Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Bukhari, Ghadeer [1], Zhang, Jingbo [2], Zhang, Wenheng [3].

Floral orientation and evolution of flower symmetry in pentapetalous angiosperms.

Observations of floral development indicate that floral orientation in pentapetalous flowers most commonly results in a medially positioned abaxial petal (MAB) instead of a medially positioned adaxial petal (MAD) during early floral initiation. In this study, we investigate the evolution of the patterns of floral orientation on a phylogenetic framework, and the relationship between early floral orientation and the development of floral symmetry. We analyzed floral diagrams representing 432 species in 350 genera of pentapetalous angiosperms, and reconstructed the evolution of floral orientation and floral symmetry using a phylogenetic approach. Our results indicate that MAB orientation is more common and represents the ancestral state of floral orientation in pentapetalous angiosperms. The MAD orientation evolved 26 times independently from the ancestral MAB orientation. Based on our data set, we found that floral zygomorphy evolved 31 times in pentapetalous angiosperms. The zygomorphic clades displayed either a MAB petal likely functioning as a landing platform or a MAD petal likely functioning as a flag to pollinators. Interestingly, although the MAB orientation is more common than the MAD orientation in early floral initiation, the frequency of zygomorphic flowered clades developing a MAB or MAD petal is about the same (16 flags versus 18 landing platforms). The findings imply that mechanisms other than establishing floral zygomorphy along a vertical medial plane of floral symmetry exist especially to establish a zygomorphic flower with a flag. We found that zygomorphic flowered clades can develop floral zygomorphy along different degrees of oblique planes of floral symmetry in addition to the vertical medial plane. Our findings suggest that flags of many zygomorphic clades evolved from the MAB orientation through distinct mechanisms.

1 - Virginia Commonwealth University, Biology, 1000 W Cary Street , Richmond, VA, 23284, USA
2 - Virginia Commonwealth University, 1000 W Cary Street, Richmond, VA, 23284, United States
3 - Virginia Commonwealth University, Biology, 1000 W Cary Street, Richmond, VA, 23284, United States

Keywords:
Flower symmetry
Flower orientation
zygomorphy
Oblique plane of floral symmetry
Pentapetalous
Medially positioned abaxial petal (MAB)
Medially positioned adaxial petal (MAD)
Flag
Landing platform
Phylogeny.

Presentation Type: Oral Paper:Papers for Topics
Session: 42
Location: Hall B/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:45 AM
Number: 42003
Abstract ID:694
Candidate for Awards:Katherine Esau Award