Pollination Ecology and Endemism of Pedicularis pulchella Pennell (Scrophulariaceae)

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Abstract
Pedicularis pulchellaPennell, endemic to sparsely vegetated areas of alpine tundra scree in southwestern Montana and northwestern Wyoming, was found to be roat‐hemiparasitic and obligately dependent for its pollination upon bumblebees of three non‐tundra species that forage primarily in an inverted position for pollen scraped from anthers concealed in the galea, This sternotribic pollination syndrome is considered related to the short (5–6mm) proboscides of pollinators on flowers with deep (12.4mm), nectariferous corolla tubes and favoring pollen as an insect attractant. Photographic and spectropholomelric analysis of the red‐purple floral color included prominent blue corolla and ultraviolet calyx reflections corresponding to dominant colors of bumblebee visual spectra. Nectar analysis by thin‐layer chromatography and refractomctry indicated, respectively, the presence of fructose and sucrose, and a sucrose‐equivalent concentration of dissolved solids exceeding 50%; both coincide with the general pattern of the genus. Analysis of pollen from corbicular loads ofP. pulchellapollinators indicated relatively low pollen‐constancy of insects and substantial foraging association with Vaccinium in the montane‐subalpine zone. By contrast, pollinators on P. cystopteridifolia and Phyllodoce glanduliflora in a diverse tundra plant community on rich alpine turf revealed broad pollinator spectra (7–8 species), high pollen‐foraging constancy on Pedicularis, and high nectar‐foraging frequency onPhyllodoce: The pollination ecology and endemism ofPedicularis pulchtellaare interpreted in terms of resource sharing, spatial competition of plant species, and selective stress of the physical environment.