## 2 Results and Discussion
### Taxonomic Misdeterminations
#### 2.3.2. Eremophila arbuscular  
The two species, _E. arbuscular_ and _E. oppositifolia_, are commonly mis-determined as one for the other due to morphological similarities. In the current study, two specimens of _E. arbuscular_ were harvested from Idalia National Park (NP), central Qld, several specimens of _E. oppositifolia_ subsp. _rubra_ and _E. oppositifolia_ subsp. _oppositifolia_ were harvested for comparison, from western NSW. Figure 8: Principal component analysis including loadings plot of essential oil components from _Eremophila sturtii_. Another specimen of _E. arbuscular_ was harvested from a private garden on two separate occasions. The garden specimen bore the same distinctive odour of one of the wild specimens, which gave a furanosesquiterpene dominated essential oil profile (Tables 4 and 10) when hydrodistilled. However, all three specimens were chemically different. The two wild specimens were collected based on a difference in the perception of aroma when the leaves were crushed and smelled, and the growth habit. In Idalia NP, the hills are populated with _E. arbuscular_, which grows into thin and tall trees (up to 10 meters) when in the ranges, but on flat soils it develops into a shorter and broader shrub. The data in Table 4 correspond to specimen Earb-486, which was collected from the ranges and Earb-487, which was from the flat plains below the same ridge. These specimens demonstrated strikingly different chemical profiles. Earb-486 expressed \(>\) 50% of a new metabolite which was characterised by NMR and assigned as _Z_-11-hydroxysodendlasin (see Supplementary A2 for NMR spectral assignments). In hydrodistillation, the hydroxy group is eliminated to afford _E_-11(12)-dehydroisodendlasin (Supplementary A2), which was also assigned by NMR. Solvent extraction of fresh leaves and GC-MS analysis proved that the heat derivative is a product of hydrodistillation. Earb-486 also expressed the known metabolite 9-hydroxydendrolasin [46], which was reported in _E. rotundifolia_ by [PERSON] [47]. In contrast, Earb-487 from the flat soils expressed \(\sim\)50% myomontanone, which is another furanosesquiterpene, but none of the dendrolasin derivatives were detected. The garden specimen was sampled twice, once in 2015 (Earb-A, Table 10) and again in 2019 (Earb-B, Table 11). This specimen consistently expressed 9-hydroxydendrolasin, which is the metabolite responsible for the characteristic odour. However, it also expressed freelingnite, which was first described in _E. freelingii_. Freelingnite dominated the profile of volatiles, comprising 36-86% according to GC-MS, but was only present in the _E. arbuscular_ in cultivation, and was not detected in the two wild specimens. This emphasises the strong chemical variability of the species. Surprisingly, subspecies of _E. oppositifolia_, i.e., subsp. _rubra_ (EopR) and subsp. _oppositifolia_ (EopO), bore no chemical resemblance to _E. arbuscular_. The volatiles profile of solvent-extracted material in Table 12 conveys that specimens of _E. oppositifolia_ (EopO-538-B; EopR-535; EopR-539), are generally chemically different. All subspecies express oppositifolic acid (5-acetoxymethyltetradeca-trans-2,trans-4,trans-6-trienoic acid) [48] in the solvent extracts of leaves, which can be detected by GC-MS. However, the hydrodistilled essential oil from two specimens (Table 4; EopR-535-B, EopO-538A) produced much lower amounts of oppositifolic acid, because of the lower vapour pressure of this compound. The difference in specimens can be partly explained by differences of hydrodistillation time, with specimen EopO-538A having a shorter distillation time, which failed to drive the oppositifolic acid into the essential oil.