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Title: Pinus ponderosa: geographic races and subspecies based on morphological variation
Author: Callaham, Robert Z.;
Source: Pinus ponderosa: geographic races and subspecies based on morphological variation. Res. Pap. PSW-RP-265. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 53 p
Publication Series: Research Paper (RP)
Description: Morphological variation of ponderosa pine (Pinus ponderosa Dougl. ex Laws.), growing north of Mexico, is described. A map shows distributions of five putative races that are analyzed and discussed. Characteristics of branches, shoots, and needles were measured for 10 or fewer trees growing on 147 plots located at 1,500-ft elevational intervals along latitudinal transects. Characteristics of cones were measured from 120 of these plots. Cones from 78 plots yielded seeds for study. Subspecific boundaries were based on both visual interpretations for many traits and statistical cluster analyses of plot means. Boundaries were tested for appropriateness by multiple discriminant analyses. Univariate analyses of variance and stepwise discriminant analyses selected characteristics most capable of differentiating among hypothesized races. On average, 98 percent of plots were correctly classified as to race. Characteristics most capable of differentiating among the hypothesized races were selected. Characteristics of trees in three common-garden plantings were analyzed to determine the genetic basis of foliar characteristics measured on trees in situ. Results of analyses and review of literature confirm existence of five morphologically distinct, geographic taxa and four transition zones.
Keywords: Ponderosa pine, geographic races, morphological variation
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Callaham, Robert Z. 2013. Pinus ponderosa: geographic races and subspecies based on morphological variation. Res. Pap. PSW-RP-265. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 53 p.
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