Tagged: floral symmetry



Grevillea rosmarinifolia

Bilateral flower symmetry developmental genetics in Proteaceae

Bilateral symmetry has evolved as an adaptive trait linked to efficient pollination and successful outcrossing, occurring over 170 times in angiosperms and in many plant groups relying upon the asymmetric expression of key transcription factors from the CYC/TB1 gene family. Citerne et al. characterise the evolution of flower symmetry in Proteaceae, a basal eudicot lineage with high diversity in floral morphology, finding that bilateral symmetry is a very labile trait in Proteaceae. The asymmetric expression of CYC/TB1 homologues implicated in the development of bilaterally symmetrical flowers suggests that these genes may have been recruited and harnessed for the control of...

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Zygomorphy evolved from disymmetry in Fumarioideae

Zygomorphy evolved from disymmetry in Fumarioideae

Floral bilateral symmetry (zygomorphy) has evolved at least 70 times during the history of angiosperms, whilst radial symmetry (actinomorphy) is the ancestral and most common state for angiosperms as a whole. Sauquet et al. reconstruct the phylogeny and floral evolution of Papaveraceae (Ranunculales) and find that in this family zygomorphy evolved from a rare, intermediate symmetry form, disymmetry, which is defined by two perpendicular planes of bilateral symmetry. This important transition occurred in subfamily Fumarioideae (fumitories) and is correlated with the loss of a nectar spur.

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Pollination, flower size variation and floral symmetry

Pollination, flower size variation and floral symmetry

The pollinator-mediated stabilizing selection hypothesis suggests that the specialized pollination system of zygomorphic flowers might cause stabilizing selection, reducing their flower size variation compared to actinomorphic flowers. By using data on 43 species from two contrasting communities, Lázaro and Totland show that zygomorphic species that are highly dependent on pollinators and ecologically specialized are less variable in flower size than ecologically generalist and selfing zygomorphic species. However, these relationships are not found in actinomorphic species. The results suggest that the relationship between flower size variation and floral symmetry may be influenced by population-dependent factors, such as ecological generalization and species’...

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