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Extinction Vortex
 
 
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Extinction vortices are a class of models through which conservation biologists
Conservation biology

Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction....
, geneticists
Conservation genetics

Conservation genetics is an interdisciplinary science that aims to apply genetics methods to the conservation and restoration of biodiversity. Researchers involved in conservation genetics come from a variety of fields including population genetics, molecular ecology, molecular biology, evolutionary biology, and systematics....
 and ecologists can understand the dynamics of and categorize extinction
Extinction

In biology and ecology, extinction is the death of every member of a species or group of taxon. The moment of extinction is generally considered to be the death of the last individual of that species ....
s in the context of their causes. Developed by M. E. Gilpin and M. E. Soulé
Michael Soule

Michael E. Soul? is a United States biologist, best known for his work in promoting the idea of conservation biology. He earned a Ph.D. in Population Biology at Stanford University under Paul R....
 in their (now) famous 1986 paper Minimum viable populations: Processes of species extinction, there are currently four classes of extinction vortices. The first two (R and D) deal with environmental
Natural environment

The natural environment, commonly referred to simply as the environment, is a term that encompasses all life and non-living things occurring nature on Earth or some region thereof....
 factors that have an effect on the ecosystem
Ecosystem

An ecosystem is a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the non-living physical factors of the environment....
 or community
Community

In biological terms, a community is a group of interacting organisms sharing an environment .In human communities, intention, belief, Natural resource, preferences, Need assessment, risks, and a number of other conditions may be present and common, affecting the Identity of the participants and their degree of cohesiveness....
 level, such as disturbance
Disturbance

In ecology, a disturbance is a temporary change in average environmental conditions that causes a pronounced change in an ecosystem. Outside disturbance forces often act quickly and with great effect, sometimes resulting in the removal of large amounts of biomass....
, pollution
Pollution

Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms ....
, habitat loss etc.






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Extinction vortices are a class of models through which conservation biologists
Conservation biology

Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction....
, geneticists
Conservation genetics

Conservation genetics is an interdisciplinary science that aims to apply genetics methods to the conservation and restoration of biodiversity. Researchers involved in conservation genetics come from a variety of fields including population genetics, molecular ecology, molecular biology, evolutionary biology, and systematics....
 and ecologists can understand the dynamics of and categorize extinction
Extinction

In biology and ecology, extinction is the death of every member of a species or group of taxon. The moment of extinction is generally considered to be the death of the last individual of that species ....
s in the context of their causes. Developed by M. E. Gilpin and M. E. Soulé
Michael Soule

Michael E. Soul? is a United States biologist, best known for his work in promoting the idea of conservation biology. He earned a Ph.D. in Population Biology at Stanford University under Paul R....
 in their (now) famous 1986 paper Minimum viable populations: Processes of species extinction, there are currently four classes of extinction vortices. The first two (R and D) deal with environmental
Natural environment

The natural environment, commonly referred to simply as the environment, is a term that encompasses all life and non-living things occurring nature on Earth or some region thereof....
 factors that have an effect on the ecosystem
Ecosystem

An ecosystem is a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the non-living physical factors of the environment....
 or community
Community

In biological terms, a community is a group of interacting organisms sharing an environment .In human communities, intention, belief, Natural resource, preferences, Need assessment, risks, and a number of other conditions may be present and common, affecting the Identity of the participants and their degree of cohesiveness....
 level, such as disturbance
Disturbance

In ecology, a disturbance is a temporary change in average environmental conditions that causes a pronounced change in an ecosystem. Outside disturbance forces often act quickly and with great effect, sometimes resulting in the removal of large amounts of biomass....
, pollution
Pollution

Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms ....
, habitat loss etc. Whereas the second two (F and A) deal with genetic factors such as inbreeding depression
Inbreeding depression

Inbreeding depression is reduced fitness in a given population as a result of breeding of related individuals. Breeding between closely related individuals, called inbreeding, results in more recessive deleterious traits manifesting themselves....
 and outbreeding depression
Outbreeding depression

In evolutionary biology, outbreeding depression refers to cases when offspring from cross-fertilization between individuals from different populations have lower fitness than progeny from crosses between individuals from the same population....
, genetic drift
Genetic drift

Genetic drift or allelic drift is the change in the relative frequency with which a gene variant occurs in a population that results from the fact that alleles in offspring are a Sampling of those in the parents, and because of the role of chance in determining whether a given individual survives and reproduces....
 etc.

Types of vortices


  • R Vortex: The R vortex is initiated when there is a disturbance which facilitates a lowering of population
    Population

    File:Population density.pngIn biology, a population is the collection of inter-breeding organisms of a particular species; in sociology, a collection of human beings....
     size (N) and a corresponding increase in variability (Var(r)). This event can make populations vulnerable to additional disturbances which will lead to further decreases in population size (N) and further increases in variability (Var(r)). A prime example of this would be the disruption of sex ratio
    Sex ratio

    Sex ratio is the ratio of males to females in a population. The primary sex ratio is the ratio at the time of conception, secondary sex ratio is the ratio at time of birth, and tertiary sex ratio is the ratio of mature organisms....
    s in a population away from the species optimum .


  • D Vortex: The D vortex is initiated when population size (N) decreases and variability (Var(r)) increases such that the spatial distribution (D) of the population is increased and the population becomes "patchy" or fragmented
    Habitat fragmentation

    Habitat fragmentation is a process of Natural environmental change important in evolution and conservation biology. As the name implies, it describes the emergence of discontinuities in an organism's preferred environment ....
    . Within these fragments, local extinction rates increase which, through positive feedback
    Positive feedback

    Positive feedback, sometimes referred to as "cumulative causation", is a feedback loop system in which the system responds to Perturbation of biological system in the same direction as the perturbation....
    , further increases D.


  • F Vortex: The F vortex is initiated by a decrease in population size (N) which leads to a decrease in individual heterozygosity (an increase in autozygosity) and increases the rate of genetic drift, resulting in increased degrees of inbreeding depression and an increase in population genetic load
    Genetic load

    In population genetics, genetic load or genetic burden is a measure of the cost of lost alleles due to selection or mutation . It is a value in the range , where 0 represents no load....
    , which over time will result in extinction.


  • A Vortex: The A vortex is a result of an increase in genetic drift and a corresponding decrease in genetic variance
    Variance

    In probability theory and statistics, the variance of a random variable, probability distribution, or sample is one measure of statistical dispersion, averaging the squared distance of its possible values from the expected value ....
     which leads to a decrease in "population adaptive potential", and eventual extinction. This vortex can result from biological invasion
    Invasive species

    Invasive species is a phrase with several definitions. The first definition expresses the phrase in terms of non-indigenous species that adversely affect the habitats they invade economically, environmentally or ecologically....
    , resulting in large scale hybridization and outbreeding depression.


See also

  • Mutational meltdown
    Mutational meltdown

    Mutational meltdown refers to the process by which a Small population size accumulates deleterious mutations, which leads to loss of fitness and decline of the population size, which may lead to further accumulation of deleterious mutations due to inbreeding depression....
  • Small population size
    Small population size

    Populations with small population size behave differently from larger populations. Often this has various harmful consequences for the survival of that population....
  • Muller's ratchet
    Muller's ratchet

    In evolutionary genetics, Muller's ratchet is the process by which the genomes of an Asexual reproduction population accumulate genetic deletion in an irreversible manner....