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Phylogenetics, morphology, and genomic evolution in Physarieae (Brassicaceae)

Posted on:2011-12-10Degree:Ph.DType:Dissertation
University:University of Missouri - Saint LouisCandidate:Fuentes-Soriano, SaraFull Text:PDF
GTID:1440390002450626Subject:Evolution & development
Abstract/Summary:
The mustard family (Brassicaceae) is economically important but the evolution of its morphology is not well understood. I investigate the evolution of morphological and genomic characters and calculate ancestral trait values in the Brassicaceae within a phylogenetic context using the tribe Physarieae as a model system. Physarieae are a unique and diverse group of American mustards characterized by multi-aperturate pollen. Phylogenetic analyses of DNA sequences (chloroplast ndhF and nuclear ITS and LUMINIDEPENDENS) were used to test the monophyly and explore evolutionary relationships of Physarieae. The phylogenetic inferences were used to identify morphological traits to delimit the tribe, to interpret the evolution of selected morphological and genomic characters, and to test alternative hypotheses related to the covariation of traits.;Results show that Physarieae are monophyletic and most closely related to three tribes (Halimolobeae, Boechereae, Camelineae) based on analyses of parsimony, likelihood, and Bayesian analyses. Two well-supported monophyletic clades in the tribe are recovered: the DDNLS clade, including Dithyrea, Dimorphocarpa, Nerisyrenia, Lyrocarpa, and Synthlipsis, and the PP clade, comprising Paysonia and Physaria . Character optimization of discrete and continuous morphological data suggest that enlarged fruits and replums, wide seeds, and long fruiting styles are potential synapomorphies of Physariae, whereas traits related to fruits, seed, trichomes, and pollen are useful to distinguish groups and genera within the tribe. Levels of phylogenetic signal, estimated by Bayesian methods, vary from being strong to almost absent across the different traits studied here. Modes of trait evolution are mostly consistent with a gradual model, but a few characters fit best with models of punctuated evolution (fruit width, replum shape, pollen size). Historically, rates of trait evolution were mostly constant, except for the rapid and recent evolution of replum shape, seed number, pollen size, and chromosome number. Although the fruit as a single organ reflects developmental and functional integration of separate elements, its individual components can evolve at different rates and modes. Change in pollen size and seed number is predominantly directional. Genome size and nucleotide composition have increased gradually and constantly according to a Brownian motion model, and more significantly than in any other tribe of the Brassicaceae. Phylogenetically-informed regression analyses identify several positively correlated characters: fruit size-seed abundance, chromosome size-genome size, and GC% content-genome size. These findings when considered altogether, lead to a better understanding of the patterns of morphological and genetic diversity within Physarieae, and allow the effects of correlated evolution and related hypotheses based on theoretical and experimental expectations to be identified for further study.
Keywords/Search Tags:Evolution, Brassicaceae, Physarieae, ITS, Phylogenetic, Genomic, Related
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