Titre
Cardenolides in nectar may be more than a consequence of allocation to other plant parts: a phylogenetic study of Asclepias
Type
article
Institution
UNIL/CHUV/Unisanté + institutions partenaires
Périodique
Auteur(s)
Manson, J.S.
Auteure/Auteur
Rasmann, S.
Auteure/Auteur
Halitschke, R.
Auteure/Auteur
Thomson, J.D.
Auteure/Auteur
Agrawal, A.A.
Auteure/Auteur
Johnson, M.
Auteure/Auteur
Liens vers les personnes
Liens vers les unités
ISSN
0269-8463
Statut éditorial
Publié
Date de publication
2012
Volume
26
Numéro
5
Première page
1100
Dernière page/numéro d’article
1110
Langue
anglais
Résumé
The primary function of secondary plant metabolites is thought to be defence against herbivores. The frequent occurrence of these same noxious compounds in floral nectar, which functions primarily to attract pollinators, has been seen as paradoxical. Although these compounds may have an adaptive purpose in nectar, they may also occur as a nonadaptive consequence of chemical defence in other plant parts. If nectar chemistry reflects physiological constraints or passive leakage from other tissues, we expect that the identity and relative concentration of nectar cardenolides to be correlated with those of other plant parts; in contrast, discordant distributions of compounds in nectar and other tissues may suggest adaptive roles in nectar. We compared the concentrations and identities of cardenolides in the nectar, leaves and flowers of 12 species from a monophyletic clade of Asclepias. To measure putative toxicity of nectar cardenolides, we then examined the effects of a standard cardenolide (digoxin) on the behaviour of bumblebees, a common generalist pollinator of Asclepias. We found that the average cardenolide concentrations in nectar, leaves and flowers of the 12 Asclepias species were positively correlated as predicted by nonadaptive hypotheses. However, significant differences in the identities and concentrations of individual cardenolides between nectar and leaves suggest that the production or allocation of cardenolides may be independently regulated at each plant part. In addition, cardenolide concentrations in leaves and nectar exhibited no phylogenetic signal. Surprisingly, bumblebees did not demonstrate an aversion to digoxin-rich nectar, which may indicate that nectar cardenolides have little effect on pollination. Although the idea that discordant patterns of secondary metabolites across tissue types may signal adaptive functions is attractive, there is evidence to suggest constraint contributes to nectar secondary chemistry. Further work testing the ecological impacts of such patterns will be critical in determining the functional significance of nectar cardenolides
PID Serval
serval:BIB_40481963EA6C
Open Access
Oui
Date de création
2012-09-14T10:30:31.737Z
Date de création dans IRIS
2025-05-20T19:26:24Z