1
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Luo M, Hu J. Alternative splicing in parallel evolution and the evolutionary potential in sticklebacks. J Anim Ecol 2024. [PMID: 39056271 DOI: 10.1111/1365-2656.14157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 06/28/2024] [Indexed: 07/28/2024]
Abstract
Repeatability of adaptation to similar environments provides opportunity to evaluate the predictability of natural selection. While many studies have investigated gene expression differences between populations adapted to contrasting environments, the role of post-transcriptional processes such as alternative splicing has rarely been evaluated in the context of parallel adaptation. To address the aforementioned knowledge gap, we reanalysed transcriptomic data from three pairs of threespine stickleback (Gasterosteus aculeatus) ecotypes adapted to marine or freshwater environment. First, we identified genes with repeated expression or splicing divergence across ecotype pairs, and compared the genetic architecture and biological processes between parallelly expressed and parallelly spliced loci. Second, we analysed the extent to which parallel adaptation was reflected at gene expression and alternative splicing levels. Finally, we tested how the two axes of transcriptional variation differed in their potential for evolutionary change. Although both repeated differential splicing and differential expression across ecotype pairs showed tendency for parallel divergence, the degree of parallelism was lower for splicing than expression. Furthermore, parallel divergences in splicing and expression were likely to be associated with distinct cis-regulatory genetic variants and functionally unique set of genes. Finally, we found that parallelly spliced genes showed higher nucleotide diversity than parallelly expressed genes, indicating splicing is less susceptible to genetic variation erosion during parallel adaptation. Our results provide novel insight into the role of splicing in parallel adaptation, and underscore the contribution of splicing to the evolutionary potential of wild populations under environmental change.
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Affiliation(s)
- Man Luo
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Center for Evolutionary Biology, School of Life Sciences, Fudan University, Shanghai, China
| | - Juntao Hu
- Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Center for Evolutionary Biology, School of Life Sciences, Fudan University, Shanghai, China
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2
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Combrink LL, Rosenthal WC, Boyle LJ, Rick JA, Mandeville EG, Krist AC, Walters AW, Wagner CE. Parallel shifts in trout feeding morphology suggest rapid adaptation to alpine lake environments. Evolution 2023; 77:1522-1538. [PMID: 37082829 PMCID: PMC10309971 DOI: 10.1093/evolut/qpad059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 03/13/2023] [Accepted: 04/14/2023] [Indexed: 04/22/2023]
Abstract
Eco-evolutionary interactions following ecosystem change provide critical insight into the ability of organisms to adapt to shifting resource landscapes. Here we explore evidence for the rapid parallel evolution of trout feeding morphology following eco-evolutionary interactions with zooplankton in alpine lakes stocked at different points in time in the Wind River Range (Wyoming, USA). In this system, trout predation has altered the zooplankton species community and driven a decrease in average zooplankton size. In some lakes that were stocked decades ago, we find shifts in gill raker traits consistent with the hypothesis that trout have rapidly adapted to exploit available smaller-bodied zooplankton more effectively. We explore this morphological response in multiple lake populations across two species of trout (cutthroat trout, Oncorhynchus clarkii, and golden trout Oncorhynchus aguabonita) and examine the impact of resource availability on morphological variation in gill raker number among lakes. Furthermore, we present genetic data to provide evidence that historically stocked cutthroat trout populations likely derive from multiple population sources, and incorporate variation from genomic relatedness in our exploration of environmental predictors of feeding morphology. These findings describe rapid adaptation and eco-evolutionary interactions in trout and document an evolutionary response to novel, contemporary ecosystem change.
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Affiliation(s)
- Lucia L Combrink
- Department of Botany, University of Wyoming, Laramie, WY, United States
| | - William C Rosenthal
- Department of Botany, University of Wyoming, Laramie, WY, United States
- Program in Ecology and Evolution, University of Wyoming, Laramie, WY, United States
| | - Lindsey J Boyle
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY, United States
| | - Jessica A Rick
- Department of Botany, University of Wyoming, Laramie, WY, United States
- Program in Ecology and Evolution, University of Wyoming, Laramie, WY, United States
| | - Elizabeth G Mandeville
- Department of Botany, University of Wyoming, Laramie, WY, United States
- Program in Ecology and Evolution, University of Wyoming, Laramie, WY, United States
| | - Amy C Krist
- Program in Ecology and Evolution, University of Wyoming, Laramie, WY, United States
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY, United States
| | - Annika W Walters
- U.S. Geological Survey, Wyoming Cooperative Fish and Wildlife Research Unit, Department of Zoology and Physiology and Program in Ecology and Evolution, University of Wyoming, Laramie, WY, United States
| | - Catherine E Wagner
- Department of Botany, University of Wyoming, Laramie, WY, United States
- Program in Ecology and Evolution, University of Wyoming, Laramie, WY, United States
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3
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Venkataram S, Kryazhimskiy S. Evolutionary repeatability of emergent properties of ecological communities. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220047. [PMID: 37004728 PMCID: PMC10067272 DOI: 10.1098/rstb.2022.0047] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 12/07/2022] [Indexed: 04/04/2023] Open
Abstract
Most species belong to ecological communities where their interactions give rise to emergent community-level properties, such as diversity and productivity. Understanding and predicting how these properties change over time has been a major goal in ecology, with important practical implications for sustainability and human health. Less attention has been paid to the fact that community-level properties can also change because member species evolve. Yet, our ability to predict long-term eco-evolutionary dynamics hinges on how repeatably community-level properties change as a result of species evolution. Here, we review studies of evolution of both natural and experimental communities and make the case that community-level properties at least sometimes evolve repeatably. We discuss challenges faced in investigations of evolutionary repeatability. In particular, only a handful of studies enable us to quantify repeatability. We argue that quantifying repeatability at the community level is critical for approaching what we see as three major open questions in the field: (i) Is the observed degree of repeatability surprising? (ii) How is evolutionary repeatability at the community level related to repeatability at the level of traits of member species? (iii) What factors affect repeatability? We outline some theoretical and empirical approaches to addressing these questions. Advances in these directions will not only enrich our basic understanding of evolution and ecology but will also help us predict eco-evolutionary dynamics. This article is part of the theme issue 'Interdisciplinary approaches to predicting evolutionary biology'.
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Affiliation(s)
- Sandeep Venkataram
- Department of Ecology, Behavior and Evolution, UC San Diego, La Jolla, CA 92093, USA
| | - Sergey Kryazhimskiy
- Department of Ecology, Behavior and Evolution, UC San Diego, La Jolla, CA 92093, USA
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4
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Abstract
The repeated adaptation of oceanic threespine sticklebacks to fresh water has made it a premier organism to study parallel evolution. These small fish have multiple distinct ecotypes that display a wide range of diverse phenotypic traits. Ecotypes are easily crossed in the laboratory, and families are large and develop quickly enough for quantitative trait locus analyses, positioning the threespine stickleback as a versatile model organism to address a wide range of biological questions. Extensive genomic resources, including linkage maps, a high-quality reference genome, and developmental genetics tools have led to insights into the genomic basis of adaptation and the identification of genomic changes controlling traits in vertebrates. Recently, threespine sticklebacks have been used as a model system to identify the genomic basis of highly complex traits, such as behavior and host-microbiome and host-parasite interactions. We review the latest findings and new avenues of research that have led the threespine stickleback to be considered a supermodel of evolutionary genomics.
