53 



August. Fruit and seed maturation occurs in 

 August, with seed dispersal likely in late 

 August or early September. Senescence of 

 flowering stems was observed even as flowers 

 were opening in the draughty 1988 field season. 

 It is likely that the basal rosettes normally 

 senesce as fruits and seeds mature. Seeds of 

 this species may require cold stratification, 

 germination (although further studies are 

 needed) , and germination is likely to occur in 

 spring (Lesica, 1988) ; see Appendix C, p. 70. 



2. Relation to climate and microclimate: Most of 

 the known sites for S. spaldingii in Montana 

 occur on north to east-facing slopes or draws, 

 often near pine trees, where snow accumulations 

 are likely to remain later into the spring. 

 Silene spaldingii flowers in late July, and it 

 is hypothesized that it is dependent on the 

 extended moisture provided by the microclimate 

 of these sites. 



D. Reproductive ecology. 



1. Types of reproduction: Silene spaldingii does 

 not reproduce vegetatively ; new individuals 

 arise from seeds. 



2. Pollination. 



a. Mechanisms: Silene spaldingii is 

 apparently dependent on insects for 

 pollination. Results of pollination 

 studies suggest that it is an obligate or 

 near-obligate outcrossing species (Lesica, 

 1988); see Appendix D, p. 71. 



b. Specific known pollinators: One known 

 pollinator of S. spaldingii is the 

 bumblebee ( Bombus sp.), and there are 

 likely to be others (Lesica, 1988) ; see 

 Appendix D, p. 71. 



c. Other suspected pollinators: Silene 

 spaldingii has flowers characteristic of 

 those pollinated by moths; however, none 

 were ever documented as visitors (Peter 

 Lesica, pers. comm.). 



d. Vulnerability of pollinators: Bumblebees 

 are relatively ubiquitous; however, 

 overgrazing or pesticide use might be 



