Lev-Yadu, S & Ne’eman, G (2012)
Review by Curtis Lanham
This paper is a theoretical consolidation by Lev-Yadun and Ne’eman (2012) following the recent increased understanding of reproductive function of the orchid genus Ophrys. Ophrys, commonly referred to as the bee-orchid, has a highly distinguishable flower resembling the colour and structure of a bee. The orchid is pollinated by pseudocopulation, where a male bee is ‘duped’ into mating with the flower. This permits the orchid’s pollen to be spread over greater geographical distances, preventing self-pollination and increasing genetic variability. The mimicked physical appearance of the flower has long been thought responsible for attraction the insects.
Figure 1: The Bee-Orchid, Genus Ophrys (Floral Image UK, 2012)
In 2009, Veerecken and Schiestl (2009) tested this long held assumption of visual attraction against an older proposal from Bertil Kullenberg in 1950, that olfactory attraction was the cause of the pseudocopulation, not appearance. Veerecken and Schiestl’s (2009) experiment concluded that release of chemicals, mimicking the female bee pheromone attracted the male bee, superseding the physical appearance. It was later identified that this pheromone containing over140 compounds. During the time the visual theory was promoted, technology to identify the complex chemical properties and resulting effects on insects was much less sophisticated. This could be identified as a possible reason for this theory from being challenge from such a large length of time.
Lev-Yadun and Ne’eman’s (2012) research extended from the questions prompted by the publication of Veerecken and Schiestl’s (2009) paper. If the bee-orchids evolution had permitted such high fidelity in scent and aesthetic, with the scent proven to be primary attractant, why has the physical plant structure evolved so highly? With bees known to have extremely low-resolution vision, could there be a secondary function to this flowers mimicry?
Tracing the evolutionary theory of sister genera, such as the Australian orchid Cryptostylis, strong functional similarity can be identified. As with the Ophrys, Crypostylis feigns both a both a potential mate with chemical compound release, but also with a combination of visible and ultraviolet light to attract specific target species to its pollen. As with the Ophrys genus, it uses rather covert and specific means of attracting the necessary target species. It also emanates colour in wavelengths, unable to be detected by the target species. This is similar to the highly defined aesthetic structure characteristic to that of the Ophrys, where it is irrelevant to the target species.
Figure 2: The Australian Genus of Cryptostylis (NSW Department of Nature & Heritage, 2012)
Lev-Yadun and Ne’eman (2012) have proposed that a secondary, highly evolved visual function could exist as protective Batesian type of mimicry. This occurs when one species mimics the defensive characteristics of another species for its own benefit. In the case of the Ophrys, this mimicry could potentially resemble a bee swarm effect, which could potentially drive away other predators and competing herbivores. It could also be suggested that there is a type of Mullerian mimicry occurring, which could drive away potential competitors or predators of the bees. Deriving this hypothesis appears to be the purpose of the paper. With Lev-Yadun’s previous research centering exclusively on plant/insect Batesian Mimicry, this paper has established the clear link and need for further research.
Floral Images United Kingdom (2012) Ophrys Orchidaceae. Accessed on the 19 August, 2012 at www.floralimages.org.uk/marston.htm&h=375&w=500&sz=34&tbnid=YEiIdsqhc-pQdM:&tbnh=90&tbnw=120&prev=/search%3Fq%3Dophrys%2Borchid%26tbm%3Disch%26tbo%3Du&zoom=1&q=ophrys+orchid&usg=__QzgaE0fwPqste98AQBbKRPgd1V8=&docid=6GuK4W
Lev-Yadu, S & Ne’eman, G (2012) ‘Does bee or wasp mimicry by orchid flowers also deter herbivores?’, Arthropod-Plant Interactions, viewed online 15 August 2012 at http://link.springer.com/article/10.1007/s11829-012-9199-y/fulltext.html
New South Wales Department of Environment and Heritage(2012), Leafless Tongue Orchid Profile. Accessed on the 19 August, 2012. www.environment.nsw. gov.au/ThreatenedSpeciesApp/profile.aspx?id=10187.
Vereecken NJ, Schiestl FP (2009) On the roles of colour and scent in a specialized floral mimicry system. Annals of Botany, Volume 104, Pages 1077–1084