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Tiddy IC, Schneider K, Elmer KR. Environmental correlates of adaptive diversification in postglacial freshwater fishes. JOURNAL OF FISH BIOLOGY 2024; 104:517-535. [PMID: 37984834 DOI: 10.1111/jfb.15621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 11/14/2023] [Accepted: 11/15/2023] [Indexed: 11/22/2023]
Abstract
Determining how environmental conditions contribute to divergence among populations and drive speciation is fundamental to resolving mechanisms and understanding outcomes in evolutionary biology. Postglacial freshwater fish species in the Northern Hemisphere are ideal biological systems to explore the effects of environment on diversification in morphology, ecology, and genetics (ecomorph divergences) within lakes. To date, various environmental factors have been implicated in the presence of multiple ecomorphs within particular lakes or regions. However, concerted evidence for generalizable patterns in environmental variables associated with speciation across geographical regions and across species and genera has been lacking. Here, we aimed to identify key biotic and abiotic factors associated with ecological divergence of postglacial freshwater fish species into multiple sympatric ecomorphs, focusing on species in the well-studied, widespread, and co-distributed genera Gasterosteus, Salvelinus, and Coregonus (stickleback, charr, and whitefish, respectively). We found that the presence of multiple sympatric ecomorphs tended to be associated with increasing lake surface area, maximum depth, and nutrient availability. In addition, predation, competition, and prey availability were suggested to play a role in divergence into multiple ecomorphs, but the effects of biotic factors require further study. Although we identified several environmental factors correlated with the presence of multiple ecomorphs, there were substantial data gaps across species and regions. An improved understanding of these systems may provide insight into both generalizable environmental factors involved in speciation in other systems, and potential ecological and evolutionary responses of species complexes when these variables are altered by environmental change.
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Affiliation(s)
- Isabelle C Tiddy
- School of Biodiversity, One Health & Veterinary Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Kevin Schneider
- School of Biodiversity, One Health & Veterinary Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Kathryn R Elmer
- School of Biodiversity, One Health & Veterinary Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
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2
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Hudson CM, Lucek K, Marques DA, Alexander TJ, Moosmann M, Spaak P, Seehausen O, Matthews B. Threespine Stickleback in Lake Constance: The Ecology and Genomic Substrate of a Recent Invasion. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2020.611672] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Invasive species can be powerful models for studying contemporary evolution in natural environments. As invading organisms often encounter new habitats during colonization, they will experience novel selection pressures. Threespine stickleback (Gasterosteus aculeatus complex) have recently colonized large parts of Switzerland and are invasive in Lake Constance. Introduced to several watersheds roughly 150 years ago, they spread across the Swiss Plateau (400–800 m a.s.l.), bringing three divergent hitherto allopatric lineages into secondary contact. As stickleback have colonized a variety of different habitat types during this recent range expansion, the Swiss system is a useful model for studying contemporary evolution with and without secondary contact. For example, in the Lake Constance region there has been rapid phenotypic and genetic divergence between a lake population and some stream populations. There is considerable phenotypic variation within the lake population, with individuals foraging in and occupying littoral, offshore pelagic, and profundal waters, the latter of which is a very unusual habitat for stickleback. Furthermore, adults from the lake population can reach up to three times the size of adults from the surrounding stream populations, and are large by comparison to populations globally. Here, we review the historical origins of the threespine stickleback in Switzerland, and the ecomorphological variation and genomic basis of its invasion in Lake Constance. We also outline the potential ecological impacts of this invasion, and highlight the interest for contemporary evolution studies.
