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Uncovering the interactions between deleterious mutations, divergent selection and migration
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Resumo(s)
Background selection (BGS) and associative overdominance (AOD) are processes describing the
effect of removal of deleterious mutations on linked neutral variation. Mathematical modelling and sim ulations predict that, in comparison to neutrality, BGS leads to reduced genetic diversity while AOD
leads to an increase, with greater effects in low recombining regions. However, little is known about
the impact of migration and hemizygosity (X-chromosomes or haplodiploid sex-determining system).
Moreover, studies about divergent selection with migration usually ignore deleterious mutations. The
objective of this thesis was to use simulations to predict genomic patterns of diversity and differenti ation resulting from the interaction between deleterious mutations, divergent selection, migration and
haplodiploidy. We used forward-in-time simulations under an isolation-with-migration model with two
populations, investigating variation in dominance, migration rate, recombination rate, and selective co efficients. To assess the impact of interactions between deleterious mutations and divergent selection,
we performed simulations according to the demographic history from two sister species of haplodiploid
Neodiprion sawflies to simulate a real-life based model.
We found that the pattern of variation of the ratio of within population nucleotide diversity over its
neutral expectation (π/πneutral) as a function of deleterious selective coefficient is only slightly influenced
by gene flow. However, the ratio of between population differentiation (FST /FSTneutral) becomes closer to
1 as migration rate increases, suggesting a migration threshold above which linked selection has no
effect on FST . We found a lower migration threshold for genomic regions under BGS than AOD. For
fully and partially recessive deleterious mutations we discovered a transition between AOD and BGS as
selective coefficients increased, both with and without migration. Finally, we introduce predictions for
the genomic patterns of haplodiploid populations experiencing divergent selection and asymmetric gene
flow.
Descrição
Tese de mestrado, Biologia Evolutiva e do Desenvolvimento, Universidade de Lisboa, Faculdade de Ciências, 2022
Palavras-chave
Background Selection Associative Overdominance Mutações Deletérias Fluxo Génico Seleção Divergente Teses de mestrado - 2022