Abstract Detail

Reproductive Processes

Sapir, Yuval [1], Gallagher, Megan [1].

What maintains flower colour variation within populations?

Flower colour variation is the most prominent (and most beautiful) expression of natural variation, the raw material of natural selection. Flower colour is a key advertisement trait for angiosperms to attract animal pollinators. The association of flower colour with floral reward affects pollinator behaviour, which, in turn, directly affects plant fitness, and in this way, pollinators exert selection on flower colour. While most flowers are uniform in colour, the cases of within-population flower colour variation may shed light on the mechanisms that maintain or erode natural variation. Flower colour variation has multiple forms: monomorphic, dimorphic, polymorphic, or continuous variation. While natural selection on flower traits is usually thought to be unimodal, little attention has been paid to the cases where selection creates polymorphism. Moreover, while a few cases of dimorphic or polymorphic flower colours have been studied, there has not yet been a synthesis of the differences and common mechanisms that lead to different patterns of flower colour variation. We review the various mechanisms that maintain stable colour variation and propose new, yet un-tested drivers which may maintain flower colour variation. The best-studied mechanism is stabilizing selection, where colour morphs are selected by multiple agents. These could be different pollinators, or different behaviours of a single pollinator. A combination of mutualists and antagonists, or biotic and abiotic selection agents, can also lead to flower colour variation. And on top of this, spatiotemporal variation in the direction and extent of selection can drive variation. Another possible mechanism requires rare allele advantages, such as in the case of deceptive polymorphic flowers, where negative frequency-dependent selection maintains rare colour morphs. Random processes may also drive flower colour variation. High mutation or migration rates can balance out directional selection and keep flower colour variation within the population. Finally, the possibility that there is no selection is usually overlooked, because flower colour is typically considered an adaptive trait due to its importance for signalling to pollinators. We argue that this could be a common phenomenon that drives and maintains flower colour variation within populations.

1 - Tel Aviv University, Tel Aviv University, Ramat Aviv, Tel aviv, , 69978, Israel

plant-pollinator interactions
pollinator-mediated selection
phenotypic variation
mutation-selection balance
random processes.

Presentation Type: Oral Paper
Session: REP3, Reproductive Processes 3
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 11:15 AM
Number: REP3006
Abstract ID:862
Candidate for Awards:None

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