FISHER'S GEOMETRICAL MODEL OF FITNESS LANDSCAPE AND VARIANCE IN FITNESS WITHIN A CHANGING ENVIRONMENT
Article first published online: 13 APR 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 66, Issue 8, pages 2350–2368, August 2012
How to Cite
Zhang, X.-S. (2012), FISHER'S GEOMETRICAL MODEL OF FITNESS LANDSCAPE AND VARIANCE IN FITNESS WITHIN A CHANGING ENVIRONMENT. Evolution, 66: 2350–2368. doi: 10.1111/j.1558-5646.2012.01610.x
- Issue published online: 26 JUL 2012
- Article first published online: 13 APR 2012
- Accepted manuscript online: 21 FEB 2012 02:56PM EST
- Received April 6, 2011 , Accepted February 6, 2012 , Data Archived: Dryad: doi:10.5061/dryad.6r138b0h
- changing environment;
- Fisher's geometrical model;
- genetic variance in fitness;
- mutation-selection balance;
- multivariate stabilizing selection
The fitness of an individual can be simply defined as the number of its offspring in the next generation. However, it is not well understood how selection on the phenotype determines fitness. In accordance with Fisher's fundamental theorem, fitness should have no or very little genetic variance, whereas empirical data suggest that is not the case. To bridge these knowledge gaps, we follow Fisher's geometrical model and assume that fitness is determined by multivariate stabilizing selection toward an optimum that may vary among generations. We assume random mating, free recombination, additive genes, and uncorrelated stabilizing selection and mutational effects on traits. In a constant environment, we find that genetic variance in fitness under mutation-selection balance is a U-shaped function of the number of traits (i.e., of the so-called “organismal complexity”). Because the variance can be high if the organism is of either low or high complexity, this suggests that complexity has little direct costs. Under a temporally varying optimum, genetic variance increases relative to a constant optimum and increasingly so when the mutation rate is small. Therefore, mutation and changing environment together can maintain high genetic variance. These results therefore lend support to Fisher's geometric model of a fitness landscape.