Disassortative mating

Last updated

Disassortative mating (also known as negative assortative mating or heterogamy) is a mating pattern in which individuals with dissimilar phenotypes mate with one another more frequently than would be expected under random mating. Disassortative mating reduces the mean genetic similarities within the population and produces a greater number of heterozygotes. The pattern is character specific, but does not affect allele frequencies. [1] This nonrandom mating pattern will result in deviation from the Hardy-Weinberg principle (which states that genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences, such as "mate choice" in this case).

Contents

Disassortative mating is different from outbreeding, which refers to mating patterns in relation to genotypes rather than phenotypes.

Due to homotypic preference (bias toward the same type), assortative mating occurs more frequently then disassortative mating. [2] [3] This is due to the fact that homotypic preferences increase relatedness between mates and between parents and offspring that would promote cooperation and increases inclusive fitness. With disassortative mating, heterotypic preference (bias towards different types) in many cases has been shown to increase overall fitness. [4] When this preference is favored, it allows a population to generate and/or maintain polymorphism (genetic variation within a population).

The fitness advantage aspect of disassortative mating seems straightforward, but the evolution of selective forces involved in disassortative mating are still largely unknown in natural populations.

Types of disassortative mating

Imprinting is one example of disassortative mating. A model shows that individuals imprint on a genetically transmitted trait during early ontogeny and choosy females later use those parental images as a basis of mate choice. A viability-reducing trait may be maintained even without the fertility cost of same-type matings. [5] With imprinting, preference can be established even if it is initially rare, when there is a fertility cost of same-type matings.

One uncommon type of disassortative mating is the female preference on rare (or novel) male phenotypes. A study on guppies, Poecilia reticulata, revealed that the female preference was sufficient to tightly maintain polymorphism in male traits. [6] This type of mate choice shows that costly preferences can persist at higher frequencies if mate choice is hindered, which would allow the alleles to approach fixation.

Effects

Disassortative mating may result in balancing selection and the maintenance of high genetic variation in the population. This is due to the excess heterozygotes that are produced from disassortative mating relative to a randomly mating population.

In humans

The best-known example of disassortative mating in humans is preference for genes in the major histocompatibility complex (MHC) region on chromosome 6. Individuals feel more attracted to odors of individuals who are genetically different in this region. [7] This promotes MHC heterozygosity in the children, making them less vulnerable to pathogens.

In non-human species

Evidence from research regarding coloration in Heliconius butterflies suggests that disassortative mating is more likely to emerge when phenotypic variation is based on self-referencing (mate preference depends on phenotype of the choosing individual, therefore dominance in relationships influence the evolution of disassortative mating). [8]

Disassortative mating has been found with traits such as body symmetry in Amphridromus inversus snails. Normally in snails, rarely are individuals of the opposite coil able to mate with individuals of a normal coil pattern. However, it has been discovered that this species of snail frequents mating between individuals of opposing coils. It is said that the chirality of the spermatophore and the females reproductive tract have a greater chance of producing offspring. [9] This example of disassortative mating promotes polymorphism within the population.

In the scale eating predator fish, Perissodus microlepis , disassortative mating allows the individuals with the rare phenotype of mouth-opening direction to have better success as predators. [10]

House mice conduct disassortative mating as they prefer mates genetically dissimilar to themselves. Specifically, odor profiles in mice are strongly linked to genotypes at the MHC loci controlling changes in the immune response. When MHC-heterozygous offspring are produced, it enhances their immunocompetence because of their ability to recognize a large range of pathogens. [11] Thus, the mice tend to prefer providing "good genes" to their offspring so they will mate with individuals with differences at the MHC loci.

In the seaweed fly, Coelopa frigida , heterozygotes at the locus alcohol dehydrogenase (Adh) have been shown to express better fitness by having higher larval density and relative viability. [12] Females displayed disassortative mating in respect to the Adh locus because they would only mate with males of the opposite Adh genotype. [13] It is suspected that they do this to maintain genetic variation in the population.

White-throated sparrows, Zonotrichia albicollis, prefer strong disassortative mating behaviors regarding the color of their head stripe. The single locus that controls this expression is only observed in heterozygotes. Additionally, the heterozygote arrangement of chromosome 2 from disassortative mating produced offspring of high aggression which is shown to be a social behavior that allows them to dominate their opponents. [14]

Related Research Articles

An allele is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. The word is a short form of "allelomorph".

<span class="mw-page-title-main">Dominance (genetics)</span> One gene variant masking the effect of another in the other copy of the gene

In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and the second recessive. This state of having two different variants of the same gene on each chromosome is originally caused by a mutation in one of the genes, either new or inherited. The terms autosomal dominant or autosomal recessive are used to describe gene variants on non-sex chromosomes (autosomes) and their associated traits, while those on sex chromosomes (allosomes) are termed X-linked dominant, X-linked recessive or Y-linked; these have an inheritance and presentation pattern that depends on the sex of both the parent and the child. Since there is only one copy of the Y chromosome, Y-linked traits cannot be dominant or recessive. Additionally, there are other forms of dominance such as incomplete dominance, in which a gene variant has a partial effect compared to when it is present on both chromosomes, and co-dominance, in which different variants on each chromosome both show their associated traits.

