Table 1 Sources of the groups (genetic lines and crosses) used in the analyses

Lines

 P₁

31

Fourth generation of the ‘fast’ line

 P₂

35

Fourth generation of the ‘slow’ line

Crosses

Offspring from

 F₁

44

P₁ females × P₂ males

 F₁m

22

males from P₁ females × P₂ males

 F₁f

15

females from P₁ females × P₂ males

 F₁R

12

P₂ females × P₁ males

 F₁Rm

4

males from P₂ females × P₁ males

 F₁Rf

4

females from P₂ females × P₁ males

 F₁

56

combined F₁ and F₁R

 B₁

0

P₁ females × F₁ males

 B₁R

6

F₁ females × P₁ males

 B₂

7

P₂ females × F₁ males

 B₂R

17

F₁ females × P₂ males