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Korfmann K, Abu Awad D, Tellier A. Weak seed banks influence the signature and detectability of selective sweeps. J Evol Biol 2023; 36:1282-1294. [PMID: 37551039 DOI: 10.1111/jeb.14204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 06/20/2023] [Accepted: 06/27/2023] [Indexed: 08/09/2023]
Abstract
Seed banking (or dormancy) is a widespread bet-hedging strategy, generating a form of population overlap, which decreases the magnitude of genetic drift. The methodological complexity of integrating this trait implies it is ignored when developing tools to detect selective sweeps. But, as dormancy lengthens the ancestral recombination graph (ARG), increasing times to fixation, it can change the genomic signatures of selection. To detect genes under positive selection in seed banking species it is important to (1) determine whether the efficacy of selection is affected, and (2) predict the patterns of nucleotide diversity at and around positively selected alleles. We present the first tree sequence-based simulation program integrating a weak seed bank to examine the dynamics and genomic footprints of beneficial alleles in a finite population. We find that seed banking does not affect the probability of fixation and confirm expectations of increased times to fixation. We also confirm earlier findings that, for strong selection, the times to fixation are not scaled by the inbreeding effective population size in the presence of seed banks, but are shorter than would be expected. As seed banking increases the effective recombination rate, footprints of sweeps appear narrower around the selected sites and due to the scaling of the ARG are detectable for longer periods of time. The developed simulation tool can be used to predict the footprints of selection and draw statistical inference of past evolutionary events in plants, invertebrates, or fungi with seed banks.
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Affiliation(s)
- Kevin Korfmann
- Department of Life Science Systems, School of Life Sciences, Technical University of Munich, München, Germany
| | - Diala Abu Awad
- Department of Life Science Systems, School of Life Sciences, Technical University of Munich, München, Germany
- Université Paris-Saclay, INRAE, CNRS, AgroParisTech, GQE-Le Moulon, Gif-sur-Yvette, France
| | - Aurélien Tellier
- Department of Life Science Systems, School of Life Sciences, Technical University of Munich, München, Germany
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Wei K, Silva-Arias GA, Tellier A. Selective sweeps linked to the colonization of novel habitats and climatic changes in a wild tomato species. THE NEW PHYTOLOGIST 2023; 237:1908-1921. [PMID: 36419182 DOI: 10.1111/nph.18634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 11/16/2022] [Indexed: 06/16/2023]
Abstract
Positive selection is the driving force underpinning local adaptation and leaves footprints of selective sweeps on the underlying major genes. Quantifying the timing of selection and revealing the genetic bases of adaptation in plant species occurring in steep and varying environmental gradients are crucial to predict a species' ability to colonize new niches. We use whole-genome sequence data from six populations across three different habitats of the wild tomato species Solanum chilense to infer the past demographic history and search for genes under strong positive selection. We then correlate current and past climatic projections with the demographic history, allele frequencies, the age of selection events and distribution shifts. Several selective sweeps occur at regulatory networks involved in root-hair development in low altitude and response to photoperiod and vernalization in high-altitude populations. These sweeps appear to occur in a concerted fashion in a given regulatory gene network at particular periods of substantial climatic change. Using a unique combination of genome scans and modelling of past climatic data, we quantify the timing of selection at genes likely underpinning local adaptation to semiarid habitats.
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Affiliation(s)
- Kai Wei
- Population Genetics, Department of Life Science Systems, School of Life Sciences, Technical University of Munich, Liesel-Beckmann Strasse 2, 85354, Freising, Germany
| | - Gustavo A Silva-Arias
- Population Genetics, Department of Life Science Systems, School of Life Sciences, Technical University of Munich, Liesel-Beckmann Strasse 2, 85354, Freising, Germany
| | - Aurélien Tellier
- Population Genetics, Department of Life Science Systems, School of Life Sciences, Technical University of Munich, Liesel-Beckmann Strasse 2, 85354, Freising, Germany
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Dittberner H, Tellier A, de Meaux J. Approximate Bayesian computation untangles signatures of contemporary and historical hybridization between two endangered species. Mol Biol Evol 2022; 39:6516021. [PMID: 35084503 PMCID: PMC8826969 DOI: 10.1093/molbev/msac015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Contemporary gene flow, when resumed after a period of isolation, can have crucial consequences for endangered species, as it can both increase the supply of adaptive alleles and erode local adaptation. Determining the history of gene flow and thus the importance of contemporary hybridization, however, is notoriously difficult. Here, we focus on two endangered plant species, Arabis nemorensis and A. sagittata, which hybridize naturally in a sympatric population located on the banks of the Rhine. Using reduced genome sequencing, we determined the phylogeography of the two taxa but report only a unique sympatric population. Molecular variation in chloroplast DNA indicated that A. sagittata is the principal receiver of gene flow. Applying classical D-statistics and its derivatives to whole-genome data of 35 accessions, we detect gene flow not only in the sympatric population but also among allopatric populations. Using an Approximate Bayesian computation approach, we identify the model that best describes the history of gene flow between these taxa. This model shows that low levels of gene flow have persisted long after speciation. Around 10 000 years ago, gene flow stopped and a period of complete isolation began. Eventually, a hotspot of contemporary hybridization was formed in the unique sympatric population. Occasional sympatry may have helped protect these lineages from extinction in spite of their extremely low diversity.
