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Phenotypic plasticity refers to some of the changes in an
organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological ...

organism
's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induced changes (e.g. morphological,
physiological Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. ...
,
behavioural Behavior (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American English ...
,
phenological
phenological
) that may or may not be permanent throughout an individual's lifespan. The term was originally used to describe developmental effects on morphological characters, but is now more broadly used to describe all phenotypic responses to environmental change, such as
acclimation Acclimatization or acclimatisation ( also called acclimation or acclimatation) is the process in which an individual organism In biology Biology is the natural science that studies life and living organisms, including their a ...
(
acclimatization Acclimatization or acclimatisation ( also called acclimation or acclimatation) is the process in which an individual organism In biology Biology is the natural science that studies life and living organisms, including their a ...
), as well as
learning Learning is the process of acquiring new understanding Understanding is a psychological process related to an abstract or physical thing, such as a person, situation, or message whereby one is able to use concepts to model that thing. Under ...

learning
. The special case when differences in environment induce discrete phenotypes is termed
polyphenism A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions. It is therefore a special case of phenotypic plasticity. There are several types of polyph ...
. Generally, phenotypic plasticity is more important for immobile organisms (e.g.
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
s) than mobile organisms (e.g. most
animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells ...

animal
s), as mobile organisms can often move away from unfavourable environments. Nevertheless, mobile organisms also have at least some degree of plasticity in at least some aspects of the
phenotype In genetics Genetics is a branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular inter ...

phenotype
. One mobile organism with substantial phenotypic plasticity is ''Acyrthosiphon pisum'' of the
aphid Aphids are small sap-sucking insects and members of the Taxonomic rank, superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white Erio ...

aphid
family, which exhibits the ability to interchange between asexual and sexual reproduction, as well as growing wings between generations when plants become too populated.


Examples


Plants

Phenotypic plasticity in plants includes the timing of transition from vegetative to reproductive growth stage, the allocation of more resources to the
root In vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from Greek τραχεῖα ἀρτηρία ''trācheia artēria'' 'windpipe' + φυτά ''phutá'' 'plants'), form a large grou ...

root
s in soils that contain low concentrations of
nutrients A nutrient is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and ta ...
, the size of the seeds an individual produces depending on the environment, and the alteration of
leaf A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaf
shape, size, and thickness. Leaves are particularly plastic, and their growth may be altered by light levels. Leaves grown in the light tend to be thicker, which maximizes photosynthesis in direct light; and have a smaller area, which cools the leaf more rapidly (due to a thinner
boundary layer In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. ...
). Conversely, leaves grown in the shade tend to be thinner, with a greater surface area to capture more of the limited light.
Dandelion ''Taraxacum'' () is a large genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxono ...

Dandelion
are well known for exhibiting considerable plasticity in form when growing in sunny versus shaded environments. The
transport proteins Transport (commonly used in the U.K.), or transportation (used in the U.S.), is the movement of humans, animals and goods In economics Economics () is the social science that studies how people interact with value; in particular, t ...
present in roots also change depending on the concentration of the nutrient and the salinity of the soil. Some plants, ''
Mesembryanthemum crystallinum ''Mesembryanthemum crystallinum'' is a prostrate succulent plant native to Africa, Sinai Peninsula, Sinai and southern Europe, and naturalized in North America, South America and Australia. The plant is covered with large, glistening bladder cell ...

Mesembryanthemum crystallinum
'' for example, are able to alter their photosynthetic pathways to use less water when they become water- or salt-stressed. Because of phenotypic plasticity, it is hard to explain and predict the traits when plants are grown in natural conditions unless an explicit environment index can be obtained to quantify environments. Identification of such explicit environment indices from a critical growth periods being highly correlated with sorghum and rice flowering time enables such predictions.


