Principle Component Analysis
Thirty leaves were successfully extracted with 112 compounds identified (Table. 7), with 11 leaves of Euc. sp. 1 and 19 leaves ofEuc. globulus . Of the 51 parasitoid -beetle pairs, damaged leaves were successfully extracted for 49 pairs. The first PCA examined allEucalyptus leaves to see if there were distinct chemoprofiles across the two species: 54.1% of the variation was explained in the first five principal components (PCs), with 21.4% in the first, and 10.7% in the second. Separation of the two Eucalyptus species was observed in PC1 (F1,28 = 24.09, P < 0.001) but not PC2 (F1,28 = 3.633, P = 0.067) (Fig. 5A; Table 3). One Euc. sp. 1 sample grouped with the Euc. globulusspecimens (VIC083 MD). This Euc. sp. 1 leaf was the only mature herbivore damaged leaf collected. This suggests that there are distinct chemoprofiles between the two species of Eucalyptus tested in this study.
For the second PCA including flush, damaged and undamaged Euc. globulus leaves, 71.1% of the variation was explained in the first 5 principal components, with 25.9% in the first, and 15.3% in the second. Clear separation between the two groups was not observed in either PC1 (F1,9 = 1.3, P = 0.284) or PC2 (F1,9 = 1.513, P = 0.25) (Fig. 5B; Table 3).
For the third PCA including leaves damaged by the four species of beetles, 75.3% of the explained variation was observed in the first five PCs, with 31.3% in the first, and 14.1% in the second. Clear separation is observed in PC2 (F3,9 = 26.1, P < 0.001) but not in PC1 (F3,90 = 2.266, P = 0.0862) (Fig. 5C; Table 3). Leaves damaged by Pst. cloelia were found to be significantly separated from those damaged by Pst. agricola (P < 0.001) and Pst. m-fuscum (P < 0.001) in the Tukeys Post Hoc analysis of PC2 (Table 4). These results suggest that Pst. cloelia prefer different plant chemoprofiles to the other species.
For the fourth PCA examining leaves damaged by beetles from whichEadya parasitoids were reared, 83% of the explained variation was observed in the first five PCs, with 30.6% in the first, and 16.5% in the second. Separation is observed in PC1 (F2,46 = 7.611, P = 0.00139), and PC2 (F2,46 = 4.183, P = 0.0214) (Fig. 5D; Table 3). Of the three species only E. daenerys andE. annleckieae were significantly separated (P > 0.0037), and only for PC1 (Table 4). These results suggest that, like the beetles, species of Eadya are attracted to species-specific chemoprofiles of Eucalyptus .