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Affiliation(s)
- Hannes Dittberner
- Institute of Plant Sciences,University of Cologne, Zülpicher str. 47b, Germany
| | - Aurelien Tellier
- Department of Life Science Systems, Technical University of Munich, Freising, Germany
| | - Juliette de Meaux
- Institute of Plant Sciences,University of Cologne, Zülpicher str. 47b, Germany
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Lennon JT, den Hollander F, Wilke-Berenguer M, Blath J. Principles of seed banks and the emergence of complexity from dormancy. Nat Commun 2021; 12:4807. [PMID: 34376641 PMCID: PMC8355185 DOI: 10.1038/s41467-021-24733-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Accepted: 07/02/2021] [Indexed: 02/07/2023] Open
Abstract
Across the tree of life, populations have evolved the capacity to contend with suboptimal conditions by engaging in dormancy, whereby individuals enter a reversible state of reduced metabolic activity. The resulting seed banks are complex, storing information and imparting memory that gives rise to multi-scale structures and networks spanning collections of cells to entire ecosystems. We outline the fundamental attributes and emergent phenomena associated with dormancy and seed banks, with the vision for a unifying and mathematically based framework that can address problems in the life sciences, ranging from global change to cancer biology.
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Affiliation(s)
- Jay T. Lennon
- grid.411377.70000 0001 0790 959XIndiana University, Department of Biology, Bloomington, USA
| | - Frank den Hollander
- grid.5132.50000 0001 2312 1970Universiteit Leiden, Mathematical Institute, Leiden, Netherlands
| | - Maite Wilke-Berenguer
- grid.7468.d0000 0001 2248 7639Humboldt-Universität zu Berlin, Institute of Mathematics, Berlin, Germany
| | - Jochen Blath
- grid.6734.60000 0001 2292 8254Technische Universität Berlin, Institute of Mathematics, Berlin, Germany
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Märkle H, John S, Cornille A, Fields PD, Tellier A. Novel genomic approaches to study antagonistic coevolution between hosts and parasites. Mol Ecol 2021; 30:3660-3676. [PMID: 34038012 DOI: 10.1111/mec.16001] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 05/09/2021] [Accepted: 05/20/2021] [Indexed: 12/13/2022]
Abstract
Host-parasite coevolution is ubiquitous, shaping genetic and phenotypic diversity and the evolutionary trajectory of interacting species. With the advances of high throughput sequencing technologies applicable to model and non-model organisms alike, it is now feasible to study in greater detail (a) the genetic underpinnings of coevolution, (b) the speed and type of dynamics at coevolving loci, and (c) the genomic consequences of coevolution. This review focuses on three recently developed approaches that leverage information from host and parasite full genome data simultaneously to pinpoint coevolving loci and draw inference on the coevolutionary history. First, co-genome-wide association study (co-GWAS) methods allow pinpointing the loci underlying host-parasite interactions. These methods focus on detecting associations between genetic variants and the outcome of experimental infection tests or on correlations between genomes of naturally infected hosts and their infecting parasites. Second, extensions to population genomics methods can detect genes under coevolution and infer the coevolutionary history, such as fitness costs. Third, correlations between host and parasite population size in time are indicative of coevolution, and polymorphism levels across independent spatially distributed populations of hosts and parasites can reveal coevolutionary loci and infer coevolutionary history. We describe the principles of these three approaches and discuss their advantages and limitations based on coevolutionary theory. We present recommendations for their application to various host (prokaryotes, fungi, plants, and animals) and parasite (viruses, bacteria, fungi, and macroparasites) species. We conclude by pointing out methodological and theoretical gaps to be filled to extract maximum information from full genome data and thereby to shed light on the molecular underpinnings of coevolution.
