Pollination and reproductive success of two colour variants of a deceptive orchid, Dactylorhiza maculata (Orchidaceae)

Abstract

Polymorphism in petal colour is common in deceptively pollinated plant species. Most of the deceptively pollinated orchids are food frauds, and in most of them, the deception is not mimetic. These plants have conspicuously coloured flowers which they use as the main attractant of naive pollinators. In a field experiment, we studied the response of bumblebees and other types of flower visitors to colour differences between experimentally paired plants of Dactylorhiza maculata, a nectarless food‐deceptive species. In addition, pollen removal, an estimate of male fitness, and fruit production, an estimate of female fitness, were measured in the two colour variants. We found a trend of bumblebee preference for the dark‐coloured flowers, but other flower visitors (as a group) showed no preference for any colour variant. No difference was found in the reproductive success between the two colour variants of D. maculata. The lack of a difference in reproductive success between plants with pale and dark inflorescences, despite the observed trend of bumblebee preference for dark inflorescences, suggests that there is some balancing factor in the pollination of the pale inflorescences. An excess of visits by some nocturnal species (or a group of species) which favours the pale colour of D. maculata inflorescences or an excess of visits during day time by some flower visitors other than bumblebees preferring the pale inflorescences over dark ones may form such a balancing factor.

Floral color variation and associations with fitness‐related traits inMalva moschata(Malvaceae)

“…2003). There have been a number of recent studies on polymorphic orchids and the data are mixed with respect to whether pollinators have preferences for rare color morphs, and whether those preferences can maintain floral color variation through negative frequency‐dependent selection (Koivisto et al . 2002; Aragón & Ackerman 2004; Ackerman & Carromero 2005; Tremblay & Ackerman 2007).…”

“…fluctuating selection), disruptive selection or selection for intermediate or rare color morphs in populations of Clarkia gracilis (Onagraceae; Jones 1996a,b), Dactylorhiza sambucina (Orchidaceae; Gigord et al 2001), Ipomoea purpurea (Convolvulaceae; Rausher & Fry 1993;Subramaniam & Rausher 2000) and Mimulus luteus (Scrophulariaceae; Medel et al 2003). There have been a number of recent studies on polymorphic orchids and the data are mixed with respect to whether pollinators have preferences for rare color morphs, and whether those preferences can maintain floral color variation through negative frequency-dependent selection (Koivisto et al 2002;Aragón & Ackerman 2004;Ackerman & Carromero 2005;Tremblay & Ackerman 2007).…”

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

“…Among the wide range of colour variants of orchid flowers, the occurrence of rare hypochromic inflorescences are regularly recorded in natural populations of the common coloured morph (Weiss 1995;Bournérias and Prat 2005;Dormont et al 2010a). In orchids, the behavioural responses of pollinators to white inflorescences in populations of a coloured morph and the possible consequences for plant reproductive success have been poorly investigated (Koivisto et al 2002;Ackerman and Carromero 2005). Dormont et al (2010a) demonstrate for the European species Orchis mascula L. that the presence of white-flowered individuals results in a fourfold increase in the percentage pollination of neighbouring purple-flowered individuals.…”

Deceptive Behavior in Plants. II. Food Deception by Plants: From Generalized Systems to Specialized Floral Mimicry

“…They concluded that natural levels of color variation might be more influenced by genetic drift than selection. Similarly, Koivisto et al (2002) found no preferences of pollinators for any color variant in Dactylorhiza maculata . It seems that not all of the color polymorphism in flowers affects pollinator activity, and that it might be either linked genetically to other adaptive characters, such as flower size or the number of inflorescences, which also impinge on the reproductive success (Wolfe 1993 ;Galen et al 1987 ;Sobrevila et al 1989) , or to the outcome of phenotypic plasticity (Schemske and Bierzychudek 2001 ;Warren and Mackenzie 2001) .…”

“…A few species exhibit discontinuous, genetically determined variation in flower color resulting in two or several more or less discrete color morphs, such as yellow and purple morphs of Dactylorhiza sambucina or D. romana (Nilsson 1980) . More rarely, petal color is polymorphic, with individuals exhibiting variable-sized spots or nectar guides on darker or lighter backgrounds, as in Dactylorhiza maculata (Koivisto et al 2002) .…”