Primula cusickiana var. maguirei (Primulaceae)

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Western North American Naturalist



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Natural history information for rare plants can help land managers better understand the threats to extinction that a taxon may face. Our focus is on the natural history of Maguire primrose (Primula cusickiana var. maguirei, Primulaceae), an endemic, threatened plant found along a narrow corridor within a single canyon in northern Utah. We examined floral morphology, air temperature, relative humidity during flowering, dichogamy, blooming period, and visits from flying insects. As with most Primula, Maguire primrose displays distinct floral distyly. Within the distylous flowers, 17% of our samples had a timing difference in the maturation of anthers and stigmas, a trait not previously recorded in any other Primula species. Temperatures during the early-spring blooming period fluctuated widely between recorded minima below 0 °C and maxima above 33 °C. We captured 8 different species of flying insects visiting Maguire primrose flowers in air temperatures ranging from 6 to 15 °C. Bloom timing was not well synchronized between different canyon locations. Between different canyon locations, we observed only a small number of plants that overlapped in their flowering phenology. This threatened primrose variety has a cool, early-season blooming period, a dependence on visiting insects for outcrossing, and disjunct populations throughout the canyon, resulting in the potential for serious challenges to reproduction.

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