Establishment of local adaptation in partly self-fertilizing populations

Genetics ◽  
2021 ◽  
Author(s):  
Bogi Trickovic ◽  
Sylvain Glémin
Keyword(s):  
Local Adaptation ◽  
Pollen Dispersal ◽  
Theoretical Background ◽  
Weak Selection ◽  
Dominance Level ◽  
Self Fertilization ◽  
Protected Polymorphism ◽  
And Migration ◽  
Closed Form Approximation ◽  
Selfing Species

Abstract Populations often inhabit multiple ecological patches and thus experience divergent selection, which can lead to local adaptation if migration is not strong enough to swamp locally adapted alleles. Conditions for the establishment of a locally advantageous allele have been studied in randomly mating populations. However, many species reproduce, at least partially, through self-fertilization, and how selfing affects local adaptation remains unclear and debated. Using a two-patch branching process formalism, we obtained a closed-form approximation under weak selection for the probability of establishment of a locally advantageous allele (P) for arbitrary selfing rate and dominance level, where selection is allowed to act on viability or fecundity, and migration can occur via seed or pollen dispersal. This solution is compared to diffusion approximation and used to investigate the consequences of a shift in a mating system on P, and the establishment of protected polymorphism. We find that selfing can either increase or decrease P, depending on the patterns of dominance in the two patches, and has conflicting effects on local adaptation. Globally, selfing favors local adaptation when locally advantageous alleles are (partially) recessive, when selection between patches is asymmetrical and when migration occurs through pollen rather than seed dispersal. These results establish a rigorous theoretical background to study heterogeneous selection and local adaptation in partially selfing species.

scholarly journals Establishment of locally advantageous allele and local adaptation in partly self-fertilizing populations

2021 ◽  
Author(s):  
Bogi Trickovic ◽  
Sylvain Glémin
Keyword(s):  
Local Adaptation ◽  
Branching Process ◽  
Pollen Dispersal ◽  
Theoretical Background ◽  
Dominance Level ◽  
Self Fertilization ◽  
Protected Polymorphism ◽  
And Migration ◽  
Close Form ◽  
Selfing Species

Populations often inhabit multiple ecological patches and thus experience divergent selection, which can lead to local adaptation if migration is not strong enough to swamp locally adapted alleles. Conditions for the establishment of a locally advantageous allele have been studied in randomly mating populations. However, many species reproduce, at least partially, through self-fertilization, and how selfing affects local adaptation remains unclear and debated. Using a two-patch branching process formalism, we obtained a close-form approximation for the probability of establishment of a locally advantageous allele (P) for arbitrary selfing rate and dominance level, where selection is allowed to act on viability or fecundity, and migration can occur via seed or pollen dispersal. This solution is used to investigate the consequences of a shift in a mating system on P, and the establishment of protected polymorphism. We find that selfing can either increase or decrease P, depending on the patterns of dominance in the two patches, and has contradictory effect on local adaptation. Globally, selfing favors local adaptation when locally advantageous alleles are (partially) recessive, when selection between patches is asymmetrical and when migration occurs through pollen rather than seed dispersal. These results establish a rigorous theoretical background to study heterogeneous selection and local adaptation in partially selfing species.

scholarly journals Model-based detection and analysis of introgressed Neanderthal ancestry in modern humans

2017 ◽  
Author(s):  
Matthias Steinrücken ◽  
Jeffrey P. Spence ◽  
John A. Kamm ◽  
Emilia Wieczorek ◽  
Yun S. Song
Keyword(s):  
Genetic Material ◽  
Genetic Load ◽  
Modern Human ◽  
Human Populations ◽  
Effective Population ◽  
Weak Selection ◽  
Modern Humans ◽  
High Coverage ◽  
Model Based ◽  
And Migration

