Selection
Since phenotyping consisted of extracting the sex pheromone gland invasively, selection was performed post-mating. Each generation, we continued with those families that had a maternal phenotype satisfying an increasingly stringent threshold. Initially, a so-called “high” and “low” line were started with offspring from females with a relative amount of acetates above 22% or below 16%, respectively. These values were based on the distribution of the relative amounts of acetates in the starting population, representing the 1st and 3rd quantile. These thresholds were kept for the first 3 generations. In subsequent generations, we increased these thresholds to >24% or <14% (generation 4 – 5), and >26% or <12% (generation 6 – 9). The high line consisted of a total of 2,236 breeding females across nine generations, ranging from 189 – 295 matings per generation. After outlier removal, a total of 1,234 high line females were phenotyped, or between 89 and 171 per generation during the selection phase. The low line consisted of 2,250 breeding females (189 – 296 per generation) and, after outlier removal, phenotypes were measured for a total of 1,180 females (57 – 169 per generation). We stopped selecting in generation 10, but continued to phenotype ~25 females per line and per generation until generation 13. Throughout the selection experiment, we also maintained a control line from which we phenotyped between 6 and 111 females (median 20 females) per generation. For detailed sample sizes see Table S1.