<span class="mw-page-title-main">Population genetics</span> Subfield of genetics

Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and population structure.

Allele frequency, or gene frequency, is the relative frequency of an allele at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that carry that allele over the total population or sample size. Microevolution is the change in allele frequencies that occurs over time within a population.

Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction. Two genetic markers that are physically near to each other are unlikely to be separated onto different chromatids during chromosomal crossover, and are therefore said to be more linked than markers that are far apart. In other words, the nearer two genes are on a chromosome, the lower the chance of recombination between them, and the more likely they are to be inherited together. Markers on different chromosomes are perfectly unlinked, although the penetrance of potentially deleterious alleles may be influenced by the presence of other alleles, and these other alleles may be located on other chromosomes than that on which a particular potentially deleterious allele is located.

<span class="mw-page-title-main">Polymorphism (biology)</span> Occurrence of two or more clearly different morphs or forms in the population of a species

In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population.

Frequency-dependent selection is an evolutionary process by which the fitness of a phenotype or genotype depends on the phenotype or genotype composition of a given population.

Balancing selection refers to a number of selective processes by which multiple alleles are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing selection is rare compared to purifying selection. It can occur by various mechanisms, in particular, when the heterozygotes for the alleles under consideration have a higher fitness than the homozygote. In this way genetic polymorphism is conserved.

A heterozygote advantage describes the case in which the heterozygous genotype has a higher relative fitness than either the homozygous dominant or homozygous recessive genotype. Loci exhibiting heterozygote advantage are a small minority of loci. The specific case of heterozygote advantage due to a single locus is known as overdominance. Overdominance is a rare condition in genetics where the phenotype of the heterozygote lies outside of the phenotypical range of both homozygote parents, and heterozygous individuals have a higher fitness than homozygous individuals.

Assortative mating is a mating pattern and a form of sexual selection in which individuals with similar phenotypes or genotypes mate with one another more frequently than would be expected under a random mating pattern. A majority of the phenotypes that are subject to assortative mating are body size, visual signals, and sexually selected traits such as crest size. The opposite of assortative is disassortative mating.

<span class="mw-page-title-main">Overdominance</span>

Overdominance is a rare condition in genetics where the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents. Overdominance can also be described as heterozygote advantage regulated by a single genomic locus, wherein heterozygous individuals have a higher fitness than homozygous individuals. However, not all cases of the heterozygote advantage are considered overdominance, as they may be regulated by multiple genomic regions. Overdominance has been hypothesized as an underlying cause for heterosis.

<span class="mw-page-title-main">Disruptive selection</span>

Disruptive selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups. In this more individuals acquire peripheral character value at both ends of the distribution curve.

<span class="mw-page-title-main">Chromosomal inversion</span> Chromosome rearrangement in which a segment of a chromosome is reversed

An inversion is a chromosome rearrangement in which a segment of a chromosome becomes inverted within its original position. An inversion occurs when a chromosome undergoes a two breaks within the chromosomal arm, and the segment between the two breaks inserts itself in the opposite direction in the same chromosome arm. The breakpoints of inversions often happen in regions of repetitive nucleotides, and the regions may be reused in other inversions. Chromosomal segments in inversions can be as small as 100 kilobases or as large as 100 megabases. The number of genes captured by an inversion can range from a handful of genes to hundreds of genes. Inversions can happen either through ectopic recombination, chromosomal breakage and repair, or non-homologous end joining.

In genetics, underdominance, also known as homozygote advantage, heterozygote disadvantage, or negative overdominance," is the opposite of overdominance. It is the selection against the heterozygote, causing disruptive selection and divergent genotypes. Underdominance exists in situations where the heterozygotic genotype is inferior in fitness to either the dominant or recessive homozygotic genotype. Compared to examples of overdominance in actual populations, underdominance is considered more unstable and may lead to the fixation of either allele.

<span class="mw-page-title-main">Mate choice</span> One of the primary mechanisms under which evolution can occur

Mate choice is one of the primary mechanisms under which evolution can occur. It is characterized by a "selective response by animals to particular stimuli" which can be observed as behavior. In other words, before an animal engages with a potential mate, they first evaluate various aspects of that mate which are indicative of quality—such as the resources or phenotypes they have—and evaluate whether or not those particular trait(s) are somehow beneficial to them. The evaluation will then incur a response of some sort.

<span class="mw-page-title-main">TAS2R38</span> Protein-coding gene in the species Homo sapiens

Taste receptor 2 member 38 is a protein that in humans is encoded by the TAS2R38 gene. TAS2R38 is a bitter taste receptor; varying genotypes of TAS2R38 influence the ability to taste both 6-n-propylthiouracil (PROP) and phenylthiocarbamide (PTC). Though it has often been proposed that varying taste receptor genotypes could influence tasting ability, TAS2R38 is one of the few taste receptors shown to have this function.

<span class="mw-page-title-main">Zygosity</span> Degree of similarity of the alleles in an organism

Zygosity is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.

