Genetic variation, population structure, and mating system in bigleaf maple (Acer macrophyllum Pursh)

Genetic diversity, population genetic structure, and mating system of bigleaf maple (Acer macrophyllum Pursh) was estimated with isozymes and compared with other North American angiosperms. On average, populations were polymorphic at 61% of the loci, with 1.71 alleles per locus. The mean expected heterozygosity (H-E = 0.152) was similar to other North American angiosperms. The level of population differentiation was moderately low (F-ST = 0.054), indicating extensive gene flow among populations (N-m = 4.39), and there was no isolation by distance. Genetic distances averaged 0.011 and ranged from 0.001 to 0.042, but no relationship between geographic distances was apparent. Outcrossing rates in two populations were high (95%) but significantly less than one, with no biparental inbreeding evident. A relatively high level of correlated matings, consistent with two to five effective pollen donors per tree, was found, indicating that low density and limited pollinator dispersal are prevalent.