Phytohormones and leaf plasticity

Leaves are very important to a plant in that they create an avenue where photosynthesis and thermoregulation can occur. Evolutionarily, the environmental contribution to leaf shape allowed for a myriad of different types of leaves to be created. Leaf shape can be determined by both genetics and the environment. Environmental factors, such as light and humidity, have been shown to affect leaf morphology, giving rise to the question of how this shape change is controlled at the molecular level. This means that different leaves could have the same gene but present a different form based on environmental factors. Plants are sessile, so this phenotypic plasticity allows the plant to take in information from its environment and respond without changing its location. In order to understand how leaf morphology works, the anatomy of a leaf must be understood. The main part of the leaf, the blade or lamina, consists of the epidermis, mesophyll, and vascular tissue. The epidermis contains
stomata In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

stomata
which allows for gas exchange and controls perspiration of the plant. The mesophyll contains most of the
chloroplast A chloroplast is a type of membrane-bound organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structure ...

chloroplast
where
photosynthesis Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Doctor Who'' audio), an episode of the audio drama ' ...

photosynthesis
can occur. Developing a wide blade/lamina can maximize the amount of light hitting the leaf, thereby increasing photosynthesis, however too much sunlight can damage the plant. Wide lamina can also catch wind easily which can cause stress to the plant, so finding a happy medium is imperative to the plants’ fitness. The Genetic Regulatory Network is responsible for creating this phenotypic plasticity and involves a variety of genes and proteins regulating leaf morphology. Phytohormones have been shown to play a key role in signaling throughout the plant, and changes in concentration of the phytohormones can cause a change in development. Studies on the aquatic plant species ''Ludwigia arcuata'' have been done to look at the role of
abscisic acid Abscisic acid (ABA) is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure. It is especially important for plants in the response to Stress (biolog ...

abscisic acid
(ABA), as ''L. arcuata'' is known to exhibit phenotypic plasticity and has two different types of leaves, the aerial type (leaves that touch the air) and the submerged type (leaves that are underwater). When adding ABA to the underwater shoots of ''L. arcuata'', the plant was able to produce aerial type leaves underwater, suggesting that increased concentrations of ABA in the shoots, likely caused by air contact or a lack of water, triggers the change from the submerged type of leaf to the aerial type. This suggests ABA's role in leaf phenotypic change and its importance in regulating stress through environmental change (such as adapting from being underwater to above water). In the same study, another phytohormone, ethylene, was shown to induce the submerged leaf phenotype unlike ABA, which induced aerial leaf phenotype. Because ethylene is a gas, it tends to stay endogenously within the plant when underwater – this growth in concentration of ethylene induces a change from aerial to submerged leaves and has also been shown to inhibit ABA production, further increasing the growth of submerged type leaves. These factors (temperature, water availability, and phytohormones) contribute to changes in leaf morphology throughout a plants lifetime and are vital to maximize plant fitness.


Animals

The developmental effects of nutrition and temperature have been demonstrated. The
gray wolf The wolf (''Canis lupus''), also known as the gray wolf or grey wolf, is a large canine Canine may refer to: Zoology * dog-like mammals (i.e. members of the canid subfamily Caninae) ** ''Canis'', a genus including dogs, wolves, coyotes, a ...

gray wolf
(''Canis lupus'') has wide phenotypic plasticity. Additionally, male speckled wood butterflies have two morphs: one with three dots on its hindwing, and one with four dots on its hindwings. The development of the fourth dot is dependent on environmental conditions – more specifically, location and the time of year. In
amphibian Amphibians are ectothermic, tetrapod vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, ter ...
s, '' Pristimantis mutabilis'' has remarkable phenotypic plasticity. Another example is the
southern rockhopper penguin The southern rockhopper penguin group (''Eudyptes chrysocome''), are two subspecies of rockhopper penguin, that together are sometimes considered distinct from the northern rockhopper penguin. It occurs in subantarctic waters of the western Pacifi ...
. Rockhopper penguins are present at a variety of climates and locations; Amsterdam Island's subtropical waters,
Kerguelen Archipelago The Kerguelen Islands ( or ; in French commonly ' but officially ', ), also known as the Desolation Islands (' in French), are a Archipelago, group of islands in the Antarctic constituting one of the two exposed parts of the Kerguelen Plateau, a ...
's subarctic coastal waters, and Crozet Archipelago's subantarctic coastal waters. Due to the species plasticity they are able to express different strategies and foraging behaviors depending on the climate and environment. A main factor that has influenced the species' behavior is where food is located.


