The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Joachim Hermisson - One of the best experts on this subject based on the ideXlab platform.
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the limits to Parapatric Speciation 3 evolution of strong reproductive isolation in presence of gene flow despite limited ecological differentiation
Philosophical Transactions of the Royal Society B, 2020Co-Authors: Joachim Hermisson, Alexandre Blanckaert, Claudia BankAbstract:Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connec...
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the limits to Parapatric Speciation 3 evolution of strong reproductive isolation in presence of gene flow despite limited ecological differentiation
bioRxiv, 2020Co-Authors: Alexandre Blanckaert, Claudia Bank, Joachim HermissonAbstract:Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connected by gene flow. We consider two selective mechanisms for the creation and maintenance of a genetic barrier: local adaptation leads to divergence among incipient species due to selection against migrants, and Dobzhansky-Muller incompatibilities (DMIs) reinforce the genetic barrier through selection against hybrids. In particular, we are interested in the maximum strength of the barrier under a limited amount of local adaptation, a challenge that may initially face many incipient species. We first confirm that with classical two-locus DMIs, the maximum amount of local adaptation is indeed a limit to the strength of a genetic barrier. However, with three or more loci and cryptic epistasis, this limit holds no longer. In particular, we identify a minimal configuration of three epistatically interacting mutations that is sufficient to confer strong reproductive isolation.
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the limits to Parapatric Speciation ii strengthening a preexisting genetic barrier to gene flow in parapatry
Genetics, 2018Co-Authors: Joachim Hermisson, Alexandre BlanckaertAbstract:By encompassing the whole continuum between allopatric and sympatric scenarios, Parapatric Speciation includes many potential scenarios for the evolution of new species. Here, we investigate how a genetic barrier to gene flow, that relies on a single postzygotic genetic incompatibility, may further evolve under ongoing migration. We consider a continent island model with three loci involved in pairwise Dobzhansky–Muller incompatibilities (DMIs). Using an analytic approach, we derive the conditions for invasion of a new mutation and its consequences for the strength and stability of the initial genetic barrier. Our results show that the accumulation of genetic incompatibilities in the presence of gene flow is under strong selective constraints. In particular, preexisting incompatibilities do not always facilitate the invasion of further barrier genes. If new mutations do invade, they will often weaken or destroy the barrier rather than strengthening it. We conclude that migration is highly effective at disrupting the so-called “snowball effect”, the accelerated accumulation of DMIs that has been described for allopatric populations en route to reproductive isolation.
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the limits to Parapatric Speciation ii strengthening a preexisting genetic barrier to gene flow in parapatry
bioRxiv, 2018Co-Authors: Alexandre Blanckaert, Joachim HermissonAbstract:Parapatric Speciation has recently received a lot of attention. By encompassing the whole continuum between allopatric and sympatric scenarios, it includes many potential scenarios for the evolution of new species. Building upon previous work, we investigate how a genetic barrier to gene flow, that relies on a single postzygotic genetic incompatibility, may further evolve. We consider a continent island model with three loci involved in pairwise Dobzhansky-Muller incompatibilities (DMIs). Using a deterministic and analytic approach, we derive the conditions for invasion of a new mutation and its consequences on an already existing genetic barrier to gene flow. We focus on quantifying the impact of the epistasis generated by the new mutation on the genetic barrier. We show that the accumulation of genetic incompatibilities in the presence of gene flow is a complex process, where new mutations can either strengthen or destroy a preexisting barrier. In particular, preexisting polymorphism and incompatibilities do not always facilitate the growth of the genetic barrier by accumulation of further barrier genes. Migration may disrupt the snowball effect (the accelerating rate of DMI accumulation in allopatry) because incompatibilities are directly tested by selection. Our results also show an ambiguous role of gene flow, which can either impede or facilitate the strengthening of the genetic barrier. Overall, our results illustrate how the inclusion of gene flow renders the building of a genetic barrier difficult to analyze.
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bounds to Parapatric Speciation a dobzhansky muller incompatibility model involving autosomes x chromosomes and mitochondria
Evolution, 2017Co-Authors: Ilse Hollinger, Joachim HermissonAbstract:We investigate the conditions for the origin and maintenance of postzygotic isolation barriers, so called (Bateson-)Dobzhansky–Muller incompatibilities or DMIs, among populations that are connected by gene flow. Specifically, we compare the relative stability of pairwise DMIs among autosomes, X chromosomes, and mitochondrial genes. In an analytical approach based on a continent-island framework, we determine how the maximum permissible migration rates depend on the genomic architecture of the DMI, on sex bias in migration rates, and on sex-dependence of allelic and epistatic effects, such as dosage compensation. Our results show that X-linkage of DMIs can enlarge the migration bounds relative to autosomal DMIs or autosome-mitochondrial DMIs, in particular in the presence of dosage compensation. The effect is further strengthened with male-biased migration. This mechanism might contribute to a higher density of DMIs on the X chromosome (large X-effect) that has been observed in several species clades. Furthermore, our results agree with empirical findings of higher introgression rates of autosomal compared to X-linked loci.
