Ecological genetics

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Ecological genetics is the study of genetics in natural populations. It combines ecology, evolution, and genetics to understand the processes behind adaptation. [1]

Contents

This contrasts with classical genetics, which works mostly on crosses between laboratory strains, and DNA sequence analysis, which studies genes at the molecular level.

Research in this field is on traits of ecological significance—traits that affect an organism's fitness, or its ability to survive and reproduce. [1] Examples of such traits include flowering time, drought tolerance, polymorphism, mimicry, and avoidance of attacks by predators. [2] [ citation needed ]

Ecological genetics is an especially useful tool when studying endangered species. [3] Meta-barcoding and eDNA are used to examine the biodiversity of species in an ecosystem. [4]

Research usually involves a mixture of field and laboratory studies. [5] Samples of natural populations may be taken back to the laboratory for their genetic variation to be analyzed. Changes in the populations at different times and places will be noted, and the pattern of mortality in these populations will be studied. Research is often done on organisms that have short generation times, such as insects and microbial communities. [6] [7]

History

Although work on natural populations had been done previously, it is acknowledged that the field was founded by the English biologist E.B. Ford (1901–1988) in the early 20th century.[ citation needed ] Ford started research on the genetics of natural populations in 1924 and worked extensively to develop his formal definition of genetic polymorphism. [8] [9] Ford's magnum opus was Ecological Genetics , which ran to four editions and was widely influential. [10]

Other notable ecological geneticists include R. A. Fisher and Theodosius Dobzhansky. Fisher helped form what is known as the modern synthesis of ecology, by mathematically merging the ideas of Darwin and Mendel. [11] Dobzhansky worked on chromosome polymorphism in fruit flies. He and his colleagues carried out studies on natural populations of Drosophila species in western USA and Mexico over many years. [12] [13] [14]

Philip Sheppard, Cyril Clarke, Bernard Kettlewell and A.J. Cain were all strongly influenced by Ford; their careers date from the post World War II era. Collectively, their work on lepidoptera and on human blood groups established the field and threw light on selection in natural populations, where its role had been once doubted.[ citation needed ]

Research

Inheritance and natural selection

Ecological genetics is closely tied to the concept of natural selection. [15] Many classical ecology works have employed aspects of ecological genetics, investigating how inheritance and the environment affect individuals.

Industrial melanism in peppered moths

Industrial melanism in the peppered moth Biston betularia is a well-known example of the process of natural selection. [16] [17] The typical wing color phenotype of B. betularia is black and white flecks, but variant 'melanic' phenotypes with increased amounts of black also occur. [16] In the nineteenth century, the frequency of these melanic variants increased rapidly. Many biologists proposed explanations for this phenomenon. It was demonstrated in the early 1910s, and again in many later studies, that the melanic variants were a result of dominant alleles at a single locus in the B. betularia genome. [16] The proposed explanations, then, centered around various environmental factors that could contribute to natural selection. In particular, it was proposed that bird predation was selecting for the melanic moth forms, which were more cryptic in industrialized areas. [17] H. B. D. Kettlewell investigated this hypothesis extensively in the early 1950s.

Uncertainty surrounding whether birds preyed on moths at all posed an initial challenge, leading Kettlewell to perform a series of experiments with captive birds. [16] [17] These experiments, while inititally unsuccessful, found that when a variety of insects are provided, the birds did preferentially prey on the most conspicuous moths: those with coloration unmatched to their surroundings. Kettlewell then performed field experiments using mark-recapture techniques to investigate the selective predation of moths in their natural habitat. These experiments found that, in woods near industrialized areas, melanic moth forms were recaptured at much higher rates than the traditional lighter-colored forms, while in non-industrialized woods, the reverse held true. [17]

More recent research has further emphasized the role of genetics in the case of industrialized melanism in B. betularia. While research had already emphasized the role of alleles in determining wing-color phenotype, it was still unknown whether the melanic alleles had a single origin or had arisen multiple times independently. The use of molecular marking and chromosomal mapping in conjunction with population surveys demonstrated in the early 2010s that the melanic B. betularia variants have one single ancestral origin. [18] Additionally, the melanic variants appear to have arisen by mutation from a typical wing-color phenotype.

