Your fun fact de jour courtesy of Gpa Bert :)

Nectarine (P. persica var. nucipersica) & Peach (P. persica) - Nectarines and Peaches are the same species, P. persica; the Nectarine is a variety of the Peach tree. They differ only by a single gene - Peaches have the gene and are fuzzy-skinned; Nectarines lack the gene and have smooth skin. Nectarines occur naturally on Peach trees and once in a while, a Nectarine tree will produce "mutant" peaches. The Nectarine tree is the same as the Peach tree, though the fruits are not.

Check It out at Botany.com