Tuesday, August 8, 1:30-5:00 pm
COS 36 - Pollination ecology I
L-13, Lobby Level, Cook Convention Center
Presiders: S Travers and R Spigler

Pollinator preferences match gender-specific pollination needs: evidence for sexual selection in a hermaphroditic herb.

Carlson, Jane*,1, 1 Louisiana State University, Baton Rouge, LA

ABSTRACT- Plants with floral phenotypes that match pollinator preferences, e.g., plants with abundant nectar, are often favored through natural selection over less-attractive conspecifics. Pollinator mediated-selection takes on a unique character, however, when pollinator preferences focus on specific flowers within plants, in addition to or instead of on individual plants. Plants that temporally separate sexual function within perfect flowers, for example, may produce more nectar in male- relative to female-phase flowers on the same plant, which should increase visits to male-phase flowers. In such cases, pollinator-mediated selection on nectar production may be considered a form of sexual selection. Nevertheless, the sexual selection conceptual framework is rarely tested in plants, particularly those with hermaphroditic flowers. Using a perfect-flowered, protandrous herb native to southern Costa Rica (Chrysothemis friedrichsthaliana, Gesneriaceae), I tested predictions of sexual selection theory in plants, to determine if the 60-70% male-bias in nectar production could be explained by sexual selection mediated by pollinators. Throughout two consecutive flowering seasons, I assembled detailed measurements of pollinator visit rates and per-flower fecundity following different numbers of visits. In accordance with sexual selection predictions, (1) the main pollinator, a hermit hummingbird (Phaethornis striigularis), visited male-phase flowers 57% more often than female-phase flowers, but did not visit flowers often enough to maximize total reproductive output, and (2) mating competition was stronger between pollen donors relative to pollen recipients, based on the positive relationship between the number of pollinator visits and male, but not female, plant reproductive success. These findings highlight the utility of including sexual selection concepts in the larger framework of pollinator-mediated selection to explain certain attractive floral traits.

Key words: pollinator-mediated selection, floral evolution, hummingbird-pollinated neotropical herb

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