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3
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Skúlason S, Parsons KJ, Svanbäck R, Räsänen K, Ferguson MM, Adams CE, Amundsen P, Bartels P, Bean CW, Boughman JW, Englund G, Guðbrandsson J, Hooker OE, Hudson AG, Kahilainen KK, Knudsen R, Kristjánsson BK, Leblanc CA, Jónsson Z, Öhlund G, Smith C, Snorrason SS. A way forward with eco evo devo: an extended theory of resource polymorphism with postglacial fishes as model systems. Biol Rev Camb Philos Soc 2019; 94:1786-1808. [PMID: 31215138 PMCID: PMC6852119 DOI: 10.1111/brv.12534] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 05/12/2019] [Accepted: 05/20/2019] [Indexed: 12/16/2022]
Abstract
A major goal of evolutionary science is to understand how biological diversity is generated and altered. Despite considerable advances, we still have limited insight into how phenotypic variation arises and is sorted by natural selection. Here we argue that an integrated view, which merges ecology, evolution and developmental biology (eco evo devo) on an equal footing, is needed to understand the multifaceted role of the environment in simultaneously determining the development of the phenotype and the nature of the selective environment, and how organisms in turn affect the environment through eco evo and eco devo feedbacks. To illustrate the usefulness of an integrated eco evo devo perspective, we connect it with the theory of resource polymorphism (i.e. the phenotypic and genetic diversification that occurs in response to variation in available resources). In so doing, we highlight fishes from recently glaciated freshwater systems as exceptionally well-suited model systems for testing predictions of an eco evo devo framework in studies of diversification. Studies on these fishes show that intraspecific diversity can evolve rapidly, and that this process is jointly facilitated by (i) the availability of diverse environments promoting divergent natural selection; (ii) dynamic developmental processes sensitive to environmental and genetic signals; and (iii) eco evo and eco devo feedbacks influencing the selective and developmental environments of the phenotype. We highlight empirical examples and present a conceptual model for the generation of resource polymorphism - emphasizing eco evo devo, and identify current gaps in knowledge.
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Affiliation(s)
- Skúli Skúlason
- Department of Aquaculture and Fish BiologyHólar UniversitySauðárkrókur, 551Iceland
- Icelandic Museum of Natural History, Brynjólfsgata 5ReykjavíkIS‐107Iceland
| | - Kevin J. Parsons
- Institute of Biodiversity, Animal Health & Comparative MedicineUniversity of GlasgowGlasgow, G12 8QQU.K.
| | - Richard Svanbäck
- Animal Ecology, Department of Ecology and Genetics, Science for Life LaboratoryUppsala University, Norbyvägen 18DUppsala, SE‐752 36Sweden
| | - Katja Räsänen
- Department of Aquatic EcologyEAWAG, Swiss Federal Institute of Aquatic Science and Technology, and Institute of Integrative Biology, ETH‐Zurich, Ueberlandstrasse 133CH‐8600DübendorfSwitzerland
| | - Moira M. Ferguson
- Department of Integrative BiologyUniversity of GuelphGuelph, Ontario N1G 2W1Canada
| | - Colin E. Adams
- Scottish Centre for Ecology and the Natural Environment, IBAHCMUniversity of GlasgowGlasgow G12 8QQU.K.
| | - Per‐Arne Amundsen
- Freshwater Ecology Group, Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and EconomicsUniversity of TromsöTromsö, N‐9037Norway
| | - Pia Bartels
- Department of Ecology and Environmental ScienceUmeå UniversityUmeå, SE‐90187Sweden
| | - Colin W. Bean
- Scottish Natural Heritage, Caspian House, Mariner Court, Clydebank Business ParkClydebank, G81 2NRU.K.
| | - Janette W. Boughman
- Department of Integrative BiologyMichigan State UniversityEast Lansing, MI 48824U.S.A.
