title: Flower color polymorphism in Iris lutescens (Iridaceae): biochemical analyses in light of plant-insect interactions.
abstract: We describe a flower color polymorphism in Iris lutescens, a species widespread in the Northern part of the Mediterranean basin. We studied the biochemical basis of the difference between purple and yellow flowers, and explored the ecological and evolutionary consequences of such difference, in particular visual discrimination by insects, a potential link with scent emitted and the association between color and scent. Anthocyanins were found to be present in much greater concentrations in purple flowers than in yellow ones, but the anthocyanin composition did not differ between color morphs. Likewise, no quantitative difference in anthocyanin content was found between vegetative tissues of the two morphs. Floral anthocyanins were dominated by delphinidin 3-O-(p-coumaroylrutinoside)-5-O-glucoside (also called delphanin) and its aliphatic derivatives. Small amounts of delphinidin 3-O-(p-caffeoylrutinoside)-5-O-glucoside and its aliphatic derivatives were also characterized. Based on a description of bumblebees' (one of the main pollinators of I. lutescens) color perception, purple and yellow flowers of I. lutescens could be visually discriminated as blue and blue-green, respectively, and likely by a wide variety of other insects. The overall chemical composition of the scent produced was not significantly different between morphs, being dominated by terpenoids, mainly myrcene, (E)-β-ocimene and limonene. A slight color-scent correlation was nevertheless detected, consistent with the shared biosynthetic origin of both pigments and volatile compounds. Therefore in this species, the difference in the amounts of pigments responsible for flower color difference seems to be the major difference between the two morphs. Pollinators are probably the main selective agent driving the evolution of flower color polymorphism in I. lutescens, which represents a suitable species for investigating how such polymorphism is maintained.
authors.affiliation: Institut des Sciences de l'Évolution de Montpellier (ISEM), UMR 5554 CNRS-Université Montpellier 2, Bâtiment 22, Université Montpellier 2, place E. Bataillon, 34095 Montpellier Cedex 5, France.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Lucie
authors.initials: L
authors.lastname: Conchou
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Bessière
authors.forename: Guillaume
authors.initials: G
authors.lastname: Cazals
authors.forename: Bertrand
authors.initials: B
authors.lastname: Schatz
authors.forename: Eric
authors.initials: E
authors.lastname: Imbert
mesh_terms: D000080462:Acyclic Monoterpenes; D000475:Alkenes / Q000032:analysis / Q000737:chemistry; D000818:Animals; D000872:Anthocyanins / Q000032:analysis / Q000737:chemistry; D001516:Bees / Q000502:physiology; D005075:Biological Evolution; D002851:Chromatography, High Pressure Liquid; D003116:Color; D035264:Flowers / Q000737:chemistry* / Q000469:parasitology; D005960:Glucosides / Q000032:analysis / Q000737:chemistry; D006790:Host-Parasite Interactions; D027621:Iridaceae / Q000737:chemistry* / Q000469:parasitology; D015394:Molecular Structure; D039821:Monoterpenes / Q000032:analysis / Q000737:chemistry; D009812:Odorants; D010858:Pigmentation / Q000502:physiology*; D054817:Pollination / Q000502:physiology*
chemical_list: D000080462:Acyclic Monoterpenes; D000475:Alkenes; D000872:Anthocyanins; D005960:Glucosides; D039821:Monoterpenes; C509595:myrcene; C017185:delphinidin
keywords: Anthocyanins; Color-scent association; Floral scent; Flower color polymorphism; Iris lutescens; Plant–insect interactions; Terpenoids