Is flower colour variation adaptive?
ID: 613 / 262
Proposed Symposium Title: Is flower colour variation adaptive?
Yuval Sapir 1, Tzlil Labin 1,2, Norah Saabnah 1,2, Esther Senden 1,3, Merav Lebel Vin 1, Yamit Bar-Lev 1, Katarzyna Roguz 4
Affiliations: (1) Yehuda Naftali Botanic Garden, Tel Aviv University, Israel (2) Haifa University, Oranim, Israel (3) University of Amsterdam, The Netherlands (4) Warsaw University Botanic Garden, Poland
The evolution of flower colour is argued to be driven by pollinators. While most flowering species are colour uniform, a minority exhibit within-population colour variation. This variation is hypothesized to result from balancing selection, assuming flower colour is an adaptive trait. Balancing selection is driven by multiple selection agents, driving balanced and equalized fitness of all colours. For example, differential pollinator behavior balances fitness of two colour morphs in Linum pubescens. Species with spatial pattern of variation suggest a more complex picture. For example, populations of Anemone coronaria in the arid climate region are red-monomorphic, while in the Mediterranean climate colour polymorphism is maintained through admixture due to partial partitioning of pollinators. Pollinators in polymorphic population of Fritillaria persica showed little discrimination among colour morphs due to lack of detection among continuous shades of flower colour. The wide range of continuous flower colour variation in Iris petrana is driven by differential expression levels of a few genes in the anthocyanin biosynthesis pathway, with no selection on flower colour likely because lack of discrimination by pollinators. These pieces of evidence suggest that flower colour variation is largely associated with either of three selection regimes: monomorphic populations are under directional selection, populations with discrete colour polymorphism are under balancing selection, and continuous colour variation is the hallmark of neutral or no selection on flower colour. Studying the rare cases of continuous flower colour variation can shed light on the evolution of flower colours and its role in communicating with pollinators.