摘要：USING PHENETIC CLASSIFICATION, WE ANALYZE THE SIMILARITY OF THE GENERIC FLORA OF MEXICAN PINYON PINE FORESTS. METHODS INCLUDED RECORDS OF 438 GENERA OF VASCULAR PLANTS FROM 32 COMMUNITIES OF PINYON PINES SUCH AS PINUS CEMBROIDES, P. JOHANNIS, P. MAXIMARTINEZII, P. MONOPHYLLA, P. QUADRIFOLIA, P. NELSONII, P. CULMINICOLA, AND P. LAGUNAE. A MATRIX OF PRESENCE/ABSENCE OF GENERA IN 32 COMMUNITIES WAS PERFORMED, AND 2 INDICES OF SIMILARITY BETWEEN COMMUNITIES WERE ESTIMATED; WE THEN APPLIED UPGMA TO CLASSIFY THE COMMUNITIES IN GROUPS, AND FINALLY THESE GROUPS WERE REPRESENTED BY A DENDROGRAM. IN GENERAL, THE COMMUNITIES WERE GROUPED BY GEOGRAPHIC AREA AND BY PINYON PINE SPECIES, AS WELL AS LOCATION IN THE SAME PHYSIOGRAPHIC PROVINCE. IT WAS OBSERVED THAT PINYON PINE COMMUNITIES OF BAJA CALIFORNIA WITH P. QUADRIFOLIA FORMED A CLOSE GROUP, AS WELL AS THE P. CEMBROIDES COMMUNITIES OF CHIHUAHUA AND P. MAXIMARTINEZII OF ZACATECAS. ONE GROUP OF SAN LUIS POTOSÍ INCLUDED P. CEMBROIDES AND P. JOHANNIS. PINUS NELSONII COMMUNITIES DID NOT FORM A COHERENT GROUP. THOSE OF SOUTHWESTERN COAHUILA WERE COSELY RELATED, BUT THEY WERE DIFFERENT FROM THE PINYON PINES IN THE NORTH OF THIS STATE. PINUS CULMINICOLA COMMUNITIES OF NUEVO LEÓN WERE THE MOST DIFFERENT WITH RESPECT TO OTHERS.