| | - Göran Englund
- Department of Ecology and Environmental ScienceUmeå UniversityUmeå, SE‐90187Sweden
| | - Jóhannes Guðbrandsson
- Institute of Life and Environmental SciencesUniversity of IcelandReykjavik, 101Iceland
| | | | - Alan G. Hudson
- Department of Ecology and Environmental ScienceUmeå UniversityUmeå, SE‐90187Sweden
| | - Kimmo K. Kahilainen
- Inland Norway University of Applied Sciences, Department of Forestry and Wildlife Management, Campus Evenstad, Anne Evenstadvei 80Koppang, NO‐2480Norway
| | - Rune Knudsen
- Freshwater Ecology Group, Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and EconomicsUniversity of TromsöTromsö, N‐9037Norway
| | | | - Camille A‐L. Leblanc
- Department of Aquaculture and Fish BiologyHólar UniversitySauðárkrókur, 551Iceland
| | - Zophonías Jónsson
- Institute of Life and Environmental SciencesUniversity of IcelandReykjavik, 101Iceland
| | - Gunnar Öhlund
- Department of Ecology and Environmental ScienceUmeå UniversityUmeå, SE‐90187Sweden
| | - Carl Smith
- School of BiologyUniversity of St Andrews, St. AndrewsFife, KY16 9AJU.K.
| | - Sigurður S. Snorrason
- Institute of Life and Environmental SciencesUniversity of IcelandReykjavik, 101Iceland
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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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5
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Lucek K, Kristjánsson BK, Skúlason S, Seehausen O. Ecosystem size matters: the dimensionality of intralacustrine diversification in Icelandic stickleback is predicted by lake size. Ecol Evol 2016; 6:5256-72. [PMID: 27551381 PMCID: PMC4984502 DOI: 10.1002/ece3.2239] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Revised: 05/10/2016] [Accepted: 05/16/2016] [Indexed: 02/03/2023] Open
Abstract
Cases of evolutionary diversification can be characterized along a continuum from weak to strong genetic and phenotypic differentiation. Several factors may facilitate or constrain the differentiation process. Comparative analyses of replicates of the same taxon at different stages of differentiation can be useful to identify these factors. We estimated the number of distinct phenotypic groups in three‐spine stickleback populations from nine lakes in Iceland and in one marine population. Using the inferred number of phenotypic groups in each lake, genetic divergence from the marine population, and physical lake and landscape variables, we tested whether ecosystem size, approximated by lake size and depth, or isolation from the ancestral marine gene pool predicts the occurrence and the extent of phenotypic and genetic diversification within lakes. We find intralacustrine phenotypic diversification to be the rule rather than the exception, occurring in all but the youngest lake population and being manifest in ecologically important phenotypic traits. Neutral genetic data further indicate nonrandom mating in four of nine studied lakes, and restricted gene flow between sympatric phenotypic groups in two. Although neither the phenotypic variation nor the number of intralacustrine phenotypic groups was associated with any of our environmental variables, the number of phenotypic traits that were differentiated was significantly positively related to lake size, and evidence for restricted gene flow between sympatric phenotypic groups was only found in the largest lakes where trait specific phenotypic differentiation was highest.
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Affiliation(s)
- Kay Lucek
- Aquatic Ecology and Evolution Institute of Ecology and Evolution University of Bern Baltzerstrasse 6CH-3012 Bern Switzerland; Department of Fish Ecology and Evolution EAWAG Swiss Federal Institute of Aquatic Science and Technology Center for Ecology, Evolution and Biogeochemistry CH-6047 Kastanienbaum Switzerland; Department of Animal and Plant Sciences University of Sheffield Sheffield UK
| | - Bjarni K Kristjánsson
- Department of Aquaculture and Fish Biology Hólar University College 550 Saudárkrókur Iceland
| | - Skúli Skúlason
- Department of Aquaculture and Fish Biology Hólar University College 550 Saudárkrókur Iceland
| | - Ole Seehausen
