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Abstract Detail

Molecular Ecology and Evolution

Schneeweiss, Gerald M. [1], Blöch, Cordula [2], Stuessy, Tod F. [2], Schneeweiss, Hanna [2].

Chromosome base number evolution in Melampodium (Asteraceae): a comparison of methods.

Chromosome number changes by polyploidy, i.e., duplication of whole chromosome sets, and dysploidy, i.e., chromosome base number reduction/increase without change in genetic content due to, e.g., chromosome fusion, are recognized as major factors contributing to plant diversification and speciation. Here, we focus on chromosome number evolution via dysploidy in the mainly Central American genus Melampodium (Millerieae, Asteracaeae), whose 40 species exhibit a wide array of different chromosome base numbers including x = 9, 10, 11, 12, 14, and 23. Focusing on the diploid species, we apply several approaches (maximum parsimony, maximum likelihood including an only recently developed method specifically aimed at chromosome number evolution, and different Bayesian methods) on phylogenetic hypotheses derived from nuclear and plastid data (ITS, matK) and assess the influence of two hypotheses on our inferences, namely that chromosome number evolution is proportional to genetic change or to time, respectively. Our aims are to test the hypotheses that (i) the ancestral chromosome base number of Melampodium is x = 10 and that (ii) descending dysploidy prevails over ascending dysploidy.

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1 - University of Vienna, Department of Biogeography, Rennweg 14, Vienna, Vienna, A-1030, Austria
2 - University of Vienna, Department of Systematic and Evolutionary Botany, Rennweg 14, Vienna, A-1030, Austria

ascending dysploidy
descending dysploidy
character evolution

Presentation Type: Oral Paper:Papers for Topics
Session: 46
Location: 552A/Convention Center
Date: Wednesday, August 4th, 2010
Time: 8:15 AM
Number: 46002
Abstract ID:296

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