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Affiliation(s)
- Kerry Reid
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794, USA;
| | - Michael A Bell
- University of California Museum of Paleontology, Berkeley, California 94720, USA
| | - Krishna R Veeramah
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794, USA;
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5
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Navon D, Hatini P, Zogbaum L, Albertson RC. The genetic basis of coordinated plasticity across functional units in a Lake Malawi cichlid mapping population. Evolution 2021; 75:672-687. [PMID: 33438760 DOI: 10.1111/evo.14157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 12/15/2020] [Accepted: 12/22/2020] [Indexed: 11/28/2022]
Abstract
Adaptive radiations are often stereotypical, as populations repeatedly specialize along conserved environmental axes. Phenotypic plasticity may be similarly stereotypical, as individuals respond to environmental cues. These parallel patterns of variation, which are often consistent across traits, have led researchers to propose that plasticity can facilitate predictable patterns of evolution along environmental gradients. This "flexible stem" model of evolution raises questions about the genetic nature of plasticity, including how complex is the genetic basis for plasticity? Is plasticity across traits mediated by many distinct loci, or few "global" regulators? To address these questions, we reared a hybrid cichlid mapping population on alternate diet regimes mimicking an important environmental axis. We show that plasticity across an array of ecologically relevant traits is generally morphologically integrated, such that traits respond in a coordinated manner, especially those with overlapping function. Our genetic data are more ambiguous. While our mapping experiment provides little evidence for global genetic regulators of plasticity, these data do contain a genetic signal for the integration of plasticity across traits. Overall, our data suggest a compromise between genetic modularity, whereby plasticity may evolve independently across traits, and low level but widespread genetic integration, establishing the potential for plasticity to experience coordinated evolution.
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Affiliation(s)
- Dina Navon
- Graduate Program in Organismal & Evolutionary Biology, University of Massachusetts Amherst, Amherst, Massachusetts, 01003.,Rutgers University Human Genetics Institute, Piscataway, New Jersey, 08854
| | - Paul Hatini
- Department of Biology, Morrill Science Center, University of Massachusetts Amherst, Amherst, Massachusetts, 01003
| | - Lily Zogbaum
- Biology Department, Swarthmore College, Swarthmore, Pennsylvania, 19081
| | - R Craig Albertson
- Graduate Program in Organismal & Evolutionary Biology, University of Massachusetts Amherst, Amherst, Massachusetts, 01003.,Department of Biology, Morrill Science Center, University of Massachusetts Amherst, Amherst, Massachusetts, 01003
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6
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Magalhaes IS, Whiting JR, D'Agostino D, Hohenlohe PA, Mahmud M, Bell MA, Skúlason S, MacColl ADC. Intercontinental genomic parallelism in multiple three-spined stickleback adaptive radiations. Nat Ecol Evol 2021; 5:251-261. [PMID: 33257817 PMCID: PMC7858233 DOI: 10.1038/s41559-020-01341-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 10/05/2020] [Indexed: 12/22/2022]
Abstract
Parallelism, the evolution of similar traits in populations diversifying in similar conditions, provides strong evidence of adaptation by natural selection. Many studies of parallelism focus on comparisons of different ecotypes or contrasting environments, defined a priori, which could upwardly bias the apparent prevalence of parallelism. Here, we estimated genomic parallelism associated with components of environmental and phenotypic variation at an intercontinental scale across four freshwater adaptive radiations (Alaska, British Columbia, Iceland and Scotland) of the three-spined stickleback (Gasterosteus aculeatus). We combined large-scale biological sampling and phenotyping with restriction site associated DNA sequencing (RAD-Seq) data from 73 freshwater lake populations and four marine ones (1,380 fish) to associate genome-wide allele frequencies with continuous distributions of environmental and phenotypic variation. Our three main findings demonstrate that (1) quantitative variation in phenotypes and environments can predict genomic parallelism; (2) genomic parallelism at the early stages of adaptive radiations, even at large geographic scales, is founded on standing variation; and (3) similar environments are a better predictor of genome-wide parallelism than similar phenotypes. Overall, this study validates the importance and predictive power of major phenotypic and environmental factors likely to influence the emergence of common patterns of genomic divergence, providing a clearer picture than analyses of dichotomous phenotypes and environments.
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Affiliation(s)
- Isabel S Magalhaes
- School of Life Sciences, University of Nottingham, University Park, Nottingham, UK.
- Department of Life Sciences, Whitelands College, University of Roehampton, London, UK.
| | - James R Whiting
- School of Life Sciences, University of Nottingham, University Park, Nottingham, UK.
- Biosciences, College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, London, UK.
| | - Daniele D'Agostino
- School of Life Sciences, University of Nottingham, University Park, Nottingham, UK
| | - Paul A Hohenlohe
- Institute for Bioinformatics and Evolutionary Studies, Department of Biological Sciences, University of Idaho, Moscow, ID, USA
| | - Muayad Mahmud
- School of Life Sciences, University of Nottingham, University Park, Nottingham, UK
- Erbil Polytechnic University, Kurdistan Region, Iraq
| | - Michael A Bell
- Museum of Paleontology, University of California, Berkeley, CA, USA
| | - Skúli Skúlason
- Department of Aquaculture and Fish Biology, Hólar University, Sauðárkrókur, Iceland
- Icelandic Museum of Natural History, Suðurlandsbraut, Reykjavík, Iceland
| | - Andrew D C MacColl
- School of Life Sciences, University of Nottingham, University Park, Nottingham, UK
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7
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Zogbaum L, Friend PG, Albertson RC. Plasticity and genetic basis of cichlid gill arch anatomy reveal novel roles for Hedgehog signaling. Mol Ecol 2021; 30:761-774. [PMID: 33278044 DOI: 10.1111/mec.15766] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 11/17/2020] [Accepted: 11/24/2020] [Indexed: 01/10/2023]
Abstract
Teleost gill arches are exquisitely evolved to maximize foraging efficiency, and include structures for the capture, filtering, and processing of prey. While both plasticity and a genetic basis for gill arch traits have been noted, the relative contributions of genetics and the environment in shaping these structures remains poorly understood. East African cichlids are particularly useful in this line of study due to their highly diverse and plastic feeding apparatus. Here we explore the gene-by-environmental effects on cichlid GRs by rearing pure bred species and their F3 hybrids in different foraging environments. We find that anatomical differences between species are dependent on the environment. The genetic architecture of these traits is also largely distinct between foraging environments. We did, however, note a few genomic "hotspots" where multiple traits map to a common region. One of these, for GR number across multiple arches, maps to the ptch1 locus, a key component of the Hedgehog (Hh) pathway that has previously been implicated in cichlid oral jaw shape and plasticity. Since Hh signalling has not previously been implicated in GR development, we explored functional roles for this pathway. Using a small molecule inhibitor in cichlids, as well as zebrafish transgenic systems, we demonstrate that Hh levels negatively regulate GR number, and are both necessary and sufficient to maintain plasticity in this trait. In all these data underscore the critical importance of the environment in determining the relationship between genotype and phenotype, and provide a molecular inroad to better understand the origins of variation in this important foraging-related trait.
