Microgeographical Patterns of Allozyme Differentiation in Douglas-Fir from Southwest-Oregon

Washington D.C.

1989

S. 3-15

1 Abb., 5 Tab., 36 Lit. Ang.

Bandaufführung

7380

16174

The genetic structure of stands of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) from 2 areas in southwest Oregon was examined. In the Little Butte Creek study area, stands on north- and south-facing slopes at each of three elevations were sampled. In the Applegate area, stands on opposing north- and south-facing aspects in each of three V-shaped canyons were sampled at a single elevation. Although considerable genetic variation was present in all stands, no significant differences among stands were found in single-locus measures of genetic diversity. The expected heterozygosity had a mean of 0.164 and a range of 0.128 to 0.189 among stands. Observed heterozygosities were not significantly different from expected heterozygosities. Associations of allele frequencies with slope aspect or elevation were either very weak or lacked consistency between the two study areas. Indeed, only 1.8% of the total genetic diversity could be apportioned among stands. Of this 1.8%, only 13% of the variation could be attributed to differences between aspects. Thus, in marked contrast to variation in the quantitative characters of seedlings as reported in other studies, there was very little allozyme differentiation between stands of different aspect or elevation within populations of Douglas-fir in southwest Oregon. Possible reasons for these conflicting findings are discussed.