Alexandre Blanckaert - One of the best experts on this subject based on the ideXlab platform.
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the limits to Parapatric Speciation 3 evolution of strong reproductive isolation in presence of gene flow despite limited ecological differentiation
Philosophical Transactions of the Royal Society B, 2020Co-Authors: Joachim Hermisson, Alexandre Blanckaert, Claudia BankAbstract:Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connec...
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the limits to Parapatric Speciation 3 evolution of strong reproductive isolation in presence of gene flow despite limited ecological differentiation
bioRxiv, 2020Co-Authors: Alexandre Blanckaert, Claudia Bank, Joachim HermissonAbstract:Gene flow tends to impede the accumulation of genetic divergence. Here, we determine the limits for the evolution of postzygotic reproductive isolation in a model of two populations that are connected by gene flow. We consider two selective mechanisms for the creation and maintenance of a genetic barrier: local adaptation leads to divergence among incipient species due to selection against migrants, and Dobzhansky-Muller incompatibilities (DMIs) reinforce the genetic barrier through selection against hybrids. In particular, we are interested in the maximum strength of the barrier under a limited amount of local adaptation, a challenge that may initially face many incipient species. We first confirm that with classical two-locus DMIs, the maximum amount of local adaptation is indeed a limit to the strength of a genetic barrier. However, with three or more loci and cryptic epistasis, this limit holds no longer. In particular, we identify a minimal configuration of three epistatically interacting mutations that is sufficient to confer strong reproductive isolation.
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the limits to Parapatric Speciation ii strengthening a preexisting genetic barrier to gene flow in parapatry
Genetics, 2018Co-Authors: Joachim Hermisson, Alexandre BlanckaertAbstract:By encompassing the whole continuum between allopatric and sympatric scenarios, Parapatric Speciation includes many potential scenarios for the evolution of new species. Here, we investigate how a genetic barrier to gene flow, that relies on a single postzygotic genetic incompatibility, may further evolve under ongoing migration. We consider a continent island model with three loci involved in pairwise Dobzhansky–Muller incompatibilities (DMIs). Using an analytic approach, we derive the conditions for invasion of a new mutation and its consequences for the strength and stability of the initial genetic barrier. Our results show that the accumulation of genetic incompatibilities in the presence of gene flow is under strong selective constraints. In particular, preexisting incompatibilities do not always facilitate the invasion of further barrier genes. If new mutations do invade, they will often weaken or destroy the barrier rather than strengthening it. We conclude that migration is highly effective at disrupting the so-called “snowball effect”, the accelerated accumulation of DMIs that has been described for allopatric populations en route to reproductive isolation.
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the limits to Parapatric Speciation ii strengthening a preexisting genetic barrier to gene flow in parapatry
bioRxiv, 2018Co-Authors: Alexandre Blanckaert, Joachim HermissonAbstract:Parapatric Speciation has recently received a lot of attention. By encompassing the whole continuum between allopatric and sympatric scenarios, it includes many potential scenarios for the evolution of new species. Building upon previous work, we investigate how a genetic barrier to gene flow, that relies on a single postzygotic genetic incompatibility, may further evolve. We consider a continent island model with three loci involved in pairwise Dobzhansky-Muller incompatibilities (DMIs). Using a deterministic and analytic approach, we derive the conditions for invasion of a new mutation and its consequences on an already existing genetic barrier to gene flow. We focus on quantifying the impact of the epistasis generated by the new mutation on the genetic barrier. We show that the accumulation of genetic incompatibilities in the presence of gene flow is a complex process, where new mutations can either strengthen or destroy a preexisting barrier. In particular, preexisting polymorphism and incompatibilities do not always facilitate the growth of the genetic barrier by accumulation of further barrier genes. Migration may disrupt the snowball effect (the accelerating rate of DMI accumulation in allopatry) because incompatibilities are directly tested by selection. Our results also show an ambiguous role of gene flow, which can either impede or facilitate the strengthening of the genetic barrier. Overall, our results illustrate how the inclusion of gene flow renders the building of a genetic barrier difficult to analyze.
Sergey Gavrilets - One of the best experts on this subject based on the ideXlab platform.
