Why quantify genetic population structure across geographical ranges?
There is growing interest in quantifying genetic population structure across the geographical ranges of species to understand why species might exhibit stable range limits and to assess the conservation value of peripheral populations.
What is genetic variation?
Genetic variation is the presence of differences in sequences of genes between individual organisms of a species. It enables natural selection, one of the primary forces driving the evolution of life.
Is restricted gene flow a barrier to geographic differentiation?
However, because species usually tend to have a limited dispersal range (e.g. in an isolation by distance model), restricted gene flow can serve as a type of barrier which encourages geographic differentiation. [9]
What is the difference between a cline and a gradient?
Clines can show smooth, continuous gradation in a character, or they may show more abrupt changes in the trait from one geographic region to the next. A cline refers to a spatial gradient in a specific, singular trait, rather than a gradient in a population as a whole.
What is genetic variation in geography?
Genetic variation is the presence of differences in sequences of genes between individual organisms of a species. It enables natural selection, one of the primary forces driving the evolution of life.
What is genetic diversity called?
Biodiversity is the variety of plants and animals inhabiting in an ecosystem. It includes species diversity, genetic diversity and ecosystem diversity. Genetic diversity is defined as genetic variability present within species.
What is a clinal gradient?
Clinal structure and terminology The steepness, or gradient, of a cline reflects the extent of the differentiation in the character across a geographic range. For example, a steep cline could indicate large variation in the colour of plumage between adjacent bird populations.
What is an example of Clinal variation?
One easily visible example of a clinal distribution seen worldwide is the patterning of human variation in skin color. Whether in southern Asia, sub-Saharan Africa, or Australia, dark brown skin is found.
What are the 3 types of genetic variation?
The different gene forms caused by genetic polymorphisms are called alleles. The genetic diversity has three different sources: mutation, recombination and immigration of genes.
What are types of variation?
Genetic variation - these are differences between individuals that are inherited from parents, such as the colour of your eyes, hair and skin. Environmental variation - these are differences between individuals that are not inherited but caused by the environment that the organism lives in, including scars and tattoos.
What is the meaning of clinal?
Pertaining to beds or restAdjective. clinal (not comparable) Pertaining to beds or rest.
What is clinal distribution?
Genetically inherited traits often have a clinal distribution. That is to say there is a continuous, progressive gradation moving from one geographic region to another. The frequency of yellow-brown hair among Australian Aborigines illustrates this trend (as shown by the map on the left below).
What is a clinal distribution map?
What is a clinal distribution map and what does it do? a continuous gradation showing regional concentrations of a chosen trait or attribute.
What is cline and examples?
Clines are gradients used for teaching gradations of meaning. Words are spaced along the gradient, for example, words to describe temperature, such as tepid, hot, boiling, cool, cold, warm, chilly, and freezing. After modelling the task, give these words to groups of students to place on the cline.
What is human variation in biology?
Human variability, or human variation, is the range of possible values for any characteristic, physical or mental, of human beings.
What is discrete variation in biology?
Variation between individuals of a species can be grouped into two large categories: discrete and continuous. Discrete variation is either/or and is often caused by the presence or absence of a small number if genes. For example, our ability to "roll" our tongues is determined by just one gene.
Is genetic diversity biodiversity?
Biodiversity is a complex term that includes not only the variety of different animals (species diversity) but also the difference between animals of the same species (genetic diversity) and between ecosystems (ecosystem diversity).
What is genetic diversity quizlet?
Genetic diversity. Refers to the number of different alleles of genes in a population. Population. All the organisms of one species in a habitat. Proteins.
What is species and genetic diversity?
Species diversity refers to the number and distribution of species in a given area, whereas genetic diversity refers to the number of genes in a given population. Species diversity is a trait of the community, whereas genetic diversity is a trait of the species.
What is species diversity in biology?
Species diversity is the number of different species in a particular area and their relative abundance. The area in question could be a habitat, a biome, or the entire biosphere.
What is normal biological variation?
