Autosomal and maternal effects on pupation behavior inDrosophila melanogaster

This study demonstrates the importance of using a complete set of 16 reciprocal crosses (F₁, backcrosses, and F₂) to thoroughly investigate both genetic and nongenetic influences on patterns of inheritance of larval pupation behavior inDrosophila melanogaster. Larvae derived from natural populations show significant variation in pupal height, defined as the distance a larva pupates above the feeding substrate. Differences in the distance a larva pupates from fruit in nature is known to affect the fitness ofDrosophila populations. In this study the heredity of pupal height is analyzed by performing crosses between high- and low-pupating strains. We found that the inheritance of pupal height fit a classical additive polygenic model of inheritance, with intermediate F₁ pupal heights and greater variances in the F₂ generation. In addition, a significant maternal effect was also found by analyzing the reciprocal backcrosses. Progeny with low-pupating mothers had lower pupation heights than those with low-pupating fathers. Similarly, progeny with high-pupating mothers tended to have higher pupal heights than those with high-pupating fathers. This maternal effect was not attributable to strain differences in permanent cytoplasmic factors, sex chromosomes, or developmental time. Finally, we speculate upon the environmental conditions under which a transient maternal effect on pupation behavior would be expected to evolve in natural populations.This work was supported by a University Research Fellowship and Operating Grant from the Natural Sciences and Engineering Research Council to M. B. Sokolowski. S. J. Bauer was the recipient of an Ontario Graduate Scholarship.