Orchid's Extravaganza
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International Journal of Research and Review www.ijrrjournal.com E-ISSN: 2349-9788; P-ISSN: 2454-2237 Review Article Orchid’s Extravaganza - an Old Wives Tale Rita Paul Department of Botany, Charuchandra College, 22- Lake Road, Kolkata-700 029 ABSTRACT Orchids are undoubtedly the most diversified flowering plants. Many of them possess most stunning and elegant blooms that are beyond our imagination. The fascinating intricate beauty of flower in the form of colouration and dramatic shapes rarely matched in the world of flora. Several orchids have adopted different forms of mimicry and baroque pollination strategies. For these they have employed different ingenious and seemingly improbable mechanisms of deception. In this presentation the different types of mimicry adopted by orchids and the smart deceptive beauties are discussed with an aim to generate an interest to all nature lovers about the dizzying diversified world of orchids. Key words: Orchids, Mimicry, Deception, Pseudocopulation. INTRODUCTION A sincere approach has been taken to Orchidaceae is the fantastically tell an old wives tale of orchid’s diverse family of flowering plants that extravaganza about the deceptive beauty employ many fascinating forms of mimicry and different types of adopted mimicry (i.e., similarity of one species to another) along with some amazing examples and and equally diverse pollination biology. The brief introductory notes with an aim to secret of the astounding diversity of orchids revisit the incredible diversified world of is simply deception (i.e., deliberate orchids and to realize how clever and smart employment of trickery aiming to induce plants the orchids are in reality! misperception). Production of sweet Types of mimicry adopted by different fragrance to attract bees, rancid smell to lure orchids:- flies, providing stealth, nectar, possessing A) Directly for reproductive purpose - striking colours are the usual means of where the actions of dupe directly aid in the orchids for attracting pollinators. But mimic’s reproduction by possessing roughly one third of orchid species do not deceptive flowers that do not provide the offer conventional food rewards to the reward they would seem to. The flowers pollinators, they evolve themselves with a falsely advertise the presence of food by its clever deceit involving visual, aromatic, bright colours and sweet scents, thus tactile or all three at once; but perhaps the limiting the ability of pollinator’s learning most interesting of all is offered by those to avoid non-rewarding members. orchids that hold out the promise of sex 1) Dodsonian mimicry (After the name of (really weird sex!). Some of the most Calaway H. Dodson) - Includes cases specialized orchids through uncanny where the model belongs to a different resemblance with other animals became the species than the mimic. By providing center of attraction to researchers for several similar sensory signals (like morphology, years. colour, smell) as the model flower (rewarding species), it (deceptive species) International Journal of Research & Review (www.gkpublication.in) 1 Vol.4; Issue: 1; January 2017 Rita Paul. Orchid’s Extravaganza – an Old Wives Tale can lure its pollinators, but no reward mimicry etc. ensure sufficient pollination (nectar/oil) is provided i.e., the orchids rate. Reproductive success of food- employ the strategy of food deception by deceptive orchids also varies according to taking the advantage of a pollinator’s innate the characteristics of rewarding co- sensory biases or tendency to associate a flowering species. Early-flowering specific perceptual cue with food. deceptive orchids get additional benefit Examples – from a higher average density of naive (i) The orchid Epidendrum ibaguense (do pollinators [7] and from lower competition not have any nectar) resembles (Fig.1A) with rewarding co-flowering species. [8] nectar bearing flowers of Lantana camara Kindlmann and Jersáková [9] showed that (Fig.1B; Verbenaceae) and Asclepias the peak of flowering of deceptive orchids curassavica (Fig.1C; Asclepiadaceae), and occur earlier compared to that of rewarding thus get pollinated by Monarch Butterflies orchids. Interestingly starting date of and perhaps hummingbirds that can’t flowering is more relevant than the discriminate between the apparently similar flowering peak – the most successful flowers. [1] individuals usually start to flower before (ii) The rewardless orchid Tolumnia their population’s flowering peak. [10] guibertiana resemble (Fig.1D) the oil 2) Pouyannian mimicry (After the name producing yellow flowers of Stigmaphyllon of Maurice Alexandre Pouyanne) – In diversifolium (Fig.1E; Malpigiaceae) and this case a flower mimics a female of a Ouratea agrophylla (Fig.1F; Ochnaceae) certain insect species, whose males try to and are pollinated by an oil gathering copulate with the flower, thus female bee (Centris poecila). [2] pseudocopulation occurs i.e., the orchids (iii) The food-deceptive orchid take the strategy of sexual deception. Traunsteinera globosa resemble (Fig.1I) the Regardless of this