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Establishment of Locally Adapted Mutations Under Divergent Selection.

ABSTRACT: We study the establishment probabilities of locally adapted mutations using a multi-type branching process framework. We find a surprisingly simple and intuitive analytical approximation for the establishment probabilities in a symmetric two-deme model under the assumption of weak (positive) selection. This is the first analytical closed-form approximation for arbitrary migration rate to appear in the literature. We find that the establishment probability lies between the weak and the strong migration limits if we condition the origin of the mutation to the deme where it is advantageous. This is not the case when we condition the mutation to first occur in a deme where it is disadvantageous. In this case we find that an intermediate migration rate maximizes the probability of establishment. We extend our results to the cases of multiple demes, two demes with asymmetric rates of gene flow, and asymmetric carrying capacities. The latter case allows us to illustrate how density regulation can affect establishment probabilities. Finally, we use our results to investigate the role of gene flow on the rate of local adaptation and identify cases in which intermediate amounts of gene flow facilitate the rate of local adaptation as compared to two populations without gene flow.

SUBMITTER: Tomasini M

PROVIDER: S-EPMC6028263 | biostudies-other | 2018 Jul

REPOSITORIES: biostudies-other

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Establishment of Locally Adapted Mutations Under Divergent Selection.

Tomasini Matteo M Peischl Stephan S

Genetics 20180517 3

We study the establishment probabilities of locally adapted mutations using a multi-type branching process framework. We find a surprisingly simple and intuitive analytical approximation for the establishment probabilities in a symmetric two-deme model under the assumption of weak (positive) selection. This is the first analytical closed-form approximation for arbitrary migration rate to appear in the literature. We find that the establishment probability lies between the weak and the strong mig ...[more]

PMID: 29773560

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Project description:BackgroundMitochondrial DNA (mtDNA) is frequently used in population genetic studies and is usually considered as a neutral marker. However, given the functional importance of the proteins encoded by the mitochondrial genome, and the prominent role of mitochondria in cellular energy production, the assumption of neutrality is increasingly being questioned.ResultsWe tested for evidence of selection on the mitochondrial genome of the Atlantic salmon, which is a locally adapted and widely farmed species and is distributed across a large latitudinal cline. We analysed 20 independent regions of the salmon mtDNA that represented nine genes (ND1, ND2, ND3, COX1, COX2, ATP6, ND4, ND5, and CYTB). These 20 mtDNA regions were sequenced using a 454 approach from samples collected across the entire European range of this species. We found evidence of positive selection at the ND1, ND3 and ND4 genes, which is supported by at least two different codon-based methods and also by differences in the chemical properties of the amino acids involved. The geographical distribution of some of the mutations indicated to be under selection was not random, and some mutations were private to artic populations. We discuss the possibility that selection acting on the Atlantic salmon mtDNA genome might be related to the need for increased metabolic efficiency at low temperatures.ConclusionsThe analysis of sequences representing nine mitochondrial genes that are involved in the OXPHOS pathway revealed signatures of positive selection in the mitochondrial genome of the Atlantic salmon. The properties of the amino acids involved suggest that some of the mutations that were identified to be under positive selection might have functional implications, possibly in relation to metabolic efficiency. Experimental evidence, and better understanding of regional phylogeographic structuring, are needed to clarify the potential role of selection acting on the mitochondrial genome of Atlantic salmon and other locally adapted fishes.

Dataset Information

Establishment of Locally Adapted Mutations Under Divergent Selection.

Publications

Establishment of Locally Adapted Mutations Under Divergent Selection.

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