Genetic diversity among natural populations of <i>Agathis borneensis</i> (Araucariaceae), a tropical rain forest conifer from Brunei Darussalam, Borneo, Southeast Asia

Abstract

Agathis is a genus of tropical conifers that occurs mainly in Southeast Asia. Because of its production of good softwood, many stands of Agathis have been harvested. We provide an estimate of genetic variation within and among populations of Agathis borneensis in Brunei Darussalam, Southeast Asia. Five populations were investigated using isozyme electrophoresis. We investigated a total of 17 putative loci, five of which were polymorphic. Estimated total heterozygosity was 0.122. Heterozygosity within populations was 0.106. The population structure did not deviate significantly from Hardy–Weinberg expectations. Nei's coefficient of gene differentiation indicated that the among-population component of genetic diversity represents 14% of the total population component. The low level of genetic diversity and the large diversity among populations were the opposite of that for conifers in the temperate zone, because of the small size of each population. The large diversity among populations indicated the restricted gene flow resulting from the asynchronous flowering of this species. The genetic distance indicated that A. borneensis in Brunei could be classified in two groups, with one isolated population considerably different from the others both genetically and ecologically. The conservation strategy is discussed from the viewpoint of genetic resources. Key words: Agathis borneensis, Araucariaceae, Brunei Darussalam, genetic diversity, isozyme, tropical rain forest.