Mimicry in plants

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The climber Boquila trifoliata varies its leaf shape to resemble the plant it is climbing on, perhaps reducing its conspicuousness to herbivores. Boquila trifoliolata (Valdivia, Chili).jpg
The climber Boquila trifoliata varies its leaf shape to resemble the plant it is climbing on, perhaps reducing its conspicuousness to herbivores.

In evolutionary biology, mimicry in plants is where a plant evolves to resemble another organism physically or chemically. Mimicry in plants has been studied far less than mimicry in animals. It may provide protection against herbivory, or may deceptively encourage mutualists, like pollinators, to provide a service without offering a reward in return. [2]

Contents

Types of plant mimicry include Bakerian, where female flowers imitate males of the same species; Dodsonian, where a plant mimics a rewarding flower, luring pollinators by mimicking another species of flower, or fruit where feeders of the other species are attracted to a fake fruit to distribute seeds; Gilbertian, where a plant has structures like butterfly eggs, dissuading egg-laying; Vavilovian, where a weed is unintentionally selected to resemble a crop plant; Pouyannian, in which a flower imitates a female mate, deceiving a male pollinating insect into pseudocopulation; Batesian, where a harmless species deter predators by mimicking the characteristics of a harmful species; and leaf mimicry, where a plant resembles a nearby plant to evade the attention of herbivores.

Introduction

Mimicry is an adaptation by a species, called the mimic, making it resemble something else, called the model, with the effect of deceiving another species, the dupe. The three are not always all distinct, as mimicry can for example be within a species. [3] The adaptation is to the evolutionary advantage of the mimic. As such it can be any mechanism that may evolve by natural selection; no conscious intention is involved. There is no essential difference between the evolution of mimicry in plants and in other organisms such as in animals, though mimicry in animals is better known. Plant mimicry can broadly be divided into reproductive mimicry that deceives pollinators into providing their service without rewarding them in return, and protective mimicry that deceives herbivores into not eating the plant. [2]

Mimicry mechanisms, including the Batesian [4] and Müllerian [5] mimicry, were described in animals in the 19th century. [3] Charles Darwin's 1862 book Fertilisation of Orchids laid the foundations for research into plant reproductive strategies co-evolved with insects. In the book, Darwin wonders why some orchids apparently mimic bees, and how orchids without nectar succeed in attracting pollinators. [6] Several mimicry mechanisms in plants were described in the 20th century, starting with Pouyannian (1916), [7] Vavilovian (1951), [8] and Gilbertian (1975). [9] Study of mimicry in plants broadened in the 21st century, with the discovery of Batesian mimicry in plants in 2003, [10] and crypsis or leaf mimicry in 2014. [1] Until then, mimicry in plants was studied infrequently, both because it is uncommon and because botanists considered mainly physical factors in plant ecology. It may be that since plants often grow in clusters, foraging herbivores are hard to deceive once they have started to feed in an area. [11]

Reproductive

Brood-site deception

Carrion flowers attract flies and other carrion-feeding insects by their smell. Orbea variegata illustrated. Stapelia lepida.jpg
Carrion flowers attract flies and other carrion-feeding insects by their smell. Orbea variegata illustrated.

Carrion flowers, including the enormous Amorphophallus titanum , [11] mimic the scent and appearance of rotting flesh to attract necrophagous (carrion-feeding) insects like flesh flies (Sarcophagidae), blowflies (Calliphoridae), house flies (Muscidae) and some beetles (e.g., Dermestidae and Silphidae) which search for dead animals to use as brood sites. [12] [13] The decaying smell of the flower comes from oligosulfides, compounds found in decayed proteins with the sulfur-containing amino acids methionine and cysteine. While carrion flowers do produce a small amount of nectar, this does not necessarily make their relationship to necrophagous insects mutualistic. Insects lay eggs on the carrion flowers, meaning they mistake the flowers for oviposition sites. The nectar acts as a lure to bring the insects closer to the reproductive parts of the flower. [12]

Bakerian

Bakerian mimicry, named after English naturalist Herbert Baker, [14] is a form of automimicry or intraspecific mimicry that occurs within a single species. In plants, the female flowers mimic male flowers of their own species, cheating pollinators out of a reward. This reproductive mimicry may not be readily apparent as members of the same species may still exhibit some degree of sexual dimorphism, i.e. the phenotypic difference between males and females of the same species. It is common in many species of Caricaceae, a family of flowering plants in the order Brassicales, found primarily in tropical regions of Central and South America, and Africa. [15] [16]

Dodsonian

Dodsonian mimicry, named after the American botanist Calaway H. Dodson, is a form of reproductive floral mimicry where the model belongs to a different species than the mimic. By providing similar sensory signals to the model's flowers, the mimic lures the model's pollinators. Like Bakerian mimics, no nectar is provided. [17]