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Affiliation(s)
- Hanna Märkle
- Professorship for Population Genetics, Department of Life Science Systems, School of Life Sciences, Technical University of Munich, Freising, Germany.,Department of Ecology and Evolution, University of Chicago, Chicago, IL, USA
| | - Sona John
- Professorship for Population Genetics, Department of Life Science Systems, School of Life Sciences, Technical University of Munich, Freising, Germany
| | - Amandine Cornille
- INRAE, CNRS, AgroParisTech, GQE - Le Moulon, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Peter D Fields
- Department of Environmental Sciences, University of Basel, Zoology, Basel, Switzerland
| | - Aurélien Tellier
- Professorship for Population Genetics, Department of Life Science Systems, School of Life Sciences, Technical University of Munich, Freising, Germany
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Sellinger TPP, Abu-Awad D, Tellier A. Limits and convergence properties of the sequentially Markovian coalescent. Mol Ecol Resour 2021; 21:2231-2248. [PMID: 33978324 DOI: 10.1111/1755-0998.13416] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 04/19/2021] [Accepted: 04/29/2021] [Indexed: 02/07/2023]
Abstract
Several methods based on the sequentially Markovian coalescent (SMC) make use of full genome sequence data from samples to infer population demographic history including past changes in population size, admixture, migration events and population structure. More recently, the original theoretical framework has been extended to allow the simultaneous estimation of population size changes along with other life history traits such as selfing or seed banking. The latter developments enhance the applicability of SMC methods to nonmodel species. Although convergence proofs have been given using simulated data in a few specific cases, an in-depth investigation of the limitations of SMC methods is lacking. In order to explore such limits, we first develop a tool inferring the best case convergence of SMC methods assuming the true underlying coalescent genealogies are known. This tool can be used to quantify the amount and type of information that can be confidently retrieved from given data sets prior to the analysis of the real data. Second, we assess the inference accuracy when the assumptions of SMC approaches are violated due to departures from the model, namely the presence of transposable elements, variable recombination and mutation rates along the sequence, and SNP calling errors. Third, we deliver a new interpretation of SMC methods by highlighting the importance of the transition matrix, which we argue can be used as a set of summary statistics in other statistical inference methods, uncoupling the SMC from hidden Markov models (HMMs). We finally offer recommendations to better apply SMC methods and build adequate data sets under budget constraints.
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Affiliation(s)
| | - Diala Abu-Awad
- Department of Life Science Systems, Technical University of Munich, Munchen, Germany
| | - Aurélien Tellier
- Department of Life Science Systems, Technical University of Munich, Munchen, Germany
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Sellinger TPP, Abu Awad D, Moest M, Tellier A. Correction: Inference of past demography, dormancy and self-fertilization rates from whole genome sequence data. PLoS Genet 2021; 17:e1009504. [PMID: 33826613 PMCID: PMC8026070 DOI: 10.1371/journal.pgen.1009504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Hämälä T, Tiffin P. Biased Gene Conversion Constrains Adaptation in Arabidopsis thaliana. Genetics 2020; 215:831-846. [PMID: 32414868 PMCID: PMC7337087 DOI: 10.1534/genetics.120.303335] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Accepted: 05/14/2020] [Indexed: 02/01/2023] Open
Abstract
Reduction of fitness due to deleterious mutations imposes a limit to adaptive evolution. By characterizing features that influence this genetic load we may better understand constraints on responses to both natural and human-mediated selection. Here, using whole-genome, transcriptome, and methylome data from >600 Arabidopsis thaliana individuals, we set out to identify important features influencing selective constraint. Our analyses reveal that multiple factors underlie the accumulation of maladaptive mutations, including gene expression level, gene network connectivity, and gene-body methylation. We then focus on a feature with major effect, nucleotide composition. The ancestral vs. derived status of segregating alleles suggests that GC-biased gene conversion, a recombination-associated process that increases the frequency of G and C nucleotides regardless of their fitness effects, shapes sequence patterns in A. thaliana Through estimation of mutational effects, we present evidence that biased gene conversion hinders the purging of deleterious mutations and contributes to a genome-wide signal of decreased efficacy of selection. By comparing these results to two outcrossing relatives, Arabidopsis lyrata and Capsella grandiflora, we find that protein evolution in A. thaliana is as strongly affected by biased gene conversion as in the outcrossing species. Last, we perform simulations to show that natural levels of outcrossing in A. thaliana are sufficient to facilitate biased gene conversion despite increased homozygosity due to selfing. Together, our results show that even predominantly selfing taxa are susceptible to biased gene conversion, suggesting that it may constitute an important constraint to adaptation among plant species.
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Affiliation(s)
- Tuomas Hämälä
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota 55108
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota 55108
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