Fig. 1.

Survival fitness landscape for San Salvador Cyprinodon Pupfish. C. variegatus (red), C. desquamator (blue), and C. brontotheroides (green) from each lake population were intercrossed in every direction to produce F₂ hybrids that were left for 3 months in an enclosure on San Salvador. Survival probability is plotted against the two axes of the discriminant morphospace, indicating a wide range of jaw phenotypes in the F₂ hybrids (modified from Martin and Wainwright 2013a). Heat colors correspond to survival probability (with blue being low and red being high). µ CT scans of the cranial skeleton of each species modified from Hernandez et al. (in revision).