## 4 Materials and Methods
### Scent Sampling and Analysis and Identification of Compounds  
For this purpose, individuals from the 11 populations were used for each species (5 for _A. acutili_s and 6 for _A. albus_). Floral volatile samples were collected by using the headspace solid-phase microextraction-sampling technique (HS-SPME). Compounds were extracted in a manual SPME holder with 10 mL glass vials and polydimethylsiloxane-divinylbenzene (PDMS-DVB) fibres with a film thickness of 100 um (Supelco Inc., Bellefonte, PA, USA), and they were conditioned according to the instructions provided by the manufacturer. To determine the VOCs emitted by the flowers of the two species, many samples were collected between 08:00 and 11:00 UTC (hours with the highest number and diversity of visitors) in 3 plants per population. Immediately after harvesting, 15 flowers of each plant were placed in a 10 mL glass vial. Then, to equilibrate the analytes, these vials were placed in a water bath at 25 \({}^{\circ}\)C for 20 min. Afterward, the SPME fibre was exposed in the sealed vial for 30 min at 25 \({}^{\circ}\)C to adsorb the analytes [78]. Furthermore, a mixture of a certain number of precisely weighted saturated n-alkanes (C7-C30) (Merck, Rahway, NJ, USA) diluted with hexane (w = 5%) was used as a standard in the vials [79]. To determine the variations that may have existed in their emissions throughout the day, a similar methodology was used, with 10 flowers per vial collected in 3 plants of the UIB population at 05:00, 08:00, 11:00, 14:00, and 17:00 UTC. For these determinations, nonyl acetate (Sigma-Aldrich, St. Louis, MO, USA) was used as the internal standard.  
The scent samples were analysed by using an Agilent 6980 GC-MDS 5975 inert XL system (Agilent Technologies, EUA). Chromatographic separation was performed by using a Supelcowax 10 capillary GC column (60 m \(\times\) 0.25 mm \(\times\) 0.25 um) with helium as a carrier gas at a flow rate of 1.3 mL min\({}^{-1}\). For thermal desorption, PDMS-DVB fibre from the SPME was aged for 3 min in the inlet of the GC. The analytical conditions used were as follows: spitless injection at 220 \({}^{\circ}\)C and ionization occurring via electron impact (70 eV; source temperature 180A \({}^{\circ}\)C). The initial oven temperature was programmed as follows: 45 \({}^{\circ}\)C for 2 min followed by an increase to 250 \({}^{\circ}\)C at a rate of 5 \({}^{\circ}\)C min\({}^{-1}\), which was kept for 5 min. These settings were enough for the quantitative desorption of all analytes studied. The MS scan range was set between 45 and 300 luma. The total ion chromatograms and mass spectra were processed by using the Turbomass version 5.1 software (Perkin-Elmer, Inc., Waltham, MA, USA).  
Chromotographic peaks were identified by comparing the mass spectra with the NIST 14 library (similarity > 80%) and with published data (NIST, [[http://webbook.nist.gov/chemistry/](http://webbook.nist.gov/chemistry/)]([http://webbook.nist.gov/chemistry/](http://webbook.nist.gov/chemistry/)) accessed on 1 July 2020; PubChem, [[http://pubchem.ncbi.nlm.nih.gov/](http://pubchem.ncbi.nlm.nih.gov/)]([http://pubchem.ncbi.nlm.nih.gov/](http://pubchem.ncbi.nlm.nih.gov/)) accessed on 1 July 2020), by comparison with their Kovats retention indexes relative to saturated alkanes C7-C30 (Merck), and by comparison with an internal database. The main compounds were also verified by comparison with standards (Sigma-Aldrich).