In the Northern Iberian System, Quercus petraea has been found in 18 localities (Soria: 7, La Rioja: 5, Burgos: 5, Zaragoza: 1), and hybrids of Q. petraea with 4 other oak species have been indentified in 14 localities. Q. subpyrenaica has been recorded in 6 localities (La Rioja: 5. Soria: 1) and Q. pubescens in 4 (La Rioja: 3, Burgos: 1). Moreover, Q. faginea has been encountered next to The Ebro Rive
