In English

Dynamics of sex ratio and genetics in populations with mixed sexual and asexual reproduction

johan fries
Göteborg : Chalmers tekniska högskola, 2014.
[Examensarbete på avancerad nivå]

Biological populations that reproduce both sexually and asexually are frequent in nature. An example is the brown algae Fucus radicans that is endemic to the Baltic Sea and reproduces both sexually and through cloning. This species displays intriguing patterns of sex ratio and genetic diversity. A speci c female genotype, sometimes referred to as the superfemale [I], is widespread and dominates in large regions [1]. Perhaps surprisingly, comprehensive experiments where plants have been cultivated in vitro show no sign of the superfemale having a higher tness than other genotypes [2]. How a joint e ect of sexual and asexual reproduction a ects this species is not fully explored, and the research could bene t from a better understanding of the consequences of this reproductive strategy. Within this master's thesis, two models for a population with mixed sexual and asexual reproduction and neutral genetics have been developed and explored. One model describes a well-mixed population, and the other a spatially structured one. Based on the results obtained for these models, we argue that populations with both reproduction types have a tendency to adopt a certain sex ratio. We nd that geographic structure favors asexual reproduction and enables one genotype without selective advantages to colonize empty habitat through cloning. This mechanism provides a clonal wave that could explain the dominating female observed in F. radicans. In the long run and if sexual reproduction is high enough, this dominant clone will be replaced by a pattern of mixed genotypes as a second sexual wave establishes sexual reproduction. Fluctuations counteract the e ect of the sexual wave and may cause the population to consist of local clonal islands of only one sex, surrounded by regions where sexual reproduction persists. We explore the question whether the mechanisms provided in the models can explain the patterns observed in F. radicans populations.



Publikationen registrerades 2015-01-27.

CPL ID: 211546

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