Fig. 3.
Reproductive fitness assays at generation 25. We selected 8 of the 10 significant populations for the evolution experiment. (A) Relative reproductive fitness for wt (black circle), novel X (triangle), and novel Y (diamonds) males. Novel treatment males no longer had a higher fitness relative to wt males after 25 generations of experimental evolution. Mean (±SE) of fitted values from the linear model. The raw data are plotted as gray points. (B) Change in relative fitness between wt and novel X (triangles) and novel Y (diamonds) populations (∆Fitness = ωnovel population − ωwild type), with bootstrap 95% confidence intervals (Materials and Methods). The asterisk indicates whether ∆Fitness was significantly greater than zero (Tukey HSD; P < 0.05). Each of the wt populations is indicated underneath its four novel populations. Uppercase letters indicate which population the novel sex chromosome originates from (D, Dahomey; I, Innisfail; L, LHM; O, Odder) and the novel sex chromosome is denoted by X or Y subscripts.