Abstract

Red pine ( Pinus resinosa Ait.) is an ecologically and economically important forest tree species of northeastern North America and is considered as one of the most genetically depauperate conifer species in the region. Traditional genetic markers have failed to identify significant genetic polymorphism in this species. In order to set conservation priorities and gain insight into the post-glacial dispersal history of red pine, highly sensitive markers such as nuclear microsatellites are valuable. I have isolated and characterized thirteen nuclear microsatellite loci by screening a partial genomic library with di-, tri-, and tetra-nucleotide repeat oligonucleotide probes. Analysis of 518 individuals representing 17 red pine populations from Manitoba through Newfoundland identified five polymorphic microsatellite loci with an average of 9 alleles per locus. The mean expected and observed heterozygosity values were 0.508 and 0.185 respectively. Private alleles were detected in six of the populations examined, and F coefficients showed significant departure from Hardy-Weinberg equilibrium with an excess of homozygosity indicating high levels of inbreeding in all populations studied. Populations were highly differentiated with approximately 31.5% of genetic variation among populations, and results assuming IAM and SMM were similar. Weak but significant isolation by distance was detected, and genetic distances revealed regional genetic breaks and distinct populations of red pine. These findings suggest a complex and highly differentiated population genetic structure for red pine uncharacteristic of most conifers. The genetic patterns identified support a multiple refugia hypothesis for red pine, which should be taken into consideration when setting conservation plans for this species.