ESTIMATION OF MATING SYSTEM PARAMETERS IN 2 ITALIAN NATURAL-POPULATIONS OF FAGUS-SYLVATICA

Mating system parameters were estimated in two Italian natural populat ions of European beech (Fagus sylvatica L.) using a mixed mating model and considering seven allozyme loci (Idh-A, Lap-A, Mdh-B, Pgd-A, Pgd- B, Pgd-C, Skd-A). High values of multilocus estimates of the outcrossi ng rate were found in both populations, ranging from 94 to 98%. Compar ison of single- and multi-locus estimates of outcrossing rates seems t o indicate the presence of consanguineous matings, probably because th e populations are substructured. This hypothesis seems to be confirmed by the presence of a heterogeneity of the pollen allele frequencies a cross female parent trees and by the significant coefficient of the re gression of pollen allele frequencies on ovule genotype. Variation in the fixation indices in different life-cycle phases was observed, indi cating possible presence of selective processes between seed set and s exual maturity. Possible explanations of these results are presented.