okcidar keel. Nature 117:624 626. 4. Ewens 19 (1967) lbr probability al sonied of a new mutant in a twthating nutriment. Heredity 21: 438 443. .5. Barton NH (1993) linkage and the limits to natural selection. Genetics 140: R21 41. 6. Campos PR ((2004) Fixation of beneficial mutations in the presence of

422: 307-312. 18. Willensdorfer M, R Burger (2003). The two-locus model of Gaussian stabilizing selection. Theor Popul Biol 64: 101-117. 2004 19. Barton NH, M Turelli (2004). Effects of genetic drift on variance components under a general model of epistasis. Evolution 58: 2111-2132. 20. Boots M, PJ Hud