## 2 Results
### Chemometrics Analysis of Volatile Organic Compounds  
In order to identify volatile compounds that contribute to differences or similarities between the species studied, data on the 66 identified volatiles were analyzed using principal component analyses (PCA). PCA is a multivariate analysis that allows the extraction of important information from a data table in which observations are described by several intercorrelated dependent variables and represents them as a set of new orthogonal variables called principal components. In Figure 2A, it is shown that the first principal component (PC1) contributes to 32.7%, and the second principal component (PC2) contributes to 17.29% of the total variance in the floral volatile peak area data. On this same figure, we can see three distinct groups; indeed, the flowers of the two forms of _T. xiphioides_ are clustered together, the flowers of the two forms of the _T. crocata_ are clustered together, and the flowers of _T. caliginosa_ form the third group. This shows a high degree of clustering of flowers belonging to the same species, thus suggesting a unique floral volatile profile for each species of the genus _Tillandsia_. PC1 allowed discrimination of LP-xiphi and HP-xiphi flowers that are clearly separated from yellow _crocata_, orange _crocata_, and _caliginosa_ flowers. This separation is due to higher intensities of monoterpenoids and sesquiterpenoids in the floral emissions of both forms of _T. xiphioides_ (Figure 2B). PC2 showed a difference in floral volatiles of _T. caliginosa_ compared to the two forms of _T. crocata_. This was due to high phenylpropanoids intensities in both forms of _T. crocata_ while _T. caliginosa_ showed higher intensities of other compounds. To better visualize the differences in volatile profiles between flowers of the two forms of _T. crocata_ and those of _T. caliginosa_, a second PCA as well as a heatmap were performed (Figures 3 and 4). The first two components of the PCA explained 43.14%  
Figure 2: PCA based on VOCs emitted from yellow crocata, orange crocata, caliginosa, HP-xiphi and LP-xiphi: (**A**) Score plot of PC1 versus PC2 scores. (**B**) Loading plot of PC1 and PC2 contributing volatile compounds. and 23.74% of the variation, explaining approximately 66% of the combined variance (Figure 3A). We can see that the two forms of _T. crocata_ have relatively different floral volatile profiles due to their higher intensities of sesquiterpenoids and phenylpropanoids, such as \(\beta\)-farnesene (23), farnesyl acetate (32), benzylacetate (37), and phenylethyl acetate (39), which have higher intensities in floral emanations of yellow _crocata_ compared to orange _crocata_ (Figure 3B). While compounds such as benzyl benzoate (48), eugenol (42), methyl eugenol (43), benzyl salicate (50), and phenethyl benzoate (49) are more abundant in orange _crocata_ flowers, _T. caliginosa_ flowers are grouped on the right due to higher intensities of other compounds, such as 1-hexadecanol (61), hexadecyl ethanoate (66), methyl tetradecanoate (56), hexadecanal (59), and some phenylpropanoids, such as methyl benzoate (35) and methyl salicate (38). This is confirmed by the heatmap (Figure 4); indeed, it is shown that the 57 volatile compounds detected in the floral emissions of _T. caliginosa_ and in the two forms of _T. crocata_, are grouped in four large groups in the dendogram of the heatmap. The 14 compounds of group 1, consisting of methyl salicate, methyl benzoate, methyl tetradecanoate, methyl palmitoate, \(\beta\)-ocimene, hexyl acetate, methyl1 hexanoate, 11-hexadecan, \(\gamma\)-terpinene, hexadecanal, \(\beta\)-fenchol, 11-hexadecenyl acetate, 1-hexadecanol, and hexadecyl ethanoate, are more abundant in the flowers of _T. caliginosa_. The 10 volatile molecules of Group 2, consisting of \(\beta\)-myrrene, limonene, \(\alpha\)-pinene, eucalypt, sabinene, \(\beta\)-phellandrene, \(\beta\)-pinene, zingerone, \(\alpha\)-terpineol, and eugenol, are relatively abundant in the floral emissions of _T.