Pseudocopulation is a behavior similar to copulation that serves a reproductive function for one or both participants but does not involve actual sexual union between the individuals. It is most generally applied to a pollinator attempting to copulate with a flower adapted to mimic a potential female mate. The resemblance may be visual, but the key stimuli are often chemical and tactile. The form of mimicry in plants that deceives an insect into pseudocopulation is called Pouyannian mimicry after the French lawyer and amateur botanist Maurice-Alexandre Pouyanne.
A non-mimetic form of pseudocopulation has been observed in some parthenogenetic, all-female species of lizard. The behaviour does not appear to be necessary to trigger parthenogenesis.
In zoology, pseudocopulation is attempted copulation that serves a reproductive function for one or both participants but does not involve actual sexual union between the individuals. In the case where an insect pollinator attempts to copulate with a flower, the process involves mimicry of an insect by the plant concerned. The form of mimicry in plants that deceives an insect into pseudocopulation is called Pouyannian mimicry after the French lawyer and amateur botanist Maurice-Alexandre Pouyanne. [1] [2]
Mimicry typically involves three species, a mimic, a model, and a dupe. In the case of Pouyannian mimicry, the model and the dupe are the female and male of the same species, so the mimicry is bipolar, involving only two species, an insect and a flower. [1]
In 1916, Pouyanne, with Henry Correvon, described his observations in Algeria: [3] [4]
Pouyanne 1916 [3] | Translation |
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Asseyez-vous, en effet, au soleil, un petit bouquet d’Ophrys speculum à la main, sur un talus au-dessus duquel les mâles de Dasyscolia ciliata exécutent leurs évolutions. Vous ne tardez pas à vous apercevoir qu’ils ont flairé, en quelque sorte, qu’ils ont repéré les fleurs que vous tenez […] Il se pose alors sur le labelle, de manière que sa tête arrive tout près du stigmate, juste sous les pollinies, et que son abdomen plonge, à l’extrémité, dans les poils longs, fauves et épais qui forment comme une couronne barbue au labelle. Le bout de l'abdomen est alors agité, contre ces poils, de mouvements désordonnés, presque convulsifs, et l'insecte tout entier se trémousse; ses mouvements, son attitude paraissent tout à fait semblables à ceux des insectes qui pratiquent des tentatives de copulation. | Sit down in the sun, with a small bouquet of Ophrys speculum in your hand, on a slope above which the males of Dasyscolia ciliata are performing their movements. You soon realize that they have scented, in some way, that they have detected the flowers you are holding [...] It then lands on the flower's labellum, so that its head is very close to the stigma, just under the pollinia, and its abdomen plunges, at the end, into the long, tawny and thick hairs which form a kind of bearded crown on the labellum. The tip of the abdomen is then agitated, against these hairs, with disordered, almost convulsive movements, and the entire insect wriggles; its movements, its attitude are like those of insects practising attempts at copulation. |
Several species of orchids mimic insects to facilitate pollination, secreting chemicals from glands (osmophores) in the sepals, petals, or labellum, that are indistinguishable from the insect's natural pheromones. The pollinator then has a pollinium attached to its body, which it transfers to the stigma of another flower when it attempts another 'copulation'. Pollinators are often bees, wasps, or flies. [5]
The cost to the pollinating insects might be seen as negligible, but pollinators of the Australian orchid Cryptostylis can waste significant amounts of sperm by ejaculating onto the flower. Thus there could be antagonistic coevolution such that pollinators become better at identifying their own species correctly, while orchids become better mimics. [6]
One mechanism is through the use of incentives or rewards. These are beneficial offerings to a pollinator, enticing it to engage with the reward and thus transfer pollen. Flowering plants that do not produce such rewards can instead attract pollinators through mimicry — a form of convergent evolution. Floral mimicry, which has independently evolved in a diverse range of plant species, involves the imitation of other plants or animals, including of coloration, morphology, egg deposition sites, provoking scents, and mating signals. [7] Such plants are called "deceptive plants" as they mimic the characteristics or rewards of other species without providing any benefit to the pollinator. [8] [9]
Several orchids (Orchidaceae) make use of floral mimicry. Using sex-based deception, these species imitate female mating signals of certain pollinator species. [10] This results in attempted copulation by males of the pollinator species, facilitating pollen transfer. Bee orchids ( Ophrys apifera ) and fly orchids ( Ophrys insectifera ), specifically, utilize flower morphology, coloration, and scent to deceive their respective pollinators. These orchids have evolved traits matching the preferences of specific pollinator niches, leading to adaptive speciation. [11]
