Analyzing correlations of three types in selected lines of Drosophila melanogaster that have evolved stable extreme geotactic performance.

The behavior-genetic analysis of Drosophila melanogaster with geotactic performance as the phenotype is an ideal model system with which to investigate the complex relations between heredity and behavior. As part of a long-term, 38-year study, we report 4 experiments that identify and analyze trait correlations in the selected high- and low-geotaxis lines. We performed F2 correlational analyses and backcrosses to examine 3 types of correlations: (a) genotype-genotype (alcohol dehydrogenase [Adh]-amylase [Amy]), (b) genotype-phenotype (Adh and Amy-geotaxis), and (c) phenotype-phenotype (mate preference-geotaxis). Only the Adh-geotaxis correlation survived meiosis and reappeared in the F2 generation, which indicates a genotype-phenotype correlation, whereas the others did not. The importance of hybrid correlational analysis to the behavior-genetic analysis of a species is discussed.