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Variation in floral longevity between populations of Campanula rotundifolia (Campanulaceae) in response to fitness accrual rate manipulation¹

Division of Biological Sciences, University of Missouri–Columbia, Columbia, Missouri 65211 USA

ABSTRACT

Floral longevity, the time between corolla expansion and senescence, contributes directly and indirectly to a plant's overall fitness. Though mating opportunities for insect-pollinated species often differ among populations, few empirical studies have addressed whether floral longevity varies in a manner consistent with these differences. I conducted experiments at thermally distinct sites to examine whether the prevailing floral longevity model predicted such variation between a montane and an alpine population of Campanula rotundifolia. Staminate phase duration was significantly shorter for montane vs. alpine C. rotundifolia flowers in the presence of pollinators, but significantly longer when pollinators were excluded. Montane flowers had a significantly higher female fitness accrual rate, significantly shorter total longevities, and, unlike alpine flowers, were not pollen-limited. Delaying pollinator access to pistillate phase flowers significantly increased total longevity in alpine flowers only. Significant differences in total longevity between populations resulted from an extended pistillate phase in alpine flowers. Overall, the prevailing model accurately predicted the total floral longevity trends found here. However, I provide novel evidence for geographic and gender-specific plasticity in the floral longevity response to fitness accrual rate variation, suggesting C. rotundifolia populations in this study may be attuned to local schedules of pollinator activity.

Key Words: Campanulaceae • Colorado • conditional response • fitness accrual rate • floral longevity • geographic variation • pollination • pollen limitation