Abstract Detail



Reproductive Processes

Peach, Kristen [1].

Rethinking floral attraction; sexual dimorphism in Clarkia unguiculata.

Most flowering plant species produce cosexual flowers that bear both male and female sex organs. Dioecy, a condition in which male and female sex organs occur on separate individuals, is more uncommon. However, sexual dimorphism (differences in primary and secondary sex characters) has primarily been examined in the context of the evolution of dioecy. Very few studies to date have examined sexual dimorphism between the functional sex stages of cosexual flowers. The temporal separation between male and female function in the cosexual flowers of dichogamous species may be associated with variation in traits that influence pollinator attraction, which may function to minimize self-fertilization or to maximize sex-specific fitness.  In this study, we describe variation in floral color, pattern and size across three discrete functional sex stages within flowers, (corresponding to the release of pollen from short stamens (stage 1), the release of pollen from long stamens (stage two), and the onset of stigma receptivity (stage 3)), and between individuals and populations of Clarkia unguiculata. We examine the ecological significance of variation in petal size, color, and pattern by determining their independent effects on pollen receipt in this species. We use a combination of modified photographic techniques and image analysis software to measure floral attributes in ~ 225 greenhouse grown individuals across three stages of floral development associated with functional sex. We record mean blue, green and ultraviolet (UV) reflectance in multiple regions of one petal per flower, the size of the UV-absorbing nectar guide, the size of the petal spot, and petal area (of one petal) for each individual. We use ~180 individuals in experimental arrays in a field study to determine the independent effects of each floral trait on pollen receipt. Petal area, UV nectar guide area, blue, green and UV reflectance differ significantly across the three functional sex stages of C. unguiculata. Female phase flowers of C. unguiculata have larger petals and larger UV-absorbing nectar guides than male phase flowers. However, of these traits, only nectar guide area has a significant positive effect on pollen receipt. Flowers with blue and green reflectance values that are the least “leaf-like” receive the most pollen. These findings suggest that cryptic features (blue and green reflectance and nectar guide area) may play an important role in pollinator attraction.


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Keywords:
Pollination
functional traits
flower color
UV floral patternsUV floral patterns
female fitness.

Presentation Type: Oral Paper
Number: 0002
Abstract ID:85
Candidate for Awards:None


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