Fig 4. Genetic variation and
correlations. The posterior mode and 95% HPD interval of the genetic
correlation between the log-contrast of Z11-16:OAc on 14:Ald and each of
the other three log-contrasts is shown for the starting generation (S,
in black), the low (blue) and high (red) lines. 111 females were
phenotyped for the starting generation. For the low line, 443, 284, and
330 phenotyped females were in generation blocks 1-3, 4-6, and 7-9,
respectively. For the high line 465, 324, and 344 phenotyped females
were in generation block 1-3, 4-6, and 7-9, respectively. Pedigree data
were obtained for 1,065 mating pairs prior to the first generation of
selection and for an additional 2,250 and 2,236 pairs for the low and
high line, respectively.
Second, the partitioning of genetic variance among gPC1 and gPC2
evolved. The first two genetic principle components changed in magnitude
of their eigenvalue (i.e. the amount of genetic variance they describe)
and in their loadings (i.e. in their correlation with the pheromone
components; Fig 5). More of the total genetic variance across the four
components was in the direction of gPC1 in the high and low lines
(~80%) compared to the starting generation (59.1%).
This means that more of the genetic variance of the sex pheromone was
biased towards a single dimensions in phenotypic space. Moreover,
variation in the component under selection, Z11-16:OAc, was more
strongly associated with gPC2 and less with gPC1 in generations after
compared to before selection, while the other traits showed a trend in
the opposite direction (Fig 5). These changes in the G matrix resulted
in a more modular pheromone blend, because Z11-16:OAc, which was under
selection here, became uncoupled from the components that were not under
selection.