Figure 4 S.— Contrasting 

 tephritid galls on C. 

 nauseosus subspecies. 



(A.) Callus gall on ssp. 

 albicaulis. (B.) Cotton 

 gall on ssp. graveolens. 



Specimens from Gould's 

 Wash J Washington Co.^ 

 Utah. 



areas. We are currently studying the absolute specificity of these galls. In areas 

 where these subspecies occur together the galls are very specific. We have observed 

 only a few cases of cross gall inoculation and then only on putative hybrid plants. 

 Wangberg (1976) independently observed some species and subspecies specificity of 

 tephritid galls on Chrysotharmus in Idaho. Wangberg (1976) found less specificity for 

 the round gall in Idaho than we did in Utah. He identified the tephritid flies that 

 induce the galls as two different species of Aaiurina. 



Hybridization. --Chry so thamnus nauseosus has a chromosome number of 2n = 18 

 (Anderson 1966, 1971; Kovanda 1972; Anderson and others 1974). This rabbitbrush is a 

 highly variable species of numerous ecotypes and biotypes from which a large number of 

 segregates have been described. Most important among these, in the Great Basin at 

 least, are the subspecies: salicifolius^ albicaulis^ graveolens^ and aonsimilis. 

 Other less common and less important subspecies include: junceus^ gnaphalodes^ holo- 

 leuGus, leiospermuSj and turbinaturs. 



L. C. Anderson (letter 4/12/72) advised using C. nauseosus in hybridization pro- 

 grams since all the natural Chrysotharmus hybrids he had found involved this species. 

 Anderson has found hybrids of C. nauseosus ssp. nauseosus X C. parryi ssp. parryi^ 

 C. albidus X C. nauseosus ^ and C. nauseosus ssp. albicaulis X Haplopappus macronema. 

 The last named combination is the putative parentage of the rare endemic C. bolanderi 

 (Anderson and Reveal 1966). In 1966 there were only 25-50 plants of this species--all 

 at Mono Pass, California. In his artificial hybridization attempts, Anderson (letter 

 4/12/72) inserted pollen between the appressed stigmatic lobes before they separated 

 naturally. This technique produced no hybrids but did block self-pollination in several 

 cases so that the recipient flowers set no seed. 



During our field studies of intermixed albicaulis-oonsimilis ^ albioaulis- 

 graveolenSy and graveolens-consimilis populations, we consistently found considerable 

 intermixing of color and leaf characteristics, indicating that introgression had oc- 

 curred. Our work with paper chromatography supports this observation (Hanks and others 

 1975). We found plants intermediate between C. nauseosus ssp. salicifolius and C. 

 parryi ssp. nevadensis and howardi. in Utah and Nevada, respectively. The subspecies of 

 C. nauseosus found in Colorado intergrade to some degree, according to Harrington (1954) . 



We agree with Hall and Clements (1923) that "improvement in any desired direction 

 may be brought about by selection, or by hybridization, or by both of these methods." 



44 