Polygenic selection

Research on ecologically important traits often focuses on single alleles. [19] However, it has been found that in many cases, phenotypes have a polygenic basis - they are controlled by many different alleles. Complex traits in particular are more likely to have a polygenic basis. [20] Advances in genetic technology have allowed scientists to more closely investigate the genetic basis of complex traits, leading to an accumulation of evidence supporting the importance of polygenic control in understanding the evolution of these traits.

A major line of evidence can be drawn from what we about artificial selection and its influence on traits. [20] Many experiments that have utilized artificial selection have found traits to respond quickly and steadily. If only a small amount of genes have a large influence on a particular trait, this would not be seen. The way that complex traits with continuous variation change in response to natural selection can most reasonably be explained by many alleles having a small effect on the phenotype of interest.

The prevalance of traits with a polygenic basis poses some issues when researching traits and adaptation in natural populations. Separating the effects of genes, environmental factors, and random genetic drift on traits can be difficult with complex traits. [15]

Limitations

Work of this kind needs long-term funding, as well as grounding in both ecology and genetics. These are both difficult requirements. Research projects can last longer than a researcher's career; for instance, research into mimicry started 150 years ago and is still going strongly. [21] [2] Funding of this type of research is still rather erratic, but at least the value of working with natural populations in the field cannot now be doubted.[ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Peppered moth</span> Species of moth

The peppered moth is a temperate species of night-flying moth. It is mostly found in the northern hemisphere in places like Asia, Europe and North America. Peppered moth evolution is an example of population genetics and natural selection.

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.

<span class="mw-page-title-main">E. B. Ford</span> British ecological geneticist (1901–1988)

Edmund Brisco "Henry" Ford was a British ecological geneticist. He was a leader among those British biologists who investigated the role of natural selection in nature. As a schoolboy Ford became interested in lepidoptera, the group of insects which includes butterflies and moths. He went on to study the genetics of natural populations, and invented the field of ecological genetics. Ford was awarded the Royal Society's Darwin Medal in 1954. In the wider world his best known work is Butterflies (1945).

<span class="mw-page-title-main">Bernard Kettlewell</span> British lepidopterist (1907–1979)

Henry Bernard Davis Kettlewell was a British geneticist, lepidopterist and medical doctor, who performed research on the influence of industrial melanism on peppered moth coloration, showing why moths are darker in polluted areas. This experiment is cited as a classic demonstration of natural selection in action. After live video record of the experiment with Niko Tinbergen, Sewall Wright called the study as "the clearest case in which a conspicuous evolutionary process has actually been observed."

Michael Eugene Nicolas Majerus was a British geneticist and professor of evolution at the University of Cambridge. He was also a teaching fellow at Clare College, Cambridge. He was an enthusiast in Darwin's theory of evolution by natural selection and became a world authority in his field of insect evolutionary biology. He was widely noted for his work on moths and ladybirds and as an advocate of the science of evolution. He was also an enthusiastic educator and the author of several books on insects, evolution and sexual reproduction. He is best remembered as an ardent supporter and champion of experiments on peppered moth evolution.

<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.

<span class="mw-page-title-main">Directional selection</span> Type of genetic selection favoring one extreme phenotype

In population genetics, directional selection is a type of natural selection in which one extreme phenotype is favored over both the other extreme and moderate phenotypes. This genetic selection causes the allele frequency to shift toward the chosen extreme over time as allele ratios change from generation to generation. The advantageous extreme allele will increase as a consequence of survival and reproduction differences among the different present phenotypes in the population. The allele fluctuations as a result of directional selection can be independent of the dominance of the allele, and in some cases if the allele is recessive, it can eventually become fixed in the population.

<span class="mw-page-title-main">Peppered moth evolution</span> Significance of the peppered moth in evolutionary biology

The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution. The frequency of dark-coloured moths increased at that time, an example of industrial melanism. Later, when pollution was reduced, the light-coloured form again predominated. Industrial melanism in the peppered moth was an early test of Charles Darwin's natural selection in action, and it remains a classic example in the teaching of evolution. In 1978, Sewall Wright described it as "the clearest case in which a conspicuous evolutionary process has actually been observed."

The Evolution of Melanism: a study of recurring necessity; with special reference to industrial melanism in the Lepidoptera is a 1973 science book by the lepidopterist Bernard Kettlewell.

<span class="mw-page-title-main">Index of evolutionary biology articles</span>

This is a list of topics in evolutionary biology.

