Figure 39. — Photograph 

 showing differential 

 deer selectivity in 

 hroiosing A. tridentata 

 from different sources. 

 An A. tridentata subsp. 

 vaseyana subgroup lb is 

 on the left and an A. 

 tridentata subsp. 

 tridentata subgroup lib 

 on the right. 



In summary, wyomingensis Id and vaseyana lb are highly preferred, other vaseyana 

 subgroups, la and Ic, are moderately preferred, and subspecies tridentata subgroups Ila, 

 lib, and lie are least preferred by grazing animals. 



Occasionally, single plants or small groups of plants within large populations of 

 heavily grazed plants are grazed far less than the rest of the population. Several 

 chromatographic analyses have been made when plants that possessed similar morphological 

 characters have been found growing side by side, but one has been heavily grazed, the 

 other ungrazed. In most instances, no important variations in chromatographic patterns 

 were found. However, in collections of this type from lower A. tridentata subsp. 

 vaseyana (lb) elevations, chromatograms of the ungrazed plants frequently show evidence 

 of hybridization with A. tridentata subsp. tridentata, which may account for the 

 difference in selectivity. 



Some evidence indicates that reduced brilliance of spot 9 and the appearance of 

 spot 26 in A. nova (fig. 19) is also associated with decreased grazing preference. 

 This apparent pattern has not been conclusively demonstrated for all sources. A 

 similar change in chromatographic pattern was observed in A. arbuscula subsp. arbusaula 

 (fig. 10), but no correlation could be drawn between this characteristic and utilization 

 by game or livestock. Further observations will be required. 



Phylogenetio relationships .--Wd.il and Clements (1923) postulated the evolution of 

 the section Tridentatae from the more primitive section Abrotanum. They further be- 

 lieved that section Tridentatae first gained a foothold in the arid southwestern United 

 States and later moved northward into the Great Basin as climatic conditions became 

 favorable for its expansion into these areas. The connecting link between the sections 

 Abrotanum and Tridentatae is probably A. biglox>ii (Hall and Clements 1923). Artemisia 

 biglovii is a fairly abundant shrub in the upper Colorado and upper Rio Grande River 

 drainages of Utah, Colorado, New Mexico, and Arizona. It produces ray-flowers character- 

 istic of Abrotanum and also the trident leaves and overall general appearance peculiar 

 to Tridentatae. Support for A. biglovii -like taxa as phylogenetic connectors between 

 the two sections, Tridentatae and Abrotanum, is gained by A. biglovii's intermediate 

 characteristics. Hall and Clements (1923), Ward (1953), and Holbo and Mozingo (1965) 

 place A. biglovii in section Abrotanum, whereas Moss (1940) and Beetle (1960) place it 



19 



