Evolution of Multicellularity and Cellular Differentiation in the Volvocine Algae

Persistent Link:
http://hdl.handle.net/10150/196054
Title:
Evolution of Multicellularity and Cellular Differentiation in the Volvocine Algae
Author:
Herron, Matthew David
Issue Date:
2009
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 evolution of multicellularity is an example of an evolutionary transition in individuality, in which a group of lower-level biological units (cells, in this case) emerges as a higher-level unit (the multicellular organism) with its own fitness, heritability and individuality. The volvocine green algae are a model system for the transition to multicellularity and for the evolution of cellular differentiation. Some of the developmental changes that collectively make up this transition have occurred more than once in the volvocine lineage; others have reverted from derived to ancestral states. The transition from cells to multicellular organisms began over 200 million years ago in this lineage, and the subsequent changes have been sporadic, with several important changes occurring early in the transition and some body plans remaining largely unchanged over long evolutionary time scales. Two suites of characters that differ among species within the genus Volvox have each evolved convergently or in parallel in lineages that diverged at least 175 million years ago. This complex history suggests that other origins of multicellularity may have involved important roles for cooperation, conflict and conflict mediation; parallel evolution of some traits; sporadic rather than constant change; and long-term coexistence of forms with different levels of complexity. Data from one species, Pleodorina starrii, support motility as a major selective pressure driving the the origins of cellular differentiation. Optimization of the proportion of soma in this species appears to be prevented by a constraint that prevents independent change in colonies with different numbers of cells. Finally, P. starrii presents an exceptionally high level of phenotypic variability, suggesting that the genotype-phenotype map has not completely shifted from the cell to the colony and that the transition to a new, higher-level individual in this species is incomplete.
Type:
text; Electronic Dissertation
Keywords:
development; evolution; individuality; multicellularity; phylogenetics; Volvox
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Ecology & Evolutionary Biology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Michod, Richard E.; Ferriere, Regis
Committee Chair:
Michod, Richard E.; Ferriere, Regis

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleEvolution of Multicellularity and Cellular Differentiation in the Volvocine Algaeen_US
dc.creatorHerron, Matthew Daviden_US
dc.contributor.authorHerron, Matthew Daviden_US
dc.date.issued2009en_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 evolution of multicellularity is an example of an evolutionary transition in individuality, in which a group of lower-level biological units (cells, in this case) emerges as a higher-level unit (the multicellular organism) with its own fitness, heritability and individuality. The volvocine green algae are a model system for the transition to multicellularity and for the evolution of cellular differentiation. Some of the developmental changes that collectively make up this transition have occurred more than once in the volvocine lineage; others have reverted from derived to ancestral states. The transition from cells to multicellular organisms began over 200 million years ago in this lineage, and the subsequent changes have been sporadic, with several important changes occurring early in the transition and some body plans remaining largely unchanged over long evolutionary time scales. Two suites of characters that differ among species within the genus Volvox have each evolved convergently or in parallel in lineages that diverged at least 175 million years ago. This complex history suggests that other origins of multicellularity may have involved important roles for cooperation, conflict and conflict mediation; parallel evolution of some traits; sporadic rather than constant change; and long-term coexistence of forms with different levels of complexity. Data from one species, Pleodorina starrii, support motility as a major selective pressure driving the the origins of cellular differentiation. Optimization of the proportion of soma in this species appears to be prevented by a constraint that prevents independent change in colonies with different numbers of cells. Finally, P. starrii presents an exceptionally high level of phenotypic variability, suggesting that the genotype-phenotype map has not completely shifted from the cell to the colony and that the transition to a new, higher-level individual in this species is incomplete.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectdevelopmenten_US
dc.subjectevolutionen_US
dc.subjectindividualityen_US
dc.subjectmulticellularityen_US
dc.subjectphylogeneticsen_US
dc.subjectVolvoxen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineEcology & Evolutionary Biologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMichod, Richard E.en_US
dc.contributor.advisorFerriere, Regisen_US
dc.contributor.chairMichod, Richard E.en_US
dc.contributor.chairFerriere, Regisen_US
dc.contributor.committeememberCushing, Jimen_US
dc.contributor.committeememberDavidowitz, Goggyen_US
dc.contributor.committeememberWalsh, Bruceen_US
dc.identifier.proquest10733en_US
dc.identifier.oclc659753545en_US
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