GENETIC DIVERSITY AND POPULATION-STRUCTURE OF DISJUNCT NEWFOUNDLAND AND CENTRAL ONTARIO POPULATIONS OF EASTERN WHITE-PINE (PINUS-STROBUS)

The dramatic decline of eastern white pine (Pinus strobus L.) populati ons in Newfoundland over the past 100 years presents an opportunity to determine and monitor population bottleneck effects on genetic divers ity in trees. To provide benchmarks and indicators for monitoring gene tic changes due to recent and future bottleneck events and to assist d evelopment of conservation strategies, we assessed genetic diversity a nd structure of six small, isolated white pine populations from two re gions at the limits of its geographical range in Newfoundland for comp arison with three populations from its central range in Ontario for 20 allozyme loci coding for 12 enzymes. On average, 47.8% of the loci we re polymorphic, the number of alleles per locus was 1.75, and the obse rved and expected heterozygosities were 0.215 and 0.195, respectively. Although most of the alleles were widespread, unique alleles were fou nd in three of the nine populations examined. The Newfoundland populat ions were as genetically variable as those from Ontario. Generally, al l populations exhibited slight excess of heterozygotes at most loci. O nly 6.1% of the detected genetic variation was among populations, and the remainder among individuals within populations. The genetic distan ces among the populations within a province or region were as great as those among populations between the provinces or regions. Canonical d iscriminant functions and cluster analysis from genetic distances sepa rated nine populations into the same four groups. Neither provincial n or regional or geographic gradient-related patterns of population vari ation and differentiation were apparent. It appears that 8000 years of postglacial geographic isolation and recent population decline have h ad little or no detectable effect on genetic diversity or differentiat ion of disjunct Newfoundland white pine populations from their ancestr al mainland populations. Assuming their adaptability, the Ontario seed sources may be acceptable for white pine restoration in Newfoundland.