Linking plant genotype, plant defensive chemistry and mammal browsing in a Eucalyptus species

1. In the field of plant-herbivore interactions a major focus of research is the importance of herbivores as selective agents on the evolution of plant resistance. Evidence to support the role of herbivores as selective agents must demonstrate that the intraspecific variation in plant resistance, and the variation in the plant resistive trait, are under genetic control. Predominantly, research in this field has concentrated on plant-insect systems, with much less emphasis on plant-mammal interactions. 2. In a common Eucalyptus species, Eucalyptus globulus (Labill.), variation in resistance to a mammalian herbivore, Trichosurus vulpecula (Kerr, 1792), is under genetic control. 3. In this paper, plants of known genetic stock grown in a common-environment field trial were used to investigate the plant characteristic responsible for resistance of E. globulus to T. vulpecula and to determine if there was a genetic basis to variation in the defensive trait. 4. The results demonstrate that a formylated phloroglucinol compound, sideroxylonal, is the dominant plant secondary metabolite that determined intake of E. globulus juvenile coppiced foliage by T. vulpecula, and that this metabolite is under significant genetic control. 5. These results are discussed in the context of the possible role T. vulpecula may play as a selective agent on the evolution of resistance in E. globulus.