Temperature

Plastic responses to
temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal energy refers to several distinct physical concept ...

temperature
are essential among ectothermic organisms, as all aspects of their physiology are directly dependent on their thermal environment. As such, thermal acclimation entails phenotypic adjustments that are found commonly across
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
, such as changes in the
lipid In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
composition of
cell membranes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membra ...
. Temperature change influences the fluidity of cell membranes by affecting the motion of the fatty acyl chains of
glycerophospholipids Glycerophospholipids or phosphoglycerides are glycerol Glycerol (; also called glycerine in British English and glycerin in American English) is a simple polyol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and ...

glycerophospholipids
. Because maintaining membrane fluidity is critical for cell function, ectotherms adjust the phospholipid composition of their cell membranes such that the strength of
van der Waals force In molecular physics Molecular physics is the study of the physical properties of molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings ...
s within the membrane is changed, thereby maintaining fluidity across temperatures.


Diet

Phenotypic plasticity of the
digestive system The human digestive system consists of the human gastrointestinal tract, gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food in ...

digestive system
allows some animals to respond to changes in dietary nutrient composition, diet quality, and energy requirements. Changes in the
nutrient A nutrient is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and t ...
composition of the diet (the proportion of lipids, proteins and carbohydrates) may occur during development (e.g. weaning) or with seasonal changes in the abundance of different food types. These diet changes can elicit plasticity in the
activity Activity may refer to: * Action (philosophy), in general * Human activity: human behavior, in sociology behavior may refer to all basic human actions, economics may study human economic activities and along with cybernetics and psychology may stud ...
of particular digestive enzymes on the
brush border A brush border (striated border or brush border membrane) is the microvilli-covered surface of simple cuboidal and simple columnar epithelium Simple columnar epithelium is a single layer of columnar epithelial cell Epithelium () is one of ...
of the
small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...

small intestine
. For example, in the first few days after hatching, nestling
house sparrow The house sparrow (''Passer domesticus'') is a bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form ...

house sparrow
s (''Passer domesticus'') transition from an insect diet, high in protein and lipids, to a seed based diet that contains mostly carbohydrates; this diet change is accompanied by two-fold increase in the activity of the enzyme
maltase Maltase (, ''alpha-glucosidase'', ''glucoinvertase'', ''glucosidosucrase'', ''maltase-glucoamylase'', ''alpha-glucopyranosidase'', ''glucosidoinvertase'', ''alpha-D-glucosidase'', ''alpha-glucoside hydrolase'', ''alpha-1,4-glucosidase'', ''alpha ...
, which digests carbohydrates. Acclimatizing animals to high protein diets can increase the activity of
aminopeptidase Aminopeptidases are enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzy ...
-N, which digests proteins. Poor quality diets (those that contain a large amount of non-digestible material) have lower concentrations of nutrients, so animals must process a greater total volume of poor-quality food to extract the same amount of energy as they would from a high-quality diet. Many species respond to poor quality diets by increasing their food intake, enlarging digestive organs, and increasing the capacity of the digestive tract (e.g.
prairie vole The prairie vole (''Microtus ochrogaster'') is a small vole found in central North America North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be described as ...

prairie vole
s,
Mongolian gerbil The Mongolian gerbil or Mongolian jird (''Meriones unguiculatus'') is a small rodent belonging to the subfamily Gerbillinae. Their body size is typically 110–135mm (4½" to 5¼"), with a 95–120mm (3¾" to 4¾") tail, and body weight 60–1 ...
s,
Japanese quail The Japanese quail, ''Coturnix japonica'', also known as the coturnix quail is a species of Old World quail Old World quail is a collective name for several genera of mid-sized birds in the tribe Coturnicini of the pheasant family Phasianidae ...

Japanese quail
,
wood duck The wood duck or Carolina duck (''Aix sponsa'') is a species of perching duck The perching ducks were previously treated as a small group of ducks in the duck Duck is the common name for numerous species in the waterfowl family (biology), ...

wood duck
s,
mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa, and has been introduced species, introduced to New Zealand, Australia, Peru, Bra ...

mallard
s). Poor quality diets also result in lower concentrations of nutrients in the lumen of the intestine, which can cause a decrease in the activity of several digestive enzymes. Animals often consume more food during periods of high energy demand (e.g. lactation or cold exposure in
endotherm An endotherm (from Ancient Greek, Greek ἔνδον ''endon'' "within" and θέρμη ''thermē'' "heat") is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily ...
s), this is facilitated by an increase in digestive organ size and capacity, which is similar to the phenotype produced by poor quality diets. During lactation, common degus (''Octodon degus'') increase the mass of their liver, small intestine, large intestine and cecum by 15–35%. Increases in food intake do not cause changes in the activity of digestive enzymes because nutrient concentrations in the intestinal lumen are determined by food quality and remain unaffected. Intermittent feeding also represents a temporal increase in food intake and can induce dramatic changes in the size of the gut; the
Burmese python The Burmese python (''Python bivittatus'') is one of the largest species of snakes Snakes are elongated, limbless, carnivorous A carnivore , meaning "meat Meat is animal flesh that is eaten as food. Humans have hunted and killed ...