occasional eureka rewarding species of Knautia (Fig.1G) and moments the system persists. By this way Scabiosa (Fig.1H) of Dipsacaceae and orchids may account for around 60% of Valeriana (Fig.1J) of Caprifoliaceae family. pollinations. Jersáková et al. [3] showed that both naive Examples – and experienced insect species approach the (i) The labellum of nearly all of the about orchids at the same rate as in the other three 300 species of Ophrys flower acts (Fig.1K) genera. as a dummy female of a species of bee or (iv) In green-veined or green winged orchid wasp (depending on the species of Ophrys), (Anacamptis morio) the flower produces a the males visit the flower and try to copulate scent that attracts the plants main pollinator with the flower; during pseudocopulation queen bumblebee – which associate the (Fig.1M) it acquires the gobbet of pollens odour with nectar; although, in this case the and subsequently transmits them to other scent profile is different from the rewarding blossoms. [11-15] species (A. coriophora) and the amount of (ii) More than 30 species of the genus scent emission was lower than the Chiloglottis are pollinated [16-18] by thynnine rewarding species. [4] wasps of the genus Neozeleboria by In the first three examples the similar pseudocopulation (Fig.1N). signals are in terms of morphology and (iii) Australian tongue orchid (Cryptostylis colour of flower but in the last example it is leptochila) which bears a sufficient in terms of smell of flower. resemblance to the female of the ichneumon Food-deceptive orchids usually bear with wasp Lissopimpla semipunctata to induce low reproductive success than their male wasp for pseudocopulation. [19-20] rewarding counterparts due to limited (iv) The labellum shape and indument of pollination, [5-6] but absence of competition Mormolyca ringens are reminiscent of an of pollinators in such orchids, relying on insect. Sexually excited drones of International Journal of Research & Review (www.gkpublication.in) 2 Vol.4; Issue: 1; January 2017 Rita Paul. Orchid’s Extravaganza – an Old Wives Tale Nannotrigona testaceicornis and Secondly, nectar besides being Scaptotrigona sp. attempt copulation with metabolically expensive for the flower to the labellum and pollinate the flower in the produce is liked by so many different process. [21] animals which comes to flower for the (v) Drakaea glyptodont (Fig.1L), an nectar and may often cause a loss of pollen endangered genus native to Australia being by not delivering it to a right target. pollinated by pseudocopulation only with Producing floral odour with only a little the thynnine wasp Zapilothynnus trilobatus. variation, orchids develop relationship with The males of this wasp species are sexually a single, highly devoted pollinator which attracted to the orchid first by a scent that can insure more precise delivery to the mimics the female wasp pheromone, [22] actual target. [19] Specializing with one then at short range by the visual similarity pollinator and appealing to it with sex, lead of the orchid labellum to the female wasp's to less precious pollen lost in the transport abdomen. [23] process and the orchid may avoid clogging In all the cases sexual deception is of stigmas with other non-compatible pollen very specific – each orchid attracts only one and subsequently show high pollination or very few insect species. [18,24] So in efficiency. [30] appealing to sex, these orchids limit their Variation in floral traits in deceptive potential pollinators, which would seem to orchids may be adaptive for the plants, as it be a reproductive disadvantage. Despite the may delay the avoidance learning of the apparent drawback, sexual deception has pollinators. [7] Moreover, variation in the evolved several times in different orchids. chemistry of floral scent can function as In most of the cases floral scent, which much as geographic isolation does in the mimics the sex pheromones of female creation of new species.[19] Pollinator shift insect, has been suggested to be the main through changes in floral scent can provide attractant of pollinators. [22,25-28] Bower and a mechanism for pollinator driven Brown [18] were of opinion that in both speciation in orchids. [31] Ophrys and Chiloglottis, floral scent For the tongue orchid (Cryptostylis composition is driven towards their sp.) the sexual deception is beyond the pollinators’ preferences in both quantity and pseudocopulation. The wasp, in the throes quality. In few cases the odour of the of its misguided sexual exertions, actually flower is a more potent attractant for the ejaculates onto the flower and thus waste male than that of the appropriate female. [29] copious sperm – the height of maladaptive Advantage of orchids to avoid a simple behavior. [19] Gaskett et al. [32] showed that nectar reward mechanism and rely on this orchid species provoking such extreme elaborate pollination mechanism – pollination behavior have the highest Firstly, the sexual frustration of a pollination success. It is found that the wasp deluded bee resulting from is a haplodiploid species – it can reproduce pseudocopulation turns out to be an with or without sperm.