<span class="mw-page-title-main">Melanism</span> Congenital excess of melanin in an organism resulting in dark pigment

Melanism is the congenital excess of melanin in an organism resulting in dark pigment.

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.

In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness. Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic trait or adaptive trait, with a functional role in each individual organism, that is maintained and has evolved through natural selection.

Arthur James Cain FRS was a British evolutionary biologist and ecologist. He was elected a Fellow of the Royal Society in 1989.

<span class="mw-page-title-main">Industrial melanism</span> Evolutionary effect

Industrial melanism is an evolutionary effect prominent in several arthropods, where dark pigmentation (melanism) has evolved in an environment affected by industrial pollution, including sulphur dioxide gas and dark soot deposits. Sulphur dioxide kills lichens, leaving tree bark bare where in clean areas it is boldly patterned, while soot darkens bark and other surfaces. Darker pigmented individuals have a higher fitness in those areas as their camouflage matches the polluted background better; they are thus favoured by natural selection. This change, extensively studied by Bernard Kettlewell (1907–1979), is a popular teaching example in Darwinian evolution, providing evidence for natural selection. Kettlewell's results have been challenged by zoologists, creationists and the journalist Judith Hooper, but later researchers have upheld Kettlewell's findings.

Many types of polymorphism can be seen in the insect order Lepidoptera. Polymorphism is the appearance of forms or "morphs" differing in color and number of attributes within a single species. In Lepidoptera, polymorphism can be seen not only between individuals in a population but also between the sexes as sexual dimorphism, between geographically separated populations in geographical polymorphism and also between generations flying at different seasons of the year. It also includes the phenomenon of mimicry when mimetic morphs fly alongside non-mimetic morphs in a population of a particular species. Polymorphism occurs both at a specific level with heritable variation in the overall morphological design of individuals as well as in certain specific morphological or physiological traits within a species.

<span class="mw-page-title-main">Reinforcement (speciation)</span> Process of increasing reproductive isolation

Reinforcement is a process of speciation where natural selection increases the reproductive isolation between two populations of species. This occurs as a result of selection acting against the production of hybrid individuals of low fitness. The idea was originally developed by Alfred Russel Wallace and is sometimes referred to as the Wallace effect. The modern concept of reinforcement originates from Theodosius Dobzhansky. He envisioned a species separated allopatrically, where during secondary contact the two populations mate, producing hybrids with lower fitness. Natural selection results from the hybrid's inability to produce viable offspring; thus members of one species who do not mate with members of the other have greater reproductive success. This favors the evolution of greater prezygotic isolation. Reinforcement is one of the few cases in which selection can favor an increase in prezygotic isolation, influencing the process of speciation directly. This aspect has been particularly appealing among evolutionary biologists.

This glossary of genetics and evolutionary biology is a list of definitions of terms and concepts used in the study of genetics and evolutionary biology, as well as sub-disciplines and related fields, with an emphasis on classical genetics, quantitative genetics, population biology, phylogenetics, speciation, and systematics. Overlapping and related terms can be found in Glossary of cellular and molecular biology, Glossary of ecology, and Glossary of biology.

