Did vicariance mold phenotypes of western North American fishes? Evidence from Gila River cyprinids

Pairwise. two- and three-way Mantel tests were used to evaluate a null hypo thesis of no significant covariation when morphological features of three c yprinid fish taxa of the genus Gila were compared. Tests involved ecologica l conditions and past and present hydrography in the Gila River Basin of we stern North America. A vicariance hypothesis was the only model statistical ly proficient in explaining diversity of fish phenotypes. Of paleohydrograp hic reconstructions compared, those of the mid-Miocene and Pliocene epochs were significantly associated with present-day distributions of phenotypes. Of these, the Pliocene was paramount.