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Affiliation(s)
| | | | - R Craig Albertson
- Department of Biology, University of Massachusetts, Amherst, MA, USA
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8
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Delgado ML, Manosalva A, Urbina MA, Habit E, Link O, Ruzzante DE. Genomic basis of the loss of diadromy in Galaxias maculatus: Insights from reciprocal transplant experiments. Mol Ecol 2020; 29:4857-4870. [PMID: 33048403 DOI: 10.1111/mec.15686] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 10/05/2020] [Accepted: 10/06/2020] [Indexed: 12/18/2022]
Abstract
Diadromy is known for having major effects on the distribution and richness of aquatic species, and so does its loss. The loss of diadromy has led to the diversification of many species, yet research focusing on understanding its molecular basis and consequences are limited. This is particularly true for amphidromous species despite being the most abundant group of diadromous species. Galaxias maculatus, an amphidromous species and one of the most widely distributed fishes in the Southern Hemisphere, exhibits many instances of nonmigratory or resident populations. The existence of naturally replicated resident populations in Patagonia can serve as an ideal system for the study of the mechanisms that lead to the loss of the diadromy and its ecological and evolutionary consequences. Here, we studied two adjacent river systems in which resident populations are genetically differentiated yet derived from the same diadromous population. By combining a reciprocal transplant experiment with genomic data, we showed that the two resident populations followed different evolutionary pathways by exhibiting a differential response in their capacity to survive in salt water. While one resident population was able to survive salt water, the other was not. Genomic analyses provided insights into the genes that distinguished (a) migratory from nonmigratory populations; (b) populations that can vs those that cannot survive a saltwater environment; and (c) between these resident populations. This study demonstrates that the loss of diadromy can be achieved by different pathways and that environmental (selection) and random (genetic drift) forces shape this dynamic evolutionary process.
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Affiliation(s)
| | - Aliro Manosalva
- Departamento de Sistemas Acuáticos, Facultad de Ciencias Ambientales y Centro EULA, Universidad de Concepción, Concepción, Chile
| | - Mauricio A Urbina
- Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Concepción, Chile.,Instituto Milenio de Oceanografía (IMO), Universidad de Concepción, Concepción, Chile
| | - Evelyn Habit
- Departamento de Sistemas Acuáticos, Facultad de Ciencias Ambientales y Centro EULA, Universidad de Concepción, Concepción, Chile
| | - Oscar Link
- Departamento de Ingeniería Civil, Facultad de Ingeniería, Universidad de Concepción, Concepción, Chile
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9
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He S, Li L, Lv LY, Cai WJ, Dou YQ, Li J, Tang SL, Chen X, Zhang Z, Xu J, Zhang YP, Yin Z, Wuertz S, Tao YX, Kuhl H, Liang XF. Mandarin fish (Sinipercidae) genomes provide insights into innate predatory feeding. Commun Biol 2020; 3:361. [PMID: 32647268 PMCID: PMC7347838 DOI: 10.1038/s42003-020-1094-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 06/12/2020] [Indexed: 01/04/2023] Open
Abstract
Mandarin fishes (Sinipercidae) are piscivores that feed solely on live fry. Unlike higher vertebrates, teleosts exhibit feeding behavior driven mainly by genetic responses, with no modification by learning from parents. Mandarin fishes could serve as excellent model organisms for studying feeding behavior. We report a long-read, chromosomal-scale genome assembly for Siniperca chuatsi and genome assemblies for Siniperca kneri, Siniperca scherzeri and Coreoperca whiteheadi. Positive selection analysis revealed rapid adaptive evolution of genes related to predatory feeding/aggression, growth, pyloric caeca and euryhalinity. Very few gill rakers are observed in mandarin fishes; analogously, we found that zebrafish deficient in edar had a gill raker loss phenotype and a more predatory habit, with reduced intake of zooplankton but increased intake of prey fish. Higher expression of bmp4, which could inhibit edar expression and gill raker development through binding of a Xvent-1 site upstream of edar, may cause predatory feeding in Siniperca.
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Affiliation(s)
- Shan He
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Ling Li
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
- Department of Ecophysiology and Aquaculture, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
| | - Li-Yuan Lv
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Wen-Jing Cai
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Ya-Qi Dou
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Jiao Li
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Shu-Lin Tang
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Xu Chen
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Zhen Zhang
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Jing Xu
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Yan-Peng Zhang
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China
| | - Zhan Yin
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China
| | - Sven Wuertz
- Department of Ecophysiology and Aquaculture, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
| | - Ya-Xiong Tao
- Department of Anatomy, Physiology & Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA
| | - Heiner Kuhl
- Department of Ecophysiology and Aquaculture, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany.
| | - Xu-Fang Liang
- College of Fisheries, Chinese Perch Research Center, Huazhong Agricultural University, Wuhan, China.
- Innovation Base for Chinese Perch Breeding, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Wuhan, China.
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10
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Ishikawa A, Kitano J. Diversity in reproductive seasonality in the three-spined stickleback, Gasterosteus aculeatus. ACTA ACUST UNITED AC 2020; 223:223/Suppl_1/jeb208975. [PMID: 32034046 DOI: 10.1242/jeb.208975] [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] [Indexed: 12/31/2022]
Abstract
The annual timing of reproduction is a key life history trait with a large effect on fitness. Populations often vary in the timing and duration of reproduction to adapt to different seasonality of ecological and environmental variables between habitats. However, little is known about the molecular genetic mechanisms underlying interpopulation variation in reproductive seasonality. Here, we demonstrate that the three-spined stickleback (Gasterosteus aculeatus) is a good model for molecular genetic analysis of variations in reproductive seasonality. We first compiled data on reproductive seasons of diverse ecotypes, covering marine-anadromous, lake and stream ecotypes, of three-spined stickleback inhabiting a wide range of latitudes. Our analysis showed that both ecotype and latitude significantly contribute to variation in reproductive seasons. Stream ecotypes tend to start breeding earlier and end later than other ecotypes. Populations from lower latitudes tend to start breeding earlier than those from higher latitudes in all three ecotypes. Additionally, stream ecotypes tend to have extended breeding seasons at lower latitudes than at higher latitudes, leading to nearly year-round reproduction in the most southern stream populations. A review of recent progress in our understanding of the physiological mechanisms underlying seasonal reproduction in the three-spined stickleback indicates that photoperiod is an important external cue that stimulates and/or suppresses reproduction in this species. Taking advantage of genomic tools available for this species, the three-spined stickleback will be a good model to investigate what kinds of genes and mutations underlie variations in the physiological signalling pathways that regulate reproduction in response to photoperiod.
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Affiliation(s)
- Asano Ishikawa
- Ecological Genetics Laboratory, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan .,Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), Yata 1111, Mishima, Shizuoka 411-8540, Japan
| | - Jun Kitano
- Ecological Genetics Laboratory, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan.,Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), Yata 1111, Mishima, Shizuoka 411-8540, Japan
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11
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Oke KB, Cunningham CJ, Quinn TP, Hendry AP. Independent lineages in a common environment: the roles of determinism and contingency in shaping the migration timing of even- versus odd-year pink salmon over broad spatial and temporal scales. Ecol Lett 2019; 22:1547-1556. [PMID: 31290586 DOI: 10.1111/ele.13337] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 03/30/2019] [Accepted: 06/13/2019] [Indexed: 01/02/2023]
Abstract
Studies of parallel evolution are seldom able to disentangle the influence of cryptic environmental variation from that of evolutionary history; whereas the unique life history of pink salmon (Oncorhynchus gorbuscha) presents an opportunity to do so. All pink salmon mature at age two and die after breeding. Hence, pink salmon bred in even years are completely reproductively isolated from those bred in odd years, even if the two lineages bred in same location. We used time series (mean = 7 years, maximum = 74 years) of paired even- and odd-year populations from 36 rivers spanning over 2000 km to explore parallelism in migration timing, a trait with a strong genetic basis. Migration timing was highly parallel, being determined almost entirely by local environmental differences among rivers. Interestingly, interannual changes in migration timing different somewhat between lineages. Overall, our findings indicate very strong determinism, with only a minor contribution of contingency.