The normal variability in the test species is called normal biological variation. The distribution of measurements typically follows a normal or Gaussian distribution. This distribution is described as a “bell-shaped” curve (as shown in Fig. 1 ), an essential underpinning of many statistical analyses. In essence, this is the background of “noise” against which backdrop observations are made. Mathematics can help clarify whether the results seen in an experiment are a result of biological “noise” or a treatment-related “signal.” Just as the experimenter cannot be sure that the treatment did have an effect, statistical analyses do not give a definite yes or no answer, rather a probability statement.
Why is biological variation important?
Biological variation is important for survival of individuals and species, and is the underpinning force behind evolution. The intricacies of human biology with its many layers of interconnecting networks and inbuilt redundancy evolved over many millions of years to maximize an individual's chance of survival.
What is the goal set up of analytical variation?
The goal set-up is that variance due to analytical error should not exceed 20% of the variation ( Fraser, 1983 ). It can be shown that this is acceptable when CV analytical ≤1/2CV intra-individual or ≤1/2CV biological ( Fraser and Harris, 1989 ).
What is normal variability in the test species?
The normal variability in the test species (normal biological variation) provides a distribution of measurements that typically follow a normal or Gaussian distribution. This distribution is described as a bell-shaped curve (as shown in Figure 30.1 ), and is an essential underpinning of many statistical analyses. In essence, this distribution is the background of “noise” against which backdrop observations are made. Mathematics can help clarify whether the results seen in an experiment are a result of biological noise or a treatment-related signal. Just as the experimenter cannot be sure that the treatment did have an effect, statistical analyses does not give a definite yes or no answer, but rather renders a probability statement regarding the likelihood that the treatment is responsible for inducing the effect.
What is the x axis of a normal biological variability curve?
FIGURE 30.1. Normal biological variability – bell shaped curve. The x-axis reports the frequency of the observation; the y -axis reports the measurement. SD, standard deviation.
How does biological variation affect our lives?
Biological variation is central to all our lives. Diversity in our own species is recognized in a number of visible characteristics, such as height, and functional characteristics, such as biotransformation abilities. The latter source of variability has led to the developing field of pharmacogenomics. Unfortunately, biological diversity interferes with efforts to test treatment effects, even when the experiment is designed and controlled a priori. No matter how inbred study animals are, and consequently how alike their physiological responses are likely to be, there is always a range of response displayed in measurements made on these animals. This fact has been confirmed many times in monozygotic human twins, and more recently in cloned animals.
Why is diversity important in biology?
Within each species, diversity is essential for survival and finding a niche in which to develop. Without exploring the theory of evolution, diversity in our own species is recognized in a number of visible characteristics, such as height, and functional characteristics, such as biotransforming abilities. The latter source of variability has led to the developing field of pharmacogenomics. Unfortunately, biological diversity interferes with efforts to test treatment effects, even when the experiment is designed and controlled a priori. No matter how inbred study animals are, there is always a range of response displayed in measurements made on these animals.
Why is a stable cline maintained when two populations join?
Because over time the effect of gene flow will tend to eventually swamp out any regional differences and cause one large homogenous population, for a stable cline to be maintained when two populations join there must usually be a selective pressure maintaining a degree of differentiation between the two populations.
What is a cline in biology?
A cline refers to a spatial gradient in a specific, singular trait, rather than a collection of traits; a single population can therefore have as many clines as it has traits, at least in principle. Additionally, Huxley recognised that these multiple independent clines may not act in concordance with each other.
How does selection maintain clines?
The mechanism of selection maintaining the clines in this scenario is often intrinsic. This means that the fitness of individuals is independent of the external environment, and selection is instead dependent on the genome of the individual. Intrinsic, or endogenous, selection can give rise to clines in characters through a variety of mechanisms. One way it may act is through heterozygote disadvantage, in which intermediate genotypes have a lower relative fitness than either homozygote genotypes. Because of this disadvantage, one allele will tend to become fixed in a given population, such that populations will consist largely of either AA ( homozygous dominant) or aa (homozygous recessive) individuals. The cline of heterozygotes that is created when these respective populations come into contact is then shaped by the opposing forces of selection and gene flow; even if selection against heterozygotes is great, if there is some degree of gene flow between the two populations, then a steep cline may be able to be maintained. Because instrinsic selection is independent of the external environment, clines generated by selection against hybrids are not fixed to any given geographical area and can move around the geographic landscape. Such hybrid zones where hybrids are a disadvantage relative to their parental lines (but which are nonetheless maintained through selection being counteracted by gene flow) are known as “tension zones”.