Burmese python
(''Python molurus bivittatus'') can triple the size of its small intestine just a few days after feeding.
AMY2B Alpha-amylase 2B is an enzyme Enzymes () are protein Proteins are large s and s that comprise one or more long chains of . Proteins perform a vast array of functions within organisms, including , , , providing and , and from one loc ...
(Alpha-Amylase 2B) is a gene that codes a protein that assists with the first step in the digestion of dietary
starch Starch or amylum is a polymeric A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance ...
and
glycogen Glycogen is a multibranched polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant found in . They are long chain carbohydrates composed of units bound together by . This carbohydrate can react with water () usi ...

glycogen
. An expansion of this gene in dogs would enable early dogs to exploit a starch-rich diet as they fed on refuse from agriculture. Data indicated that the wolves and dingo had just two copies of the gene and the Siberian Husky that is associated with hunter-gatherers had just three or four copies, whereas the
Saluki The Saluki is a standardised breed developed from sighthound : characteristic long legs, deep chest, and narrow waist of a sighthound Sighthounds, also called gazehounds, are a Dog type, type of dog, hounds that hunt primarily by sight and sp ...

Saluki
that is associated with the
Fertile Crescent The Fertile Crescent is a crescent-shaped region in the Middle East The Middle East ( ar, الشرق الأوسط, ISO 233 The international standard An international standard is a technical standard A technical standard is an establishe ...

Fertile Crescent
where agriculture originated had 29 copies. The results show that on average, modern dogs have a high copy number of the gene, whereas wolves and dingoes do not. The high copy number of AMY2B variants likely already existed as a standing variation in early domestic dogs, but expanded more recently with the development of large agriculturally based civilizations.


Parasitism

Infection with
parasites Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is adaptation (biology), adapted structurally to this w ...
can induce phenotypic plasticity as a means to compensate for the detrimental effects caused by parasitism. Commonly,
invertebrates Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart from the chordata, chordate subphylum vertebrate, Vertebrat ...
respond to
parasitic castration Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part, to its own benefit. This is one of six major strategies within parasitism. For example, ''Hemioniscus balani'', a parasitic castrator ...
or increased parasite
virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most contexts, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host (biology), host. The Pathogen#Pathogenicity, ...
with
fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the wor ...
compensation in order to increase their reproductive output, or fitness. For example,
water fleas The Diplostraca or Cladocera, commonly known as water fleas, are a superorder (biology), superorder of small crustaceans that feed on microscopic chunks of organic matter (excluding some predatory forms). Over 1000 species have been recognised s ...
(''
Daphnia magna ''Daphnia magna'' is a small planktonic crustacean (adult length 1.5–5.0 mm) that belongs to the subclass Phyllopoda. It inhabits a variety of freshwater environments, ranging from acidic swamps to rivers made of snow runoff, and is broadly ...

Daphnia magna
''), exposed to
microsporidia Microsporidia are a group of spore )'', growing on a thinning, thinned hybrid black poplar ''(populus, Populus x canadensis)''. The last stage of the moss#Life cycle, moss lifecycle is shown, where the sporophytes are visible before dispersi ...
n parasites produce more offspring in the early stages of exposure to compensate for future loss of reproductive success. A reduction in fecundity may also occur as a means of re-directing nutrients to an immune response, or to increase
longevity The word "longevity The word "wikt:longevity, longevity" is sometimes used as a synonym for "life expectancy" in demography. However, the term ''longevity'' is sometimes meant to refer only to especially long-lived members of a population, ...

longevity
of the host. This particular form of plasticity has been shown in certain cases to be mediated by host-derived molecules (e.g. schistosomin in snails ''
Lymnaea stagnalis ''Lymnaea stagnalis'', common name, better known as the great pond snail, is a species of large air-breathing freshwater snail, an Aquatic animal, aquatic pulmonate gastropod mollusk in the family (biology), family Lymnaeidae. ''Limnaea stagnal ...

