Variation and population structure at enzyme gene loci in Araucaria angustifolia (Bert.) O. Ktze

We describe alloenzyme variation in A. angustifolia populations of three separate geographical areas in southern Brazil. The genetic structure of populations was examined in seed-trees, embryos and effective pollen. Seven out of 24 enzyme loci were polymorphic. The average number of alleles per locus (24 loci) was 1.54, with 2.44 alleles per polymorphic locus. Mean expected and observed heterozygosities at the polymorphic loci were H-e = 0.128 and H-o = 0.132 for seed-trees, and H-e = 0.142 and H-o = 0.161 for embryos. All measures of genetic variability were highest in the most northern populations. Differences among localities explained 84.14% and 92.06% of the total genetic diversity in embryos and seed trees, respectively. Sex ratio was 1:1 in almost all populations. Female and male gene pools differed in allele frequencies, most significantly at loci 6-Pgdh-B and Skdh-B. This explains the excess of heterozygotes detected among embryos. No inbreeding or excess of heterozygotes was detected among adult seed trees. Genetic variation in A. angustifolia revealed a latitudinal gradient.