Sex-specific floral attraction traits in a sequentially hermaphroditic species

Ecology and Evolution: DOI: 10.1002/ece3.5987

Abstract

● Many angiosperms are hermaphroditic and produce bisexual flowers in which male

(pollen export) and female (stigma receptivity) functions are separated temporally.

This sequential hermaphroditism may be associated with variation in flower size,

color, or pattern, all of which may influence pollinator attraction. In this study, we

describe variation in these traits across discrete functional sex stages within and

between 225 greenhouse-grown individuals of Clarkia unguiculata (Onagraceae).

In addition, to identify the effects of floral phenotype on pollinator attraction in

this species, we examine the effects of these floral traits on pollen receipt in ~180

individuals in an experimental field array.

● Petal area, ultraviolet (UV)-absorbing nectar guide area, and blue and green mean

petal reflectance differ significantly across the functional sex stages of C. unguiculata.

Male- and female-phase flowers display significantly different pollinator attraction

traits. Petal and UV nectar guide area increase as flowers progress from

male phase to female phase, while blue reflectance and green reflectance peak

during anther maturation.

● In field arrays of C. unguiculata, female-phase flowers with large UV nectar guides

receive more pollen than those with small nectar guides, and female-phase flowers

with high mean blue reflectance values are more likely to receive pollen than

those with low blue reflectance. Female-phase flowers with green mean reflectance

values that differ most from background foliage also receive more pollen

than those that are more similar to foliage. These findings indicate that components

of flower color and pattern influence pollen receipt, independent of other

plant attributes that may covary with floral traits. We discuss these results in the

context of hypotheses that have been proposed to explain sex-specific floral attraction

traits, and we suggest future research that could improve our understanding

of sexual dimorphism in sequentially hermaphroditic species and the evolution

of features that promote outcrossing.