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APPENDIX A: GENETIC FLEXIBILITY OF A POPULATION 



Genetic flexibility is estimated as o\ (additive genetic variance) 

 or as a ratio of total phenotypic variance (heritability, h^ ): 



, ^A 



Estimates of h^ or o\ are obtained from (1) offspring— 

 midparent regression and from covariances (2) between half-sibs and 

 (3) between full-sibs: 



{l)boP =h2 

 (2)COVHS = 0.25a^ 



(3) COVps ^ 0.5aj^ + nonadditive genetic and environmental 



components common to broods 



COVp^g and COVpg are obtained from analysis of variance of 

 half-sib and full-sib families: 



The symbols a^ , oj, and o^ are components of variance within 

 broods, between female parents, and between male parents, respec- 

 tively, and m, f, and w are the number of male parents, the number 

 of females bred to each male, and the number of offspring per brood, 

 respectively. Clearly, the design will not always be perfectly 

 balanced. The appropriate coefficients must then be estimated 

 (Falconer, 1960; 1963; Roberts, 1967). aj^ is an estimate of 

 COVj^g, and a^ + oj is an estimate of COVpg. 