Epidendrum ibaguense , a species of epiphytic orchid of the genus Epidendrum that occurs in the northern part of South America, resembles flowers of Lantana camara and Asclepias curassavica . Epidendrum ibaguense is pollinated by monarch butterfly (Danaus plexippus) and perhaps hummingbirds. [18] Similar cases are seen in some other species of the same family. The mimetic species may still have pollinators of its own; for example, a Lamellicorn beetle helps to pollinate Ophrys species mainly pollinated by bees. [19]

Pouyannian

Bee orchid flower resembles a female bee closely enough to attract males in search of a mate Ophrys apifera flower1.jpg
Bee orchid flower resembles a female bee closely enough to attract males in search of a mate

In Pouyannian mimicry, [20] [7] named after the French lawyer and amateur botanist Maurice-Alexandre Pouyanne, [21] flowers mimic a male pollinator's potential female mate, visually or with other stimuli. [22] Many orchids, including the Ophrys bee orchids, deceive male insects into pseudocopulation in this way, using them to transfer pollen. [23] For instance, the orchid Epipactis helleborine is physiologically and morphologically adapted to attract social wasps as their primary pollinators. Social wasps feed their larvae on insects such as caterpillars. To locate that prey, they use a combination of visual and olfactory cues. The flowers of E. helleborine and E. purpurata emit green-leaf volatiles attractive to foragers of the social wasps Vespula germanica and V. vulgaris . E. helleborine emits several green-leaf volatiles that induce a response in wasp antennae. These same volatiles are also produced by cabbage leaves infested with caterpillars ( Pieris brassicae), which are common prey items for wasps. Despite a large nectar reward, the species is almost entirely overlooked by other pollinators. [24]

Defensive

Batesian

In Batesian mimicry, named after the English naturalist Henry Walter Bates, a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator. Batesian mimicry of thorns [10] and possibly of spider webs [25] has been observed in plants.

Thorn mimicry of two types has been observed in plants. The first, a special case of intra-organismic Batesian mimicry characteristic of Aloe species (Liliaceae), Washingtonia filifera (Arecaceae), and dozens of species of Agave , including A. applanta, A. salmiana , and A. obscura . These plants develop thornlike imprints or colorations on the face of their leaves due to the teeth along the margins of that leaf (or another leaf) pressing sustained indentations into the flesh of the non-spiny parts. The second type of thorn mimicry, a more classic case of Batesian mimicry, involves the pointed, colorful organs like buds, leaves and fruit of mimetic plant species that mimic warning-coloured aposematic colorful thorns not found anywhere else in the organism. [10]

Several plants from different parts of the world may be mimics of spider webs. Dense, white trichomes are produced on newly extended stems and leaves that deter herbivory due to predatory habit or toxicity. This may be a case of visual mimicry or perceptual exploitation. Case examples include the new buds of Onopordum from Israel, Carthamus species from Greece, flower heads of Arctium tomentosum from Estonia, a fledgling leaf of Tussilago farfara from Estonia, and new fronds of Osmunda japonica from Japan. [25]

Another plant leaf pattern has been suggested to be mimetic: irregular white blotches on leaves of plants such as Pulmonaria officinalis perhaps protect against large herbivores through their resemblance to bird droppings, which could be avoided as possible sources of disease. [2]

Gilbertian

Gilbertian [26] or colonisation mimicry [2] is bipolar, involving only two species. The potential host (or prey) drives away its parasite (or predator) by mimicking it, the reverse of host–parasite aggressive mimicry. Georges Pasteur named it after the American ecologist Lawrence E. Gilbert, who described it in 1975. [26] [9] The classical instance of Gilbertian mimicry is in the plant genus Passiflora , which is grazed by the micropredator larvae of some Heliconius butterflies. The host plants have evolved stipules, small outgrowths at the base of each leaf, that mimic mature Heliconius eggs near the point of hatching. The butterflies avoid laying eggs near existing ones, reducing intraspecific competition between caterpillars, which are also cannibalistic, so those that lay on vacant leaves provide their offspring with a greater chance of survival. The stipules thus appear to have evolved as Gilbertian mimics of butterfly eggs, under selection pressure from these caterpillars. [26] [27]

