Abstract
BackgroundIt is estimated that floral deception has evolved in at least 7500 species of angiosperms, of which two thirds are orchids. Epipactis veratrifolia (Orchidaceae) is a model system of aphid mimicry as aphidophagous hoverflies lay eggs on false brood sites on their flowers. To understand the evolutionary ecology of floral deception, we investigated the pollination biology of E. veratrifolia across 10 populations in the Eastern Himalayas. We reconstructed the phylogeny of Epipactis and mapped the known pollination systems of previously studied species onto the tree.ResultsSome inflorescences of E. veratrifolia were so infested with aphids while they were still in bud that the some larvae of hoverflies developed to the third instar while flower buds opened. This indicated that adult female hoverflies were partly rewarded for oviposition. Although flowers failed to secrete nectar, they mimicked both alarm pheromones and aphid coloring of to attract female hoverflies as their exclusive pollinators. Phylogenetic mapping indicate that pollination by aphidophagous hoverflies is likely an ancestral condition in the genus Epipactis. We suggest that the biological interaction of aphid (prey), orchid (primary producer) and hoverfly (predator) may represent an intermediate stage between mutualism and deception in the evolution of pollination-by-deceit in E. veratrifolia.ConclusionsOur analyses indicate that this intermediate stage may be used as a model system to interpret the origin of oviposition (brood site) mimicry in Epipactis. We propose the hypothesis that some deceptive pollination systems evolved directly from earlier (partly) mutualistic systems that maintained the fidelity of the original pollinator(s) even though rewards (nectar/ brood site) were lost.
Highlights
It is estimated that floral deception has evolved in at least 7500 species of angiosperms, of which two thirds are orchids
The most important pollinator appeared to be Eupeodes corollae based on its relative abundance and the high proportion of individuals carrying pollinaria
The Eastern Himalayas (EH) are located far from the Mediterranean basin (MB), E. veratrifolia is pollinated by aphidophagous hoverflies in both regions
Summary
It is estimated that floral deception has evolved in at least 7500 species of angiosperms, of which two thirds are orchids. Epipactis veratrifolia (Orchidaceae) is a model system of aphid mimicry as aphidophagous hoverflies lay eggs on false brood sites on their flowers. It is estimated that deceptive pollination systems occur in at least 7500 extant angiosperm species but at least two thirds of these species are in the family Orchidaceae [4,5,6,7]. Brood-site mimicry is dependent on deceiving female insects seeking an oviposition site. This pollination system evolved independently in several unrelated angiosperm lineages including the Araceae, Aristolochiaceae, Asclepiadaceae and Orchidaceae [18]. It is estimated that 11 genera of deceptive orchids, including Epipactis and Paphiopedilum, produce flowers with this mode of deceit [8,20]
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