Species of Cypripedium . like many orchids, are known to hybridize. In British Columbia 

 C calceolus (C parviflorurrO hybridizes with C montanum to make Cypripedium X 

 columbianum (Sheviak 1992). There is evidence of hybridization between C calceolus 

 var. parviflorum and C. montanum from several sites in Montana, notably on the Lewis 

 and Clark National Forest along the Rocky Mountain Front Range. There, populations of 

 yellow lady's slippers have plants with white and cream colored flowers. There is also 

 evidence of hybridization between these two taxa at Libby Dam (040) and a report of 

 plants with off colored flowers at Butler Creek (013) on the KNF (L. Kuennen, pers. 

 commun.). Specimens from Libby Dam were sent to Dr. Charles Sheviak (New York 

 State Museum) to determine if they are hybrids. Sheviak (1992) postulates that 

 hybridization and introgression between C calceolus (C^ parviflorum ) and Cypripedium 

 montanum may have played an important role in creating the variation seen in 

 northwestern yellow lady's slippers today. Although C calceolus var. parviflorum and C. 

 passerinum grow together at several sites on the KNF, no hybrids were seen; this may be 

 partially due to the small size of the latter's lip which adapts it to smaller pollinators 

 (Bernhardt 1990) and its capacity for self pollination (Catling 1983). However, a putative 

 hybrid between these two taxa has been reported from the Rocky Mountain Front Range 

 in Montana on the Lewis and Clark National Forest. 



G. Population ecology 



1. Competition: Cypripedium calceolus var. parviflorum usually grows in areas with very 

 high plant cover and at some sites displays a degree of dominance in its habitat. Its 

 rhizomatous habitat probably helps it to compete successfully with other plants, 

 especially other forbs. However, plants were not found adjacent to populations in areas 

 dominated by rhizomatous sedges (e.g. Carex utriculata . Carex vesjcaria), suggesting it is 

 not competitive with such species. At Ant Flat (025) Cypripedium calceolus var. 

 parviflorum grows in an unusual "meadow" habitat with heavy competition from 

 graminoids and shrubs and the plants are widely scattered and unusually small; part of 

 this area may have been burned in 1992 (see Element Occurrence Record in Appendix 

 A). Canopy cover also seems to effect reproductive success; plants growing in heavy 

 shade are often vegetative and of low vigor. Studies on another species of lady's slipper, 

 Cypripedium candidum . which grows in a rich fen in western New York, showed that 

 large flowering genets were associated with higher levels of light than smaller vegetative 

 genets (Falb and Leopold 1993). 



2. Positive Interactions: The orchid family is characterized by strong mycotrophy 

 (Cronquist 1988). Although seeds of Cypripedium calceolus var. parviflorum have been 

 germinated under laboratory conditions without a fungal symbiont (e.g. De Pau and 

 Remphrey 1993) it is unlikely that seeds germinate in nature before penetration by fungal 

 hyphae (Wells 1981). The plants remain colorless underground, dependent on a fungus, 

 for a some years before they produce their first photosynthetic leaf (Wells 1981). The 

 fungal symbiont of orchids is usually a species of Rhizoctonia (Wells 1981), a genus of 

 soil fungi which includes many plant pathogens (Agrios 1978). 



3. Herbivory: Herbivory has not been noted on Element Occurrence Records from the 

 KNF or elsewhere in Montana, although at one site "damage" by deer was noted. It is not 

 known if cattle eat Cypripedium calceolus var. parviflorum but the species is absent from 

 heavily grazed areas and little evidence of cattle was observed in the known population 

 areas. 



H. Land ownership: All of the known populations in the area of the KNF occur on Forest 

 Service land, but at Libby Dam (040) most of the population is on Army Corps of 



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