A COMPARISON OF ISOZYME AND QUANTITATIVE GENETIC-VARIATION IN PINUS-CONTORTA SSP LATIFOLIA BY F-ST

We employed F-statistics to analyze quantitative and isozyme variation among five populations of Pinus contorta ssp. latifolia, a wind-polli nated outcrossing conifer with wide and continuous distribution in wes t North America. Estimates of population differentiation (F-ST) for si x quantitative traits were compared with the overall estimate of the d ifferentiation (F-ST) from 19 isozymes that tested neutral to examine whether similar evolutionary processes were involved in morphological and isozyme differentiation While the F-ST estimates for specific gra vity, stem diameter, stem height and branch length were significantly greater than the F-ST estimate, as judged from the 95% confidence int ervals by bootstrapping, the F-ST. estimates for branch angle and bran ch diameter were indistinguishable from the F-ST estimate. Differenti ation in stem height and stem diameter might reflect the inherent adap tation of the populations for rapid growth to escape suppression by ne ighboring plants during establishment and to regional differences in p hotoperiod, precipitation and temperature. In contrast, divergences in wood specific gravity and branch length might be correlated responses to population differentiation in stem growth. Possible bias in the es timation of F-ST due to Hardy-Weinberg disequilibrium (F-IS not equal 0), linkage disequilibrium, maternal effects and nonadditive genetic e ffects was discussed with special reference to P. contorta ssp. latifo lia.