- Aquatic Ecology and Evolution Institute of Ecology and Evolution University of Bern Baltzerstrasse 6CH-3012 Bern Switzerland; Department of Fish Ecology and Evolution EAWAG Swiss Federal Institute of Aquatic Science and Technology Center for Ecology, Evolution and Biogeochemistry CH-6047 Kastanienbaum Switzerland
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6
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Ólafsdóttir GÁ, Andreou A, Magellan K, Kristjánsson BK. Divergence in social foraging among morphs of the three-spined stickleback, Gasterosteus aculeatus. Biol J Linn Soc Lond 2014. [DOI: 10.1111/bij.12320] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - Alexandreou Andreou
- Research Centre of the Westfjords; University of Iceland; Adalstraeti 21 Bolungarvik IS415 Iceland
| | - Kit Magellan
- Institut d'Ecologia Aquàtica; Universitat de Girona; E-17071 Girona España
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7
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Lucek K, Sivasundar A, Kristjánsson BK, Skúlason S, Seehausen O. Quick divergence but slow convergence during ecotype formation in lake and stream stickleback pairs of variable age. J Evol Biol 2014; 27:1878-92. [DOI: 10.1111/jeb.12439] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 05/08/2014] [Accepted: 05/25/2014] [Indexed: 01/27/2023]
Affiliation(s)
- K. Lucek
- Aquatic Ecology and Evolution; Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Department of Fish Ecology and Evolution; EAWAG Swiss Federal Institute of Aquatic Science and Technology; Center for Ecology, Evolution and Biogeochemistry; Kastanienbaum Switzerland
| | - A. Sivasundar
- Aquatic Ecology and Evolution; Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Department of Fish Ecology and Evolution; EAWAG Swiss Federal Institute of Aquatic Science and Technology; Center for Ecology, Evolution and Biogeochemistry; Kastanienbaum Switzerland
| | - B. K. Kristjánsson
- Department of Aquaculture and Fish Biology; Hólar University College; Sauðárkrókur Iceland
| | - S. Skúlason
- Department of Aquaculture and Fish Biology; Hólar University College; Sauðárkrókur Iceland
| | - O. Seehausen
- Aquatic Ecology and Evolution; Institute of Ecology & Evolution; University of Bern; Bern Switzerland
- Department of Fish Ecology and Evolution; EAWAG Swiss Federal Institute of Aquatic Science and Technology; Center for Ecology, Evolution and Biogeochemistry; Kastanienbaum Switzerland
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8
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Millet A, Kristjánsson BK, Einarsson A, Räsänen K. Spatial phenotypic and genetic structure of threespine stickleback (Gasterosteus aculeatus) in a heterogeneous natural system, Lake Mývatn, Iceland. Ecol Evol 2013; 3:3219-32. [PMID: 24223263 PMCID: PMC3797472 DOI: 10.1002/ece3.712] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 12/04/2022] Open
Abstract
Eco-evolutionary responses of natural populations to spatial environmental variation strongly depend on the relative strength of environmental differences/natural selection and dispersal/gene flow. In absence of geographic barriers, as often is the case in lake ecosystems, gene flow is expected to constrain adaptive divergence between environments – favoring phenotypic plasticity or high trait variability. However, if divergent natural selection is sufficiently strong, adaptive divergence can occur in face of gene flow. The extent of divergence is most often studied between two contrasting environments, whereas potential for multimodal divergence is little explored. We investigated phenotypic (body size, defensive structures, and feeding morphology) and genetic (microsatellites) structure in threespine stickleback (Gasterosteus aculeatus) across five habitat types and two basins (North and South) within the geologically young and highly heterogeneous Lake Mývatn, North East Iceland. We found that (1) North basin stickleback were, on average, larger and had relatively longer spines than South basin stickleback, whereas (2) feeding morphology (gill raker number and gill raker gap width) differed among three of five habitat types, and (3) there was only subtle genetic differentiation across the lake. Overall, our results indicate predator and prey mediated phenotypic divergence across multiple habitats in the lake, in face of gene flow.
