For life-span experiments, larvae were reared at standard density in 200-mL glass bottles containing 70 mL of 1.0 SY food (36 ). Flies emerged over 24 hours, were tipped into fresh bottles, and were allowed 48 hours to mate. Females were then separated from males under light CO2 anesthesia and randomly allocated to different food treatments at a density of 10 females per vial. Flies were transferred to fresh vials, and deaths were scored at least every 2 days. The yeast comparison experiment was performed in two batches, the first containing SYBaker’s, SYBrewer’s, and SYTorula, and the second containing SYBaker’s, SYBrewer’s, SYExtract, and CSYExtract. Due to the similarity between the two trials of SYBaker’s and SYBrewer’s (Supplementary Figure 1 and Supplementary Table 1 ), the data were combined. For each condition in each experiment, 100 flies were used.
For fecundity measurements, the same experimental flies as those used for life spans were kept in the same glass vials for between 18 and 24 hours; they were then transferred to fresh food. The eggs in the vacated vials were counted manually under a microscope. For the sugar concentration experiment, egg counts were performed on days 3, 7, 10, 14, and 21 of treatment. For the first yeast comparison experiment (SYBaker’s, SYBrewer’s, and SYTorula), eggs were counted on days 5, 9, 12, 16, 19, 23, 26, 30; for the second experiment (SYBaker’s, SYBrewer’s, SYExtract and CSYExtract), eggs were counted on days 4, 8, 11, 15, 18, 22, 25, and 29. Eggs were counted on days 3, 6, 10, 13, 17, 26, 31, and 38 for the water add-back experiment and on days 4, 11, 18, 25, 32, 46, and 60 for the agar concentration range experiment. As an index of lifetime fecundity, the sum of eggs laid during 24 hours on the days of counting by an average female was calculated. These sampling points cover the period of heaviest laying, and are therefore indicative of relative lifetime fecundity (6 ).
For fecundity measurements, the same experimental flies as those used for life spans were kept in the same glass vials for between 18 and 24 hours; they were then transferred to fresh food. The eggs in the vacated vials were counted manually under a microscope. For the sugar concentration experiment, egg counts were performed on days 3, 7, 10, 14, and 21 of treatment. For the first yeast comparison experiment (SYBaker’s, SYBrewer’s, and SYTorula), eggs were counted on days 5, 9, 12, 16, 19, 23, 26, 30; for the second experiment (SYBaker’s, SYBrewer’s, SYExtract and CSYExtract), eggs were counted on days 4, 8, 11, 15, 18, 22, 25, and 29. Eggs were counted on days 3, 6, 10, 13, 17, 26, 31, and 38 for the water add-back experiment and on days 4, 11, 18, 25, 32, 46, and 60 for the agar concentration range experiment. As an index of lifetime fecundity, the sum of eggs laid during 24 hours on the days of counting by an average female was calculated. These sampling points cover the period of heaviest laying, and are therefore indicative of relative lifetime fecundity (6 ).
