Distribution of foliar formylated phloroglucinol derivatives amongst Eucalyptus species
Eschler, BM, Pass, DM, Willis, R & Foley, WJ 2000, Biochemical Systematics and Ecology, vol. 28, no. 1, pp. 813-824.
Formylated phloroglucinol compounds (FPCs) are an important feeding deterrent in Eucalyptus foliage, with samples of 27 out of 41 Eucalyptus species found to have masses characteristic of FPCs. The subgenus Monocalyptus lacked any known FPCs, while the most commonly identified FPC group was the sideroxylonals.
The study used electrospray ionisation, Fourier transform ion cyclotron resonance mass spectrometry to find masses in leaf samples that matched known FPCs. The subgenus Monocalyptus had none of these, but there were many masses of unknown compounds which could potentially be unknown FPCs. This was also the case for the subgenus Idiogenes (however, it only has one member), several species of Corymbia and E. globulus. NMR was also used semi-quantitatively by comparing the aldehyde proton peak to a known standard to determine the number of aldehydes in the sample and therefore approximate the FPC concentration. Sideroxylonal-rich species were determined to have greater total FPC concentrations than euglobal- and macrocarpal-rich species on average.
Previous studies of FPCs had only investigated the subgenus Symphyomyrtus; therefore, this study significantly broadened the range of Eucalyptus species studied with regards to FPCs. E. globulus had previously been used as source for isolation of multiple euglobals and macrocarpals, so the complete lack of FPC masses in this experiment was unusual. This difference was likely due to the significant variation in FPC concentrations within each species, as it may be a polymorphic trait in Eucalyptus suggesting, therefore, that this experiment would have benefited from wider sampling. The lack of FPCs in the entire subgenus Monocalyptus, however, is consistent with other research, indicating that the result is significant.
Knowledge of which Eucalyptus species contain which FPCs would be helpful in determining whether animals would be deterred from eating their foliage, thus contributing to our understanding of the dietary habits and mechanisms of folivorous marsupials such as the koala.
Summarised by Laura Wait
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