Figure 3.

Mean CI values and SE of 4 day-old tester male flies of four species (D. melanogaster Canton-S; D. sechellia 228; D. simulans Seychelles; D. mauritiana 163.1) with intact D. melanogaster females of various types. To control for interspecific differences in vigor, the CI for each pair was expressed as a percentage of the mean intraspecific CI for the male, and means and SE were calculated accordingly. Mean intraspecific CIs were as follows: D. melanogaster = 56.1 ± 2.8; D. sechellia = 21.5 ± 4.8; D. simulans = 34.0 ± 2.9; D. mauritiana = 42.8 ± 3.7. hs-tra, heat-shocked tra; non-hs tra, non-heat-shocked tra; hs-tra+mel, heat-shocked tra females that carry hydrocarbons from adult D. melanogaster females; hs-tra+sim, heat-shocked tra females that carry hydrocarbons from adult D. simulans females. Data from control females [D. melanogaster C(1)DX, not shown] were not significantly different from those for non-hs tra. Intact living flies were used in this experiment to allow mating to be observed (Table 1). n ≥ 30 for all crosses except non-hs tra (n = 20). The same series of experiments was carried out with decapitated females. No qualitative differences were found compared with the results presented here, but a lower amplitude was observed for all points, except for D. simulans, which showed similar CIs with intact and decapitated females (data not shown). In D. melanogaster and D. sechellia, the main female cuticular hydrocarbon is 7,11-HD; in D. simulans and D. mauritiana, it is 7-T. GC analysis revealed the following levels of cuticular hydrocarbons: 7,11 HD = 30.6% ± 1.4 for D. melanogaster control and 25.4% ± 0.7 for D. sechellia. 7-T = 61.2% ± 3.1 for D. simulans and 58.3% ± 0.8 for D. mauritiana. These results are close to those previously reported (18).