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Adaptation and the ‘shifting balance’

Published online by Cambridge University Press:  14 April 2009

N. H. Barton  and
S. Rouhani
N. H. Barton
Affiliation:
Division of Biology, University of Edinburgh, King's Buildings, Edinburgh EH9 3JT, U.K.
S. Rouhani
Affiliation:
Physics Department, Sharif University of Technology, Tehran, PO Box 11365-9161, Iran
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Wright proposed that there is a ‘shifting balance’ between selection within demes, random drift, and selection between demes at different ‘adaptive peaks’. We investigate the establishment and spread of new adaptive peaks, considering a chromosome rearrangement, and a polygenic character under disruptive selection. When the number of migrants (Nm) is small, demes fluctuate independently, with a bias towards the fitter peak. When Nm is large, the whole population can move to one of two stable equilibria, and so can be trapped near the lower peak. These two regimes are separated by a sharp transition at a critical Nm of order 1. Just below this critical point, adaptation is most efficient, since the shifting balance greatly increases the proportion of demes that reach the global optimum. This is so even if one peak is only slightly fitter than the other (ΔW≈1/N), and for both strong and weak selection (Ns (Ns ≪ 1 or Ns ≫ 1). Provided that Nm varies sufficiently gradually from place to place, the fitter peak can be established in regions where Nm≈1, and can then spread through the rest of the range. Our analysis confirms Wright's argument that if selection, migration and drift are of the same order, the ‘shifting balance’ leads to efficient evolution towards the global optimum.

Type
Research Article
Information
Genetics Research , Volume 61 , Issue 1 , February 1993 , pp. 57 - 74
Copyright
Copyright © Cambridge University Press 1993

References

Akin, E. (1979). The Geometry of Population Genetics. Lecture Notes in Biomathematics 31. Springer-Verlag, Berlin.Google Scholar
Barton, N. H. (1985). The effects of linkage and densitydependent regulation on gene flow. Heredity 57, 415–426.CrossRefGoogle Scholar
Barton, N. H. (1989). The divergence of a polygenic system under stabilising selection, mutation and drift. Genetical Research (Cambridge) 54, 59–77.CrossRefGoogle Scholar
Barton, N. H. (1992). On the spread of new gene combinations in the third phase of Wright's shifting balance. Evolution 46, 551–557.Google ScholarPubMed
Barton, N. H. & Charlesworth, B. (1984). Genetic revolutions, founder effects and speciation. Annual Review of Ecology and Systematics 15, 133–164.CrossRefGoogle Scholar
Barton, N. H. & Rouhani, S. (1987). The frequency of peak shifts between alternative equilibria. Journal of Theoretical Biology 125, 397–418.CrossRefGoogle Scholar
Barton, N. H. & Rouhani, S. (1991). The probability of fixation of a new karyotype in a continuous population. Evolution 45, 499–517.CrossRefGoogle Scholar
Barton, N. H. & Turelli, M. (1987). Adaptive landscapes, genetic distance and the evolution of quantitative characters. Genetical Research (Cambridge) 49, 157–173.CrossRefGoogle ScholarPubMed
Bengtsson, B. O. & Bodmer, W. F. (1976). The fitness of human translocation carriers. Annals of Human Genetics 40, 253–257.CrossRefGoogle ScholarPubMed
Crow, J. F., Engels, W. R. & Denniston, C. (1990). Phase three of Wright's shifting balance theory. Evolution 44, 233–247.CrossRefGoogle ScholarPubMed
Feynman, R. P. (1972). Statistical Mechanics. W. A. Benjamin, Reading, Mass.Google Scholar
Gardiner, C. W. (1983). Handbook of Stochastic Methods. Springer Verlag, Berlin.CrossRefGoogle Scholar
Gilpin, M. & Hanski, I. (eds) (1991). Metapopulation Dynamics: Empirical and Theoretical Investigations. Academic Press, London. First published in Biological Journal of the Linnean Society 42 (1, 2).Google Scholar
Hastings, A. (1981). Stable cycling in discrete time genetic models. Proceedings of the National Academy of Science {U.S.A.) 78, 7224–7225.CrossRefGoogle ScholarPubMed
Kaufman, S. A. & Johnsen, S. (1992). Co-evolution to the edge of chaos: coupled fitness landscapes, poised states, and coevolutionary avalanches. In Artificial Life II (ed. Langton, C. G., Taylor, C., Fanner, J. D. and Rasmussen, S.), pp. 325–370. Addison-Wesley, Redwood City, California.Google Scholar
Kirkpatrick, M. (1982). Quantum evolution and punctuated equilibria in continuous genetic characters. American Naturalist 119, 833–848.CrossRefGoogle Scholar
Kirkpatrick, S., Gelatt, CD. & Vecchi, M. P. (1983). Optimization by simulated annealing. Science IVS, 671–680.CrossRefGoogle ScholarPubMed
Lande, R. (1976). Natural selection and random genetic drift in phenotypic evolution. Evolution 30, 314–334.CrossRefGoogle ScholarPubMed
Lande, R. (1979). Effective deme size during long term evolution estimated from rates of chromosomal rearrangement. Evolution 33, 234–251.CrossRefGoogle Scholar
Lande, R. (1985). The fixation of chromosomal rearrangements in a subdivided population with local extinction and colonization. Heredity 54, 323–332.CrossRefGoogle Scholar
Lofsvold, D. (1988). Quantitative genetics of morphological differentiation in Peromyscus. II. Analysis of selection and drift. Evolution 42, 54–67.Google ScholarPubMed
Mayr, E. (1963). Animal Species and Evolution. Harvard University Press, Cambridge, Mass.CrossRefGoogle Scholar
Poston, T. & Stewart, I. (1978). Catastrophe Theory and Applications. Pitman, London.Google Scholar
Provine, W. (1986). Sewall Wright and Evolutionary Biology. Univ. of Chicago Press, Chicago, 111.Google Scholar
Rand, D. M. & Harrison, R. G. (1989). Ecological genetics of a mosaic hybrid zone: mitochondrial, nuclear, and reproductive differentiation of crickets by soil type. Evolution 43, 432–449.CrossRefGoogle ScholarPubMed
Rouhani, S. & Barton, N. H. (1987). Speciation and the ‘shifting balance’ in a continuous population. Theoretical Population Biology 31, 465–492.CrossRefGoogle Scholar
Slatkin, M. (1980). The distribution of mutant alleles in a subdivided population. Genetics 95, 503–524.CrossRefGoogle Scholar
Slatkin, M. (1980). Gene flow and the geographic structure of natural populations. Science 236, 787–792.CrossRefGoogle Scholar
Wright, S. (1931). Evolution in Mendelian populations. Genetics 16, 97–159.CrossRefGoogle ScholarPubMed
Wright, S. (1932). The role of mutation, inbreeding crossbreeding and selection in evolution. Proceedings of the 6th. International Congress of Genetics, 356–366.Google Scholar
Wright, S. (1937). The distribution of gene frequencies in populations. Science 85, 504.CrossRefGoogle ScholarPubMed
Wright, S. (1988). Surfaces of selective value revisited. American Naturalist 131, 115–123.CrossRefGoogle Scholar