Genetic complexity of host-selection behavior in Drosophila.

Genetic variation for settling responses to different types of food and for oviposition behavior exists within natural populations of Drosophila tripunctata. After flies from two isofemale strains and F(2) derived from crosses between them were released in the wild and recaptured at either mushroom or tomato baits, the oviposition preferences of females for these foods were determined in the laboratory. Whereas settling behavior and oviposition-site preference were negatively correlated in the parental strains, there was no association of these behaviors in the F(2) generation. Furthermore, lines produced by crossing these two strains followed by inbreeding did not manifest such a negative correlation. Together, these results indicate that two important aspects of host selection are under independent genetic control. These findings caution against using a single component of the process of host selection as indicative of the probability that a particular resource will be utilized in the field, and they bear on the question of how speciation based on genetic variation for host selection may be accomplished.