Genetic differentiation among 22 mature populations of green alder (Alnuscrispa) in central Quebec

Abstract

Electrophoretically demonstrable diversity of 11 enzymes encoded by a total of 16 structural loci was analyzed in 22 sexually mature populations of Alnuscrispa (Ait.) Pursh (green alder, Betulaceae) in central Quebec. On average, 45% of the loci per population were polymorphic, with a mean of 2.39 alleles per polymorphic locus. Approximately 5% of the total genetic diversity resided among populations, with a mean genetic distance between populations of 0.01. Most populations thus appeared homogeneous, likely linked by high gene flow, as demonstrated by analysis of conditional average frequencies of alleles. Geoclimatic similarity among sites was also considered as a possible contributing factor to this apparent homogeneity. Heterogeneity of allele frequencies among populations was noted at seven loci. However, the presence of four populations that appeared to be more differentiated accounted for much of the observed heterogeneity. The early successional nature of this species and the partial isolation of these four populations seemed the most likely factors causing the observed differentiation.