AbstractGenetic evidence has revealed that the ancestors of modern human populations outside of Africa and their hominin sister groups, notably the Neanderthals, exchanged genetic material in the past. The distribution of these introgressed sequence-tracts along modern-day human genomes provides insight into the ancient structure and migration patterns of these archaic populations. Furthermore, it facilitates studying the selective processes that lead to the accumulation or depletion of introgressed genetic variation. Recent studies have developed methods to localize these introgressed regions, reporting long regions that are depleted of Neanderthal introgression and enriched in genes, suggesting negative selection against the Neanderthal variants. On the other hand, enriched Neanderthal ancestry in hair- and skin-related genes suggests that some introgressed variants facilitated adaptation to new environments. Here, we present a model-based method called diCal-admix and apply it to detect tracts of Neanderthal introgression in modern humans. We demonstrate its efficiency and accuracy through extensive simulations. We use our method to detect introgressed regions in modern human individuals from the 1000 Genomes Project, using a high coverage genome from a Neanderthal individual from the Altai mountains as reference. Our introgression detection results and findings concerning their functional implications are largely concordant with previous studies, and are consistent with weak selection against Neanderthal ancestry. We find some evidence that selection against Neanderthal ancestry was due to higher genetic load in Neanderthals, resulting from small effective population size, rather than Dobzhansky-Müller incompatibilities. Finally, we investigate the role of the X-chromosome in the divergence between Neanderthals and modern humans.

scholarly journals Evolution of polygenic traits under global vs local adaptation

Genetics ◽  
2022 ◽  
Vol 220 (1) ◽  
Author(s):  
Sam Yeaman
Keyword(s):  
Local Adaptation ◽  
Complex Traits ◽  
Genetic Architecture ◽  
Population Genomics ◽  
Natural Populations ◽  
Evolutionary Process ◽  
Frequency Effect ◽  
Theoretical Predictions ◽  
Using Data ◽  
And Migration

Abstract Observations about the number, frequency, effect size, and genomic distribution of alleles associated with complex traits must be interpreted in light of evolutionary process. These characteristics, which constitute a trait’s genetic architecture, can dramatically affect evolutionary outcomes in applications from agriculture to medicine, and can provide a window into how evolution works. Here, I review theoretical predictions about the evolution of genetic architecture under spatially homogeneous, global adaptation as compared with spatially heterogeneous, local adaptation. Due to the tension between divergent selection and migration, local adaptation can favor “concentrated” genetic architectures that are enriched for alleles of larger effect, clustered in a smaller number of genomic regions, relative to expectations under global adaptation. However, the evolution of such architectures may be limited by many factors, including the genotypic redundancy of the trait, mutation rate, and temporal variability of environment. I review the circumstances in which predictions differ for global vs local adaptation and discuss where progress can be made in testing hypotheses using data from natural populations and lab experiments. As the field of comparative population genomics expands in scope, differences in architecture among traits and species will provide insights into how evolution works, and such differences must be interpreted in light of which kind of selection has been operating.

scholarly journals Variation in competitive ability with mating system, ploidy and range expansion in four Capsella species

2017 ◽  
Author(s):  
Xuyue Yang ◽  
Martin Lascoux ◽  
Sylvain Glémin
Keyword(s):  
Mating System ◽  
Range Expansion ◽  
Evolutionary Biology ◽  
Competitive Ability ◽  
Vegetative Traits ◽  
Evolutionary Trajectories ◽  
Self Fertilization ◽  
Peer Community ◽  
Meta Analyses ◽  
Selfing Species

AbstractThis preprint has been reviewed and recommended by Peer Community In Evolutionary Biology (https://dx.doi.org/10.24072/pci.evolbiol.100054)Self-fertilization is often associated with ecological traits corresponding to the ruderal strategy in Grime’s Competitive-Stress-tolerant-Ruderal (CSR) classification of ecological strategies. Consequently, selfers are expected to be less competitive than outcrossers, either because of a colonization/competition trade-off or because of the deleterious genetic effects of selfing. Range expansion could reduce further competitive ability while polyploidy could mitigate the effects of selfing. Although suggested by meta-analyses, these predictions have not been directly tested yet. We compared the competitive ability of four Capsella species differing by their mating system and ploidy level. For vegetative traits we found no difference in competitive ability neither among species nor among populations. For flower production, we found that the two diploid selfing species (C. rubella and C. orientalis) were more sensitive to competition than the diploid outcrosser (C. grandiflora), and that the tetraploid selfer (C. bursa-pastoris) was intermediate. Within C. bursa-pastoris, we also found that sensitivity to competition increased in parallel to range expansion. These results highlight the possible roles of ecological context and ploidy in the evolutionary trajectories of selfing species.

