Some species of Cypripedium are known to hybridize, for example C calceolus var. 

 parviflorum and C montanum produce apparent hybrids at Libby Dam (see discussion 

 under this heading for C, calceolus var. parviflorum ). 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). 

 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: The sites where Cypripedium passerinum are found on the KNF usually 

 have high vegetative cover but the sensitive plant is very scarce, suggesting that it may 

 have poor competitive ability. The habitats are usually shared with C calceolus var. 

 parviflorum which is always more abundant. The two species of lady's slippers occupy 

 similar microhabitats but were not seen growing in close association, thus C. calceolus 

 var. parviflorum may be a superior competitor, to the exclusion of C. passerinum . 

 Flowers were observed on plants growing in deep shade. 



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

 (Cronquist 1988). Although seeds of some species of Cypripedium (De Pau and 

 Remphry 1993) have been germinated under laboratory conditions without a fungal 

 symbiont, 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: On the KNF in past years, light herbivory was noted at Rattlebone Lake 

 (020) and browsing by game was noted at Laughing Water Creek (024). At Brimstone 

 Creek (025), the single clump of Cypripedium passerinum found was growing under 

 brush, a possible indication of vulnerability to herbivores. Severe grazing and trampling 

 by cattle was noted at one site on the Lewis and Clark National Forest along the Rocky 

 Mountain Front Range (Shelly 1988). 



H. Land ownership: All occurrences are on KNF land on the Fortine District except Jumbo 

 Lake (022) which is on state land but possibly extends onto the KNF Fortine District. 



I. Assessment and management recommendations 



1. Threats to currently known populations: Potential threats to Cypripedium passerinum 



are essentially the same as for Cypripedium calceolus var. parviflorum : see this heading 

 for that species for a more complete discussion. These threats include grazing, road 

 building, logging, and plant collecting. There are more reports of herbivory to 

 Cypripedium passerinum than to Cypripedium calceolus var. parviflorum . a possible 

 indication that it is more palatable and thus more susceptible to grazing. Its lower 

 numbers on the KNF could be a reflection of extreme susceptibility to grazing and 

 browsing by game, although there is no direct evidence of this. Its extreme rarity on the 

 KNF make it especially vulnerable to extirpation caused not only by human caused 

 disturbances but also due to natural population fluctuations, disease, and herbivory. The 

 flowers of Cypripedium passerinum are quite inconspicuous and not showy, thus 

 collection by people for cut flowers and propagation as ornamentals may be less of a 

 threat to this species. 



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