<span class="mw-page-title-main">Host–parasite coevolution</span> Mutually adaptive genetic change of a host and a parasite

Host–parasite coevolution is a special case of coevolution, where a host and a parasite continually adapt to each other. This can create an evolutionary arms race between them. A more benign possibility is of an evolutionary trade-off between transmission and virulence in the parasite, as if it kills its host too quickly, the parasite will not be able to reproduce either. Another theory, the Red Queen hypothesis, proposes that since both host and parasite have to keep on evolving to keep up with each other, and since sexual reproduction continually creates new combinations of genes, parasitism favours sexual reproduction in the host.

<span class="mw-page-title-main">Major histocompatibility complex and sexual selection</span> Adaptive immune gene selection

The major histocompatibility complex in sexual selection concerns how major histocompatibility complex (MHC) molecules allow for immune system surveillance of the population of protein molecules in a host's cells. In 1976, Yamazaki et al. demonstrated a sexual selection mate choice by male mice for females of a different MHC.

This glossary of evolutionary biology is a list of definitions of terms and concepts used in the study of evolutionary biology, population biology, speciation, and phylogenetics, as well as sub-disciplines and related fields. For additional terms from related glossaries, see Glossary of genetics, Glossary of ecology, and Glossary of biology.

References

  1. ↑ Lewontin, Richard; Kirk, Dudley; Crow, James (1963). "Selective mating, assortative mating, and inbreeding: Definitions and implications". Eugenics Quarterly. 15 (2): 141–143. doi:10.1080/19485565.1968.9987764. PMID   5702329.
  2. ↑ Thiessen; Gregg (1980). "Human assortative mating and genetic equilibrium: An evolutionary perspective". Ethology and Sociobiology. 1 (2): 111–140. doi:10.1016/0162-3095(80)90003-5.
  3. ↑ Wallace, B (January 1958). The role of heterozygosity in drosophila populations (Technical report). OSTI   4289507.
  4. ↑ Burley, Nancy (1983). "The meaning of assortative mating". Ethology and Sociobiology. 4 (4): 191–203. doi:10.1016/0162-3095(83)90009-2.
  5. ↑ Ihara, Yasuo; Feldman, Marcus (2003). "Evolution of disassortative and assortative mating preferences based on imprinting". Theoretical Population Biology. 64 (2): 193–200. doi:10.1016/s0040-5809(03)00099-6. PMID   12948680.
  6. ↑ Kokko, Hanna; Jennions, Michael; Houde, Anne (2007). "Evolution of frequency-dependent mate choice: keeping up with fashion trends". Proceedings. Biological Sciences. 274 (1615): 1317–1324. doi:10.1098/rspb.2007.0043. PMC   2176183 . PMID   17360285.
  7. ↑ Wedekind, Claus (1995). "MHC-dependent mate preferences in humans". Proceedings of the Royal Society of London. Series B: Biological Sciences. 260 (1359): 245–249. doi:10.1098/rspb.1995.0087. PMID   7630893. S2CID   34971350.
  8. ↑ Maisonneuve, Ludovic; Joron, Mathieu; Chouteau, Mathieu; Llaurens, Violaine (2020). "Evolution and genetic architecture of disassortative mating at a locus under heterozygote advantage". Evolution. 75 (1): 149–165. bioRxiv   10.1101/616409 . doi:10.1111/evo.14129. PMID   33210282. S2CID   227063195.
  9. ↑ Schilthuizen, M. (2007). "Sexual selection maintains whole‐body chiral dimorphism in snails". Journal of Evolutionary Biology. 20 (5): 1941–1949. doi:10.1111/j.1420-9101.2007.01370.x. PMC   2121153 . PMID   17714311.
  10. ↑ Hori, Michio (1993). "Frequency-Dependent Natural Selection in the Handedness of Scale-Eating Cichlid Fish". Science. 260 (5105): 216–219. Bibcode:1993Sci...260..216H. doi:10.1126/science.260.5105.216. PMID   17807183. S2CID   33113282.
  11. ↑ Penn, Dustin; Potts, Wayne (1999). "The Evolution of Mating Preferences and Major Histocompatibility Complex Genes". The American Naturalist. 153 (2): 145–164. doi:10.1086/303166. PMID   29578757. S2CID   4398891.
  12. ↑ Butlin, R; Collins, P; Day, T (1984). "The effect of larval density on an inversion polymorphism in the seaweed fly Coelopa frigida". Heredity. 52 (3): 415–423. doi:10.1038/hdy.1984.49. S2CID   20675225.
  13. ↑ Day, T; Butlin, R (1987). "Non-random mating in natural populations of the seaweed fly, Coelopa frigida". Heredity. 58 (2): 213–220. doi:10.1038/hdy.1987.35. S2CID   24811609.
  14. ↑ Horton, Brent (2013). "Behavioral Characterization of a White-Throated Sparrow Homozygous for the ZAL2m Chromosomal Rearrangement". Behavior Genetics. 43 (1): 60–70. doi:10.1007/s10519-012-9574-6. PMC   3552124 . PMID   23264208.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.