The genetic variability held within individuals and populations can provide critical insights into the structure and dynamics of populations that would otherwise be difficult or impossible to study. For example, variation in allele frequencies among populations can be used to assess the genetic structure of populations, summarized by FSt (calculated as the variance in allele frequencies standardized by the mean) or related measures. From these measures, with appropriate assumptions, it is often possible to infer additional information on the biological dynamics in those populations, including attributes such as effective population size (Ne), degree of inbreeding, and rates of gene flow or migration. Genetic variability also provides the opportunity for tracing the history of populations, species, and their ancestors through methods that recognize the genealogical nature of genetic material.

A second application that uses information on genetic variation is in the area of insect pest management. For example, an understanding of the genetic basis of resistance to chemical insecticides (whether administered externally or through genetic modification of plants) has been critical in the development of strategies to delay the evolution of resistance in herbivorous insects. Genetic variability is also important in the ability of insects imported for biological control to establish themselves, as well as in their potential to attack nontarget hosts.

Finally, genetic information has been of great value in the area of conservation biology and biodiversity, as for example in efforts to determine which insect species or populations are most worthy of protection. Specific applications include genetic estimation of population sizes and spread and assessment of genetic or phylogenetic uniqueness for assignment of conservation priorities. The full value of such measures based on genetic variability has yet to be realized, and future developments will almost certainly provide further insights into both past histories and future trajectories.

See Also the Following Articles

Chromosomes • Conservation • Industrial Melanism • Insecticide and Acaricide Resistance • Ladybugs

Further Reading

Berlocher, S. H., and Feder, J. L. (2002). Sympatric speciation in phytophagous insects: Moving beyond controversy? Annu. Rev. Entomol.

Falconer, D. S., and MacKay, T. F. C. (1996). "Introduction to Quantitative

Genetics," 3rd ed. Longman, Harlow. Ford, E. B. (1971). "Ecological Genetics," 3rd ed. Chapman & Hall, London.

Futuyma, D. J. (1997). "Evolutionary Biology," 3rd ed. Sinauer, Sunderland, MA.

Graur, D., and Li, W.-H. (1999). "Fundamentals of Molecular Evolution,"

2nd ed. Sinauer, Sunderland, MA. Hartl, D. L., and Clark, A. G. (1997). "Principles of Population Genetics,"

3rd ed. Sinauer, Sunderland, MA. Howard, D. J., and Berlocher, S. H. (eds.) (1998). "Endless Forms: Species and Speciation." Oxford University Press, Oxford. Kettlewell, H. B. D. (1973). "The Evolution of Melanism." Clarendon Press, Oxford.

Price, P. W. (1996). "Biological Evolution." Saunders College, Fort Worth.

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