Allozyme variability in natural populations of green alder (Alnus crispa) in Quebec

Abstract

Vegetative and sexual tissues from 22 populations of Alnus crispa (Ait.) Pursh (green alder, Betulaceae) in Quebec were analyzed for electrophoretically demonstrable diversity of 11 enzymes encoded by 16 structural loci in sexually mature populations. Of these 16 loci, 9 were found polymorphic. A total of 28 different alleles were detected with no more than three alleles per locus. No two-locus linkage disequilibrium was observed between eight polymorphic loci analyzed. Assuming a diploid model, average level of expected heterozygosity was 0.14 in the mature generation, with nearly all populations in Hardy–Weinberg equilibrium for the set of polymorphic loci investigated. Mean outcrossing rate was 0.95. Fixation indices revealed low inbreeding with no specific subpopulation structure. Hence, an important level of gene flow would exist within the populations. Without any strong evidence for polyploidy, and in the light of results obtained, the species could be classified equally well as a diploid or a diploidized allotetraploid. Key words: actinorhizal plant, alder, allozymes, Alnus, fixation indices, heterozygosity, outcrossing rate, polyploidy.