Genetic diversity in Nothofagus alessandrii (Fagaceae), an endangered endemic tree species of the coastal maulino forest of Central Chile.

BACKGROUND AND AIMS The endemic tree Nothofagus alessandrii (Fagaceae) has been historically restricted to the coastal range of Region VII of central Chile, and its forests have been increasingly destroyed and fragmented since the end of the 19th century. In this study, the patterns of within- and among-population genetic diversity in seven fragments of this endangered narrowly endemic tree were examined. METHODS Allozyme electrophoresis of seven loci of N. alessandrii was used to estimate genetic diversity, genetic structure and gene flow. KEY RESULTS High levels of genetic diversity were found as shown by mean expected heterozygosity (H(e) = 0.182 +/- 0.034), percentage of polymorphic loci (P(p) = 61.2 %), mean number of alleles per locus (A = 1.8) and mean number of alleles per polymorphic locus (A(p) = 2.3). Genetic differentiation was also high (G(ST) = 0.257 and Nm = 0.7). These values are high compared with more widespread congeneric species. CONCLUSIONS Despite its endemic status and restricted geographical range N. alessandrii showed high levels of genetic diversity. The observed patterns of diversity are explained in part by historical processes and more recent human fragmentation.