Abstract Detail


Martinez-Gomez, Jesus  [1], Rose , Irving Jason [1], Freyman, William [2], Specht, Chelsea [1].

Where do umbels come from? Incorporating prior information of developmental genetics in trait evolution with the threshold model to generate more realistic models of morphological evolution.

Development constrains morphological evolution, shaping patterns of trait distribution across a phylogeny. However, current models of trait evolution do not account for prior knowledge of developmental processes. We investigate whether incorporating prior knowledge of development allows for more adequate and realistic models of evolution, using the flower branching architecture of the Amaryllis family (Amaryllidaceae) as a case study. The branching structure of Amaryllidaceae is characterized as an ‘umbel’ and multiple hypotheses based on comparative morphology have been proposed to explain its evolutionary origin. The hypothesis put forth by the Bravais brothers (1837) states that umbels in Amaryllidaceae are formed from condensation of a cymous structure based on developmental evidence . We collect data on mature inflorescence morphology from the botanical literature (e.g. morphological studies, species description). We infer the ancestral state of the Amaryllidaceae using two methods  (a) continuous time markov models (CTMM) commonly used to model categorical morphological traits and (b) the threshold model in which the discrete state of the trait is determined by an unobserved continuous "liability" with thresholds a priori informed by an independent morphospace analysis of branching architecture. Ancestral state reconstruction under CTMM unexpectedly infers a raceme-derived origin of the umbel in contrast to the Bravais hypothesis. Ancestral inference under the threshold model contains too much uncertainty to resolve the ancestral node. We discuss the role of model based approaches in studying complex trait evolution, and how incorporating data from developmental genetics and morphology may lead toward more realistic models of morphological trait evolution.

1 - Cornell University, School of Integrative Plant Science and L.H. Bailey Hortorium, 502 Mann Library, Ithaca, NY, 14850, USA
2 - University Of California Berkeley, University Herbarium And Departmenty Of Integrative Biology, 1001 Valley Life Science Building, Berkeley, CA, 94720, United States

Threshold Model
ancestral state reconstruction
phylogenetic comparative methods
statistical phylogenetics.

Presentation Type: Oral Paper
Number: MACRO1002
Abstract ID:771
Candidate for Awards:None

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