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

This account presents an analysis of allopatric, sympatric and juxtaposed p opulations 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 quali tative and quantitative database for populations has been assembled and use d for a cluster and ordination analysis using NTSYS. It was found that indi vidual populations of the taxa were distinguishable. The emergence of morph ological intermediate populations between Il cembroides and P. johannis was confirmed. The pattern of variation in P. johannis was found to be discret e, showing three geographical groups. The phenetic similarity between P. jo hannis from Zacatecas and P. johannis from San Luis Potosi and Queretaro wa s lower than that of P. johannis from Zacatecas and P. culminicola from Nue vo Leon. The following traits distinguish Il cembroides and the other two s pecies: colour and fertility of seeds; cone shape; colour and width of need les; physiognomy; seed dimensions. This last trait can be used to distingui sh three subgroups of pines with white endosperm in the northern, central a nd southern regions of the Mexican highlands. (C) 2000 The Linnean Society of London.