A HYDRODYNAMICS APPROACH TO THE EVOLUTION OF MULTICELLULARITY: FLAGELLAR MOTILITY AND THE EVOLUTION OF GERM-SOMA DIFFERENTIATION IN VOLVOCALEAN GREEN ALGAE

Persistent Link:
http://hdl.handle.net/10150/194798
Title:
A HYDRODYNAMICS APPROACH TO THE EVOLUTION OF MULTICELLULARITY: FLAGELLAR MOTILITY AND THE EVOLUTION OF GERM-SOMA DIFFERENTIATION IN VOLVOCALEAN GREEN ALGAE
Author:
Solari, Cristian Alejandro
Issue Date:
2005
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 fitness of any evolutionary unit can be understood in terms of its two basic components: fecundity and viability. The trade-offs between these fitness components drive the evolution of a variety of life-history traits in extant multicellular lineages. Here, I show evidence that the evolution of germ-soma separation and the emergence of individuality at a higher level during the unicellular-multicellular transition are also consequences of these trade-offs. The transition from unicellular to larger multicellular organisms has benefits, costs, and requirements. I argue that germ-soma separation evolved as a means to counteract the increasing costs and requirements of larger multicellular colonies. Volvocalean green algae are uniquely suited for studying this transition since they range from unicells to undifferentiated colonies, to multicellular individuals with complete germ-soma separation. In these flagellated organisms, the increase in cell specialization observed as colony size increases can be explained in terms of increased requirements for self-propulsion and to avoid sinking. The collective flagellar beating also serves to enhance molecular transport of nutrients and wastes. Standard hydrodynamic measurements and concepts are used to analyze motility (self-propulsion) and its consequences for different degrees of cell specialization in the Volvocales as colony size increases. This approach is used to calculate the physical hydrodynamic limits on motility to the spheroid colony design. To test the importance of collective flagellar beating on nutrient uptake, the effect of advective dynamics on the productivity of large colonies is quantified. I conclude first, that when colony size exceeds a threshold, a specialized and sterile soma must evolve, and the somatic to reproductive cell ratio must increase as colony size increases to keep colonies buoyant and motile. Second, larger colonies have higher motility capabilities with increased germ-soma specialization due to an enhancement of colony design. Third, advection has a significant effect on the productivity of large colonies. And fourth, there are clear trade-offs between investing in reproduction, increasing colony size (i.e. colony radius), and motility. This work shows that the evolution of cell specialization is the expected outcome of reducing the cost of reproduction in order to realize the benefits associated with increasing size.
Type:
text; Electronic Dissertation
Keywords:
cost of reproduction; hydrodynamics; body size; cell specialization; motility; Volvox
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Ecology & Evolutionary Biology; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Michod, Richard E.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleA HYDRODYNAMICS APPROACH TO THE EVOLUTION OF MULTICELLULARITY: FLAGELLAR MOTILITY AND THE EVOLUTION OF GERM-SOMA DIFFERENTIATION IN VOLVOCALEAN GREEN ALGAEen_US
dc.creatorSolari, Cristian Alejandroen_US
dc.contributor.authorSolari, Cristian Alejandroen_US
dc.date.issued2005en_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 fitness of any evolutionary unit can be understood in terms of its two basic components: fecundity and viability. The trade-offs between these fitness components drive the evolution of a variety of life-history traits in extant multicellular lineages. Here, I show evidence that the evolution of germ-soma separation and the emergence of individuality at a higher level during the unicellular-multicellular transition are also consequences of these trade-offs. The transition from unicellular to larger multicellular organisms has benefits, costs, and requirements. I argue that germ-soma separation evolved as a means to counteract the increasing costs and requirements of larger multicellular colonies. Volvocalean green algae are uniquely suited for studying this transition since they range from unicells to undifferentiated colonies, to multicellular individuals with complete germ-soma separation. In these flagellated organisms, the increase in cell specialization observed as colony size increases can be explained in terms of increased requirements for self-propulsion and to avoid sinking. The collective flagellar beating also serves to enhance molecular transport of nutrients and wastes. Standard hydrodynamic measurements and concepts are used to analyze motility (self-propulsion) and its consequences for different degrees of cell specialization in the Volvocales as colony size increases. This approach is used to calculate the physical hydrodynamic limits on motility to the spheroid colony design. To test the importance of collective flagellar beating on nutrient uptake, the effect of advective dynamics on the productivity of large colonies is quantified. I conclude first, that when colony size exceeds a threshold, a specialized and sterile soma must evolve, and the somatic to reproductive cell ratio must increase as colony size increases to keep colonies buoyant and motile. Second, larger colonies have higher motility capabilities with increased germ-soma specialization due to an enhancement of colony design. Third, advection has a significant effect on the productivity of large colonies. And fourth, there are clear trade-offs between investing in reproduction, increasing colony size (i.e. colony radius), and motility. This work shows that the evolution of cell specialization is the expected outcome of reducing the cost of reproduction in order to realize the benefits associated with increasing size.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectcost of reproductionen_US
dc.subjecthydrodynamicsen_US
dc.subjectbody sizeen_US
dc.subjectcell specializationen_US
dc.subjectmotilityen_US
dc.subjectVolvoxen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineEcology & Evolutionary Biologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairMichod, Richard E.en_US
dc.contributor.committeememberNedelcu, Auroraen_US
dc.contributor.committeememberKessler, Johnen_US
dc.contributor.committeememberHuxman, Travisen_US
dc.contributor.committeememberEnquist, Brianen_US
dc.identifier.proquest1165en_US
dc.identifier.oclc659747443en_US
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