Phylogenetic relationships of basal monocots and the evolution of genome size.

Persistent Link:
http://hdl.handle.net/10150/186567
Title:
Phylogenetic relationships of basal monocots and the evolution of genome size.
Author:
Bharathan, Geeta.
Issue Date:
1993
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The diversification of monocotyledons into major lines, and the evolution of genome size have been studied in this work. The diversification of major lineages of monocots was examined through the phylogenetic analysis of morphological and molecular data. Data on genome sizes were collected and assessed in the context of these hypotheses of relationships. Parsimony analyses of morphological and rDNA sequence data suggest that there are three major groups within monocots: "Liliiflorae," the Alismatid-Aroid group, and a group of derived monocots, "eumonocots". The morphological data suggest that "Liliiflorae" is basal and paraphyletic, and Dioscoreales is one of the earliest branches. However, molecular data suggest a basal bifurcation into the Alismatiflorae-Araceae and the Liliiflorae-"eumonocot" lineages. According to molecular data, Acorus is linked with Piperales, an anomalous position. In morphological analyses it is in a traditional position in the Alismatid-Aroid clade. Different types of exploratory analyses led to the assessment that support for both hypotheses is relatively weak. The overall conclusion is that studies of the evolutionary history of monocots are preliminary in nature. Much needs to be done, in collecting more information on little known taxa and characters, and in identifying new characters (both molecular and morphological), before conclusive statements can be made about monocot relationships. Genome sizes of paleoherb species were determined using flow-cytometry. The data were optimized under parsimony, on different hypotheses of monocot relationships. Despite disagreement among the different phylogenetic results, several conclusions can be made about the evolution of genome size in this group. There was no major increase in genome size during the evolution of monocots. The ancestral condition in most lineages is to have small genomes. Large genomes (2C > 18 pg) occur in only a few lines. Both substantial increases and decreases are noted within monocots. Phylogenetically based statistical tests showed that bisporic and tetrasporic embryo sacs tend to evolve in clades with large genomes. The mechanistic basis for this correlation is unknown. It is hypothesized that the developmental variation may be connected with variation in cell cycle and size, both of which are correlated with genome size.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Dissertations, Academic.; Molecular biology.; Botany.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Ecology and Evolutionary Biology; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Donoghue, Michael J.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titlePhylogenetic relationships of basal monocots and the evolution of genome size.en_US
dc.creatorBharathan, Geeta.en_US
dc.contributor.authorBharathan, Geeta.en_US
dc.date.issued1993en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe diversification of monocotyledons into major lines, and the evolution of genome size have been studied in this work. The diversification of major lineages of monocots was examined through the phylogenetic analysis of morphological and molecular data. Data on genome sizes were collected and assessed in the context of these hypotheses of relationships. Parsimony analyses of morphological and rDNA sequence data suggest that there are three major groups within monocots: "Liliiflorae," the Alismatid-Aroid group, and a group of derived monocots, "eumonocots". The morphological data suggest that "Liliiflorae" is basal and paraphyletic, and Dioscoreales is one of the earliest branches. However, molecular data suggest a basal bifurcation into the Alismatiflorae-Araceae and the Liliiflorae-"eumonocot" lineages. According to molecular data, Acorus is linked with Piperales, an anomalous position. In morphological analyses it is in a traditional position in the Alismatid-Aroid clade. Different types of exploratory analyses led to the assessment that support for both hypotheses is relatively weak. The overall conclusion is that studies of the evolutionary history of monocots are preliminary in nature. Much needs to be done, in collecting more information on little known taxa and characters, and in identifying new characters (both molecular and morphological), before conclusive statements can be made about monocot relationships. Genome sizes of paleoherb species were determined using flow-cytometry. The data were optimized under parsimony, on different hypotheses of monocot relationships. Despite disagreement among the different phylogenetic results, several conclusions can be made about the evolution of genome size in this group. There was no major increase in genome size during the evolution of monocots. The ancestral condition in most lineages is to have small genomes. Large genomes (2C > 18 pg) occur in only a few lines. Both substantial increases and decreases are noted within monocots. Phylogenetically based statistical tests showed that bisporic and tetrasporic embryo sacs tend to evolve in clades with large genomes. The mechanistic basis for this correlation is unknown. It is hypothesized that the developmental variation may be connected with variation in cell cycle and size, both of which are correlated with genome size.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academic.en_US
dc.subjectMolecular biology.en_US
dc.subjectBotany.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineEcology and Evolutionary Biologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairDonoghue, Michael J.en_US
dc.contributor.committeememberGalbraith, David W.en_US
dc.contributor.committeememberMcDade, Lucinda A.en_US
dc.contributor.committeememberKidwell, Margaret G.en_US
dc.identifier.proquest9421773en_US
dc.identifier.oclc721978257en_US
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