| Summary: | Geographic variation was investigated among 225 locations from five geographically disjunct regions in central Oregon. Characters included: germination speed and uniformity in two test environments
differing in stratification period and incubation temperature; weight, three dimensions and three 'angles' of seeds; weight and three dimensions of wings; cone length and scale weight; the relative cover of 14 colors on the seed coat; and three sets of principal components (germination, morphology, color). The major objectives were to investigate: (1) the distribution of character variation within and among locations; (2) correlations among characters; (3) clinal relationships with several location variables (latitude, longitude, elevation, slope/aspect, soil characteristics, associated conifers); and (4) if the three major regions differed in the distribution of variation, correlations among characters, clinal relationships, and character means. In general, the major conclusions are: (1) much of the variation
in all characters occurs within locations; (2) variation among locations is greater, and clines are steeper in germination than in
morphological characters; (3) regions differ in several seed colors and morphological characters, and in several correlations among
germination and morphological characters; (4) the Deschutes region has greater location-related variation, steeper clines, and stronger correlations between germination and morphological characters than do the two major regions farther east of the Cascade Mountain Range; (5) local aspect accounts for much of the variation in germination and morphological characters; (6) soil characteristics account for more variation in morphological than germination characters.
Variation patterns are mainly interpreted as adaptive responses to the length of the growing season, which is strongly limited by
summer drought in central Oregon. In general, drier locations appear to favor trees with faster and more uniform germination, and with longer, heavier seeds but shorter wings and cones. Seed colors are also correlated with several location variables. Effects of seed predators on seed size, shape and color are also considered. === Graduation date: 1989
|
|---|
