20 



incapable of sexual reproduction. 



8. Population ecology of taxon. 



A. General summary: Tr i setum or t hoc hae turn , as 

 discussed above, occurs in small, scattered 

 clusters in meadow-forest ecotone areas. At all 

 known sites it occurs in mixed populations with 

 the two putative parents, T. canescens and T. 

 wolf i i . No other specific obligate relationships 

 are known. 



B. Positive and neutral interactions: None known- 



C. Negative interactions. 



1. Herbivores, predators, pests, parasites, and 

 diseases: When the Granite Creek South site 

 was re-visited on 6 August, the majority of 

 the observed inflorescences were infested 

 with aphids (family Aphididae). No other 

 negative interactions were observed. 



8. Competition. 



a. Intraspecif ic : No information; the 

 populations are probably too small and 

 scattered for i ntraspec if ic competition 

 to be evident or important. 



b. Interspecific: No information; the 

 taxon occurs in dense graminoid 

 communities where interspecific 

 competition, especially in the seedling 

 stages, is probably very strong. 



3. Toxic and allelopathic interactions: 



Unknown . 



D. Hybridization. 



1. Naturally occurring: The possibility that 

 Tr isetum or thochaetum is an interspecific 

 hybrid between T. canescens and J_. wo If i i 

 has long been recognized by several 

 botanists. Hitchcock et. al. (1969) stated 

 that "(b)ecause of its apparently non- 

 functional anthers and its morphological 

 intermediacy between T. wolf i i and T. 

 canescens , it is difficult not to theorize 

 about the parentage of this peculiar plant." 

 In his letter to the University of Montana 

 Herbarium of 13 January 1986 (Appendix A, 

 p. 33), Dr. LeRoy H. Harvey stated that 

 "(m)y feeling is that this is a hybrid 

 between T. wolf i i and T. canescens which 



