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Møller C, March-Salas M, Kuppler J, De Frenne P, Scheepens JF. Intra-individual variation in Galium odoratum is affected by experimental drought and shading. Ann Bot 2023; 131:411-422. [PMID: 36546703 PMCID: PMC10072115 DOI: 10.1093/aob/mcac148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 12/08/2022] [Indexed: 06/17/2023]
Abstract
BACKGROUND AND AIMS Climate-change induced warmer spring temperatures advance tree leaf-out and result in earlier shading of the forest floor. Climate change also leads to more frequent droughts. Forest understorey herbs may respond to these environmental changes by varying traits at different hierarchical levels of organization. While trait mean variation at the inter-individual level in response to environmental changes is well-studied, little is known about how variation at the intra-individual level responds. METHODS We sampled genets of the forest understorey herb Galium odoratum from 21 populations in three regions in Germany, varying in microclimatic conditions. The genets were transplanted into a common garden, where we applied shading and drought treatments. We measured plant height and leaf length and width, and calculated the coefficient of variation (CV) at different hierarchical levels: intra-population, intra-genet, intra-ramet and intra-shoot. KEY RESULTS Variance partitioning showed that intra-shoot CV represented most of the total variation, followed by intra-ramet CV. We found significant variation in CV of plant height and leaf width among populations of origin, indicating that CV is at least partly genetically based. The soil temperature at populations' origins correlated negatively with CV in plant height, suggesting adaptation to local conditions. Furthermore, we observed that early shade led to increased intra-ramet CV in leaf length, while drought reduced intra-shoot CV in leaf width. Finally, intra-shoot leaf width mean and CV were independent under control conditions but correlated under drought. CONCLUSIONS Our experimental results reveal correlations of intra-individual variation with soil temperature, indicating that intra-individual variation can evolve and may be adaptive. Intra-individual variation responded plastically to drought and shading, suggesting functional changes to improve light capture and reduce evapotranspiration. In conclusion, intra-individual variation makes up the majority of total trait variation in this species and can play a key role in plant adaptation to climatic change.
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Affiliation(s)
- Charlotte Møller
- Plant Evolutionary Ecology, Faculty of Biological Sciences, Goethe University Frankfurt, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany
| | - Martí March-Salas
- Plant Evolutionary Ecology, Faculty of Biological Sciences, Goethe University Frankfurt, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany
| | - Jonas Kuppler
- Institute of Evolutionary Ecology and Conservation Genomics, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Pieter De Frenne
- Forest & Nature Lab, Faculty of Bioscience Engineering, Ghent University, Geraardsbergsesteenweg 267, 9090 Gontrode, Belgium
| | - J F Scheepens
- Plant Evolutionary Ecology, Faculty of Biological Sciences, Goethe University Frankfurt, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany
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2
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Fieschi-Méric L, van Leeuwen P, Denoël M, Lesbarrères D. Encouraging news for in situ conservation: Translocation of salamander larvae has limited impacts on their skin microbiota. Mol Ecol 2023. [PMID: 36872055 DOI: 10.1111/mec.16914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 02/07/2023] [Accepted: 03/02/2023] [Indexed: 03/07/2023]
Abstract
The key role of symbiotic skin bacteria communities in amphibian resistance to emerging pathogens is well recognized, but factors leading to their dysbiosis are not fully understood. In particular, the potential effects of population translocations on the composition and diversity of hosts' skin microbiota have received little attention, although such transfers are widely carried out as a strategy for amphibian conservation. To characterize the potential reorganization of the microbiota over such a sudden environmental change, we conducted a common-garden experiment simulating reciprocal translocations of yellow-spotted salamander larvae across three lakes. We sequenced skin microbiota samples collected before and 15 days after the transfer. Using a database of antifungal isolates, we identified symbionts with known function against the pathogen Batrachochytrium dendrobatidis, a major driver of amphibian declines. Our results indicate an important reorganization of bacterial assemblages throughout ontogeny, with strong changes in composition, diversity and structure of the skin microbiota in both control and translocated individuals over the 15 days of monitoring. Unexpectedly, the diversity and community structure of the microbiota were not significantly affected by the translocation event, thus suggesting a strong resilience of skin bacterial communities to environmental change-at least across the time-window studied here. A few phylotypes were more abundant in the microbiota of translocated larvae, but no differences were found among pathogen-inhibiting symbionts. Taken together, our results support amphibian translocations as a promising strategy for this endangered animal class, with limited impact on their skin microbiota.
