Abstract Detail

Systematics

Bukhari, Ghadeer [1], Zhang, Jingbo [2], Stevens, Peter [3], Zhang, Wenheng [4].

Floral symmetry and the evolution of floral characters in pentamerous and trimerous angiosperms.

The development of floral patterns in monocots was thought to be distinctively different from that in the Pentapetalae. For examples, the monocots usually have a single adaxial or lateral prophyll/bracteole while the Pentapetalae commonly have two lateral ones. The presence and position of prophyll/bracteole were considered to play a critical role in floral organ orientation in monocots but not so much in Pentapetalae. Here, we place the evolution of floral characters in a phylogenetic framework, mainly focusing on the influence of the bract and bracteoles on floral organ initiation and floral symmetry development. We analyzed patterns of floral organ initiation and floral symmetry, and presence and position of bract and bracteole, that we extracted from floral diagrams representing 49 orders, 178 families, and 566 taxa (405 pentamerous, 161 trimerous flowers) including basal angiosperms, magnoliids, monocots, and eudicots in the context of a phylogeny using ancestral state reconstructions. Our preliminary analyses indicated that the median-abaxial (MAB) petal/inner tepal initiation was the ancestral state of floral organ initiation in angiosperms. In monocots, two major shifts to the median-adaxial (MAD) initiation occurred in the most recent common ancestor (MRCA) of Asparagales + commelinids and the MRCA of the core Alismatales excluding Araceae and Tofieldiaceae. In eudicots, there were multiple shifts to the MAD initiation that agreed with our previous findings. Furthermore, the absence of bracts and bracteoles are ancestral in angiosperms. Bracts and bracteoles evolved three main times, in the MRCA of core eudicots, the MRCA of Liliales + Asparagales + commelinids (ambiguous for bracteoles), and the MRCA of Magnoliales + Laurales (ambiguous for bracteoles). Bracteoles were subsequently lost more frequently than bracts. Most importantly, we found a strong correlation between the presence of bracts and floral zygomorphy in angiosperms, suggesting that the bract is a key structure in promoting the origin and/or maintenance of floral zygomorphy. We demonstrate that comparative studies including both pentamerous and trimerous angiosperms are critical in revealing general patterns of floral development and evolution.

1 - Virginia Commonwealth University, 1000 W Cary Street, Richmond, VA, 23284.0, United States
2 - Department Of Biology, Virginia Commonwealth University, 1000 West Cary Street, Life Science Building 336, Richmond, VA, 23284, United States
3 - University of Missouri-St. Louis, Department of Biology, 1 University Blvd, St. Louis, MO, 63121, USA
4 - Virginia Commonwealth University, Department Of Biology, 1000 W Cary Street, Richmond, VA, 23284, United States

Keywords:
monocots
eudicots
Trimerous
Pentamerous
Bract
Bracteole
Floral zygomorphy
floral symmetry
phylogeny
Ancestral state reconstruction
floral morphology
Floral organ initiation
homoplasy
angiosperms
Pentapetalae
Prophyll
Magnoliids.

Presentation Type: Poster
Session: P, Systematics
Location: Grand Ballroom - Exhibit Hall/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 5:30 PM This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PSY031
Abstract ID:853
Candidate for Awards:None