scholarly journals Establishment of locally adapted mutations under divergent selection

2018 ◽  
Author(s):  
Matteo Tomasini ◽  
Stephan Peischl
Keyword(s):  
Gene Flow ◽  
Local Adaptation ◽  
Migration Rate ◽  
Analytical Approximation ◽  
Multitype Branching Process ◽  
Process Framework ◽  
Establishment Probability ◽  
Two Populations ◽  
Closed Form Approximation

AbstractWe study the establishment probabilities of locally adapted mutations using a multitype 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.

scholarly journals The role of self-incompatibility systems in the prevention of bi-parental inbreeding

2017 ◽  
Author(s):  
Tara N Furstenau ◽  
Reed A Cartwright
Keyword(s):  
Inbreeding Depression ◽  
Pollen Dispersal ◽  
Dispersal Distance ◽  
Inbreeding Avoidance ◽  
Self Incompatibility ◽  
Plant Populations ◽  
Population Sizes ◽  
Self Fertilization ◽  
Individual Based Simulation

Hermaphroditic plants experience inbreeding through both self-fertilization and bi-parental inbreeding. Therefore, many plant species have evolved either heteromorphic (morphology-based) or homomorphic (molecular-based) self-incompatibility (SI) systems. These SI systems limit extreme inbreeding through self-fertilization and, in the case of homomorphic SI systems, have the potential to limit bi-parental inbreeding, which is common when dispersal is restricted to a local region. Homomorphic SI species are prevalent across the angiosperms, and it is often assumed that the potential to reduce bi-parental inbreeding may be a factor in their success. To test this assumption, we developed a spatially-explicit, individual-based simulation of plant populations with either heteromorphic SI or one of three different types of homomorphic SI. In our simulations, we varied dispersal distance and the presence of inbreeding depression. We found that autozygosity in the homomorphic SI populations was significantly lower than in the heteromorphic SI populations and that this reduction was due to bi-parental inbreeding avoidance. As expected, the differences between the homomorphic and heteromorphic SI populations were more pronounced when seed and pollen dispersal was limited. However, levels of homozygosity and inbreeding depression between these plant populations were not different. At low dispersal, homomorphic SI populations also suffered reduced female fecundity and had smaller census population sizes. Our results suggest that bi-parental inbreeding avoidance was unlikely to be a major driver in the evolution of homomorphic SI systems.

scholarly journals The role of self-incompatibility systems in the prevention of bi-parental inbreeding

2017 ◽  
Author(s):  
Tara N Furstenau ◽  
Reed A Cartwright
Keyword(s):  
Inbreeding Depression ◽  
Pollen Dispersal ◽  
Dispersal Distance ◽  
Inbreeding Avoidance ◽  
Self Incompatibility ◽  
Plant Populations ◽  
Population Sizes ◽  
Self Fertilization ◽  
Individual Based Simulation

Hermaphroditic plants experience inbreeding through both self-fertilization and bi-parental inbreeding. Therefore, many plant species have evolved either heteromorphic (morphology-based) or homomorphic (molecular-based) self-incompatibility (SI) systems. These SI systems limit extreme inbreeding through self-fertilization and, in the case of homomorphic SI systems, have the potential to limit bi-parental inbreeding, which is common when dispersal is restricted to a local region. Homomorphic SI species are prevalent across the angiosperms, and it is often assumed that the potential to reduce bi-parental inbreeding may be a factor in their success. To test this assumption, we developed a spatially-explicit, individual-based simulation of plant populations with either heteromorphic SI or one of three different types of homomorphic SI. In our simulations, we varied dispersal distance and the presence of inbreeding depression. We found that autozygosity in the homomorphic SI populations was significantly lower than in the heteromorphic SI populations and that this reduction was due to bi-parental inbreeding avoidance. As expected, the differences between the homomorphic and heteromorphic SI populations were more pronounced when seed and pollen dispersal was limited. However, levels of homozygosity and inbreeding depression between these plant populations were not different. At low dispersal, homomorphic SI populations also suffered reduced female fecundity and had smaller census population sizes. Our results suggest that bi-parental inbreeding avoidance was unlikely to be a major driver in the evolution of homomorphic SI systems.

Sign in / Sign up

Export Citation Format

Share Document