Ecotype
Encyclopedia
In evolutionary ecology
, an ecotype,Greek: οίκος = home and τύπος = type, coined by Göte Turesson
in 1922 sometimes called ecospecies, describes a genetically distinct geographic variety, population or race
within species
(or among closely related), which is adapted
to specific environmental conditions.
Typically, ecotypes exhibit phenotypic
differences (such as in morphology
or physiology
) stemming from environmental heterogeneity and are capable of interbreeding with other geographically adjacent ecotypes without loss of fertility or vigor.
) interbreed, thus overcoming local selection. However other studies reveal that the opposite may happen, i.e. ecotypes revealing at very small scales (of the order of 10 m), within populations, and despite hybridization.
In ecotypes, it is common for continuous, gradual geographic variation to impose analogous phenotypic and/or genetic variation. This situation is called cline. A well-known example of cline is the skin color gradation in indigenous human populations worldwide, which is related to latitude and amounts of sunlight. But often the distribution of ecotypes is bimodal
or multimodal. This means that ecotypes may display two or more distinct and discontinuous phenotypes even within the same population. Such phenomenon may lead to speciation
and can occur if conditions in a local environment change dramatically through space or time.
. However some scientists consider them "taxonomically equivalent to subspecies
". This is true in the sense that ecotypes can be sometimes classified as subspecies and the opposite.
Ecotypes are closely related to morphs. In the context of evolutionary biology, genetic polymorphism
is the occurrence in equilibrium of two or more distinctly different phenotypes within a population of a species, in other words, the occurrence of more than one form or morph. The frequency of these discontinuous forms (even that of the rarest) is too high to be explained by mutation
. In order to be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (whose all members can potentially interbreed). Polymorphism is actively and steadily maintained in populations of species by natural selection (most famously sexual dimorphism
in humans) in contrast to transient polymorphisms where conditions in a habitat change in such a way that a "form" is being replaced completely by another.
In fact, Begon, Townsend and Harper assert that
The notions "form" and "ecotype" may appear to correspond to a static phenomenon, however this is not always the case. Evolution occurs continuously both in time and space, so that two ecotypes or forms may qualify as distinct species in only a few generations. Begon, Townsend and Harper use an illuminating analogy on this:
Thus ecotypes and morphs can be thought of as precursory steps of potential speciation
.
Evolutionary ecology
Evolutionary ecology lies at the intersection of ecology and evolutionary biology. It approaches the study of ecology in a way that explicitly considers the evolutionary histories of species and the interactions between them. Conversely, it can be seen as an approach to the study of evolution that...
, an ecotype,Greek: οίκος = home and τύπος = type, coined by Göte Turesson
Göte Turesson
Göte Wilhelm Turesson was a Swedish evolutionary botanist who made significant contributions to ecological genetics, and coined the terms ecotype and agamospecies. He conducted extensive work to demonstrate that there is a genetic basis to the differentiation of plant populations...
in 1922 sometimes called ecospecies, describes a genetically distinct geographic variety, population or race
Race (biology)
In biology, races are distinct genetically divergent populations within the same species with relatively small morphological and genetic differences. The populations can be described as ecological races if they arise from adaptation to different local habitats or geographic races when they are...
within species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
(or among closely related), which is adapted
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
to specific environmental conditions.
Typically, ecotypes exhibit phenotypic
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
differences (such as in morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
or physiology
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...
) stemming from environmental heterogeneity and are capable of interbreeding with other geographically adjacent ecotypes without loss of fertility or vigor.
Range and distribution
Experiments indicate that sometimes ecotypes manifest only when separated by great spatial distances (of the order of 1000 km). This is due to hybridization whereby different but adjacent varieties of the same species (or generally of the same taxonomic rankTaxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
) interbreed, thus overcoming local selection. However other studies reveal that the opposite may happen, i.e. ecotypes revealing at very small scales (of the order of 10 m), within populations, and despite hybridization.
In ecotypes, it is common for continuous, gradual geographic variation to impose analogous phenotypic and/or genetic variation. This situation is called cline. A well-known example of cline is the skin color gradation in indigenous human populations worldwide, which is related to latitude and amounts of sunlight. But often the distribution of ecotypes is bimodal
Bimodal distribution
In statistics, a bimodal distribution is a continuous probability distribution with two different modes. These appear as distinct peaks in the probability density function, as shown in Figure 1....
or multimodal. This means that ecotypes may display two or more distinct and discontinuous phenotypes even within the same population. Such phenomenon may lead to speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
and can occur if conditions in a local environment change dramatically through space or time.
Examples
- TundraTundraIn physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...
reindeer and forest (or woodland) reindeer are two ecotypes of reindeerReindeerThe reindeer , also known as the caribou in North America, is a deer from the Arctic and Subarctic, including both resident and migratory populations. While overall widespread and numerous, some of its subspecies are rare and one has already gone extinct.Reindeer vary considerably in color and size...
