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Schlötterer C. How predictable is adaptation from standing genetic variation? Experimental evolution in Drosophila highlights the central role of redundancy and linkage disequilibrium. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220046. [PMID: 37004724 PMCID: PMC10067264 DOI: 10.1098/rstb.2022.0046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023] Open
Abstract
Experimental evolution is well-suited to test the predictability of evolution without the confounding effects of inaccurate forecasts about future environments. Most of the literature about parallel (and thus predictable) evolution has been carried out in asexual microorganisms, which adapt by de novo mutations. Nevertheless, parallel evolution has also been studied in sexual species at the genomic level. Here, I review the evidence for parallel evolution in Drosophila, the best-studied obligatory outcrossing model for adaptation from standing genetic variation in the laboratory. Similar to asexual microorganisms, evidence for parallel evolution varies between the focal hierarchical levels. Selected phenotypes consistently respond in a very predicable way, but the underlying allele frequency changes are much less predictable. The most important insight is that the predictability of the genomic selection response for polygenic traits depends highly on the founder population and to a much lesser extent on the selection regime. This implies that predicting adaptive genomic response is challenging and requires a good understanding of the adaptive architecture (including linkage disequilibrium) in the ancestral populations. This article is part of the theme issue 'Interdisciplinary approaches to predicting evolutionary biology'.
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Affiliation(s)
- Christian Schlötterer
- Institut für Populationsgenetik, Vetmeduni Vienna, Veterinärplatz 1, 1210 Wien, Austria
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2
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Repeated genetic adaptation to altitude in two tropical butterflies. Nat Commun 2022; 13:4676. [PMID: 35945236 PMCID: PMC9363431 DOI: 10.1038/s41467-022-32316-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 07/26/2022] [Indexed: 01/02/2023] Open
Abstract
Repeated evolution can provide insight into the mechanisms that facilitate adaptation to novel or changing environments. Here we study adaptation to altitude in two tropical butterflies, Heliconius erato and H. melpomene, which have repeatedly and independently adapted to montane habitats on either side of the Andes. We sequenced 518 whole genomes from altitudinal transects and found many regions differentiated between highland (~ 1200 m) and lowland (~ 200 m) populations. We show repeated genetic differentiation across replicate populations within species, including allopatric comparisons. In contrast, there is little molecular parallelism between the two species. By sampling five close relatives, we find that a large proportion of divergent regions identified within species have arisen from standing variation and putative adaptive introgression from high-altitude specialist species. Taken together our study supports a role for both standing genetic variation and gene flow from independently adapted species in promoting parallel local adaptation to the environment. Here, the authors study adaptation to altitude in 518 whole genomes from two species of tropical butterflies. They find repeated genetic differentiation within species, little molecular parallelism between these species, and introgression from closely related species, concluding that standing genetic variation promotes parallel local adaptation.
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Johri P, Aquadro CF, Beaumont M, Charlesworth B, Excoffier L, Eyre-Walker A, Keightley PD, Lynch M, McVean G, Payseur BA, Pfeifer SP, Stephan W, Jensen JD. Recommendations for improving statistical inference in population genomics. PLoS Biol 2022; 20:e3001669. [PMID: 35639797 PMCID: PMC9154105 DOI: 10.1371/journal.pbio.3001669] [Citation(s) in RCA: 43] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The field of population genomics has grown rapidly in response to the recent advent of affordable, large-scale sequencing technologies. As opposed to the situation during the majority of the 20th century, in which the development of theoretical and statistical population genetic insights outpaced the generation of data to which they could be applied, genomic data are now being produced at a far greater rate than they can be meaningfully analyzed and interpreted. With this wealth of data has come a tendency to focus on fitting specific (and often rather idiosyncratic) models to data, at the expense of a careful exploration of the range of possible underlying evolutionary processes. For example, the approach of directly investigating models of adaptive evolution in each newly sequenced population or species often neglects the fact that a thorough characterization of ubiquitous nonadaptive processes is a prerequisite for accurate inference. We here describe the perils of these tendencies, present our consensus views on current best practices in population genomic data analysis, and highlight areas of statistical inference and theory that are in need of further attention. Thereby, we argue for the importance of defining a biologically relevant baseline model tuned to the details of each new analysis, of skepticism and scrutiny in interpreting model fitting results, and of carefully defining addressable hypotheses and underlying uncertainties.
