Presence, distribution and effect of white, pink and purple morphs on pollination in the orchid Orchis mascula

Abstract

How floral polymorphism of flowering plants can be maintained in evolutionary time has long intrigued ecologists and is still debated. In particular, how floral colour polymorphism influences reproductive success is still poorly understood. Here, we investigated the case of Orchis mascula, a deceptive orchid species in which the presence of rare white-flowered individuals is known to increase the percentage pollination of co-occurring coloured morphs. In a brief review, we report all the orchid species for which rare colour morphs are recorded and show that colour polymorphism occurs in most orchid genera occurring in France. In this study, more than 20,000 individuals of O. mascula were surveyed and some rare clear pink morphs were recorded. The frequencies of white-flowered and clear pink-flowered individuals were 0.59% and 0.28%, respectively. These two rare-colour flowered individuals were not randomly distributed and restricted to a few populations. In addition, the presence of pink-flowered individuals and the use of experimental pink lures resulted in an increase in the percentage pollination of surrounding purple-flowered individuals, as previously shown for white-flowered individuals and white lures. These new observations favour kin selection as the means by which floral colour polymorphism is maintained in this species. We suggest conducting comparative studies of other species in order to evaluate the importance of this mechanism in orchid pollination and that of other plant families.

Habitat effects and differences in the reproductive success of Orchis punctulata and Orchis purpurea (Orchidaceae)

“…Orchis punctulata and O. purpurea usually grow in small-sized populations (Vakhrameeva et al, 2008). Although the female reproductive success of O. purpurea in the study area was higher compared to the data provided for other deceptive orchids (Claessens and Kleynen, 2011), the respective percentages of O. punctulata were low and similar to those of other nonrewarding orchids (e.g., Schatz et al, 2013). The fact that O. punctulata at the edges of its distribution range is characterized by an almost equal pollination success compared to other populations occurring near the center of its distribution range (Kretzschmar et al, 2007) might demonstrate that its distribution in its westernmost area is not delimited by factors related to its pollination effectiveness.…”

Positive effect of the yellow morph on female reproductive success in the flower colour polymorphic Iris lutescens (Iridaceae), a deceptive species

“…At the population scale, such a positive effect of the yellow morph on the global reproductive success has been observed in the deceptive D. sambucina (Pellegrino et al ., ; Smithson et al ., ) and D. incarnata (Vallius et al ., ). This visually attractive effect of pale‐coloured flowers has also been observed in O. mascula (Dormont et al ., ; Schatz et al ., ), in which the presence of a light morph individual increased the reproductive success of all neighbouring individuals (Dormont et al ., ). In a different ecological situation, Levin & Kerster () observed a positive relationship between frequency of the pink morph and seed production in Phlox pilosa , which they interpreted as resulting from the effect of optimal image (pink colour) on pollinator behaviour.…”

“…Food deception is an unusual pollination strategy in which the plant species give no reward to pollinators (Renner, ). Because flower colour is one of the most important cues used by insects to locate flowers (Menzel & Shmida, ; Schoonhoven et al ., ), the three main mechanisms usually invoked to explain the maintenance of deception as a pollination strategy are based on colour: mimicry of a rewarding species (Johnson et al ., ; Juillet et al ., ), exploitation of innate perceptual biases of insects (Peter & Johnson, ; Schaefer & Ruxton, ) and exploitation of naivety of recently emerged pollinators (Jersáková et al ., ; Dormont et al ., ,b; Schatz et al ., ). Whatever the mechanism involved, deceptive plant species are expected to show high variation in floral traits, such as flower colour, because intraspecific variation will delay avoidance learning by the pollinators.…”

Flower colour polymorphism in the Mediterranean Basin: occurrence, maintenance and implications for speciation

“…This last situation is common in some species or groups such as orchids, where mutations causing non‐pigmented or albino flowers are recurrent (Schatz et al . ).…”