Moore Ben D, Foley William J, Wallis Ian R, Cowling Ann, Handasyde Kathrine A
School of Botany and Zoology, Australian National University, Canberra ACT 0200, Australia.
Biol Lett. 2005 Mar 22;1(1):64-7. doi: 10.1098/rsbl.2004.0255.
The koala is the quintessential specialist herbivore, feeding almost exclusively on Eucalyptus foliage. Consequently, the limitations imposed on the koala's diet by plant defences indicate the extent to which evolutionary adaptations allow mammalian herbivores to circumvent such defences. We tested whether a recently discovered group of plant secondary metabolites, the formylated phloroglucinol compounds (FPCs), deters koalas from feeding on some eucalypt foliage. We found that captive koalas ate less foliage in a single night from trees with high FPC concentrations. Individual trees also differ in the types of FPC they possess, but for a given eucalypt species, most FPCs were similarly effective deterrents. Two closely related and sympatric eucalypt species could be clearly separated by the amounts that koalas ate from each; however, this difference could not be explained by total FPC concentrations alone. We suggest, that in this case, the presence of a distinct type of FPC deters koala herbivory on the less palatable species, and may have facilitated the evolutionary divergence of these species. We conclude that plant defences probably play an important role in determining the distribution and abundance of koalas.
考拉是典型的专性食草动物，几乎只以桉树叶为食。因此，植物防御对考拉饮食造成的限制表明了进化适应使哺乳动物食草动物规避此类防御的程度。我们测试了最近发现的一组植物次生代谢产物，即甲酰化间苯三酚化合物（FPCs），是否会阻止考拉取食某些桉树叶。我们发现，圈养的考拉在一个晚上从FPC浓度高的树上吃的叶子较少。不同的树木所含FPC的类型也有所不同，但对于某一特定的桉树种来说，大多数FPC的威慑效果相似。两种亲缘关系密切且同域分布的桉树种，可以通过考拉从每种树上取食的量清楚地区分开来；然而，这种差异不能仅用FPC的总浓度来解释。我们认为，在这种情况下，一种独特类型的FPC的存在会阻止考拉取食口感较差的树种，并且可能促进了这些树种的进化分化。我们得出结论，植物防御可能在决定考拉的分布和数量方面起着重要作用。
