Random amplified polymorphic DNA diversity of marginal and central populations in Pinus contorta subsp latifolia

Fifteen populations of lodgepole pine (Pinus contorta subsp. latifolia) wer e surveyed for diversity across 52 random amplified polymorphic DNAs (RAPDs ). The objective was to compare single-locus and multilocus structures in f our marginal, three intermediate, and eight central populations. Single-loc us estimates indicated average observed and expected heterozygosity to be 0 .19 and 0.17, respectively. When these estimates were split into population categories, a clear trend of increasing diversity was detected in the dire ction of marginal to central populations. F-statistics indicated an excess of heterozygotes, with F-IS ranging from -0.08 for marginal populations to -0.15 for central populations and averaging -0.12 over 15 populations. The estimates of F-ST decreased towards the margins of the species range, indic ating increased population differentiation. Forty-nine of 52 RAPDs tested n eutral in the Ewens-Watterson analysis. Multilocus analysis showed signific ant two-locus and high-order gametic disequilibria in all 15 populations. T he most prominent components of the two-locus analysis were the variance of disequilibrium (VD, 46.2%) and the multilocus Wahlund effect (31.9%). This high value for VD indicated that founder effects could explain much of the observed multilocus associations. When analyzed by population categories, the VD showed a decreasing trend indicating that variation due to founder e ffects was more prominent in marginal populations. The two-locus Wahlund ef fect (WC) that is characteristic of strong population subdivision was highe st in the central populations. This indicated significant levels of gene fl ow between populations with different allelic combinations.