Evolutionary Genetics of Dictyostelids: Cryptic Species, Sociality and Sex

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dc.contributor.advisorStrassmann, Joan E.en_US
dc.creatorKalla, Sara Edithen_US
dc.date.accessioned2013-03-08T00:34:53Zen_US
dc.date.available2013-03-08T00:34:53Zen_US
dc.date.issued2011en_US
dc.description.abstractDictyostelium discoideum serves as an ideal system to study social evolution because of the social stage of its lifecycle, where individuals aggregate to build a multicellular structure. However, much of its basic biology remains unknown and this limits its utility. I used three separate projects to fill these gaps. In my first project, I examined how speciation and genetic diversity affects kin discrimination using a related dictyostelid, Polysphondylium violaceum . I sequenced the ribosomal DNA of 90 clones of P. violaceum and found that P. violaceum is split into several morphologically identical groups. When allowed to cooperate in pairwise mixes, I found that some clones cooperated with others in their group, but in mixes between groups, clones did not cooperate. For my second project, I looked at whether D. discoideum has sex in natural populations. While sex has been observed in laboratory clones of D. discoideum , it is unclear whether sex occurs in natural populations, and sex can influence the evolution of traits. I used a dataset of microsatellites in 24 clones of D. discoideum to look for a decrease in linkage disequilibrium as a molecular sign of sex. Linkage disequilibrium is higher between physically close loci than between loci on different chromosomes. From this, I conclude that D. discoideum undergoes recombination in nature. Lastly, I used the genome sequence of D. discoideum to look at large scale patterns of evolution. Mutations tend to be biased towards A/T from G/C so, on average, mutations should lower the nucleotide content of sequences. The removal of these mutations, purifying selection, should preserve nucleotide content. I used the genomes of D. discoideum and Plasmodium falciparum identify classes of sequences that should be under different amounts of purifying selection and compared their nucleotide contents. In all cases, those sequences under more purifying selection had higher GC contents than sequences under less purifying selection. Looking at relative nucleotide content may thus serve as an indicator purifying selection. These three studies add insight on how cooperation works in dictyostelids as well as adding an understanding of how traits, social and otherwise, would evolve in this system.en_US
dc.format.extent122 p.en_US
dc.format.mimetypeapplication/pdfen_US
dc.identifier.citationKalla, Sara Edith. "Evolutionary Genetics of Dictyostelids: Cryptic Species, Sociality and Sex." (2011) Diss., Rice University. <a href="https://hdl.handle.net/1911/70286">https://hdl.handle.net/1911/70286</a>.en_US
dc.identifier.digitalKallaSen_US
dc.identifier.urihttps://hdl.handle.net/1911/70286en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.subjectBiological sciencesen_US
dc.subjectDictyostelidsen_US
dc.subjectCryptic speciesen_US
dc.subjectSpeciationen_US
dc.subjectEvolution & developmenten_US
dc.titleEvolutionary Genetics of Dictyostelids: Cryptic Species, Sociality and Sexen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentEcology and Evolutionary Biologyen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.nameDoctor of Philosophyen_US
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