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Affiliation(s)
- Krista B Oke
- Department of Biology and Redpath Museum, McGill University, Montreal, QC, H3A 2K6, Canada
| | - Curry J Cunningham
- Fisheries, Aquatic Science & Technology Laboratory, Alaska Pacific University, 4101 University Dr, Anchorage, AK, 99508, USA
| | - Thomas P Quinn
- School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, 98195, USA
| | - Andrew P Hendry
- Department of Biology and Redpath Museum, McGill University, Montreal, QC, H3A 2K6, Canada
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12
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Fisher KJ, Kryazhimskiy S, Lang GI. Detecting genetic interactions using parallel evolution in experimental populations. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180237. [PMID: 31154981 DOI: 10.1098/rstb.2018.0237] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Eukaryotic genomes contain thousands of genes organized into complex and interconnected genetic interaction networks. Most of our understanding of how genetic variation affects these networks comes from quantitative-trait loci mapping and from the systematic analysis of double-deletion (or knockdown) mutants, primarily in the yeast Saccharomyces cerevisiae. Evolve and re-sequence experiments are an alternative approach for identifying novel functional variants and genetic interactions, particularly between non-loss-of-function mutations. These experiments leverage natural selection to obtain genotypes with functionally important variants and positive genetic interactions. However, no systematic methods for detecting genetic interactions in these data are yet available. Here, we introduce a computational method based on the idea that variants in genes that interact will co-occur in evolved genotypes more often than expected by chance. We apply this method to a previously published yeast experimental evolution dataset. We find that genetic targets of selection are distributed non-uniformly among evolved genotypes, indicating that genetic interactions had a significant effect on evolutionary trajectories. We identify individual gene pairs with a statistically significant genetic interaction score. The strongest interaction is between genes TRK1 and PHO84, genes that have not been reported to interact in previous systematic studies. Our work demonstrates that leveraging parallelism in experimental evolution is useful for identifying genetic interactions that have escaped detection by other methods. This article is part of the theme issue 'Convergent evolution in the genomics era: new insights and directions'.
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Affiliation(s)
- Kaitlin J Fisher
- 1 Department of Biological Sciences, Lehigh University , Bethlehem, PA 18015 , USA
| | - Sergey Kryazhimskiy
- 2 Division of Biological Sciences, University of California San Diego , La Jolla, CA 92093 , USA
| | - Gregory I Lang
- 1 Department of Biological Sciences, Lehigh University , Bethlehem, PA 18015 , USA
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Wucherpfennig JI, Miller CT, Kingsley DM. Efficient CRISPR-Cas9 editing of major evolutionary loci in sticklebacks. EVOLUTIONARY ECOLOGY RESEARCH 2019; 20:107-132. [PMID: 34899072 PMCID: PMC8664273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
BACKGROUND Stickleback fish are widely used to study the genetic and ecological basis of phenotypic evolution. Although several major loci have now been identified that contribute to evolutionary differences between wild populations, further study of the phenotypes associated with particular genes and mutations has been limited by the difficulty of generating targeted mutations at precise locations in the stickleback genome. APPROACH AND AIMS We compared different methods of expressing single-guide RNAs (sgRNAs) and Cas9 activity in fertilized stickleback eggs. We used an easily scored pigmentation gene (SLC24A5) to screen for molecular lesions, phenotypic effects, and possible germline transmission of newly induced alleles. We then used the optimized CRISPR methods to target two major evolutionary loci in sticklebacks, KITLG and EDA. We hypothesized that coding region mutations in the KITLG gene would alter body pigmentation and possibly sex determination, and that mutations in the EDA gene would disrupt the formation of most armor plates, fin rays, spines, teeth, and gill rakers. RESULTS Targeted deletions were successfully induced at each target locus by co-injecting one-cell stage stickleback embryos with either Cas9 mRNA or Cas9 protein, together with sgRNAs designed to protein-coding exons. Founder animals were typically mosaic for multiple mutations, which they transmitted through the germline at overall rates of 21 to 100%. We found that the copy of KITLG on the X chromosome (KITLGX) has diverged from the KITLG on the Y chromosome (KITLGY). Predicted loss-of-function mutations in the KITLGX gene dramatically altered pigmentation in both external skin and internal organ, but the same was not true for KITLGY mutations. Predicted loss-of-function mutations in either the KITLGX or KITLGY genes did not lead to sex reversal or prevent fertility. Homozygous loss-of-function mutations in the EDA gene led to complete loss of armor plates, severe reduction or loss of most soft rays in the dorsal, anal, and caudal fins, and severe reductions in tooth and gill raker number. In contrast, long dorsal and pelvic spines remained intact in EDA mutant animals, suggesting that common co-segregation of plate loss and spine reduction in wild populations is unlikely to be due to pleiotropic effects of EDA mutations. CONCLUSION CRISPR-Cas9 approaches can be used to induce germline mutations in key evolutionary loci in sticklebacks. Targeted coding region mutations confirm an important role for KITLG and EDA in skin pigmentation and armor plate reduction, respectively. They also provide new information about the functions of these genes in other body structures.
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Affiliation(s)
- Julia I Wucherpfennig
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305-5329, USA
| | - Craig T Miller
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, California 94720, USA
| | - David M Kingsley
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305-5329, USA
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305-5329, USA
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14
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Hohenlohe PA, Magalhaes IS. The Population Genomics of Parallel Adaptation: Lessons from Threespine Stickleback. POPULATION GENOMICS 2019. [DOI: 10.1007/13836_2019_67] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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15
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Cleves PA, Hart JC, Agoglia RM, Jimenez MT, Erickson PA, Gai L, Miller CT. An intronic enhancer of Bmp6 underlies evolved tooth gain in sticklebacks. PLoS Genet 2018; 14:e1007449. [PMID: 29902209 PMCID: PMC6019817 DOI: 10.1371/journal.pgen.1007449] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 06/26/2018] [Accepted: 05/25/2018] [Indexed: 12/30/2022] Open
Abstract
Threespine stickleback fish offer a powerful system to dissect the genetic basis of morphological evolution in nature. Marine sticklebacks have repeatedly invaded and adapted to numerous freshwater environments throughout the Northern hemisphere. In response to new diets in freshwater habitats, changes in craniofacial morphology, including heritable increases in tooth number, have evolved in derived freshwater populations. Using a combination of quantitative genetics and genome resequencing, here we fine-mapped a quantitative trait locus (QTL) regulating evolved tooth gain to a cluster of ten QTL-associated single nucleotide variants, all within intron four of Bone Morphogenetic Protein 6 (Bmp6). Transgenic reporter assays revealed this intronic region contains a tooth enhancer. We induced mutations in Bmp6, revealing required roles for survival, growth, and tooth patterning. Transcriptional profiling of Bmp6 mutant dental tissues identified significant downregulation of a set of genes whose orthologs were previously shown to be expressed in quiescent mouse hair stem cells. Collectively these data support a model where mutations within a Bmp6 intronic tooth enhancer contribute to evolved tooth gain, and suggest that ancient shared genetic circuitry regulates the regeneration of diverse vertebrate epithelial appendages including mammalian hair and fish teeth.
