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Abstract The descriptions of the species of the genus Dioon by taxonomists have shown variations that put in doubt the characterization of different taxa. Hence, we analyzed the populations distributed along the Paci?c slope of Mexico to study the morphological variation of Dioon using a principal components analysis, a multivariate method. We sampled 12 localities, from Sonora to Chiapas states, and compared the species with D. edule and D. spinulosum, three localities from the Gulf of Mexico slope. The results showed ?ve groups. The Paci?c slope groups exhibited a clinal morphological variation pattern north"south, except for the Sonora populations, which showed a multivariate effect similar to that of the Gulf ™s populations. With these results, the identity of D. sonorense was con?rmed to be the northernmost population in Mexico. Principal components analysis supports the results of previous work on the morphological variation clinal of D. edule. In addition, a close relationship exists among populations from the southern and western Paci?c, showing that individuals from the type localities of D. holmgrenii and D. tomasellii shared similar morphological characteristics in such a way that the two taxa established a morphological complex.