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waiting time to Parapatric Speciation
Proceedings of The Royal Society B: Biological Sciences, 2000Co-Authors: Sergey GavriletsAbstract:Using a weak migration and weak mutation approximation, I studied the average waiting time to Parapatric Speciation. The description of reproductive isolation used is based on the classical Dobzhansky model and its recently proposed multilocus generalizations. The dynamics of Parapatric Speciation are modelled as a biased random walk performed by the average genetic distance between the residents and immigrants. If a small number of genetic changes is sufficient for complete reproductive isolation, mutation and random genetic drift alone can cause Speciation on the time-scale of ten to 1,000 times the inverse of the mutation rate over a set of loci underlying reproductive isolation. Even relatively weak selection for local adaptation can dramatically decrease the waiting time to Speciation. The actual duration of the Parapatric Speciation process (that is the duration of intermediate forms in the actual transition to a state of complete reproductive isolation) is shorter by orders of magnitude than the overall waiting time to Speciation. For a wide range of parameter values, the actual duration of Parapatric Speciation is of the order of one over the mutation rate. In general, Parapatric Speciation is expected to be triggered by changes in the environment.
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patterns of Parapatric Speciation
Evolution, 2000Co-Authors: Sergey Gavrilets, Michael D VoseAbstract:Geographic variation may ultimately lead to the splitting of a subdivided population into reproductively isolated units in spite of migration. Here, we consider how the waiting time until the first split and its location depend on different evolutionary factors including mutation, migration, random genetic drift, genetic architecture, and the geometric structure of the habitat. We perform large-scale, individual-based simulations using a simple model of reproductive isolation based on a classical view that reproductive isolation evolves as a by-product of genetic diver- gence. We show that rapid Parapatric Speciation on the time scale of a few hundred to a few thousand generations is plausible even when neighboring subpopulations exchange several individuals each generation. Divergent selection for local adaptation is not required for rapid Speciation. Our results substantiates the claims that species with smaller range sizes (which are characterized by smaller local densities and reduced dispersal ability) should have higher Speciation rates. If mutation rate is small, local abundances are low, or substantial genetic changes are required for reproductive isolation, then central populations should be the place where most splits take place. With high mutation rates, high local densities, or with moderate genetic changes sufficient for reproductive isolation, Speciation events are expected to involve mainly peripheral populations.
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waiting time to and duration of Parapatric Speciation
arXiv: Adaptation and Self-Organizing Systems, 2000Co-Authors: Sergey GavriletsAbstract:Using a weak migration and weak mutation approximation, I study the average waiting time to and the average duration of Parapatric Speciation. The description of reproductive isolation used is based on the classical Dobzhansky model and its recently proposed multilocus generalizations. The dynamics of Parapatric Speciation is modeled as a biased random walk with absorption performed by the average genetic distance between the residents and immigrants. If a small number of genetic changes is sufficient for complete reproductive isolation, mutation and random genetic drift alone can cause Speciation on the time scale of 10-1000 times the inverse of the mutation rate. Even relatively weak selection for local adaptation can dramatically decrease the waiting time to Speciation. The duration of Parapatric Speciation is shorter by orders of magnitude than the waiting time to Speciation. For a wide range of parameter values, the duration of Speciation is order one over the mutation rate. In general, Parapatric Speciation is expected to be triggered by changes in the environment.
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rapid Parapatric Speciation on holey adaptive landscapes
Proceedings of The Royal Society B: Biological Sciences, 1998Co-Authors: Sergey Gavrilets, Michael D VoseAbstract:A classical view of Speciation is that reproductive isolation arises as a byproduct of genetic divergence. Here, individualbased simulations are used to evaluate whether the mechanisms implied by t...
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rapid Parapatric Speciation on holey adaptive landscapes
arXiv: Adaptation and Self-Organizing Systems, 1998Co-Authors: Sergey Gavrilets, Michael D VoseAbstract:A classical view of Speciation is that reproductive isolation arises as a by-product of genetic divergence. Here, individual-based simulations are used to evaluate whether the mechanisms implied by this view may result in rapid Speciation if the only source of genetic divergence are mutation and random genetic drift. Distinctive features of the simulations are the consideration of the complete process of Speciation (from initiation until completion), and of a large number of loci, which was only one order of magnitude smaller than that of bacteria. It is demonstrated that rapid Speciation on the time scale of hundreds of generations is plausible without the need for extreme founder events, complete geographic isolation, the existence of distinct adaptive peaks or selection for local adaptation. The plausibility of Speciation is enhanced by population subdivision. Simultaneous emergence of more than two new species from a subdivided population is highly probable. Numerical examples relevant to the theory of centrifugal Speciation and to the conjectures about the fate of ``ring species'' and ``sexual continuums'' are presented.
Brandon P Matheny - One of the best experts on this subject based on the ideXlab platform.