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Affiliation(s)
- Parul Johri
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Charles F. Aquadro
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, United States of America
| | - Mark Beaumont
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - Brian Charlesworth
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Laurent Excoffier
- Institute of Ecology and Evolution, University of Berne, Berne, Switzerland
| | - Adam Eyre-Walker
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Peter D. Keightley
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Michael Lynch
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Gil McVean
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Bret A. Payseur
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Susanne P. Pfeifer
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | | | - Jeffrey D. Jensen
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
- * E-mail:
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4
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Stephenson BP, Velani Z, Ihász N. The effect of albinism on avian predator attack rates in eastern garter snakes. ZOOLOGY 2021; 150:125987. [PMID: 34971911 DOI: 10.1016/j.zool.2021.125987] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 12/10/2021] [Accepted: 12/20/2021] [Indexed: 10/19/2022]
Abstract
Albinism is a conspicuous and distinctive phenotype arising from the absence of melanin in the integument that has been documented in all major vertebrate groups. With few exceptions, albinism is rare in natural populations, suggesting that it incurs significant fitness costs as compared to wild-type phenotypes. One possible explanation for this rarity is that albinos experience higher predation risk as compared to wild-type individuals. We tested this hypothesis by comparing rates of attack by avian predators on immobile clay model proxies that mimicked wild-type and albino eastern garter snakes (Thamnophis s. sirtalis) at Bond Swamp in central Georgia, USA; two mixed pattern treatments provided intermediate phenotypes for comparison. Surprisingly, we found no difference in attack rate across all four model treatments, nor among pairs of treatments (i.e., wild-type-like vs. albino-like models). This indicates that albino garter snakes are not subject to higher predation risk from birds due to coloration alone, and that other factors (correlated pathologies of albinism, thermoregulatory challenges, mate selection) are likely to be more important in explaining the rarity of albinism in snakes and perhaps other vertebrate groups.
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Affiliation(s)
- Barry P Stephenson
- 1501 Mercer University Dr., Department of Biology, Mercer University, Macon, GA, 31207, USA.
| | - Zeshan Velani
- 1501 Mercer University Dr., Department of Biology, Mercer University, Macon, GA, 31207, USA; 3001 Mercer University Dr., Mercer University Health Sciences Center, Atlanta, GA, 30341, USA.
| | - Nikolett Ihász
- 1501 Mercer University Dr., Department of Psychology, Mercer University, Macon, GA, 31207, USA.
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Fjeldså J, Bowie RCK. Evolutionary and Ecological Explanations for the Elevational Flexibility of Several East African Bird Species Complexes. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.768062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Africa’s montane areas are broken up into several large and small units, each isolated as forest-capped “sky islands” in a “sea” of dry lowland savanna. Many elements of their biota, including montane forest birds, are shared across several disjunct mountains, yet it has been difficult to rigorously define an Afromontane forest avifauna, or determine its evolutionary relationships with the birds of the surrounding lowland forests. In order to trace the historical relationship between lowland and highland avifaunas, we review cases of species or groups of closely related species with breeding populations at different elevations, and use phylogeographic methods to explore the historical connections between such populations within the biodiversity hotspot of East Africa. The study reveals several idiosyncratic patterns, but also a prominent number of cases of gene flow between populations in southern areas, mainly around the Malawi Rift, and mountains and coastal forests to the north, close to the equator. This may reflect more continuous past distributions through northern Mozambique and coastal Tanzania, or seasonal migrations between areas with different rainfall regimes. Over time, these distributional dynamics have resulted in a higher persistence of lineages, and an accumulation of forest-dependent lineages within the Eastern Arc Mountains of Tanzania and the northern part of the coastal forest mosaic.