Although bee and fly orchids are visual mimics of their pollinators, visual traits are not the only (nor the most important) ones mimicked to increase attraction. [12] [8] Floral odors have been identified as the most prominent way of attracting pollinators, because these odors imitate the sex pheromones of females of the pollinator species. [10] Male pollinators then track these scents over long distances. [8] The proportions of such odor compounds have been found to be varied in different populations of orchids (in a variety of locations), playing a crucial role in attracting specific pollinators at the population level. The evolution of these interactions between plants and pollinators involve natural selection favoring local adaptation, leading to a more precise imitation of the scents produced by local pollinators. [10]
Chemical compounds (more specifically, alkanes and alkenes), while used for sexual deception, are produced in many species of Ophrys, and likely were preadapted for other functions before being co-opted for mimicry. [7] These orchids increased ancestral levels of alkene production to mimic the female pheromones that attract male pollinators, a form of sensory exploitation called a sensory trap. [13]
Although mimetic plants typically receive fewer interactions with pollinators than truly-rewarding plants do, the evolution of sexual deception appears to be linked to benefits associated with mating behavior. Sex-based mimicry results in pollinator fidelity, the continued revisiting of flowers of the same species by a pollinator, as a result of sexual deception. In support of this, sex-based deception in an Australian orchid results in a higher proportion of pollen reaching stigmas than food-based deception. In another study, deception of male pollinators results in a long-distance dispersal of pollen. [8]
Some lizard species, such as the Laredo striped whiptail (Aspidoscelis [Cnemidophorus] laredoensis) and the Desert grassland whiptail lizard (A. uniparens), consist only of females, which reproduce by parthenogenesis. Some of these species have been observed to practise pseudocopulation in captivity, but it does not appear to be required to trigger parthenogenesis. [14] [15]
Ophrys apifera, known in Europe as the bee orchid, is a perennial herbaceous plant of the genus Ophrys, in the family of Orchidaceae. It serves as an example of sexually deceptive pollination and floral mimicry, a highly selective and highly evolved plant–pollinator relationship.
A pollinator is an animal that moves pollen from the male anther of a flower to the female stigma of a flower. This helps to bring about fertilization of the ovules in the flower by the male gametes from the pollen grains.
In biology, coevolution occurs when two or more species reciprocally affect each other's evolution through the process of natural selection. The term sometimes is used for two traits in the same species affecting each other's evolution, as well as gene-culture coevolution.
The genus Ophrys is a large group of orchids from the alliance Orchis in the subtribe Orchidinae. They are widespread across much of Europe, North Africa, Caucasus, the Canary Islands, and the Middle East as far east as Turkmenistan.
In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry functions to protect a species from predators, making it an anti-predator adaptation. Mimicry evolves if a receiver perceives the similarity between a mimic and a model and as a result changes its behaviour in a way that provides a selective advantage to the mimic. The resemblances that evolve in mimicry can be visual, acoustic, chemical, tactile, or electric, or combinations of these sensory modalities. Mimicry may be to the advantage of both organisms that share a resemblance, in which case it is a form of mutualism; or mimicry can be to the detriment of one, making it parasitic or competitive. The evolutionary convergence between groups is driven by the selective action of a signal-receiver or dupe. Birds, for example, use sight to identify palatable insects and butterflies, whilst avoiding the noxious ones. Over time, palatable insects may evolve to resemble noxious ones, making them mimics and the noxious ones models. In the case of mutualism, sometimes both groups are referred to as "co-mimics". It is often thought that models must be more abundant than mimics, but this is not so. Mimicry may involve numerous species; many harmless species such as hoverflies are Batesian mimics of strongly defended species such as wasps, while many such well-defended species form Müllerian mimicry rings, all resembling each other. Mimicry between prey species and their predators often involves three or more species.
Entomophily or insect pollination is a form of pollination whereby pollen of plants, especially but not only of flowering plants, is distributed by insects. Flowers pollinated by insects typically advertise themselves with bright colours, sometimes with conspicuous patterns leading to rewards of pollen and nectar; they may also have an attractive scent which in some cases mimics insect pheromones. Insect pollinators such as bees have adaptations for their role, such as lapping or sucking mouthparts to take in nectar, and in some species also pollen baskets on their hind legs. This required the coevolution of insects and flowering plants in the development of pollination behaviour by the insects and pollination mechanisms by the flowers, benefiting both groups. Both the size and the density of a population are known to affect pollination and subsequent reproductive performance.
