Genetic variation in natural populations of Araucaria angustifolia (Bert.) O. Kuntze in Brazil

The natural distribution of "pinheiro do Parana" (Araucaria angustifolia) is restricted to the southern hemisphere, occurring mainly in Brazil, small areas in Argentina as well as Paraguay. The continuous distribution in Brazil is situated almost exclusively in the three southernmost Brazilian states: Parana (PR), Santa Catarina (SC) and Rio Grande do Sul (RS). There are small populations in the northernmost part of the range where the forests can be found between 1200 and 1800 m above sea level. It is a species of economic importance for the southern region of Brazil, and for many years it has played an important role in generating export revenues. Due to exploitation, the primary forests were drastically reduced to less than 0.66% of the original area. If the present rate of exploitation is maintained, the last remnants of the valuable primary forests containing A. angustifolia will soon disappear. Therefore, studies are necessary to elucidate the genetic basis of the remaining populations aiming at their genetic conservation. Seed from 130 trees from populations representing 3 geographic locations (Campos do Jordao - SP, Irati - PR and Cacador - SC) were analyzed using 8 enzyme gene loci (GOT-A, GOT-B, GOT-C, PGM-A, SKDH-A, SKDH-B, MDH-B and 6-PGDH-B) to determine patterns of genetic structure and variation. Populations were polymorphic at 49% of the loci. They had an average of 1.58 alleles per locus and 2.10 alleles per polymorphic locus. Mean expected heterozygosity (H-e) was 0.142, and mean observed heterozygosity (H-a) was 0.141. The northern population was much more variable than the southern populations as measured by several parameters. The northern population was also strongly differentiated from the southern populations, which differed little from each other. A provisional evaluation of part of the data revealed a relationship between geographic distance among populations and their genetic distance.