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Decoding the Evolution of Melanin in Vertebrates. Trends Ecol Evol 2021; 36:430-443. [DOI: 10.1016/j.tree.2020.12.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 12/18/2020] [Accepted: 12/23/2020] [Indexed: 02/08/2023]
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7
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First record of albinism in spiny rats of genus Proechimys (Rodentia: Echimyidae) from Western Amazon. MAMMALIA 2020. [DOI: 10.1515/mammalia-2019-0133] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractAlbinism is a rare condition in natural populations. One of the factors that would lead to higher allele frequency for the albino phenotype is bottleneck events, causing small population sizes and loss of genetic diversity. Here, we report the first record of albinism in one specimen of Proechimys gardneri from Porto Velho, Rondônia, Brazil. This is also the first record of albinism for the genus and for the family Echimyidae. We identified the specimen through morphology and confirmed the identification by 801 base pairs (bp) of mitochondrial marker cytochrome b (Cyt b). We also discuss the selection against albino phenotype in natural populations.
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Abstract
The diversity of mammalian coat colors, and their potential adaptive significance, have long fascinated scientists as well as the general public. The recent decades have seen substantial improvement in our understanding of their genetic bases and evolutionary relevance, revealing novel insights into the complex interplay of forces that influence these phenotypes. At the same time, many aspects remain poorly known, hampering a comprehensive understanding of these phenomena. Here we review the current state of this field and indicate topics that should be the focus of additional research. We devote particular attention to two aspects of mammalian pigmentation, melanism and pattern formation, highlighting recent advances and outstanding challenges, and proposing novel syntheses of available information. For both specific areas, and for pigmentation in general, we attempt to lay out recommendations for establishing novel model systems and integrated research programs that target the genetics and evolution of these phenotypes throughout the Mammalia.
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Affiliation(s)
- Eduardo Eizirik
- Laboratory of Genomics and Molecular Biology, School of Health and Life Sciences, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Porto Alegre, Rio Grande do Sul 90619-900, Brazil;
| | - Fernanda J Trindade
- Laboratory of Genomics and Molecular Biology, School of Health and Life Sciences, Pontifical Catholic University of Rio Grande do Sul (PUCRS), Porto Alegre, Rio Grande do Sul 90619-900, Brazil;
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9
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Jones MR, Mills LS, Jensen JD, Good JM. The Origin and Spread of Locally Adaptive Seasonal Camouflage in Snowshoe Hares. Am Nat 2020; 196:316-332. [DOI: 10.1086/710022] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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10
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Polygenic adaptation: a unifying framework to understand positive selection. Nat Rev Genet 2020; 21:769-781. [DOI: 10.1038/s41576-020-0250-z] [Citation(s) in RCA: 144] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/12/2020] [Indexed: 12/20/2022]
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Jones MR, Mills LS, Jensen JD, Good JM. Convergent evolution of seasonal camouflage in response to reduced snow cover across the snowshoe hare range*. Evolution 2020; 74:2033-2045. [DOI: 10.1111/evo.13976] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/26/2020] [Accepted: 04/02/2020] [Indexed: 12/14/2022]
Affiliation(s)
- Matthew R. Jones
- Division of Biological Sciences University of Montana Missoula Montana 59812
| | - L. Scott Mills
- Wildlife Biology Program University of Montana Missoula Montana 59812
- Office of Research and Creative Scholarship University of Montana Missoula Montana 59812
| | - Jeffrey D. Jensen
- School of Life Sciences Arizona State University Tempe Arizona 85281
| | - Jeffrey M. Good
- Division of Biological Sciences University of Montana Missoula Montana 59812
- Wildlife Biology Program University of Montana Missoula Montana 59812
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12
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Burgon JD, Vieites DR, Jacobs A, Weidt SK, Gunter HM, Steinfartz S, Burgess K, Mable BK, Elmer KR. Functional colour genes and signals of selection in colour-polymorphic salamanders. Mol Ecol 2020; 29:1284-1299. [PMID: 32159878 DOI: 10.1111/mec.15411] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 03/06/2020] [Accepted: 03/09/2020] [Indexed: 12/11/2022]
Abstract