Ophrys insectifera, the fly orchid, is a species of orchid and the type species of the genus Ophrys. It is remarkable as an example of the use of sexually deceptive pollination and floral mimicry, as well as a highly selective and highly evolved plant–pollinator relationship.
Sexual mimicry occurs when one sex mimics the opposite sex in its behavior, appearance, or chemical signalling.
Hymenopus coronatus is a mantis from the tropical forests of Southeast Asia. It is known by various common names, including walking flower mantis, orchid-blossom mantis and (pink) orchid mantis. It is one of several species known as flower mantis, a reference to their unique physical form and behaviour, which often involves moving with a “swaying” motion, as if being “blown” in the breeze. Several species have evolved to mimic orchid flowers as a hunting and camouflaging strategy, “hiding” themselves in plain view and preying upon pollinating insects that visit the blooms. They are known to grab their prey with blinding speed.
Ophrys fusca, commonly known as the sombre bee-orchid or the dark bee-orchid, is a species of orchid native to the Mediterranean from southwestern Europe and northern Africa to western Asia. Most subspecies of the Ophrys fusca are pollinated by males Andrena bees.
Cryptostylis, commonly known as tongue orchids, is a genus of flowering plants from the orchid family. Tongue orchids are terrestrial herbs with one to a few stalked leaves at the base of the flowering stem, or leafless. One to a few dull coloured flowers are borne on an erect flowering stem. The most conspicuous part of the flower is the labellum, compared to the much reduced sepals and petals. At least some species are pollinated by wasps when they attempt to mate with the flower. There are about twenty five species found in South Asia, Southeast Asia and the South Pacific.
Chemical mimicry is a type of biological mimicry involving the use of chemicals to dupe an operator.
Lissopimpla excelsa, commonly known as the orchid dupe wasp, is a wasp of the family Ichneumonidae native to Australia. Although also found in New Zealand, where it is known as the dusky-winged ichneumonid, it has probably been introduced there. However, another source states that it may be native to New Zealand.
In evolutionary biology, mimicry in plants is where a plant evolves to resemble another organism physically or chemically, increasing the mimic's Darwinian fitness. Mimicry in plants has been studied far less than mimicry in animals, with fewer documented cases and peer-reviewed studies. However, it may provide protection against herbivory, or may deceptively encourage mutualists, like pollinators, to provide a service without offering a reward in return.
Pollination traps or trap-flowers are plant flower structures that aid the trapping of insects, mainly flies, so as to enhance their effectiveness in pollination. The structures of pollination traps can include deep tubular corollas with downward pointing hairs, slippery surfaces, adhesive liquid, attractants, flower closing and other mechanisms.
Ophrys speculum, the mirror orchid, is a species of Ophrys distributed throughout the Mediterranean that is pollinated exclusively by a single species of scoliid wasp.
Argogorytes mystaceus is a species of solitary wasp in the family Crabronidae.
Floral biology is an area of ecological research that studies the evolutionary factors that have moulded the structures, behaviours and physiological aspects involved in the flowering of plants. The field is broad and interdisciplinary and involves research requiring expertise from multiple disciplines that can include botany, ethology, biochemistry, and entomology. A slightly narrower area of research within floral biology is sometimes called pollination biology or anthecology.
Floral Isolation is a form of reproductive isolation found in angiosperms. Reproductive isolation is the process of species evolving mechanisms to prevent reproduction with other species. In plants, this is accomplished through the manipulation of the pollinator’s behavior or through morphological characteristics of flowers that favor intraspecific pollen transfer. Preventing interbreeding prevents hybridization and gene flow between the species (introgression), and consequently protects genetic integrity of the species. Reproductive isolation occurs in many organisms, and floral isolation is one form present in plants. Floral isolation occurs prior to pollination, and is divided into two types of isolation: morphological isolation and ethological isolation. Floral isolation was championed by Verne Grant in the 1900s as an important mechanism of reproductive isolation in plants.
The pollination of orchids is a complex chapter in the biology of this family of plants that are distinguished by the complexity of their flowers and by intricate ecological interactions with their pollinator agents. It has captured the attention of numerous scientists over time, including Charles Darwin, father of the theory of evolution by natural selection. Darwin published in 1862 the first observations of the fundamental role of insects in orchid pollination, in his book The Fertilization of Orchids. Darwin stated that the varied stratagems orchids use to attract their pollinators transcend the imagination of any human being.