Population morphological differentiation of Magnolia rzedowskiana (Magnoliaceae): endemic species in danger of extinction of the Sierra Madre Oriental, Mexico

Magnolia rzedowskiana is a newly described species, with few relict populations, of low density and endemic to the cloud forest of the Sierra Madre Oriental, Mexico. In order to determine their morphological variation in their distribution area, 40 individuals from four locations were selected. In each tree, 5 flowers and 10 leaves were collected to analyze 26 morphological characters, through descriptive statistics, cluster analysis (CA), principal components (PCA) and discriminant analysis. In the CA, both of the floral and foliar characteristics, it was possible to define 3 groups that correspond in general to different geographical areas. In the ACP, the first 4 components explained 75% of the floral variation, and the first 2 components, 78% of the foliar variation. The first 2 discriminant functions explained 93.37% and 97.67% of the floral and foliar variation, respectively. The characters with the greatest contribution to population differentiation were: number and length of carpels and stamens, petiole diameter, and maximum width of the lamina. The data on distribution, general characteristics and morphological variation of M. rzedowskiana, are fundamental to define management strategies, and to propose their inclusion in some category of risk in national and international legislation.