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Abstract Detail


Hancock, Lillian [1], Edwards, Erika [2].

A new look at an old method for isotopically characterizing low-level CAM activity.

Most important organismal adaptations are not actually single traits, but complex trait syndromes that are evolutionarily integrated into a single ‘emergent’ phenotype. Two alternative photosynthetic pathways, C4 photosynthesis and Crassulacean Acid Metabolism (CAM), are primary plant adaptations of this sort, each requiring multiple biochemical and anatomical modifications. Phylogenetic methods are a promising approach for teasing apart the order of character acquisition during the evolution of complex traits, and the phylogenetic placement of intermediate phenotypes as sister taxa to fully optimized syndromes has been taken as good evidence of an ‘ordered’ evolutionary trajectory. But how much power does the phylogenetic approach have to detect ordered evolution? In this study, we simulated ordered and unordered character evolution across a diverse set of phylogenetic trees to understand how tree size, models of evolution, and sampling efforts influence our ability to detect an evolutionary trajectory. We find that small trees (15 taxa) do not contain enough information to correctly infer either an ordered or unordered trajectory, though inference improves as tree size and sampling increases. However, even when working with a 1000-taxon tree, the possibility of inferring the incorrect evolutionary model (type I/ type II error) remains. We urge caution in interpreting the phylogenetic placement of intermediate phenotypes, especially in small lineages. Such patterns can provide a line of evidence for the existence of a particular evolutionary trajectory, but they should be coupled with other types of data to infer the stepwise evolution of a complex character trait.

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1 - Brown University, Ecology and Evolutionary Biology, 80 Waterman St., Box G-W, Providence, Rhode Island, 02912, United States
2 - Brown University, Box G-W, 80 Waterman St, Providence, RI, 02912, USA

Intermediate phenotypes
CAM photosynthesis

Presentation Type: Poster:Posters for Topics
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PEP011
Abstract ID:211
Candidate for Awards:Genetics Section Poster Award

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