Lawler I R, Foley W J, Eschler B M, Pass D M, Handasyde K
Department of Zoology and Tropical Ecology, James Cook University of North Queensland, Townsville, 4811, Queensland, Australia e-mail:
Department of Molecular Sciences, James Cook University of North Queensland, Townsville, 4811, Queensland, Australia, , , , , , AU.
Oecologia. 1998 Aug;116(1-2):160-169. doi: 10.1007/s004420050575.
Traditional approaches to the question of the effects of plant secondary metabolites on the feeding choices of folivores of Eucalyptus have focused on the tree species level, although numerous field studies of foraging behaviour have identified selection at the level of the individual trees. Attempts to relate these decisions to deterrency resulting from secondary leaf chemistry have been inconclusive because assays used have focused on broad groups of compounds such as "total" phenolics. In this study we have conducted no-choice feeding trials with two arboreal mammalian folivores, the common ringtail possum (Pseudocheirus peregrinus) and the koala (Phascolarctos cinereus), to measure deterrency of individual trees of two species of Eucalyptus, E. ovata and E. viminalis. Average daily intakes of E. ovata foliage by common ringtail possums ranged from 2.5 to 50 g kg body mass. Koala intakes of foliage from the same individual trees ranged from 22.4 to 36.3 g kg body mass. When fed foliage from different individual E. viminalis trees, common ringtail possums ate between 1.26 and 6.28 g kg body mass while koalas ate from 14.3 to 45.9 g kg body mass. Correlative analyses showed no relationships between feeding and several measures of nutritional quality, nor with total phenolics or condensed tannins. They did, however, identify two groups of plant secondary metabolites that may cause deterrency: terpenes, and a defined group of phenolic compounds, the diformylphloroglucinols (DFPs). Further bioassay experiments with common ringtail possums showed that only the DFPs could cause the effects seen with the foliage experiments at concentrations similar to those found in the leaves. We argue that, when in sufficiently high concentrations, DFPs determine the level of food intake by these animals irrespective of other questions of nutritional quality of the leaves.
关于植物次生代谢产物对桉树食叶动物取食选择的影响这一问题，传统研究方法一直聚焦于树种层面，尽管众多觅食行为的野外研究已确定在个体树木层面存在选择行为。试图将这些取食决策与叶片次生化学物质产生的威慑作用联系起来的研究尚无定论，因为所采用的分析方法聚焦于宽泛的化合物类别，如“总”酚类。在本研究中，我们对两种树栖食叶哺乳动物——普通环尾袋貂（Pseudocheirus peregrinus）和考拉（Phascolarctos cinereus）进行了无选择取食试验，以测定两种桉树——卵叶桉（E. ovata）和多枝桉（E. viminalis）的单株树木的威慑作用。普通环尾袋貂对卵叶桉树叶的日均摄入量为每千克体重2.5至50克。考拉对同一单株树木树叶的摄入量为每千克体重22.4至36.3克。当给普通环尾袋貂投喂来自不同多枝桉单株树木的树叶时，其摄入量为每千克体重1.26至6.28克，而考拉的摄入量为每千克体重14.3至45.9克。相关性分析表明，取食与几种营养质量指标之间没有关系，与总酚或缩合单宁也没有关系。然而，这些分析确实确定了两组可能导致威慑作用的植物次生代谢产物：萜类化合物，以及一组特定的酚类化合物，即二甲酰基间苯三酚（DFPs）。对普通环尾袋貂进行的进一步生物测定实验表明，只有DFPs在与叶片中发现的浓度相似时，才能产生在树叶实验中观察到的效果。我们认为，当DFPs浓度足够高时，它们会决定这些动物的食物摄入量水平，而不考虑树叶营养质量的其他问题。
