Ecological Genetics of Pinus 

 contorta in the Upper Snake 

 River Basin of Eastern Idaho 

 and Wyoming 



Q. E. Rehfeldt 



INTRODUCTION 



Ecological genetics is devoted to exploring the ecologi- 

 cal bases for adaptive differentiation between popula- 

 tions. In lodgepole pine {Pinus contorta var. lati folia 

 Engelm.), differentiation of populations from both 

 Canada (Lindgren and others 1980; Hagner 1980; Ying 

 and others 1985) and the United States (Rehfeldt 1985b) 

 is related to the geographic origin and elevation of the 

 seed source. Adaptive clines, however, reflect environ- 

 mental gradients. As a result, clines in British Columbia 

 reflect the relatively gentle environmental gradients 

 associated with a region of dissected plateaus. But in 

 the rugged Rocky Mountains of the United States, adap- 

 tive clines tend to be steep for a variety of traits that 

 include growth potential, morphology, and cold hardi- 

 ness (Rehfeldt 1980, 1983), patterns of shoot elongation 

 (Rehfeldt and Wykoff 1981; Stoneman 1985; Rehfeldt 

 1985a), and resistance to insects and diseases (Hoff 

 1985). Regardless of geographic region, populations 

 appear as physiological specialists for relatively small 

 segments of the environmental gradient. 



Steep adaptive clines have direct relevance to forest 

 management. Artificial reforestation carries the implicit 

 goal of maximizing productivity while maintaining 

 adaptedness. Steep clines require that seed for reforesta- 

 tion be transferred only short distances along the 

 environmental gradient if maladaptation and resultant 

 losses in productivity are to be controlled. 



The present study is part of a series that (1) examines 

 adaptive variation between lodgepole pine populations, 

 (2) relates patterns of variation to geography, topogra- 

 phy, physiography, and climate, and (3) develops seed 

 transfer guidelines for reforestation. 



MATERIALS AND METHODS 



The study of population differentiation included seed- 

 lings from 60 populations, 51 of which represented the 

 geographic distribution and ecologic amplitude of the 

 species in the upper Snake River Basin (fig. 1). Addi- 

 tional populations from peripheral areas provided a link 

 to other studies in this series: four were from the 

 Wasatch Mountains of Utah and southeastern Idaho; 



and location of populations. 



1 



