Spatial genetic structure of allozyme polymorphisms within populations of Pinus strobus (Pinaceae)

The population structure of genetic variation for four allozyme loci was in vestigated for two populations (one old growth, OG, and the other logged, S S) of eastern white pine (Pinus strobus). Both seedlings and reproductive a dults were studied for both study populations. Spatial autocorrelation stat istics were used to examine the distribution of allozyme polymorphisms. The spatial genetic structure in adults of population OG indicated that indivi dual genotypes were distributed in a structured, isolation-by-distance mann er. consistent with observed levels of pollen and seed dispersal. In contra st, adult genotypes in population SS were nearly randomly distributed, prob ably as a result of logging. Nonetheless, spatial structuring of genotypes of seedlings occurred at both sites, indicating the power of limited seed f low. as well as temporal Wahlund effects. to create structure. None of li,u r loci in both seedling populations showed a significant departure from Har dy-Weinberg proportions, whereas one and two significant deviations were fo und for loci in the two respective adult populations. These departures may be attributed to episodic reproductive events.