Crypsis

In ecology, crypsis is an organism's ability to avoid detection by other organisms. In cryptic mimicry, a prey organism deceives a potential predator by providing false, usually visual, signals or a lack of signals, with the effect of camouflaging itself. Boquila trifoliata , a South American member of the family Lardizabalaceae, is a climbing vine with a highly variable appearance (phenotype). It is capable of mimicking the leaf features of plant species that it clings to, such as their coloration, size, and shape. By camouflaging its leaves, Boquila reduces damage from herbivorous animals. [1] It has been speculated that such plants may make use of "some kind of vision" using ocelli, or "delicate chemical sensing", to account for the mimic's ability to cope with such a large number of variables in its model's appearance, [29] including the ability to mimic the foliage of an artificial host plant made of plastic. [30] Another plant that could well be a cryptic mimic of its host is the parasitic Australian mistletoe, Amyema cambagei , which has an "uncanny resemblance" to the foliage of Casuarina trees. [2]

Some hundreds of species in the Mesembryanthemaceae (ice plants) of Southern Africa are camouflaged as small stones, especially Lithops , which are known as pebble plants or living stones. By appearing non-living, they are less likely to be eaten by herbivores, and in dusty dry conditions among stones are extremely difficult to detect. [11]

In cultivation

Vavilovian

Vavilovian mimicry (also known as crop mimicry or weed mimicry [31] ) is named after the Russian plant geneticist who identified the centres of origin of cultivated plants, Nikolai Vavilov. [8] It is a form of mimicry in plants where a weed comes to share one or more characteristics with a domesticated plant through generations of unintentional selection. Selection against the weed may occur by killing a young or adult weed, separating its seeds from those of the crop (winnowing), or both. This has been done manually since Neolithic times, and in more recent years by agricultural machinery. [32]

Darwin's open questions about orchid fertilisation stimulated popularizers such as Grant Allen to write on the topic, and led the science fiction writer H. G. Wells to tell a tale of killer orchids, his 1896 "The Flowering of the Strange Orchid". The vampire-like plant attacks people using "tentacle-like aerial rootlets". Other authors followed with similar tales of their own. [6] [33]

See also

Related Research Articles

<span class="mw-page-title-main">Hoverfly</span> Family of insects

Hoverflies, also called flower flies or syrphids, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, while the larvae (maggots) eat a wide range of foods. In some species, the larvae are saprotrophs, specifically detritivores, eating decaying plant and animal matter in the soil or in ponds and streams. In other species, the larvae are insectivores, preying on aphids, thrips, and other plant-sucking insects.

<span class="mw-page-title-main">Coevolution</span> Two or more species influencing each others evolution

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.

<span class="mw-page-title-main">Mimicry</span> Evolutionary strategy

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. In the simplest case, as in Batesian mimicry, a mimic resembles a model, so as to deceive a dupe, all three being of different species. A Batesian mimic, such as a hoverfly, is harmless, while its model, such as a wasp, is harmful, and is avoided by the dupe, such as an insect-eating bird. Birds hunt by sight, so the mimicry in that case is visual, but in other cases mimicry may make use of any of the senses. Most types of mimicry, including Batesian, are deceptive, as the mimics are not harmful, but Müllerian mimicry, where different harmful species resemble each other, is honest, as when species of wasps and of bees all have genuinely aposematic warning coloration. More complex types may be bipolar, involving only two species, such as when the model and the dupe are the same; this occurs for example in aggressive mimicry, where a predator in wolf-in-sheep's-clothing style resembles its prey, allowing it to hunt undetected. Mimicry is not limited to animals; in Pouyannian mimicry, an orchid flower is the mimic, resembling a female bee, its model; the dupe is the male bee of the same species, which tries to copulate with the flower, enabling it to transfer pollen, so the mimicry is again bipolar. In automimicry, another bipolar system, model and mimic are the same, as when blue lycaenid butterflies have 'tails' or eyespots on their wings that mimic their own heads, misdirecting predator dupes to strike harmlessly. Many other types of mimicry exist.

<span class="mw-page-title-main">Pseudocopulation</span> Biological process

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.

<span class="mw-page-title-main">Batesian mimicry</span> Bluffing imitation of a strongly defended species

Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. It is named after the English naturalist Henry Walter Bates, who worked on butterflies in the rainforests of Brazil.

<span class="mw-page-title-main">Müllerian mimicry</span> Mutually beneficial mimicry of strongly defended species

Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Müllerian mimics is that predators only need one unpleasant encounter with one member of a set of Müllerian mimics, and thereafter avoid all similar coloration, whether or not it belongs to the same species as the initial encounter. It is named after the German naturalist Fritz Müller, who first proposed the concept in 1878, supporting his theory with the first mathematical model of frequency-dependent selection, one of the first such models anywhere in biology.

<i>Ophrys insectifera</i> Species of flowering plant in the orchid family Orchidaceae

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.

