Abstract Detail

Macroevolution

Martinez-Gomez, Jesus  [1], Specht, Chelsea [2].

Phylogenetic Comparative Method illuminates Macroevolutionary origin of the Amaryllidaceae Umbel.

As sessile organism, plants have achieved unique methods of locomotion-free fertilization and seed dispersal. The placement of the flowers along the axis of a plant is one such method, as it influences pollinator attraction, pollen deposition, and seed scattering or diffusion. The arrangement of flowers is determined by a high specialized floral branch, the inflorescence. While inflorescent architecture has been topologically described and model based simulations have predicted a diversity of architectures, most studies are ahistorical - lacking a phylogenetic framework to understand biological diversity – and not all forms have been predicted. This has inhibited our understanding of the development of inflorescence morphology through evolutionary time. In order to investigate the macroevolutionary origins of inflorescence architectural diversity, we assess an inflorescence type not predicted by many contemporary models: the Amaryllidaceae umbel. Umbels are traditional described as all flowers arising from a single point. Multiple evolutionary hypotheses explain the evolutionary origin of the umbel, with the ancestral form being either (1) a cymose lateral branch, as proposed by the Bravis brothers for Amaryllidaceae, (2) a dichasial branch or (3) a racemose branch, the classic hypothesis as articulated by Stebbins. In order to address the trajectory of inflorescence evolution that gave rise to the Amaryllidaceae umbel, we use a comparative phylogenetic framework to test models of phenotypic evolution and infer ancestral states. Descriptions of adult inflorescence morphology at the generic level was obtained from members of Amaryllidaceae, Asparagaceae and Asphodelaceae. A molecular phylogeny containing members of all three clades was constructed based on published sequence data using Bayesian inference. Competing evolutionary hypotheses were formalized as Continuous-Time Markov Models and were fit to a posterior distribution of possible phylogenies for parameter estimation in a Markov Chain Monte Carlo framework. This approach takes into account uncertainty in phylogenetic inference and allows for model-fit comparison through Bayes Factors in an attempt to infer probabilities for ancestral states. This study provides insights into the evolutionary mode of inflorescence architectural diversity and complements current model-based simulation approaches by explicitly accounting for phylogeny.

1 - University of California Berkeley, Integrative Biology, Berkeley, CA, United States
2 - Cornell University, Ithaca, NY, USA

Keywords:
Macroevolution
Inflorescence development
RevBayes
Trait Evolution.

Presentation Type: Poster
Session: P, Macroevolution
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: PME001
Abstract ID:606
Candidate for Awards:None