How are clines generated?
Clines generated through this mechanism have arisen through the joining of two formerly isolated populations which differentiated in allopatry, creating an intermediate zone. This secondary contact scenario may occur, for example, when climatic conditions change, allowing the ranges of populations to expand and meet. Because over time the effect of gene flow will tend to eventually swamp out any regional differences and cause one large homogenous population, for a stable cline to be maintained when two populations join there must usually be a selective pressure maintaining a degree of differentiation between the two populations.
What is the difference between a cline and an ecotype?
While the terms " ecotype " and "cline" are sometimes used interchangeably, they do in fact differ in that "ecotype" refers to a population which differs from other populations in a number of characters, rather than the single character that varies amongst populations in a cline.
Is geographic isolation necessary for speciation?
However, the existence of particular types of clines, such as ring species, in which populations did not differentiate in allopatry but the terminal ends of the cline nonetheless do not interbreed, cast into doubt whether complete geographical isolation of populations is an absolute requirement for speciation.
Can a cline be created by genetic drift?
While selection can therefore clearly play a key role in creating clines, it is theoretically feasible that they might be generated by genetic drift alone. It is unlikely that large-scale clines in genotype or phenotype frequency will be produced solely by drift. However, across smaller geographical scales and in smaller populations, drift could produce temporary clines. The fact that drift is a weak force upholding the cline however means that clines produced this way are often random (i.e. uncorrelated with environmental variables) and subject to breakdown or reversal over time. Such clines are therefore unstable and sometimes called “transient clines”.
What are the principles of geographic variation?
Introduction. Evolutionary principles of geographic variation began to emerge early as the field of evolutionary biology developed within the biological sciences. Geographic variation of species, sometimes featuring distinct subspecies and often having characteristic traits, is determined by geographic variables such as climate or ecological niche ...
What did Darwin's observations of geographic variation lead to?
Together with Darwin 1896 on domesticated animals and plants, and using comparisons with the fossil record, the author’s observations of geographic variation were used as evidence for natural selection and led to the view that geographic races can potentially evolve into closely related but separate species.
Who wrote the variation in animals and plants under domestication?
Darwin, C. 1896. The variation in animals and plants under domestication. Vol. 1. New York: D. Appleton.
What is genetic variance?
Genetic variance is a concept outlined by the English biologist and statistician Ronald Fisher in his fundamental theorem of natural selection which he outlined in his 1930 book The Genetical Theory of Natural Selection which postulates that the rate of change of biological fitness can be calculated by the genetic variance of the fitness itself. Fisher tried to give a statistical formula about how the change of fitness in a population can be attributed to changes in the allele frequency. Fisher made no restrictive assumptions in his formula concerning fitness parameters, mate choices or the number of alleles and loci involved.
What is the term for how much of the phenotypic variance is due to variance in genetic factors?
Heritability refers to how much of the phenotypic variance is due to variance in genetic factors. Usually after we know the total amount of genetic variance that is responsible for a trait, we can calculate the trait heritability.
What is the measuring method for genetic variance?
Measuring method. 1.Traditionally, using pedigree data in humans, plants, and livestock species to estimate additive genetic variance. 2. Using a single-nucleotide polymorphisms ( SNP) regression method to quantify the contribution of additive, dominance, and imprinting variance to the total genetic variance. 3.
What influences phenotypic variance?
The phenotypic variance (V P) in a population is influenced by genetic variance (V G) and environmental sources (V E )
What is the difference between dominance and epistatic variance?
Epistatic variance involves an interaction between different alleles in different loci.
What is a G matrix?
Genetic variance–covariance (G) matrices conveniently summarize the genetic relationships among a suite of traits and are a central parameter in the determination of the multivariate response to selection.
What is the difference between broad sense and narrow sense heritability?
Broad-sense heritability, H 2 = V G /V P, Involves the proportion of phenotypic variation due to the effects of additive, dominance, and epistatic variance. Narrow-sense heritability, h 2 = V A /V P, refers to the proportion of phenotypic variation that is due to additive genetic values (V A ).