Abstract
This study on Barlia robertiana aims to: (1) assess whether scent is variable between populations; (2) evaluate whether scent composition may be related to geographical variables; (3) assess whether there are VOC differences during the flowering phase; and (4) assess whether there are yearly VOC variabilities. SPME sampling was used. Fourteen plants, collected along an ecological gradient, were analyzed. A multivariate analysis was performed through ordination and hierarchical cluster analysis. Compositions versus geographic distances were also analyzed using Mantel test. Seventy compounds were identified. Multivariate analyses and Mantel tests detected no correlations between VOC composition and both geographic and ecological variables. These results may suggest that there is no adaptation of floral scent to local environments. VOC compositions during the flowering phase showed a slight change but a strong variability between individuals. A huge difference was found in the pairwise comparison of the plants analyzed in different years. The high scent variability can be interpreted as a strategy of a non-rewarding but allogamous species to not allow the learning by pollinators. In fact, disrupting the association among floral scent signals with the lack of nectar may enhance the fruit set via a higher probability of being visited by insects.
Highlights
Orchidaceae are one of the largest families of vascular plants [1]; since Darwin [2], they have attracted the interests of a plethora of naturalists for the amazing floral variations and the complex pollination mechanisms which they evolved [3]
We aim to describe the spatial and temporal variability of the spectrum of volatile compounds emitted by flowers of B. robertiana, testing the ability of this species to adapt to different environmental conditions to be attractive to different potential pollinators
We identified a very high number of volatile compounds (VOCs) emitted by Barlia robertiana: considering all the analyzed samples, more than 100 compounds were identified
Summary
Orchidaceae are one of the largest families of vascular plants [1]; since Darwin [2], they have attracted the interests of a plethora of naturalists for the amazing floral variations and the complex pollination mechanisms which they evolved [3]. One-third of Orchidaceae are believed to deceive insect pollinators [4,5]; among the mechanisms of deception, generalized food deception is one of the most common mechanisms developed by orchids for efficient pollen exportation [5,6]. These species can exploit the existing plant–pollinator relationships and achieve pollination through deception in the absence of floral rewards for pollinators. In order to deceive pollinators, these orchids exploit general floral signals typical for rewarding plant species, including flower color and scent [8]. Reward-less species undoubtedly benefit from the simultaneous flowering of nectariferous species present in the same habitat that increase the possibility of being visited by local pollinators [12]
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