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Affiliation(s)
- Phillip A. Cleves
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley CA, United States of America
| | - James C. Hart
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley CA, United States of America
| | - Rachel M. Agoglia
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley CA, United States of America
| | - Monica T. Jimenez
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley CA, United States of America
| | - Priscilla A. Erickson
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley CA, United States of America
| | - Linda Gai
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley CA, United States of America
| | - Craig T. Miller
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley CA, United States of America
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16
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Environmental selection during the last ice age on the mother-to-infant transmission of vitamin D and fatty acids through breast milk. Proc Natl Acad Sci U S A 2018; 115:E4426-E4432. [PMID: 29686092 PMCID: PMC5948952 DOI: 10.1073/pnas.1711788115] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The frequency of the human-specific EDAR V370A isoform is highly elevated in North and East Asian populations. The gene is known to have several pleiotropic effects, among which are sweat gland density and ductal branching in the mammary gland. The former has led some geneticists to argue that the near-fixation of this allele was caused by selection for modulation of thermoregulatory sweating. We provide an alternative hypothesis, that selection instead acted on the allele’s effect of increasing ductal branching in the mammary gland, thereby amplifying the transfer of critical nutrients to infants via mother’s milk. This is likely to have occurred during the Last Glacial Maximum when a human population was genetically isolated in the high-latitude environment of the Beringia. Because of the ubiquitous adaptability of our material culture, some human populations have occupied extreme environments that intensified selection on existing genomic variation. By 32,000 years ago, people were living in Arctic Beringia, and during the Last Glacial Maximum (LGM; 28,000–18,000 y ago), they likely persisted in the Beringian refugium. Such high latitudes provide only very low levels of UV radiation, and can thereby lead to dangerously low levels of biosynthesized vitamin D. The physiological effects of vitamin D deficiency range from reduced dietary absorption of calcium to a compromised immune system and modified adipose tissue function. The ectodysplasin A receptor (EDAR) gene has a range of pleiotropic effects, including sweat gland density, incisor shoveling, and mammary gland ductal branching. The frequency of the human-specific EDAR V370A allele appears to be uniquely elevated in North and East Asian and New World populations due to a bout of positive selection likely to have occurred circa 20,000 y ago. The dental pleiotropic effects of this allele suggest an even higher occurrence among indigenous people in the Western Hemisphere before European colonization. We hypothesize that selection on EDAR V370A occurred in the Beringian refugium because it increases mammary ductal branching, and thereby may amplify the transfer of critical nutrients in vitamin D-deficient conditions to infants via mothers’ milk. This hypothesized selective context for EDAR V370A was likely intertwined with selection on the fatty acid desaturase (FADS) gene cluster because it is known to modulate lipid profiles transmitted to milk from a vitamin D-rich diet high in omega-3 fatty acids.
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Genetic Dissection of a Supergene Implicates Tfap2a in Craniofacial Evolution of Threespine Sticklebacks. Genetics 2018; 209:591-605. [PMID: 29593029 DOI: 10.1534/genetics.118.300760] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 03/26/2018] [Indexed: 02/07/2023] Open
Abstract
In nature, multiple adaptive phenotypes often coevolve and can be controlled by tightly linked genetic loci known as supergenes. Dissecting the genetic basis of these linked phenotypes is a major challenge in evolutionary genetics. Multiple freshwater populations of threespine stickleback fish (Gasterosteus aculeatus) have convergently evolved two constructive craniofacial traits, longer branchial bones and increased pharyngeal tooth number, likely as adaptations to dietary differences between marine and freshwater environments. Prior QTL mapping showed that both traits are partially controlled by overlapping genomic regions on chromosome 21 and that a regulatory change in Bmp6 likely underlies the tooth number QTL. Here, we mapped the branchial bone length QTL to a 155 kb, eight-gene interval tightly linked to, but excluding the coding regions of Bmp6 and containing the candidate gene Tfap2a Further recombinant mapping revealed this bone length QTL is separable into at least two loci. During embryonic and larval development, Tfap2a was expressed in the branchial bone primordia, where allele specific expression assays revealed the freshwater allele of Tfap2a was expressed at lower levels relative to the marine allele in hybrid fish. Induced loss-of-function mutations in Tfap2a revealed an essential role in stickleback craniofacial development and show that bone length is sensitive to Tfap2a dosage in heterozygotes. Combined, these results suggest that closely linked but genetically separable changes in Bmp6 and Tfap2a contribute to a supergene underlying evolved skeletal gain in multiple freshwater stickleback populations.
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18
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Peichel CL, Marques DA. The genetic and molecular architecture of phenotypic diversity in sticklebacks. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2015.0486. [PMID: 27994127 DOI: 10.1098/rstb.2015.0486] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/12/2016] [Indexed: 11/12/2022] Open
Abstract
A major goal of evolutionary biology is to identify the genotypes and phenotypes that underlie adaptation to divergent environments. Stickleback fish, including the threespine stickleback (Gasterosteus aculeatus) and the ninespine stickleback (Pungitius pungitius), have been at the forefront of research to uncover the genetic and molecular architecture that underlies phenotypic diversity and adaptation. A wealth of quantitative trait locus (QTL) mapping studies in sticklebacks have provided insight into long-standing questions about the distribution of effect sizes during adaptation as well as the role of genetic linkage in facilitating adaptation. These QTL mapping studies have also provided a basis for the identification of the genes that underlie phenotypic diversity. These data have revealed that mutations in regulatory elements play an important role in the evolution of phenotypic diversity in sticklebacks. Genetic and molecular studies in sticklebacks have also led to new insights on the genetic basis of repeated evolution and suggest that the same loci are involved about half of the time when the same phenotypes evolve independently. When the same locus is involved, selection on standing variation and repeated mutation of the same genes have both contributed to the evolution of similar phenotypes in independent populations.This article is part of the themed issue 'Evo-devo in the genomics era, and the origins of morphological diversity'.
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Affiliation(s)
- Catherine L Peichel
- Divisions of Basic Sciences and Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA
| | - David A Marques
- Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.,Department of Fish Ecology and Evolution, Eawag, Swiss Federal Institute for Aquatic Science and Technology, 6047 Kastanienbaum, Switzerland
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19
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Currey MC, Bassham S, Perry S, Cresko WA. Developmental timing differences underlie armor loss across threespine stickleback populations. Evol Dev 2017; 19:231-243. [PMID: 29115024 DOI: 10.1111/ede.12242] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Comparing ontogenetic patterns within a well-described evolutionary context aids in inferring mechanisms of change, including heterochronies or deletion of developmental pathways. Because selection acts on phenotypes throughout ontogeny, any within-taxon developmental variation has implications for evolvability. We compare ontogenetic order and timing of locomotion and defensive traits in three populations of threespine stickleback that have evolutionarily divergent adult forms. This analysis adds to the growing understanding of developmental genetic mechanisms of adaptive change in this evolutionary model species by delineating when chondrogenesis and osteogenesis in two derived populations begin to deviate from the developmental pattern in their immediate ancestors. We found that differences in adult defensive morphologies arise through abolished or delayed initiation of these traits rather than via an overall heterochronic shift, that intra-population ontogenetic variation is increased for some derived traits, and that altered armor developmental timing differentiates the derived populations from each other despite parallels in adult lateral plate armor phenotypes. We found that changes in ossified elements of the pelvic armor are linked to delayed and incomplete development of an early-forming pelvic cartilage, and that this disruption likely presages the variable pelvic vestiges documented in many derived populations.
