Genetic Diversity and Differentiation within and among Chilean Populations of Araucaria araucana (Araucariaceae) Based on Allozyme Variability

Genetic diversity within and among Chilean Araucaria araucana populations was estimated using allozyme variability. A total of 537 individuals were sampled from nine populations. Twelve loci were scored in all populations and used for analyses. In general, the genetic variability of A. araucana were high as shown by mean expected heterozygosity ($H_{{\rm E}}$ = 0.151), percentage of polymorphic loci (P = 91.7%), mean number of alleles per locus (A = 1.73) and mean number of alleles per polymorphic locus ($A_{{\rm P}}$ = 2.4). Although the most of this genetic variation was within populations ($H_{{\rm S}}$ = 0.151), an important proportion of the total genetic diversity ($H_{{\rm T}}$ = 0.212) was among population ($G_{{\rm ST}}$ = 0.287). To analyze the relationships between populations we constructed a tree based on Nei's genetic distances using UPGMA methods, and calculated $F_{{\rm ST}}$ between population pairs. Our results showed complex patterns of genetic relationships among Chilean Araucaria araucana populations. Tree topology suggested the existence of three distinct groups of populations: The first group included populations from low-elevation central Andean range and Coastal range populations. The second group, included northern Andean populations. The third group of populations was composed of central high-elevation Andean populations. These patterns of population clustering are congruent with multiple glacial refugia hypothesis. In order to understand the present patterns of distribution of the genetic diversity and post-glacial colonization routes of Araucaria araucana, paleogeographical, paleoclimatic and biogeographical evidence is discussed.