Figures ZZ- 34 . — Repre- 

 sentative two-dimen- 

 sional chromatograms 

 of methanol- soluble 

 extracts from the 

 leaves of putative 

 hybrids A. tripartita 

 X A. tridentata subsp. 

 vaseyana subgroup la 

 (fig. Z3) and A. tri- 

 dentata subsp. vaseyana 

 subgroup lb X k. tri- 

 dentata subsp. tri- 

 dentata subgroup lib 

 (fig. 24). 



This type of introgression 

 has wide distribution within the sagebrush populations. Collections taken from ecotones 

 between populations of different species, subspecies, or ecotypes frequently express 

 both morphological and chromatographic evidence of interbreeding. 



Chromatographic evidence for hybridization between the following taxa was observed: 

 A. tridentata subsp. vaseyana X A. tridentata subsp. tridentata; A. tridentata subsp. 

 vaseyana X A. arbusoula subsp. arbuscula; A. tridentata subsp. vaseyana X A. nova^ 

 A. tridentata subsp. vaseyana X A. tripartita subsp. tripartita; A. tridentata subsp. 

 vaseyana X A. eana. subsp. visaidula; A. tridentata subsp. tridentata X A. tripartita 

 subsp. tripartita; A. aana subsp. visaidula X A, tripartita subsp. tripartita. Examples 

 are illustrated in figures 33 and 34. We are confident that many others will come to 

 light as this technique is more widely applied. 



Ecological distribution. --The following observations have been made regarding the 

 ecological distribution of the chromatographic groups of big sagebrush, primarily 

 within the Great Basin. Collections of Group I (Artemisia tridentata subsp. vaseyana 

 and subsp. wyomingensis) have come mostly from mountain habitats extending from the upper 

 elevational limits of the big sagebrush zone to, and slightly beyond, the base of 

 the foothills. Specimens of vaseyana Ic, which were all collected from the upper eleva- 

 tions of the big sagebrush zone, appear to be widely distributed, as is evidenced by 

 collections of this subgroup {vaseyana Ic) from Utah, Idaho, Nevada, Wyoming, and 

 Colorado. Vaseyana Ic may include A. tridentata subsp. vaseyana f. spiciformis 

 (Beetle 1960; Winward 1970). The distribution of vaseyana la extends downward from 

 the vaseyana Ic zone to the lower foothills, overlapping considerably with vaseyana Ic 

 in the upper elevations and vaseyana lb in the foothills. Subgroup vaseyana lb 

 predominates in the lower foothill pinyon- juniper zone and extends into peripheral 

 lowland areas where it overlaps with tridentata lib. It is interesting that Winward 

 (1970) recognized an analogous or perhaps identical taxon to our vaseyana lb in his 

 taxonomic and ecological study of Idaho big sagebrush. He tentatively referred to this 

 taxon as A. tridentata subsp. vaseyana f. xericensis . However, that name has not been 

 validly published (Winward 1970). 



Subgroup wyomingensis Id (which occurs in Wyoming, Montana, southern Idaho, north- 

 ern Nevada, and northern Colorado) overlaps vaseyana lb, the lower end of vaseyana la, 

 and to a greater extent, the upper end of tridentata lib. Beetle and Young (1965) 

 maintain that A. tridentata subsp. wyomingensis is intermediate in ecology, morphology, 

 and distribution between A. tridentata subsp. vaseyana and A. tridentata subsp. tri- 

 dentata. Our chromatographic data (table 1) support their recognition of subsp. wyo- 

 mingensis as a valid separate subspecies and corroborate Young's (1965) thin-layer 

 chromatographic evidence for three subspecies. However, our data indicate that subsp. 

 wyomingensis has closer affinities to subsp. vaseyana than to subsp. tridentata. 



14 



