Abstract Detail

Evolution, Development, and BSA Genetics of Floral Display - Form, Size, and Arrangement

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

Patterns of floral organ initiation and evolution of floral symmetry in pentapetalous angiosperms.

Observations of floral development indicate that floral organ initiation in pentapetalous flowers most commonly results in a medially positioned abaxial petal (MAB) instead of a medially positioned adaxial petal (MAD) during early floral development. It was proposed that the conservation of floral organ initiation might impose a developmental constraint that leads to the evolution of limited types of floral zygomorphy in Asteridae. Here, we investigate whether this developmental constraint leads to bias in the evolution of certain patterns of floral zygomorphy in pentapetalous angiosperms. We analyzed floral diagrams representing 405 species in 330 genera of pentapetalous angiosperms to determine patterns of floral organ initiation, patterns of floral zygomorphy, and the developmental mechanisms that give arise to floral zygomorphy on a phylogenetic framework. Our results indicate that MAB initiation is more common and represents the ancestral state of floral organ initiation in pentapetalous angiosperms. The MAD initiation evolved 28 times independently from the ancestral MAB initiation. Based on our data, floral zygomorphy evolved 29 times independently in pentapetalous angiosperms. Previous studies in Asteridae indicated that the dominant MAB initiation of the group correlated with limited types of floral zygomorphy, which always resulted in a single ventral petal. Interestingly, our data indicate that although the MAB initiation is more common in pentapetalous angiosperms, the frequency for zygomorphic flowered clades to develop a pattern with a single ventral petal (landing platform pattern) or a pattern with a single dorsal petal (flag pattern) is about the same (15 landing platforms versus 14 flags). The discrepancy is explained by developmental mechanisms that result in floral zygomorphy along oblique planes of floral symmetry in addition to along the vertical medial plane in pentapetalous angiosperms. These findings suggest that early floral initiation does not impose a limitation for the evolution of patterns of floral zygomorphy in pentapetalous angiosperms. We argue that identification of multiple developmental mechanisms that give arise to floral zygomorphy will help us to understand how these mechanisms link with the genetic pathways responsible for the independent origins of floral zygomorphy.

1 - Virginia Commonwealth University, Biology, 1000 West Cary Street, Richmond, VA, 23284, USA

Keywords:
floral symmetry
floral organ initiation
floral evolution
floral zygomorphy
pentapetalous angiosperms
medially positioned abaxial petal
medially positioned adaxial petal
oblique plane of floral symmetry
phylogeny
flag
landing platform.

Presentation Type: Symposium Presentation
Session: SY05, Evolution, Development, and Genetics of Floral Display - Form, Size, and Arrangement
Location: Chatham Ballroom - B/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 8:45 AM
Number: SY05003
Abstract ID:472
Candidate for Awards:None