. The first migrate (travelling 5000 km) annually between the two environments in large numbers whereas the other (who are much fewer) remain in the forest for the summer. Currently, and since 1961 classification, tundra reindeer comprise five subspecies and woodland reindeer two.
- Arabis fecundaArabisArabis , or rockcress, is a genus of flowering plants, within the family Brassicaceae, subfamily Brassicoideae.Though traditionally recognized as a large genus with many Old World and New World members, more recent evaluations of the relationships among these species using genetic data suggest that...
, a herb endemic to some calcareousCalcareousCalcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
soils of Montana, USA, can be divided into two ecotypes. The one "low elevation" group lives near the ground in an arid, warm environment and has thus developed a significantly greater tolerance against drought than the "high elevation" group. The two ecotypes are separated by a horizontal distance of about 100 km.
- It is commonly accepted that the TucuxiTucuxiThe Tucuxi , alternately bufeo gris or bufeo negro is a dolphin found in the rivers of the Amazon Basin. The word "tucuxi" is derived from the Tupi language word tuchuchi-ana and has now been adopted as the species' common name...
dolphin has two ecotypes - the riverine ecotype found in some South American rivers and the pelagic ecotype found in the South Atlantic Ocean. Similarly, it is accepted that the Common Bottlenose DolphinCommon Bottlenose DolphinTursiops truncatus, commonly known as the Common Bottlenose Dolphin, is the most well-known species from the family Delphinidae.Common bottlenose dolphins are the most familiar dolphins due to the wide exposure they receive in captivity in marine parks, dolphinarias, in movies, and television...
has two ecotypes in the Western North Atlantic.
- The Warbler finchWarbler FinchThe Warbler Finch is a species of bird, one of Darwin's finches in the tanager family Thraupidae. Sometimes classified in the family Emberizidae, more recent studies have shown it to belong in the tanager family. It is the only member of the genus Certhidea...
and the Cocos Island FinchCocos Island FinchThe Cocos Island Finch or Cocos Finch, Pinaroloxias inornata, is the only one of Darwin's finches not native to the Galápagos Islands, and the only member of the genus Pinaroloxias. Sometimes classified in the family Emberizidae, more recent studies have shown it to belong in the tanager family...
are viewed as separate ecotypes.
- The Scots PineScots PinePinus sylvestris, commonly known as the Scots Pine, is a species of pine native to Europe and Asia, ranging from Scotland, Ireland and Portugal in the west, east to eastern Siberia, south to the Caucasus Mountains, and as far north as well inside the Arctic Circle in Scandinavia...
(Pinus sylvestris) has 20 different ecotypes in an area from Scotland to Siberia, all capable of interbreeding.
- A very subtle case of ecotype is the following: It has been observed that two populations of the same Helix (gastropod) species separated by a only few hundred kilometers prefer not to cross-mate, i.e. they reject one another as mates. This event probably occurs during the process of courtship, which may last for hours.
Terminology
Ecotypes have no main taxonomic rank in modern biological classificationBiological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....
. However some scientists consider them "taxonomically equivalent to subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
". This is true in the sense that ecotypes can be sometimes classified as subspecies and the opposite.
Ecotypes are closely related to morphs. In the context of evolutionary biology, genetic polymorphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
is the occurrence in equilibrium of two or more distinctly different phenotypes within a population of a species, in other words, the occurrence of more than one form or morph. The frequency of these discontinuous forms (even that of the rarest) is too high to be explained by mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
. In order to be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population (whose all members can potentially interbreed). Polymorphism is actively and steadily maintained in populations of species by natural selection (most famously sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in humans) in contrast to transient polymorphisms where conditions in a habitat change in such a way that a "form" is being replaced completely by another.
In fact, Begon, Townsend and Harper assert that
The notions "form" and "ecotype" may appear to correspond to a static phenomenon, however this is not always the case. Evolution occurs continuously both in time and space, so that two ecotypes or forms may qualify as distinct species in only a few generations. Begon, Townsend and Harper use an illuminating analogy on this:
Thus ecotypes and morphs can be thought of as precursory steps of potential speciation
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
.
See also
- EvolutionEvolutionEvolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
- AdaptationAdaptationAn adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
- SpeciationSpeciationSpeciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
- Polymorphism (biology)Polymorphism (biology)Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
- Cline (biology)
- Species problemSpecies problemThe species problem or species concept is a mixture of difficult, related questions that often come up when biologists identify species and when they define the word "species"....
- Ring speciesRing speciesIn biology, a ring species is a connected series of neighboring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene...
- Biological classificationBiological classificationBiological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....