Phenetic analysis of the Mexican midland pinyon pines, Pinus cembroides and Pinus johannis

This account presents an analysis of allopatric, sympatric and juxtaposed populations of the pinyon pines, Pinus cembroides Zucc. and P. johannis M.-F. Robert, based on phenetic analysis of morphological data, and draws on a comparison and differentiation of P. culminicola Andresen & Beaman. A qualitative and quantitative database for populations has been assembled and used for a cluster and ordination analysis using NTSYS. It was found that individual populations of the taxa were distinguishable. The emergence of morphological intermediate populations between P. cembroides and P. johannis was confirmed. The pattern of variation in P. johannis was found to be discrete, showing three geographical groups. The phenetic similarity between P. johannis from Zacatecas and P. johannis from San Luis Potosi and Queretaro was lower than that of P. johannis from Zacatecas and P. culminicola from Nuevo Leon. The following traits distinguish P. cembroides and the other two species: colour and fertility of seeds; cone shape; colour and width of needles; physiognomy; seed dimensions. This last trait can be used to distinguish three subgroups of pines with white endosperm in the northern, central and southern regions of the Mexican highlands.