References

  1. 1 2 Conner, Jeffrey K.; Hartl, Daniel L. (2004). A primer of ecological genetics. Sunderland, Mass: Sinauer Associates. ISBN   978-0-87893-202-3.
  2. 1 2 Ruxton G.D. Sherratt T.N. and Speed M.P. 2004. Avoiding attack: the evolutionary ecology of crypsis, warning signals & mimicry. Oxford University Press.
  3. ↑ Vaishnav, V; Mahesh, S; Kumar, P (2019). "Assessment of genetic structure of the endangered forest species Boswellia serrata population in central India". Journal of Tropical Forest Science. 31 (2): 200–210. doi:10.26525/jtfs2019.31.2.200210. ISSN   0128-1283. JSTOR   26626991. S2CID   196656543.
  4. ↑ Bista, Iliana; Carvalho, Gary R.; Walsh, Kerry; Seymour, Mathew; Hajibabaei, Mehrdad; Lallias, Delphine; Christmas, Martin; Creer, Simon (2017-01-18). "Annual time-series analysis of aqueous eDNA reveals ecologically relevant dynamics of lake ecosystem biodiversity". Nature Communications. 8 (1): 14087. Bibcode:2017NatCo...814087B. doi: 10.1038/ncomms14087 . ISSN   2041-1723. PMC   5253663 . PMID   28098255.
  5. ↑ Ford E.B. 1981. Taking genetics into the countryside. Weidenfeld & Nicolson, London.
  6. ↑ Fellowes, Mark, ed. (2005). Insect evolutionary ecology: proceedings of the Royal Entomological Society's 22nd Symposium. Proceedings of the Royal Entomological Society's ... symposium. Wallingford: CABI Publ. ISBN   978-0-85199-812-1.
  7. ↑ Kassen, Rees; Rainey, Paul B. (October 2004). "The Ecology and Genetics of Microbial Diversity". Annual Review of Microbiology. 58 (1): 207–231. doi:10.1146/annurev.micro.58.030603.123654. ISSN   0066-4227. PMID   15487936.
  8. ↑ Ford E.B. 1940. Polymorphism and taxonomy. In Huxley J. The new systematics. Oxford University Press.
  9. ↑ Ford E.B. 1965. Genetic polymorphism. All Souls Studies, Faber & Faber, London.
  10. ↑ Ford E.B. 1975. Ecological genetics, 4th ed. Chapman and Hall, London.
  11. ↑ Berry, Andrew; Browne, Janet (2022-07-26). "Mendel and Darwin". Proceedings of the National Academy of Sciences of the United States of America. 119 (30): e2122144119. Bibcode:2022PNAS..11922144B. doi: 10.1073/pnas.2122144119 . ISSN   0027-8424. PMC   9335214 . PMID   35858395.
  12. ↑ Dobzhansky, Theodosius. Genetics and the origin of species. Columbia, N.Y. 1st ed 1937; second ed 1941; 3rd ed 1951.
  13. ↑ Dobzhansky, Theodosius 1970. Genetics of the evolutionary process. Columbia, New York.
  14. ↑ Dobzhansky, Theodosius 1981. Dobzhansky's genetics of natural populations I-XLIII. R.C. Lewontin, J.A. Moore, W.B. Provine & B. Wallace, eds. Columbia University Press, New York 1981. (reprints the 43 papers in this series, all but two of which were authored or co-authored by Dobzhansky)
  15. 1 2 Beebee, Trevor J. C.; Rowe, Graham (2008). An introduction to molecular ecology (2nd ed.). Oxford; New York: Oxford University Press. ISBN   978-0-19-929205-9.
  16. 1 2 3 4 Cook, L M; Saccheri, I J (2013). "The peppered moth and industrial melanism: evolution of a natural selection case study". Heredity. 110 (3): 207–212. doi:10.1038/hdy.2012.92. ISSN   0018-067X. PMC   3668657 . PMID   23211788.
  17. 1 2 3 4 Rudge, David W. (2005). "The Beauty of Kettlewell's Classic Experimental Demonstration of Natural Selection". BioScience. 55 (4): 369. doi:10.1641/0006-3568(2005)055[0369:TBOKCE]2.0.CO;2. ISSN   0006-3568.
  18. ↑ van't Hof, Arjen E.; Edmonds, Nicola; Dalíková, Martina; Marec, František; Saccheri, Ilik J. (2011). "Industrial Melanism in British Peppered Moths Has a Singular and Recent Mutational Origin". Science. 332 (6032): 958–960. Bibcode:2011Sci...332..958V. doi:10.1126/science.1203043. ISSN   0036-8075. JSTOR   29784314. PMID   21493823.
  19. ↑ Fuhrmann, Nico; Prakash, Celine; Kaiser, Tobias S (2023-02-28). Weigel, Detlef (ed.). "Polygenic adaptation from standing genetic variation allows rapid ecotype formation". eLife. 12: e82824. doi: 10.7554/eLife.82824 . ISSN   2050-084X. PMC   9977305 . PMID   36852484.
  20. 1 2 Sella, Guy; Barton, Nicholas H. (2019-08-31). "Thinking About the Evolution of Complex Traits in the Era of Genome-Wide Association Studies". Annual Review of Genomics and Human Genetics. 20 (1): 461–493. doi:10.1146/annurev-genom-083115-022316. ISSN   1527-8204. PMID   31283361.
  21. ↑ Mallet J. and Joron M. 1999. Evolution in diversity in warning color and mimicry: polymorphisms, shifting balance and speciation. Annual Review of Ecological Systematics 1999. 30 201–233

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