Two-trait Selection and the Genetic Correlation I. Prediction of Responses in Single-trait and in Two-trait Selection

Abstract

Selection using independent culling levels (20% overall selection intensity) was done for the four combinations of high or low third coxal bristle number with high or low sternopleural bristle number in Drosophila melanogaster. Single-trait lines from the base population were selected at 20 % selection intensity for 10 generations for high or low bristle number. Realized heritabilities and genetic correlations were estimated after 10 and 22 generations of selection in the two-trait lines, and also from the single-trait lines. There was considerable variation among replicate lines within treatments in selection responses, and in realized heritabilities and genetic correlations. Although average estimates of the realized parameters were all less than those made from a diallel analysis of the base population, the average base population genetic correlation and the average realized genetic corre-lations from single-trait and two-trait selection lines were reasonably similar. Predicted selection responses in both single-trait and two-trait lines using genetic parameters derived from a diallel analysis of the base population were greater than average realized responses. However, predicted selection responses in the two-trait lines using realized genetic parameters from the single-trait lines were in reasonable agreement with average realized responses.