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Affiliation(s)
- Mark C Currey
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon
| | - Susan Bassham
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon
| | - Stephen Perry
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon
| | - William A Cresko
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon
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20
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Sequence-Based Mapping and Genome Editing Reveal Mutations in Stickleback Hps5 Cause Oculocutaneous Albinism and the casper Phenotype. G3-GENES GENOMES GENETICS 2017; 7:3123-3131. [PMID: 28739598 PMCID: PMC5592937 DOI: 10.1534/g3.117.1125] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Here, we present and characterize the spontaneous X-linked recessive mutation casper, which causes oculocutaneous albinism in threespine sticklebacks (Gasterosteus aculeatus). In humans, Hermansky-Pudlak syndrome results in pigmentation defects due to disrupted formation of the melanin-containing lysosomal-related organelle (LRO), the melanosome. casper mutants display not only reduced pigmentation of melanosomes in melanophores, but also reductions in the iridescent silver color from iridophores, while the yellow pigmentation from xanthophores appears unaffected. We mapped casper using high-throughput sequencing of genomic DNA from bulked casper mutants to a region of the stickleback X chromosome (chromosome 19) near the stickleback ortholog of Hermansky-Pudlak syndrome 5 (Hps5). casper mutants have an insertion of a single nucleotide in the sixth exon of Hps5, predicted to generate an early frameshift. Genome editing using CRISPR/Cas9 induced lesions in Hps5 and phenocopied the casper mutation. Injecting single or paired Hps5 guide RNAs revealed higher incidences of genomic deletions from paired guide RNAs compared to single gRNAs. Stickleback Hps5 provides a genetic system where a hemizygous locus in XY males and a diploid locus in XX females can be used to generate an easily scored visible phenotype, facilitating quantitative studies of different genome editing approaches. Lastly, we show the ability to better visualize patterns of fluorescent transgenic reporters in Hps5 mutant fish. Thus, Hps5 mutations present an opportunity to study pigmented LROs in the emerging stickleback model system, as well as a tool to aid in assaying genome editing and visualizing enhancer activity in transgenic fish.
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21
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Martin CH, Erickson PA, Miller CT. The genetic architecture of novel trophic specialists: larger effect sizes are associated with exceptional oral jaw diversification in a pupfish adaptive radiation. Mol Ecol 2016; 26:624-638. [PMID: 27873369 DOI: 10.1111/mec.13935] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 10/20/2016] [Accepted: 10/25/2016] [Indexed: 12/14/2022]
Abstract
The genetic architecture of adaptation is fundamental to understanding the mechanisms and constraints governing diversification. However, most case studies focus on loss of complex traits or parallel speciation in similar environments. It is still unclear how the genetic architecture of these local adaptive processes compares to the architecture of evolutionary transitions contributing to morphological and ecological novelty. Here, we identify quantitative trait loci (QTL) between two trophic specialists in an excellent case study for examining the origins of ecological novelty: a sympatric radiation of pupfishes endemic to San Salvador Island, Bahamas, containing a large-jawed scale-eater and a short-jawed molluscivore with a skeletal nasal protrusion. These specialized niches and trophic traits are unique among over 2000 related species. Measurements of the fitness landscape on San Salvador demonstrate multiple fitness peaks and a larger fitness valley isolating the scale-eater from the putative ancestral intermediate phenotype of the generalist, suggesting that more large-effect QTL should contribute to its unique phenotype. We evaluated this prediction using an F2 intercross between these specialists. We present the first linkage map for pupfishes and detect significant QTL for sex and eight skeletal traits. Large-effect QTL contributed more to enlarged scale-eater jaws than the molluscivore nasal protrusion, consistent with predictions from the adaptive landscape. The microevolutionary genetic architecture of large-effect QTL for oral jaws parallels the exceptional diversification rates of oral jaws within the San Salvador radiation observed over macroevolutionary timescales and may have facilitated exceptional trophic novelty in this system.
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Affiliation(s)
- Christopher H Martin
- Department of Biology, University of North Carolina at Chapel Hill, Campus Box 3280, 120 South Rd, Chapel Hill, NC 27599-3280, USA
| | - Priscilla A Erickson
- Molecular and Cell Biology Department, University of California, Berkeley, CA 94720, USA.,Department of Biology, University of Virginia, 229 Gilmer Hall, 485 McCormick Road, P.O. Box 400328, Charlottesville, VA 22904, USA
| | - Craig T Miller
- Molecular and Cell Biology Department, University of California, Berkeley, CA 94720, USA
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22
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Marques DA, Lucek K, Haesler MP, Feller AF, Meier JI, Wagner CE, Excoffier L, Seehausen O. Genomic landscape of early ecological speciation initiated by selection on nuptial colour. Mol Ecol 2016; 26:7-24. [DOI: 10.1111/mec.13774] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 06/30/2016] [Accepted: 07/14/2016] [Indexed: 12/12/2022]
Affiliation(s)
- David Alexander Marques
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Eawag: Swiss Federal Institute of Aquatic Science and Technology; Kastanienbaum Switzerland
| | - Kay Lucek
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Eawag: Swiss Federal Institute of Aquatic Science and Technology; Kastanienbaum Switzerland
- University of Sheffield; Sheffield UK
| | - Marcel Philipp Haesler
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Eawag: Swiss Federal Institute of Aquatic Science and Technology; Kastanienbaum Switzerland
| | - Anna Fiona Feller
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Eawag: Swiss Federal Institute of Aquatic Science and Technology; Kastanienbaum Switzerland
| | - Joana Isabel Meier
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Eawag: Swiss Federal Institute of Aquatic Science and Technology; Kastanienbaum Switzerland
| | - Catherine E. Wagner
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Eawag: Swiss Federal Institute of Aquatic Science and Technology; Kastanienbaum Switzerland
- Department of Botany, Biodiversity Institute; University of Wyoming; Laramie WY USA
| | - Laurent Excoffier
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Swiss Institute of Bioinformatics; Lausanne Switzerland
| | - Ole Seehausen
- Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Eawag: Swiss Federal Institute of Aquatic Science and Technology; Kastanienbaum Switzerland
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23
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Erickson PA, Ellis NA, Miller CT. Microinjection for Transgenesis and Genome Editing in Threespine Sticklebacks. J Vis Exp 2016. [PMID: 27214565 DOI: 10.3791/54055] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The threespine stickleback fish has emerged as a powerful system to study the genetic basis of a wide variety of morphological, physiological, and behavioral phenotypes. The remarkably diverse phenotypes that have evolved as marine populations adapt to countless freshwater environments, combined with the ability to cross marine and freshwater forms, provide a rare vertebrate system in which genetics can be used to map genomic regions controlling evolved traits. Excellent genomic resources are now available, facilitating molecular genetic dissection of evolved changes. While mapping experiments generate lists of interesting candidate genes, functional genetic manipulations are required to test the roles of these genes. Gene regulation can be studied with transgenic reporter plasmids and BACs integrated into the genome using the Tol2 transposase system. Functions of specific candidate genes and cis-regulatory elements can be assessed by inducing targeted mutations with TALEN and CRISPR/Cas9 genome editing reagents. All methods require introducing nucleic acids into fertilized one-cell stickleback embryos, a task made challenging by the thick chorion of stickleback embryos and the relatively small and thin blastomere. Here, a detailed protocol for microinjection of nucleic acids into stickleback embryos is described for transgenic and genome editing applications to study gene expression and function, as well as techniques to assess the success of transgenesis and recover stable lines.
