Interplay between timing, size, and sex

Ishii and Harder have an accepted paper in the Journal titled “Phenological associations of within- and among-plant variation in gender with floral morphology and integration in protandrous Delphinium glaucum“.  Read the paper here.

The authors have provided a short synopsis of the paper and two photos of their study species, Delphinium glaucum.

Delphinium glaucum inflorescences. Credit: Ishii & Harder.

In plant species that produce flowers with distinct female- and male-phases, early flowers commonly differ from late flowers within individual plants.  For example, the relative production of ovules and pollen by flowers shifts to emphasize whichever sex role is least common during a specific period of the population’s flowering period.  In addition to this pattern, we demonstrate corresponding variation in flower size, pollen production and male-phase duration among Delphinium glaucum plants with contrasting flowering periods. In this species, flowers have a male- then female-phase, and early plants and early flowers are more female than late plants and flowers, as the population floral sex ratio shifts from male- to female-biased.  This consistent pattern suggests that natural selection actively maintains variation among and within plants, especially when they differ in flowering times, which may itself be a result of selection to limit competition for pollinator service.  Whether such variation promotes a plant’s joint success as a female and male parent remains to be tested.

Delphinium glaucum flowers. Credit: Ishii & Harder.

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