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Aims

The calyx, the outermost whorl of a flower (usually green), has been considered to function to protect flowers. In some species, however, calyces are colorful and retained during seed development. Limonium species have been exploited as cut flower crops because the calyces persist for several months after the corolla has closed. To explore the adaptive significance of the persistent calyx in a desert plant Limonium leptolobum, we ask whether persistence of calyces can enhance pollinator attraction by enlarging floral displays, increasing reproductive success in this self-incompatible species.

Methods

The yellow flower of L. leptolobum lasted 1-2 days but its white, membranous calyx extended fully after the corolla closed, and persisted for over 2 months in the field, making hundreds of ’showy flowers’ on one individual. To examine the ecological function of calyces, we test the pollinator attraction hypothesis. In an experimental population, we compared the difference in visit frequency and visitor behavior between intact inflorescences and inflorescences with their calyces removed on the same individual plants.

Important findings

In four experimental plots four types of floral visitors were observed including bees, butterflies, syrphid flies and day-flying moths. No significant preference was observed between calyx-free and intact inflorescences for both first arrivals and total visit frequency of all types of floral visitors, indicating that the persistence of calyces did not make plants more attractive to potential pollinators. The pollinator attraction hypothesis for the showy calyces was not supported by the current data. Whether the calyx in this desert plant helps seed development or has other functions needs further study.