-choice experiments, and manipulative experiments in which concentrations of sideroxylonals or 1,8-cineole were altered. We used two species of host Eucalyptus, one species of non-host Eucalyptus, and three species of non-host non-Eucalyptus trees. Leaf consumption by Christmas beetles was negatively correlated with the concentrations of sideroxylonals and 1,8-cineole. Artificial increases in the concentration of sideroxylonals or 1,8-cineole reduced leaf consumption by Christmas beetles. An artificial reduction in foliar monoterpenes had no effect on leaf consumption by the beetles when leaves contained high or very low concentrations of sideroxylonals. However, when the concentration of sideroxylonals was moderate, a reduction in the foliar monoterpenes increased leaf consumption by the beetles. Therefore, monoterpenes such as 1,8-cineole may be used as a negative cue by Christmas beetles. The pattern of food consumption on non-host Eucalyptus species and non-host non-Eucalyptus species suggest that both positive and negative cues may be used by Christmas beetles to select host trees.
澳大利亚东南部的个别桉树在对食草动物的易感性上差异很大。一方面，对昆虫食草动物的研究表明，叶中单萜浓度的变化与易感性的变化有关。另一方面，对有袋类食草动物的研究表明，侧柏酮（一组甲酰基间苯三酚化合物）浓度的变化是导致易感性变化的原因。我们通过非选择性实验、选择/非选择实验以及操纵实验，研究了 Christmas 甲虫（鞘翅目：金龟子科）对侧柏酮和 1,8-桉树脑（一种主要的单萜）在宿主树选择中的相对重要性，实验中改变了侧柏酮和 1,8-桉树脑的浓度。我们使用了两种宿主桉树、一种非宿主桉树和三种非宿主非桉树。Christmas 甲虫对叶片的消耗与侧柏酮和 1,8-桉树脑的浓度呈负相关。人工增加侧柏酮或 1,8-桉树脑的浓度会降低 Christmas 甲虫对叶片的消耗。当叶片中含有高浓度或极低浓度的侧柏酮时，人工降低叶片中单萜的浓度对甲虫的叶片消耗没有影响。然而，当侧柏酮浓度适中时，降低叶片中单萜的浓度会增加甲虫对叶片的消耗。因此，像 1,8-桉树脑这样的单萜可能被 Christmas 甲虫用作负面线索。对非宿主桉树物种和非宿主非桉树物种的食物消耗模式表明，Christmas 甲虫可能使用正面和负面线索来选择宿主树。