Lymnaea stagnalis
'' infected with
trematodes Trematoda is a class within the phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical category of number. ...
''Trichobilharzia ocellata'') that interfere with the action of reproductive hormones on their target organs. Changes in reproductive effort during infection is also thought to be a less costly alternative to mounting resistance or defence against invading parasites, although it can occur in concert with a defence response. Hosts can also respond to parasitism through plasticity in physiology aside from reproduction. House mice infected with intestinal
nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a bro ...

nematode
s experience decreased rates of
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
transport in the intestine. To compensate for this, mice increase the total mass of mucosal cells, cells responsible for glucose transport, in the intestine. This allows infected mice to maintain the same capacity for glucose uptake and body size as uninfected mice. Phenotypic plasticity can also be observed as changes in behaviour. In response to infection, both vertebrates and invertebrates practice
self-medication Self-medication is a human behavior Human behavior is the potential and expressed capacity (Energy (psychological), mentally, Physical activity, physically, and Social actions, socially) of human individuals or groups to respond to internal a ...
, which can be considered a form of adaptive plasticity. Various species of non-human primates infected with intestinal worms engage in leaf-swallowing, in which they ingest rough, whole leaves that physically dislodge parasites from the intestine. Additionally, the leaves irritate the
gastric mucosa The gastric mucosa is the mucous membrane layer of the stomach, which contains the glands and the gastric pits. In humans, it is about 1 mm thick, and its surface is smooth, soft, and velvety. It consists of simple columnar epithelium, lamina ...
, which promotes the secretion of gastric acid and increases , effectively flushing parasites from the system. The term "self-induced adaptive plasticity" has been used to describe situations in which a behavior under selection causes changes i
subordinate traits
that in turn enhance the ability of the organism to perform the behavior. For example, birds that engage in
altitudinal migration Altitudinal migration is a short-distance animal migration Animal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of Migration (ecology), migration in ecology. It i ...
might make "trial runs" lasting a few hours that would induce physiological changes that would improve their ability to function at high altitude. Woolly bear caterpillars ('' Grammia incorrupta'') infected with
tachinid flies The Tachinidae are a large and variable family of true fly, flies within the insect order Fly, Diptera, with more than 8,200 known species and many more to be discovered. Over 1300 species have been described in North America alone. Insects in thi ...

tachinid flies
increase their survival by ingesting plants containing toxins known as
pyrrolizidine alkaloid Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high ...
s. The physiological basis for this change in behaviour is unknown; however, it is possible that, when activated, the immune system sends signals to the taste system that trigger plasticity in feeding responses during infection. Reproduction The red-eyed tree frog, '''', is an arboreal frog (hylid) that resides in the tropics of Central America. Unlike many frogs, the red-eyed tree frog has arboreal eggs which are laid on leaves hanging over ponds or large puddles and, upon hatching, the tadpoles fall into the water below. One of the most common predators encountered by these arboreal eggs is the cat-eyed snake, ''Leptodeira septentrionalis''. In order to escape predation, the red-eyed tree frogs have developed a form of adaptive plasticity, which can also be considered phenotypic plasticity, when it comes to hatching age; the clutch is able to hatch prematurely and survive outside of the egg five days after oviposition when faced with an immediate threat of predation. The egg clutches take in important information from the vibrations felt around them and use it to determine whether or not they are at risk of predation. In the event of a snake attack, the clutch identifies the threat by the vibrations given off which, in turn, stimulates hatching almost instantaneously. In a controlled experiment conducted by Karen Warkentin, hatching rate and ages of red-eyed tree frogs were observed in clutches that were and were not attacked by the cat-eyed snake. When a clutch was attacked at six days of age, the entire clutch hatched at the same time, almost instantaneously. However, when a clutch is not presented with the threat of predation, the eggs hatch gradually over time with the first few hatching around seven days after oviposition, and the last of the clutch hatching around day ten. Karen Warkentin's study further explores the benefits and trade-offs of hatching plasticity in the red-eyed tree frog.


