Lying to Pinocchio: floral deception in an orchid pollinated by long-proboscid flies

Abstract

Plants that lack floral rewards may nevertheless attract pollinators if their flowers sufficiently resemble those of rewarding plants. Flowers of the South African terrestrial orchid Disa nervosa are similar in floral dimensions and spectral reflectance to those of a sympatric nectar-producing irid ( Watsonia densiflora s.l. ). Observations showed that the orchid and Watsonia share the same pollinator, a long-proboscid tabanid fly Philoliche aethiopica . These flies visited inflorescences of both species during their foraging bouts and most (64%) observed or captured on Watsonia inflorescences carried pollinaria of the orchid on their proboscides. They probe an average of 6.3 flowers on Watsonia inflorescences, but just 1.9 flowers on the Disa inflorescences, a behaviour which would strongly promote crosspollination in the self-compatible orchid. The orchid generally achieves high levels of pollination success, with approximately 50% of flowers receiving or exporting pollen at some sites. Pollination success was also high at one site that lacked Watsonia plants, suggesting that the orchid does not have an obligate dependence on Watsonia . Its pollination system may therefore be characterized as intermediate between generalized food deception and specific floral mimicry.

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

“…In this chapter, we will argue that incorporating questions relevant to the field of animal-centered host-parasite interactions into investigations on the evolutionary ecology of orchid pollination by deception will provide important insights at both the proximate (or mechanistic) and at the ultimate (or evolutionary) levels. Although several examples of Batesian food-deceptive mimicry have been reported in the literature (Dafni and Ivri 1981 ;Nilsson 1983 ;Dafni 1987 ;Johnson 1994Johnson , 2000Galizia et al 2005 ;Johnson and Shelah 2006) (see also the chapter by Jeraskova et al), here we shall limit ourselves mostly to orchid pollination by sexual deceit, i.e., the imitation of female insects by orchid flowers, since research in this field has been particularly prominent over the past decade. This chapter aims to encourage investigations of mimicry systems from a behavioral perspective, by pointing out specific gaps in our knowledge and possible avenues for future research that will help to fill them.…”

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

“…Similarly, Gigord et al (2002) found that a strong resemblance in floral morphology or traits other than color between the model and the mimic were not necessary for a Batesian mimic to be favored by bumblebees. A low importance of floral shape in the presence of color stimulus was also demonstrated for another pollinator group by Johnson and Morita (2006) , who found that long-tongued flies readily probed misshaped and damaged flowers of an orchid Disa nervosa mimicking an iris Watsonia densiflora . On the other hand, Anderson et al (2006) found a strong geographical correlation between the flower diameters of the orchid Disa nivea and its putative model Zaluzianskya microsiphon , which could be interpreted as evidence for selection on flower size in a mimicry system.…”

A phylogeny of long-tongued horse flies (Diptera:Tabanidae:Philoliche) with the first cladistic review of higher relationships within the family

“…Consequently, South African members of this group have been the focus of many pollination biologists (Goldblatt et al 1995;Johnson and Steiner 1995;Goldblatt and Manning 1996;Johnson and Steiner 1997;Manning and Goldblatt 1997;Goldblatt et al 1998;Goldblatt and Manning 2000;Goldblatt et al 2000a;Johnson 2000;Johnson and Morita 2006). The nominal subgenus is the only Philoliche subgenus found outside Africa, with species described from central Asia, south-east Asia and Indonesia, and New Caledonia.…”