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Sexual dimorphism and sex-specific floral attraction traits in a cosexual species


Peach, Kristen; Mazer, Susan; Liu, Jasen; Klitgaard, Kristen (2019), Sexual dimorphism and sex-specific floral attraction traits in a cosexual species, UC Santa Barbara Dash, Dataset, https://doi.org/10.25349/D9QG65


The examination of sexual dimorphism in plants has primarily been restricted to dioecious taxa. However, most angiosperms produce cosexual flowers in which male and female function are separated temporally, which may also generate sexual dimorphism (between the male and female stages of floral lifespan). The temporal separation between male and female function in such flowers may be associated with variation in traits that influence pollinator attraction and 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 discrete functional sex stages within flowers, and between individuals of Clarkia unguiculata (Onagraceae).  In addition, we examine the effects of these floral traits on pollen receipt (female fitness).

We use a combination of photographic techniques and image analysis to measure floral attributes in 225 greenhouse grown individuals across stages of floral development associated with functional sex. We use ~180 individuals in experimental arrays in the field to determine the independent effects of each floral trait on pollen receipt.

Male-phase and female-phase flowers of C. unguiculata display distinct pollinator attraction traits. Petal area, Ultraviolet (UV) nectar guide area, and flower color differ significantly across the functional sex stages of C. unguiculata. Flowers with large UV-absorbing nectar guides receive more pollen than those with small nectar guides. Flowers with blue and green mean reflectance values that differ most from background foliage also receive more pollen than those with reflectance values that are similar to foliage.