<span class="mw-page-title-main">Plant defense against herbivory</span> Evolutionary mechanism

Plant defense against herbivory or host-plant resistance is a range of adaptations evolved by plants which improve their survival and reproduction by reducing the impact of herbivores. Many plants produce secondary metabolites, known as allelochemicals, that influence the behavior, growth, or survival of herbivores. These chemical defenses can act as repellents or toxins to herbivores or reduce plant digestibility. Another defensive strategy of plants is changing their attractiveness. Plants can sense being touched, and they can respond with strategies to defend against herbivores. To prevent overconsumption by large herbivores, plants alter their appearance by changing their size or quality, reducing the rate at which they are consumed.

In plant biology and agriculture, Vavilovian mimicry is a form of mimicry in plants where a weed evolves to share characteristics with a crop plant through generations of involuntary artificial selection. It is named after the Russian plant geneticist Nikolai Vavilov.

Sexual mimicry occurs when one sex mimics the opposite sex in its behavior, appearance, or chemical signalling.

<i>Hymenopus coronatus</i> Species of praying mantis

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.

<span class="mw-page-title-main">Ant mimicry</span> Animals that resemble ants

Ant mimicry or myrmecomorphy is mimicry of ants by other organisms; it has evolved over 70 times. Ants are abundant all over the world, and potential predators that rely on vision to identify their prey, such as birds and wasps, normally avoid them, because they are either unpalatable or aggressive. Some arthropods mimic ants to escape predation, while some predators of ants, especially spiders, mimic them anatomically and behaviourally in aggressive mimicry. Ant mimicry has existed almost as long as ants themselves; the earliest ant mimics in the fossil record appear in the mid-Cretaceous alongside the earliest ants.

<span class="mw-page-title-main">Flower mantis</span> Species of mantis camouflaged to resemble flowers to lure their prey

Flower mantises are praying mantises that use a special form of camouflage referred to as aggressive mimicry, which they not only use to attract prey, but avoid predators as well. These insects have specific colorations and behaviors that mimic flowers in their surrounding habitats.

<span class="mw-page-title-main">Aggressive mimicry</span> Deceptive mimicry of a harmless species by a predator

Aggressive mimicry is a form of mimicry in which predators, parasites, or parasitoids share similar signals, using a harmless model, allowing them to avoid being correctly identified by their prey or host. Zoologists have repeatedly compared this strategy to a wolf in sheep's clothing. In its broadest sense, aggressive mimicry could include various types of exploitation, as when an orchid exploits a male insect by mimicking a sexually receptive female, but will here be restricted to forms of exploitation involving feeding. For example, indigenous Australians who dress up as and imitate kangaroos when hunting would not be considered aggressive mimics, nor would a human angler, though they are undoubtedly practising self-decoration camouflage. Treated separately is molecular mimicry, which shares some similarity; for instance a virus may mimic the molecular properties of its host, allowing it access to its cells. An alternative term, Peckhamian mimicry, has been suggested, but it is seldom used.

<span class="mw-page-title-main">Gilbertian mimicry</span> Form of mimicry in plants

In evolutionary biology, Gilbertian mimicry is a rare type of mimicry in plants involving only two species, a host or prey animal which is the mimic, and its parasite or predator, which is both the model for the mimicry, and the dupe that is deceived by it. The mechanism provides a measure of protection for the mimic, as parasites and predators rarely attack their own species.

<span class="mw-page-title-main">Pouyannian mimicry</span> Evolutionary strategy

Pouyannian mimicry is a form of mimicry in plants that deceives an insect into attempting to copulate with a flower. The flower mimics a potential female mate of a male insect, which then serves the plant as a pollinator. The mechanism is named after the French lawyer and amateur botanist Maurice-Alexandre Pouyanne. The resemblance that he noted is visual, but the key stimuli that deceive the pollinator are often chemical and tactile.

<span class="mw-page-title-main">Chemical mimicry</span> Biological mimicry using chemicals

Chemical mimicry is a type of biological mimicry involving the use of chemicals to dupe an operator.

<i>Disa ferruginea</i> Species of flowering plant

Disa ferruginea also known as the cluster disa, is a species of orchid from South Africa.

<span class="mw-page-title-main">Pollination of orchids</span>

The pollination of orchids represents a complex aspect of the biology of this plant family, characterized by intricate flower structures and diverse ecological interactions with pollinator. Notably, the topic has garnered significant scientific interest over time, including the attention of Charles Darwin, who is recognized for his contributions to the theory of evolution by natural selection. In 1862, Darwin published his observations on the essential role of insects in orchid pollination in his work The Fertilization of Orchids. He noted that the various strategies employed by orchids to attract their pollinators are complex.

<span class="mw-page-title-main">Lawrence E. Gilbert</span>

Lawrence E. Gilbert is an American biologist, known for his discovery of Gilbertian mimicry.

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