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Affiliation(s)
- Antoine Millet
- Department of Aquaculture and Fish Biology, Hólar University College IS-551, Sauðárkrókur, Iceland
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9
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Karvonen A, Kristjánsson BK, Skúlason S, Lanki M, Rellstab C, Jokela J. Water temperature, not fish morph, determines parasite infections of sympatric Icelandic threespine sticklebacks (Gasterosteus aculeatus). Ecol Evol 2013; 3:1507-17. [PMID: 23789063 PMCID: PMC3686187 DOI: 10.1002/ece3.568] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 03/18/2013] [Accepted: 03/19/2013] [Indexed: 12/01/2022] Open
Abstract
Parasite communities of fishes are known to respond directly to the abiotic environment of the host, for example, to water quality and water temperature. Biotic factors are also important as they affect the exposure profile through heterogeneities in parasite distribution in the environment. Parasites in a particular environment may pose a strong selection on fish. For example, ecological differences in selection by parasites have been hypothesized to facilitate evolutionary differentiation of freshwater fish morphs specializing on different food types. However, as parasites may also respond directly to abiotic environment the parasite risk does not depend only on biotic features of the host environment. It is possible that different morphs experience specific selection gradients by parasites but it is not clear how consistent the selection is when abiotic factors change. We examined parasite pressure in sympatric morphs of threespine stickleback (Gasterosteus aculeatus) across a temperature gradient in two large Icelandic lakes, Myvatn and Thingvallavatn. Habitat-specific temperature gradients in these lakes are opposite. Myvatn lava rock morph lives in a warm environment, while the mud morph lives in the cold. In Thingvallavatn, the lava rock morph lives in a cold environment and the mud morph in a warm habitat. We found more parasites in fish living in higher temperature in both lakes, independent of the fish morph, and this pattern was similar for the two dominating parasite taxa, trematodes and cestodes. However, at the same time, we also found higher parasite abundance in a third morph living in deep cold-water habitat in Thingvallavatn compared to the cold-water lava morph, indicating strong effect of habitat-specific biotic factors. Our results suggest complex interactions between water temperature and biotic factors in determining the parasite community structure, a pattern that may have implications for differentiation of stickleback morphs.
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Affiliation(s)
- Anssi Karvonen
- Department of Biological and Environmental Science, University of JyväskyläP.O. Box 35, FI-40014, Jyväskylä, Finland
| | - Bjarni K Kristjánsson
- Department of Aquaculture and Fish Biology, Holar University CollegeIS-550, Saudarkrokur, Iceland
| | - Skúli Skúlason
- Department of Aquaculture and Fish Biology, Holar University CollegeIS-550, Saudarkrokur, Iceland
| | - Maiju Lanki
- Department of Biosciences, University of HelsinkiP.O.Box 65, FI-00014, Helsinki, Finland
| | - Christian Rellstab
- Department of Biological and Environmental Science, University of JyväskyläP.O. Box 35, FI-40014, Jyväskylä, Finland
- Swiss Federal Research Institute WSLZürcherstrasse 111, CH-8903, Birmensdorf, Switzerland
| | - Jukka Jokela
- Eawag, Swiss Federal Institute of Aquatic Science and TechnologyP.O. Box 611, CH-8600, Dübendorf, Switzerland
- ETH Zürich, Institute of Integrative BiologyCH-8092, Zürich, Switzerland
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10
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Reist JD, Power M, Dempson JB. Arctic charr (Salvelinus alpinus): a case study of the importance of understanding biodiversity and taxonomic issues in northern fishes. ACTA ACUST UNITED AC 2013. [DOI: 10.1080/14888386.2012.725338] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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11
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ÓLAFSDÓTTIR GUÐBJÖRGÁ, SNORRASON SIGURÐURS. Parallels, nonparallels, and plasticity in population differentiation of threespine stickleback within a lake. Biol J Linn Soc Lond 2009. [DOI: 10.1111/j.1095-8312.2009.01318.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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12
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Hendry AP, Bolnick DI, Berner D, Peichel CL. Along the speciation continuum in sticklebacks. JOURNAL OF FISH BIOLOGY 2009; 75:2000-2036. [PMID: 20738669 DOI: 10.1111/j.1095-8649.2009.02419.x] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Speciation can be viewed as a continuum, potentially divisible into several states: (1) continuous variation within panmictic populations, (2) partially discontinuous variation with minor reproductive isolation, (3) strongly discontinuous variation with strong but reversible reproductive isolation and (4) complete and irreversible reproductive isolation. Research on sticklebacks (Gasterosteidae) reveals factors that influence progress back and forth along this continuum, as well as transitions between the states. Most populations exist in state 1, even though some of these show evidence of disruptive selection and positive assortative mating. Transitions to state 2 seem to usually involve strong divergent selection coupled with at least a bit of geographic separation, such as parapatry (e.g. lake and stream pairs and mud and lava pairs) or allopatry (e.g. different lakes). Transitions to state 3 can occur when allopatric or parapatric populations that evolved under strong divergent selection come into secondary contact (most obviously the sympatric benthic and limnetic pairs), but might also occur between populations that remained in parapatry or allopatry. Transitions to state 4 might be decoupled from these selective processes, because the known situations of complete, or nearly complete, reproductive isolation (Japan Sea and Pacific Ocean pair and the recognized gasterosteid species) are always associated with chromosomal rearrangements and environment-independent genetic incompatibilities. Research on sticklebacks has thus revealed complex and shifting interactions between selection, adaptation, mutation and geography during the course of speciation.
