Evidence for pollinator sharing in Mediterranean nectar-mimic orchids: absence of premating barriers?

Abstract

Pollinator specificity has traditionally been considered the main reproductive isolation mechanism in orchids. Among Mediterranean orchids, however, many species attract and deceive pollinators by mimicking nectar-rewarding plants. To test the extent to which deceptive orchid species share pollinators, we collected and identified hemipollinaria-carrying insects, and used ribosomal sequences to identify the orchid species from which hemipollinaria were removed. We found that social and solitary bees, and also flies, carried hemipollinaria belonging to nine orchid species with different degrees of specialization. In particular, Anacamptis morio, Dactylorhiza romana and Orchis mascula used a large set of pollinator species, whereas others such as Orchis quadripunctata seemed to be pollinated by one pollinator species only. Out of the insects with hemipollinaria, 19% were found to carry hemipollinaria from more than one orchid species, indicating that sympatric food-deceptive orchids can share pollinators. This sharing was apparent even among orchid sister-species, thus revealing an effective overlap in pollinator sets among closely related species. These results suggest varying degrees of pollinator specificity in these orchids, and indicate that pollinator specificity cannot always act as the main isolation mechanism in food-deceptive temperate orchids.

Deceptive Behavior in Plants. I. Pollination by Sexual Deception in Orchids: A Host–Parasite Perspective

“…Furthermore, behavioral bioassays performed with the male insects have conclusively demonstrated that although pollinators are more attracted by the floral scent of the parasitic orchid they are associated with, heterotaxic visits occur and might under certain circumstances lead to successful pollination and the formation of natural hybrids (Stokl 2007;Cortis et al 2008;Vereecken et al, unpublished manuscripts). Reproductive isolation in Ophrys is thought to be primarily mediated by host specificity, and post-mating barriers have been reported to be relatively weak compared to other European orchid genera where pollinator specificity is low (Cozzolino et al 2005) and post-mating barriers generally keep co-occurring species reproductively isolated (Moccia et al 2007 ;Scopece et al 2007) .…”

Strong post-pollination pre-zygotic isolation between sympatric, food-deceptive Mediterranean orchids

“…O. papilionacea has been reported to be pollinated by bees (Eucera sp.) and bumblebees (Vogel 1972;Cozzolino et al 2005).…”

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

“…O. mascula flowers depend on being pollinated by insects (Nilsson 1983;B. Schatz unpublished) and are visited and pollinated by several hymenoptera (bumblebees, cuckoo bumblebees, solitary bees) (Nilsson 1983;Bournerias and Prat 2005;Cozzolino et al 2005;Dormont et al 2010a). Flowering occurs early in spring, and O. mascula is known to exploit newly emerged insect pollinators, suggesting that pollination in this species is effected mainly by visits of naïve, inexperienced insects (Nilsson 1983;Van der Cingel 1995;Dormont et al 2010a).…”