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Affiliation(s)
| | - Nicholas A Ellis
- Department of Molecular and Cell Biology, University of California, Berkeley
| | - Craig T Miller
- Department of Molecular and Cell Biology, University of California, Berkeley;
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24
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Ellis NA, Miller CT. Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton. J Vis Exp 2016. [PMID: 27213248 DOI: 10.3791/54056] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The posterior pharyngeal segments of the vertebrate head give rise to the branchial skeleton, the primary site of food processing in fish. The morphology of the fish branchial skeleton is matched to a species' diet. Threespine stickleback fish (Gasterosteus aculeatus) have emerged as a model system to study the genetic and developmental basis of evolved differences in a variety of traits. Marine populations of sticklebacks have repeatedly colonized countless new freshwater lakes and creeks. Adaptation to the new diet in these freshwater environments likely underlies a series of craniofacial changes that have evolved repeatedly in independently derived freshwater populations. These include three major patterning changes to the branchial skeleton: reductions in the number and length of gill raker bones, increases in pharyngeal tooth number, and increased branchial bone lengths. Here we describe a detailed protocol to dissect and flat-mount the internal branchial skeleton in threespine stickleback fish. Dissection of the entire three-dimensional branchial skeleton and mounting it flat into a largely two-dimensional prep allows for the easy visualization and quantification of branchial skeleton morphology. This dissection method is inexpensive, fast, relatively easy, and applicable to a wide variety of fish species. In sticklebacks, this efficient method allows the quantification of skeletal morphology in genetic crosses to map genomic regions controlling craniofacial patterning.
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Affiliation(s)
- Nicholas A Ellis
- Department of Molecular and Cell Biology, University of California, Berkeley
| | - Craig T Miller
- Department of Molecular and Cell Biology, University of California, Berkeley;
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25
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Erickson PA, Glazer AM, Killingbeck EE, Agoglia RM, Baek J, Carsanaro SM, Lee AM, Cleves PA, Schluter D, Miller CT. Partially repeatable genetic basis of benthic adaptation in threespine sticklebacks. Evolution 2016; 70:887-902. [PMID: 26947264 DOI: 10.1111/evo.12897] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 02/10/2016] [Accepted: 02/23/2016] [Indexed: 12/13/2022]
Abstract
The extent to which convergent adaptation to similar ecological niches occurs by a predictable genetic basis remains a fundamental question in biology. Threespine stickleback fish have undergone an adaptive radiation in which ancestral oceanic populations repeatedly colonized and adapted to freshwater habitats. In multiple lakes in British Columbia, two different freshwater ecotypes have evolved: a deep-bodied benthic form adapted to forage near the lake substrate, and a narrow-bodied limnetic form adapted to forage in open water. Here, we use genome-wide linkage mapping in marine × benthic F2 genetic crosses to test the extent of shared genomic regions underlying benthic adaptation in three benthic populations. We identify at least 100 Quantitative Trait Loci (QTL) harboring genes influencing skeletal morphology. The majority of QTL (57%) are unique to one cross. However, four genomic regions affecting eight craniofacial and armor phenotypes are found in all three benthic populations. We find that QTL are clustered in the genome and overlapping QTL regions are enriched for genomic signatures of natural selection. These findings suggest that benthic adaptation has occurred via both parallel and nonparallel genetic changes.
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Affiliation(s)
- Priscilla A Erickson
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Andrew M Glazer
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Emily E Killingbeck
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Rachel M Agoglia
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Jiyeon Baek
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Sara M Carsanaro
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Anthony M Lee
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Phillip A Cleves
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720
| | - Dolph Schluter
- Biodiversity Research Centre and Zoology Department, University of British Columbia, Vancouver, British Columbia, Canada
| | - Craig T Miller
- Department of Molecular and Cell Biology, University of California, Berkeley, California, 94720.
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26
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Marques DA, Lucek K, Meier JI, Mwaiko S, Wagner CE, Excoffier L, Seehausen O. Genomics of Rapid Incipient Speciation in Sympatric Threespine Stickleback. PLoS Genet 2016; 12:e1005887. [PMID: 26925837 PMCID: PMC4771382 DOI: 10.1371/journal.pgen.1005887] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 01/29/2016] [Indexed: 01/18/2023] Open
Abstract
Ecological speciation is the process by which reproductively isolated populations emerge as a consequence of divergent natural or ecologically-mediated sexual selection. Most genomic studies of ecological speciation have investigated allopatric populations, making it difficult to infer reproductive isolation. The few studies on sympatric ecotypes have focused on advanced stages of the speciation process after thousands of generations of divergence. As a consequence, we still do not know what genomic signatures of the early onset of ecological speciation look like. Here, we examined genomic differentiation among migratory lake and resident stream ecotypes of threespine stickleback reproducing in sympatry in one stream, and in parapatry in another stream. Importantly, these ecotypes started diverging less than 150 years ago. We obtained 34,756 SNPs with restriction-site associated DNA sequencing and identified genomic islands of differentiation using a Hidden Markov Model approach. Consistent with incipient ecological speciation, we found significant genomic differentiation between ecotypes both in sympatry and parapatry. Of 19 islands of differentiation resisting gene flow in sympatry, all were also differentiated in parapatry and were thus likely driven by divergent selection among habitats. These islands clustered in quantitative trait loci controlling divergent traits among the ecotypes, many of them concentrated in one region with low to intermediate recombination. Our findings suggest that adaptive genomic differentiation at many genetic loci can arise and persist in sympatry at the very early stage of ecotype divergence, and that the genomic architecture of adaptation may facilitate this.
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Affiliation(s)
- David A. Marques
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution & Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Computational and Molecular Population Genetics Lab, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- * E-mail:
| | - Kay Lucek
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution & Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Department of Animal and Plant Science, University of Sheffield, Sheffield, United Kingdom
| | - Joana I. Meier
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution & Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Computational and Molecular Population Genetics Lab, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Salome Mwaiko
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution & Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
| | - Catherine E. Wagner
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution & Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
- Biodiversity Institute, University of Wyoming, Wyoming, United States of America
| | - Laurent Excoffier
- Computational and Molecular Population Genetics Lab, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Ole Seehausen
- Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Fish Ecology and Evolution, Centre of Ecology, Evolution & Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland
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Lesoway MP. The future of Evo-Devo: the inaugural meeting of the Pan American Society for evolutionary developmental biology. Evol Dev 2016; 18:71-7. [PMID: 26773456 DOI: 10.1111/ede.12181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
What is the future of evolutionary developmental biology? This question and more were discussed at the inaugural meeting for the Pan American Society for Evolutionary Developmental Biology, held August 5-9, 2015, in Berkeley, California, USA. More than 300 participants attended the first meeting of the new society, representing the current diversity of Evo-Devo. Speakers came from throughout the Americas, presenting work using an impressive range of study systems, techniques, and approaches. Current research draws from themes including the role of gene regulatory networks, plasticity and the role of the environment, novelty, population genetics, and regeneration, using new and emerging techniques as well as traditional tools. Multiple workshops and a discussion session covered subjects both practical and theoretical, providing an opportunity for members to discuss the current challenges and future directions for Evo-Devo. The excitement and discussion generated over the course of the meeting demonstrates the current dynamism of the field, suggesting that the future of Evo-Devo is bright indeed.