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Affiliation(s)
- A P Hendry
- Redpath Museum & Department of Biology, McGill University, 859 Sherbrooke St. W., Montréal, Québec, H3A 2K6 Canada.
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13
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Morphometrics parallel genetics in a newly discovered and endangered taxon of Galápagos tortoise. PLoS One 2009; 4:e6272. [PMID: 19609441 PMCID: PMC2707613 DOI: 10.1371/journal.pone.0006272] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2009] [Accepted: 06/07/2009] [Indexed: 11/19/2022] Open
Abstract
Galápagos tortoises represent the only surviving lineage of giant tortoises that exhibit two different types of shell morphology. The taxonomy of Galápagos tortoises was initially based mainly on diagnostic morphological characters of the shell, but has been clarified by molecular studies indicating that most islands harbor monophyletic lineages, with the exception of Isabela and Santa Cruz. On Santa Cruz there is strong genetic differentiation between the two tortoise populations (Cerro Fatal and La Reserva) exhibiting domed shell morphology. Here we integrate nuclear microsatellite and mitochondrial data with statistical analyses of shell shape morphology to evaluate whether the genetic distinction and variability of the two domed tortoise populations is paralleled by differences in shell shape. Based on our results, morphometric analyses support the genetic distinction of the two populations and also reveal that the level of genetic variation is associated with morphological shell shape variation in both populations. The Cerro Fatal population possesses lower levels of morphological and genetic variation compared to the La Reserva population. Because the turtle shell is a complex heritable trait, our results suggest that, for the Cerro Fatal population, non-neutral loci have probably experienced a parallel decrease in variability as that observed for the genetic data.
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14
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Affiliation(s)
- Patrik Nosil
- Zoology Department and Biodiversity Research Centre, University of British Columbia, Vancouver BC, Canada.
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15
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Olafsdóttir GA, Snorrason SS, Ritchie MG. Postglacial intra-lacustrine divergence of Icelandic threespine stickleback morphs in three neovolcanic lakes. J Evol Biol 2007; 20:1870-81. [PMID: 17714304 DOI: 10.1111/j.1420-9101.2007.01375.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The geographical context of divergence and local adaptation of lacustrine fish is controversial. Despite recent theoretical support for sympatric and parapatric divergence, empirical studies providing unequivocal support for this remain scant. An important component of such a case would be where multiple lakes have different morphs and a range of markers, both mitochondrial and nuclear, show monophyly within lakes. Here we describe such a situation for threespine sticklebacks in three lakes in Iceland. By analysing the variation at nuclear and mitochondrial markers in several freshwater and marine populations as well as three pairs of intra-lacustrine morphs we infer their phylogenetic relationships and colonization pattern. There were high levels of microsatellite variation in all populations and no evidence was found for either repeated colonization of marine fish or colonization from distinct glacial refugia. Intra-lacustrine threespine stickleback morphs in all three lakes show significant genetic divergence probably indicating restricted gene flow.
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Affiliation(s)
- G A Olafsdóttir
- Environmental and Evolutionary Biology, University of St Andrews, St Andrews, UK.
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