Fig. 4. The response of male sterility and fertility to gradual experimental warming in five species of Drosophila.

Mean male sterility ± SEM (proportion of fertile males, solid black dash) and fertility (number of offspring, coloured boxplots denoting the median (solid horizontal lines), upper and lower quartiles (boxes), 1.5× interquartile range (vertical lines) and outliers (circles)) across four replicate control (aqua) and four replicate selected lines (purple) of a widespread D. buzzatii after 1.2, 2.2, 3.4 and 4.2 °C of warming; b widespread D. melanogaster after 1.2 and 2.2 °C of warming; c widespread D. hydei after 1.2 °C of warming; d tropical D. pseudoananassae after 1.2 °C of warming; and e tropical D. bipectinata after 1.2 °C of warming. Fertility/sterility was estimated by reciprocally transplanting eggs from control and selected lines to developmental temperatures reflecting both the control thermal regime (26 ± 3 °C, open boxes) and the warming thermal regime (solid boxes) at the generation of testing (e.g., 27.2 ± 3 °C after 1.2 °C of warming) and estimating male fertility/sterility at those developmental temperatures. Significant differences (two-sided Tukey post hoc test) between selection lines/developmental temperature within a generation of warming are shown by lines with corresponding P values or differing letters (a versus b: P < 0.01, a versus d: P < 0.001). n = total number of individuals per temperature/treatment. Source data are provided as a Source Data file.