REPRODUCTIVE CHARACTERISTICS OF THE FLOWER BREEDING DROSOPHILA-HIBISCI BOCK (DROSOPHILIDAE) IN EASTERN AUSTRALIA - GENETIC AND ENVIRONMENTAL DETERMINANTS OF OVARIOLE NUMBER

Quantitative genetic analysis of the ovariole number of the Australian Hibiscus flower-breeding Drosophila hibisci Bock was conducted on pop ulations from two localities along a latitudinal cline in ovariole num ber previously observed in the species (Starmer et al., in press). Par ental strains, F-1, F-1r (reciprocal), F-2, backcross, and backcross r eciprocal generations were used in a line-cross (generation means) ana lysis. This analysis revealed both additive and epistatic effects as i mportant determinants of variation in ovariole number when larvae were reared at 25 degrees C. Maternal effects and maternal-by-progeny gene tic interactions were not significant. These results are comparable to previous studies that document epistatic components as genetic determ inants of ovariole number in D. melanogaster. Parallel studies on ovar iole number in D. hibisci parental and hybrid generations (F-1 and F-1 r,) reared as larvae at three temperatures (18 degrees, 21.5 degrees, and 25 degrees C) showed environmental effects and genotype-by-environ ment interactions as significant influences on the phenotype. Maternal effects were present when temperature of larval development was consi dered and significant, nonlinear environmental effects were detected. Field collections of D, hibisci females showed that held conditions re sult in significant departure of ovariole number from comparable labor atory reared females. The significant epistatic genetic effects, genot ype-by-environment interactions, and maternal effects indicate that th e genetic architecture of traits, such as ovariole number, may be more complex than often acknowledged and thus may be compatible with Wrigh t's view of a netlike relationship between the genome and complex char acters (Wright 1968).