Fig. 1

Morphology and sampling locations of San Salvador Island pupfishes. a Map of San Salvador Island indicating sites where wild parental fish used in the experiment were sourced. Wild fish of two endemic species, C. brontotheroides and C. desquamator, were collected from Crescent Pond at the north end of the island (inset). Two distinct populations of a third species, C. variegatus, were sourced from both Crescent Pond and a marine lagoon at the south end of the island. b Representative images illustrate the phenotypes of these 3 wild caught species. Shown are adult male fish in lateral view and the accompanying images of the skulls of these same fish stained with alizarin to visualize bone (red). Camera lucida drawings of cleared and stained fish highlight species differences in jaw morphology. Note the elongation of the jaws in the scale-biter, C. desquamator, the robust short jaws of the durophage, C. brontotheroides, and the similar jaw morphology of the inland and marine forms of the omnivore, C. variegatus. Scale bars = 1 mm unless noted. Map of San Salvador is based on [96]