ALLOZYME VARIATION AND POPULATION SIZE OF HAYA MEXICANA (Fagus grandifolia subsp. mexicana) IN THE SIERRA MADRE ORIENTAL

Abstract

Fagus grandifolia Ehrh. subsp. mexicana (Martínez) E. Murray grows in isolated populations at Sierra Madre Oriental in México. Seven populations of this species were sampled to determine alloenzymatic variation in vegetative buds. A total of ten loci were analyzed on eight enzymatic systems, and 26 alleles were observed. The percentage of polymorphic loci was 62.9 % in average among populations, and the number of alleles per locus was 1.9. Expected and observed heterozygosity were 0.202 and 0.253, respectively. Wright´s F_ST (0.057) showed moderate genetic differentiation. The gene flow rate (Nem) was 5.26 individuals for generation. Nei’s genetic distances ranged from 0.001 to 0.027 (average 0.012). Population density ranged from 251 to 416 trees ha^-1 in Agua Fría and in the summit of Acatlán Volcano, respectively. A total number of 45 533 adult trees were estimated in the seven populations of F. gradifolia subsp. mexicana. The largest number of trees (14 903) was found at La Mojonera while the shortest one (250) was found at the summit of the Acatlán Volcano. No correlation was found between parameters of genetic diversity and the size and density of populations. Allozyme variation found in the populations of F. grandifolia subsp. mexicana was moderate.