Coloration has been associated with multiple biologically relevant traits that drive adaptation and diversification in many taxa. However, despite the great diversity of colour patterns present in amphibians the underlying molecular basis is largely unknown. Here, we use insight from a highly colour-variable lineage of the European fire salamander (Salamandra salamandra bernardezi) to identify functional associations with striking variation in colour morph and pattern. The three focal colour morphs-ancestral black-yellow striped, fully yellow and fully brown-differed in pattern, visible coloration and cellular composition. From population genomic analyses of up to 4,702 loci, we found no correlations of neutral population genetic structure with colour morph. However, we identified 21 loci with genotype-phenotype associations, several of which relate to known colour genes. Furthermore, we inferred response to selection at up to 142 loci between the colour morphs, again including several that relate to coloration genes. By transcriptomic analysis across all different combinations, we found 196 differentially expressed genes between yellow, brown and black skin, 63 of which are candidate genes involved in animal coloration. The concordance across different statistical approaches and 'omic data sets provide several lines of evidence for loci linked to functional differences between colour morphs, including TYR, CAMK1 and PMEL. We found little association between colour morph and the metabolomic profile of its toxic compounds from the skin secretions. Our research suggests that current ecological and evolutionary hypotheses for the origins and maintenance of these striking colour morphs may need to be revisited.
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Affiliation(s)
- James D Burgon
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - David R Vieites
- Museo Nacional de Ciencias Naturales (MNCN), Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Arne Jacobs
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Stefan K Weidt
- Glasgow Polyomics, Wolfson Wohl Cancer Research Centre, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Helen M Gunter
- Edinburgh Genomics, King's Buildings, University of Edinburgh, Edinburgh, UK
| | - Sebastian Steinfartz
- Department of Evolutionary Biology, Unit Molecular Ecology, Zoological Institute, Technische Universität Braunschweig, Braunschweig, Germany
| | - Karl Burgess
- Glasgow Polyomics, Wolfson Wohl Cancer Research Centre, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Barbara K Mable
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Kathryn R Elmer
- Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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13
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Apata M, Pfeifer SP. Recent population genomic insights into the genetic basis of arsenic tolerance in humans: the difficulties of identifying positively selected loci in strongly bottlenecked populations. Heredity (Edinb) 2020; 124:253-262. [PMID: 31776483 PMCID: PMC6972707 DOI: 10.1038/s41437-019-0285-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 10/22/2019] [Accepted: 11/13/2019] [Indexed: 02/06/2023] Open
Abstract
Recent advances in genomics have enabled researchers to shed light on the evolutionary processes driving human adaptation, by revealing the genetic architectures underlying traits ranging from lactase persistence, to skin pigmentation, to hypoxic response, to arsenic tolerance. Complicating the identification of targets of positive selection in modern human populations is their complex demographic history, characterized by population bottlenecks and expansions, population structure, migration, and admixture. In particular, founder effects and recent strong population size reductions, such as those experienced by the indigenous peoples of the Americas, have severe impacts on genetic variation that can lead to the accumulation of large allele frequency differences between populations due to genetic drift rather than natural selection. While distinguishing the effects of demographic history from selection remains challenging, neglecting neutral processes can lead to the incorrect identification of candidate loci. We here review the recent population genomic insights into the genetic basis of arsenic tolerance in Andean populations, and utilize this example to highlight both the difficulties pertaining to the identification of local adaptations in strongly bottlenecked populations, as well as the importance of controlling for demographic history in selection scans.
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Affiliation(s)
- Mario Apata
- Center for Evolution & Medicine, School of Life Sciences, Arizona State University, Tempe, AZ, 85821, USA
| | - Susanne P Pfeifer
- Center for Evolution & Medicine, School of Life Sciences, Arizona State University, Tempe, AZ, 85821, USA.
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