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Premise of research. Floral longevity, the amount of time from anthesis to floral senescence, is a key floral trait that determines the opportunity for pollinator visitation. However, the causes and consequences of variation in longevity have primarily been studied among species, which may not reflect patterns of variation within populations. Methodology. To determine the causes and consequences of within-population variation in floral longevity, we exposed Mimulus guttatus to either an ambient- or reduced-pollination treatment. We measured floral longevity to test whether reduced pollinator access (which simulates pollinator decline) causes a plastic extension in floral longevity. We also measured two traits—flower size and anther-stigma distance—that could cause floral longevity to vary and two traits—daily display size and flowering duration—that could vary in response to longevity. Pivotal results. Floral longevity was not affected by experimentally reducing pollinator access or by anther-stigma distance. However, longevity was reduced in M. guttatus plants with larger flowers. Variation in floral longevity did not affect the flowering duration of M. guttatus plants and (depending on the pollination treatment) had either a negative effect or no effect on daily display size. Conclusions. We found evidence that within-population variation in floral longevity in M. guttatus can be caused by correlations with flower size and can have consequences for daily display size that vary depending on the pollination environment. These results contrast with among-species studies of variation in floral longevity, which have not included display size but have found that longevity either is extended in species with larger flowers or is not related to flower size. Consequently, predictions about the causes of within-population variation in floral longevity based on among-species studies may be misleading. [ABSTRACT FROM AUTHOR]