MAXIMUM VARIANCE LINEAR COMBINATIONS FROM PHENOTYPIC, GENETIC, AND ENVIRONMENTAL COVARIANCE MATRICES.

Vectors of weights derived from principal components analysis of stan- dardized phenotypic, genetic, and environmental covariance matrices were applied to open-field behavioral scores from mice in order to obtain composite scores with maximum phenotypic (Vp), genetic (Va), and environmental (Ve)variance, respectively. Since Va associated with the composite from the genetic covariance matrix is derived as maximum, and since Vp associated with this combination cannot be as large as that associated with the phenotypic com- posite, heritability of the genetic composite must exceed that of the phenotypic composite. In addition, since Ve associated with the environmental composite is maximum and since Vp associated with this score cannot exceed Vp from the phenotypic composite, Va associated with the phenotypic composite should exceed that from the environmental composite. Thus, heritability of the pheno- typic composite scores should exceed that for the environmental composite. The predicted rank order of the heritabilities was observed. Pooled estimates of the heritabilities of the genetic, phenotypic, and environmental components were 0.24, 0.19, and 0.17, respectively.