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coalescent based delimitation and species tree estimations reveal appalachian origin and neogene diversification in russula subsection roseinae
Molecular Phylogenetics and Evolution, 2020Co-Authors: Brian P Looney, Slavomir Adamcik, Brandon P MathenyAbstract:Numerous lineages of mushroom-forming fungi have been subject to bursts of diversification throughout their evolutionary history, events that can impact our ability to infer well-resolved phylogenies. However, groups that have undergone quick genetic change may have the highest adaptive potential. As the second largest genus of mushroom-forming fungi, Russula provides an excellent model for studying hyper-diversification and processes in evolution that drives it. This study focuses on the morphologically defined group - Russula subsection Roseinae. Species hypotheses based on morphological differentiation and multi-locus phylogenetic analyses are tested in the Roseinae using different applications of the multi-species coalescent model. Based on this combined approach, we recognize fourteen species in Roseinae including the Albida and wholly novel Magnarosea clades. Reconstruction of biogeographic and host association history suggest that Parapatric Speciation in refugia during glacial cycles of the Pleistocene drove diversification within the Roseinae, which is found to have a Laurasian distribution with an evolutionary origin in the Appalachian Mountains of eastern North America. Finally, we detect jump dispersal at a continental scale that has driven diversification since the most recent glacial cycles.
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miocene and pliocene Speciation of russula subsection roseinae in temperate forests of eastern north america
bioRxiv, 2019Co-Authors: Brian Looney, Slavomir Adamcik, Brandon P MathenyAbstract:Abstract Numerous lineages of mushroom-forming fungi have been subject to bursts of diversification throughout their evolutionary history, events that can impact our ability to infer well-resolved phylogenies. However, groups that have undergone quick genetic change may have the highest adaptive potential. As the second largest genus of mushroom-forming fungi, Russula provides an excellent model for studying hyper-diversification and processes in evolution that drives it. This study focuses on the morphologically defined group – Russula subsection Roseinae. Species hypotheses based on morphological differentiation and multi-locus phylogenetic analyses are tested in the Roseinae using different applications of the multi-species coalescent model. Based on this combined approach, we recognize fourteen species in Roseinae including the Albida and wholly novel Magnarosea clades. Reconstruction of biogeographic and host association history suggest that Parapatric Speciation in refugia during glacial cycles of the Pleistocene drove diversification within the Roseinae, which is found to have a Laurasian distribution with an evolutionary origin in the Appalachian Mountains of eastern North America. Finally, we detect jump dispersal at a continental scale that has driven diversification since the most recent glacial cycles.
Michael D Vose - One of the best experts on this subject based on the ideXlab platform.
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patterns of Parapatric Speciation
Evolution, 2000Co-Authors: Sergey Gavrilets, Michael D VoseAbstract:Geographic variation may ultimately lead to the splitting of a subdivided population into reproductively isolated units in spite of migration. Here, we consider how the waiting time until the first split and its location depend on different evolutionary factors including mutation, migration, random genetic drift, genetic architecture, and the geometric structure of the habitat. We perform large-scale, individual-based simulations using a simple model of reproductive isolation based on a classical view that reproductive isolation evolves as a by-product of genetic diver- gence. We show that rapid Parapatric Speciation on the time scale of a few hundred to a few thousand generations is plausible even when neighboring subpopulations exchange several individuals each generation. Divergent selection for local adaptation is not required for rapid Speciation. Our results substantiates the claims that species with smaller range sizes (which are characterized by smaller local densities and reduced dispersal ability) should have higher Speciation rates. If mutation rate is small, local abundances are low, or substantial genetic changes are required for reproductive isolation, then central populations should be the place where most splits take place. With high mutation rates, high local densities, or with moderate genetic changes sufficient for reproductive isolation, Speciation events are expected to involve mainly peripheral populations.
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rapid Parapatric Speciation on holey adaptive landscapes
Proceedings of The Royal Society B: Biological Sciences, 1998Co-Authors: Sergey Gavrilets, Michael D VoseAbstract:A classical view of Speciation is that reproductive isolation arises as a byproduct of genetic divergence. Here, individualbased simulations are used to evaluate whether the mechanisms implied by t...
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rapid Parapatric Speciation on holey adaptive landscapes
arXiv: Adaptation and Self-Organizing Systems, 1998Co-Authors: Sergey Gavrilets, Michael D VoseAbstract:A classical view of Speciation is that reproductive isolation arises as a by-product of genetic divergence. Here, individual-based simulations are used to evaluate whether the mechanisms implied by this view may result in rapid Speciation if the only source of genetic divergence are mutation and random genetic drift. Distinctive features of the simulations are the consideration of the complete process of Speciation (from initiation until completion), and of a large number of loci, which was only one order of magnitude smaller than that of bacteria. It is demonstrated that rapid Speciation on the time scale of hundreds of generations is plausible without the need for extreme founder events, complete geographic isolation, the existence of distinct adaptive peaks or selection for local adaptation. The plausibility of Speciation is enhanced by population subdivision. Simultaneous emergence of more than two new species from a subdivided population is highly probable. Numerical examples relevant to the theory of centrifugal Speciation and to the conjectures about the fate of ``ring species'' and ``sexual continuums'' are presented.