D-1 



A Preliminary Stucfy of the Pollination 



Biology of Spalding's Catchfly in the Tcbacxxi Valley, 



Lincoln CJounty, Mcaitana 



INIRDDUCnCN 



Conservation of rare species is one of the principle goals of The 

 Nature Conservancy. Frequently, this requires more than sinply protecting 

 populations of a species. In the case of plants that are obligate 

 outcrossers, it is also necessary to protect or enhance the habitat of the 

 plant's pollinators in order to ensure continued recruitment. 



Spalding's catchfly (Silene spaldinqii Wats.) is a perennial herb that 

 is potentially threatened or endangered throughout its range in the 

 Pacific Northwest. It does not reproduce vegetatively; all new 

 individuals must start from seed. It occurs in relatively pristine 

 bunchgrass grasslands in the Palouse Region of eastern Washington, 

 northeastern Oregon, adjacent Idaho and northwestern Montana (Heidel 1980, 

 Lesica, field observations). Flowers of Spalding's catchfly are 

 relatively large (ca. 2 cm long) and inconspicuously colored with v^ite 

 petals that are mostly enclosed by the green, broadly cylindrical calyx. 

 At anthesis the flowers are presented horizontally in an open cyme. These 

 characteristics suggest that Spalding's catchfly is adapted for 

 pollination by bees or hovering moths (Faegri and van der Pijl 1971) ; 

 hCTvever, the pollinators of this species are not currently known. In 

 addition, it is not known to what extent Spalding's catchfly is capable of 

 self-fertilization. 



Ihe purpose of this study is to determine the pollinators of 

 Spalding's catchfly on The Nature Conservancy's prcposed Dancing Prairie 

 Preserve in northwestern Montana and to discover the extent to v^ich this 

 species is capable of setting seed in the absence of pollinators, 



MEIHDDS 



I observed pollinators of Spalding's catchfly at the proposed Dancing 

 Prairie Preserve in northeastern Lincoln County, Montana on July 12-14, 

 1988. I spent a total of 28 hours watching a large patch (ca. 30 plants) 

 of Spalding's catchfly in the north-central area of section 26. Part of 

 this time was also spent making observations at other patches in the area. 

 Since many moth pollinators are crepuscular, on all three days I made 

 observations during the early mornings and at dusk. Weather during this 

 three-day period was cold, rainy and windy. 



In order to determine whether Spalding's catchfly can set seed in the 

 absence of pollinators, I excluded insects from the inflorescences of 21 

 plants in four colonies in the north-central area of section. 26. For each 

 experimental plant, I removed all flowers that had already opened as well 

 as all insect predators that I detected. I then placed a fine-mesh nylon 

 bag around the inflorescence and tied it closed at the base. These bags 

 allow flowers to open and develop in partial sunlight while excluding any 

 insects larger than 1 mm wide. Plants were bagged on July 14, 1988. 

 Seventeen days later on August 1, I collected the bagged inflorescences 