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Affiliation(s)
- Maryna P Lesoway
- Department of Biology, McGill University, 1205 Avenue Dr Penfield, Montreal, QC, Canada, H3A-1B1.,Smithsonian Tropical Research Institute, Apartado Postal 0843-03092, Balboa, Ancon, Republic of Panama
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28
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Abstract
How rapidly can animal populations in the wild evolve when faced with sudden environmental shifts? Uplift during the 1964 Great Alaska Earthquake abruptly created freshwater ponds on multiple islands in Prince William Sound and the Gulf of Alaska. In the short time since the earthquake, the phenotypes of resident freshwater threespine stickleback fish on at least three of these islands have changed dramatically from their oceanic ancestors. To test the hypothesis that these freshwater populations were derived from oceanic ancestors only 50 y ago, we generated over 130,000 single-nucleotide polymorphism genotypes from more than 1,000 individuals using restriction site-associated DNA sequencing (RAD-seq). Population genomic analyses of these data support the hypothesis of recent and repeated, independent colonization of freshwater habitats by oceanic ancestors. We find evidence of recurrent gene flow between oceanic and freshwater ecotypes where they co-occur. Our data implicate natural selection in phenotypic diversification and support the hypothesis that the metapopulation organization of this species helps maintain a large pool of genetic variation that can be redeployed rapidly when oceanic stickleback colonize freshwater environments. We find that the freshwater populations, despite population genetic analyses clearly supporting their young age, have diverged phenotypically from oceanic ancestors to nearly the same extent as populations that were likely founded thousands of years ago. Our results support the intriguing hypothesis that most stickleback evolution in fresh water occurs within the first few decades after invasion of a novel environment.
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29
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Oke KB, Bukhari M, Kaeuffer R, Rolshausen G, Räsänen K, Bolnick DI, Peichel CL, Hendry AP. Does plasticity enhance or dampen phenotypic parallelism? A test with three lake–stream stickleback pairs. J Evol Biol 2015; 29:126-43. [DOI: 10.1111/jeb.12767] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 09/18/2015] [Accepted: 09/21/2015] [Indexed: 12/19/2022]
Affiliation(s)
- K. B. Oke
- Redpath Museum and Department of Biology McGill University Montreal QC Canada
| | - M. Bukhari
- Redpath Museum and Department of Biology McGill University Montreal QC Canada
| | - R. Kaeuffer
- Redpath Museum and Department of Biology McGill University Montreal QC Canada
| | - G. Rolshausen
- Redpath Museum and Department of Biology McGill University Montreal QC Canada
| | - K. Räsänen
- Department of Aquatic Ecology Eawag and Institute of Integrative Biology ETH‐Zurich Duebendorf Switzerland
| | - D. I. Bolnick
- Department of Integrative Biology University of Texas at Austin Austin TX USA
| | - C. L. Peichel
- Divisions of Basic Sciences and Human Biology Fred Hutchinson Cancer Research Center Seattle WA USA
| | - A. P. Hendry
- Redpath Museum and Department of Biology McGill University Montreal QC Canada
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30
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Parallel molecular routes to cold adaptation in eight genera of New Zealand stick insects. Sci Rep 2015; 5:13965. [PMID: 26355841 PMCID: PMC4564816 DOI: 10.1038/srep13965] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 08/12/2015] [Indexed: 12/20/2022] Open
Abstract
The acquisition of physiological strategies to tolerate novel thermal conditions allows organisms to exploit new environments. As a result, thermal tolerance is a key determinant of the global distribution of biodiversity, yet the constraints on its evolution are not well understood. Here we investigate parallel evolution of cold tolerance in New Zealand stick insects, an endemic radiation containing three montane-occurring species. Using a phylogeny constructed from 274 orthologous genes, we show that stick insects have independently colonized montane environments at least twice. We compare supercooling point and survival of internal ice formation among ten species from eight genera, and identify both freeze tolerance and freeze avoidance in separate montane lineages. Freeze tolerance is also verified in both lowland and montane populations of a single, geographically widespread, species. Transcriptome sequencing following cold shock identifies a set of structural cuticular genes that are both differentially regulated and under positive sequence selection in each species. However, while cuticular proteins in general are associated with cold shock across the phylogeny, the specific genes at play differ among species. Thus, while processes related to cuticular structure are consistently associated with adaptation for cold, this may not be the consequence of shared ancestral genetic constraints.
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31
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Ellis NA, Glazer AM, Donde NN, Cleves PA, Agoglia RM, Miller CT. Distinct developmental genetic mechanisms underlie convergently evolved tooth gain in sticklebacks. Development 2015; 142:2442-51. [PMID: 26062935 DOI: 10.1242/dev.124248] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 06/02/2015] [Indexed: 12/14/2022]
Abstract
Teeth are a classic model system of organogenesis, as repeated and reciprocal epithelial and mesenchymal interactions pattern placode formation and outgrowth. Less is known about the developmental and genetic bases of tooth formation and replacement in polyphyodonts, which are vertebrates with continual tooth replacement. Here, we leverage natural variation in the threespine stickleback fish Gasterosteus aculeatus to investigate the genetic basis of tooth development and replacement. We find that two derived freshwater stickleback populations have both convergently evolved more ventral pharyngeal teeth through heritable genetic changes. In both populations, evolved tooth gain manifests late in development. Using pulse-chase vital dye labeling to mark newly forming teeth in adult fish, we find that both high-toothed freshwater populations have accelerated tooth replacement rates relative to low-toothed ancestral marine fish. Despite the similar evolved phenotype of more teeth and an accelerated adult replacement rate, the timing of tooth number divergence and the spatial patterns of newly formed adult teeth are different in the two populations, suggesting distinct developmental mechanisms. Using genome-wide linkage mapping in marine-freshwater F2 genetic crosses, we find that the genetic basis of evolved tooth gain in the two freshwater populations is largely distinct. Together, our results support a model whereby increased tooth number and an accelerated tooth replacement rate have evolved convergently in two independently derived freshwater stickleback populations using largely distinct developmental and genetic mechanisms.
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Affiliation(s)
- Nicholas A Ellis
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Andrew M Glazer
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Nikunj N Donde
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Phillip A Cleves
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Rachel M Agoglia
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720, USA
| | - Craig T Miller
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, CA 94720, USA
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32
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Genome Assembly Improvement and Mapping Convergently Evolved Skeletal Traits in Sticklebacks with Genotyping-by-Sequencing. G3-GENES GENOMES GENETICS 2015; 5:1463-72. [PMID: 26044731 PMCID: PMC4502380 DOI: 10.1534/g3.115.017905] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Marine populations of the threespine stickleback (Gasterosteus aculeatus) have repeatedly colonized and rapidly adapted to freshwater habitats, providing a powerful system to map the genetic architecture of evolved traits. Here, we developed and applied a binned genotyping-by-sequencing (GBS) method to build dense genome-wide linkage maps of sticklebacks using two large marine by freshwater F2 crosses of more than 350 fish each. The resulting linkage maps significantly improve the genome assembly by anchoring 78 new scaffolds to chromosomes, reorienting 40 scaffolds, and rearranging scaffolds in 4 locations. In the revised genome assembly, 94.6% of the assembly was anchored to a chromosome. To assess linkage map quality, we mapped quantitative trait loci (QTL) controlling lateral plate number, which mapped as expected to a 200-kb genomic region containing Ectodysplasin, as well as a chromosome 7 QTL overlapping a previously identified modifier QTL. Finally, we mapped eight QTL controlling convergently evolved reductions in gill raker length in the two crosses, which revealed that this classic adaptive trait has a surprisingly modular and nonparallel genetic basis.
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