Evolution

Plasticity is usually thought to be an
evolutionary adaptation In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...

evolutionary adaptation
to environmental variations that is reasonably predictable and occurs within the lifespan of an individual organism, as it allows individuals to 'fit' their phenotype to different environments. If the optimal phenotype in a given environment changes with environmental conditions, then the ability of individuals to express different traits should be advantageous and thus selected for. Hence, phenotypic plasticity can evolve if Darwinian fitness is increased by changing phenotype. A similar logic should apply in
artificial evolution In computational intelligence (CI), an evolutionary algorithm (EA) is a subset of evolutionary computation, a generic population-based metaheuristic optimization (mathematics), optimization algorithm. An EA uses mechanisms inspired by biological ev ...

artificial evolution
attempting to introduce phenotypic plasticity to artificial agents. However, the fitness benefits of plasticity can be limited by the energetic costs of plastic responses (e.g. synthesizing new proteins, adjusting expression ratio of
isozyme In biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable exp ...
variants, maintaining sensory machinery to detect changes) as well as the predictability and reliability of environmental cues (see Beneficial acclimation hypothesis).
Freshwater snail Freshwater snails are gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underl ...
s (''Physa virgata''), provide an example of when phenotypic plasticity can be either adaptive or
maladaptive A maladaptation () is a trait Trait may refer to: * Phenotypic trait in biology, which involve genes and characteristics of organisms * Trait (computer programming), a model for structuring object-oriented programs (a template class in the C++ p ...
. In the presence of a predator, , these snails make their shell shape more rotund and reduce growth. This makes them more crush-resistant and better protected from predation. However, these snails cannot tell the difference in chemical cues between the predatory and non-predatory sunfish. Thus, the snails respond inappropriately to non-predatory sunfish by producing an altered shell shape and reducing growth. These changes, in the absence of a predator, make the snails susceptible to other predators and limit
fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the wor ...
. Therefore, these freshwater snails produce either an adaptive or maladaptive response to the environmental cue depending on whether predatory sunfish are present or not. Given the profound ecological importance of temperature and its predictable variability over large spatial and temporal scales, adaptation to thermal variation has been hypothesized to be a key mechanism dictating the capacity of organisms for phenotypic plasticity. The magnitude of thermal variation is thought to be directly proportional to plastic capacity, such that species that have evolved in the warm, constant
climate Climate is the long-term pattern of weather Weather is the state of the atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a la ...

climate
of the
tropics The tropics are the region of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% ...

tropics
have a lower capacity for plasticity compared to those living in variable
temperate In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its populati ...
habitats. Termed the "climatic variability hypothesis", this idea has been supported by several studies of plastic capacity across
latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use the ...

latitude
in both plants and animals. However, recent studies of ''
Drosophila ''Drosophila'' () is a genus of fly, flies, belonging to the family (biology), family Drosophilidae, whose members are often called "small fruit flies" or (less frequently) pomace flies, vinegar flies, or wine flies, a reference to the character ...

Drosophila
'' species have failed to detect a clear pattern of plasticity over latitudinal gradients, suggesting this hypothesis may not hold true across all taxa or for all traits. Some researchers propose that direct measures of environmental variability, using factors such as precipitation, are better predictors of phenotypic plasticity than latitude alone. Selection experiments and
experimental evolution Experimental evolution is the use of laboratory experiments or controlled field manipulations to explore evolutionary dynamics. Evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance ...
approaches have shown that plasticity is a trait that can evolve when under direct selection and also as a correlated response to selection on the average values of particular traits.


Plasticity and climate change

Unprecedented rates of
climate change Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...
are predicted to occur over the next 100 years as a result of human activity. Phenotypic plasticity is a key mechanism with which organisms can cope with a changing climate, as it allows individuals to respond to change within their lifetime. This is thought to be particularly important for species with long generation times, as evolutionary responses via natural selection may not produce change fast enough to mitigate the effects of a warmer climate. The American red squirrel, North American red squirrel (''Tamiasciurus hudsonicus'') has experienced an increase in average temperature over this last decade of almost 2 °C. This increase in temperature has caused an increase in abundance of white spruce cones, the main food source for winter and spring reproduction. In response, the mean lifetime parturition date of this species has advanced by 18 days. Food abundance showed a significant effect on the breeding date with individual females, indicating a high amount of phenotypic plasticity in this trait.


See also

* Acclimation * Allometric engineering * Baldwin effect * Beneficial acclimation hypothesis * Developmental biology * Evolutionary physiology * Genetic assimilation * Rapoport's rule *Developmental plasticity


References


Further reading

* * See also:


External links

*Special issue of the ''Journal of Experimental Biology'' concernin
phenotypic plasticity
*''Developmental Plasticity and Evolution''
review of the book
from ''American Scientist'' {{Evolution Evolutionary biology Extended evolutionary synthesis Genetics