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Affiliation(s)
- Léa Fieschi-Méric
- Laboratory of Ecology and Conservation of Amphibians (LECA), Freshwater and OCeanic science Unit of reSearch (FOCUS), Université de Liège, Liège, Belgium.,Biology Department, Laurentian University, Sudbury, Ontario, Canada
| | - Pauline van Leeuwen
- Biology Department, Laurentian University, Sudbury, Ontario, Canada.,Conservation Genetics Laboratory, University de Liège, Liège, Belgium
| | - Mathieu Denoël
- Laboratory of Ecology and Conservation of Amphibians (LECA), Freshwater and OCeanic science Unit of reSearch (FOCUS), Université de Liège, Liège, Belgium
| | - David Lesbarrères
- Biology Department, Laurentian University, Sudbury, Ontario, Canada.,Environment and Climate Change Canada, Ottawa, Ontario, Canada
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3
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Oduor AMO, Adomako MO, Yuan Y, Li JM. Older populations of the invader Solidago canadensis exhibit stronger positive plant-soil feedbacks and competitive ability in China. Am J Bot 2022; 109:1230-1241. [PMID: 35819013 DOI: 10.1002/ajb2.16034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 06/08/2022] [Accepted: 06/10/2022] [Indexed: 06/15/2023]
Abstract
PREMISE The enemy release hypothesis predicts that release from natural enemies, including soil-borne pathogens, liberates invasive plants from a negative regulating force. Nevertheless, invasive plants may acquire novel enemies and mutualists in the introduced range, which may cause variable effects on invader growth. However, how soil microorganisms may influence competitive ability of invasive plants along invasion chronosequences has been little explored. METHODS Using the invasive plant Solidago canadensis, we tested whether longer residence times are associated with stronger negative plant-soil feedbacks and thus weaker competitive abilities at the individual level. We grew S. canadensis individuals from 36 populations with different residence times across southeastern China in competition versus no competition and in three different types of soils: (1) conspecific rhizospheric soils; (2) soils from uninvaded patches; and (3) sterilized soil. For our competitor treatments, we constructed synthetic communities of four native species (Bidens parviflora, Solanum nigrum, Kalimeris indica, and Mosla scabra), which naturally co-occur with Solidago canadensis in the field. RESULTS Solidago canadensis populations with longer residence times experienced stronger positive plant-soil feedbacks and had greater competitive responses (i.e., produced greater above-ground biomass and grew taller) in conspecific rhizospheric soils than in sterilized or uninvaded soils. Moreover, S. canadensis from older populations significantly suppressed above-ground biomass of the native communities in rhizospheric and uninvaded soils but not in sterilized soil. CONCLUSIONS The present results suggest that older populations of S. canadensis experience stronger positive plant-soil feedbacks, which may enhance their competitive ability against native plant communities.
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Affiliation(s)
- Ayub M O Oduor
- Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou, 318000, China
- Department of Applied Biology, Technical University of Kenya, P.O. Box, 52428, Nairobi, Kenya
| | - Michael Opoku Adomako
- Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou, 318000, China
| | - Yongge Yuan
- Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou, 318000, China
| | - Jun-Min Li
- Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou, 318000, China
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Oomen RA, Hutchings JA. Genomic reaction norms inform predictions of plastic and adaptive responses to climate change. J Anim Ecol 2022; 91:1073-1087. [PMID: 35445402 PMCID: PMC9325537 DOI: 10.1111/1365-2656.13707] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 04/05/2022] [Indexed: 12/11/2022]
Abstract
Genomic reaction norms represent the range of gene expression phenotypes (usually mRNA transcript levels) expressed by a genotype along an environmental gradient. Reaction norms derived from common‐garden experiments are powerful approaches for disentangling plastic and adaptive responses to environmental change in natural populations. By treating gene expression as a phenotype in itself, genomic reaction norms represent invaluable tools for exploring causal mechanisms underlying organismal responses to climate change across multiple levels of biodiversity. Our goal is to provide the context, framework and motivation for applying genomic reaction norms to study the responses of natural populations to climate change. Here, we describe the utility of integrating genomics with common‐garden‐gradient experiments under a reaction norm analytical framework to answer fundamental questions about phenotypic plasticity, local adaptation, their interaction (i.e. genetic variation in plasticity) and future adaptive potential. An experimental and analytical framework for constructing and analysing genomic reaction norms is presented within the context of polygenic climate change responses of structured populations with gene flow. Intended for a broad eco‐evo readership, we first briefly review adaptation with gene flow and the importance of understanding the genomic basis and spatial scale of adaptation for conservation and management of structured populations under anthropogenic change. Then, within a high‐dimensional reaction norm framework, we illustrate how to distinguish plastic, differentially expressed (difference in reaction norm intercepts) and differentially plastic (difference in reaction norm slopes) genes, highlighting the areas of opportunity for applying these concepts. We conclude by discussing how genomic reaction norms can be incorporated into a holistic framework to understand the eco‐evolutionary dynamics of climate change responses from molecules to ecosystems. We aim to inspire researchers to integrate gene expression measurements into common‐garden experimental designs to investigate the genomics of climate change responses as sequencing costs become increasingly accessible.
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Affiliation(s)
- Rebekah A Oomen
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.,Centre for Coastal Research (CCR), University of Agder, Kristiansand, Norway
| | - Jeffrey A Hutchings
- Centre for Coastal Research (CCR), University of Agder, Kristiansand, Norway.,Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada.,Institute of Marine Research, Flødevigen Marine Research Station, His, Norway
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Eckert S, Herden J, Stift M, Joshi J, van Kleunen M. Manipulation of cytosine methylation does not remove latitudinal clines in two invasive goldenrod species in Central Europe. Mol Ecol 2020; 30:222-236. [PMID: 33150604 DOI: 10.1111/mec.15722] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 10/03/2020] [Accepted: 10/23/2020] [Indexed: 12/23/2022]
Abstract
Invasive species frequently differentiate phenotypically in novel environments within a few generations, often even with limited genetic variation. For the invasive plants Solidago canadensis and S. gigantea, we tested whether such differentiation might have occurred through heritable epigenetic changes in cytosine methylation. In a 2-year common-garden experiment, we grew plants from seeds collected along a latitudinal gradient in their non-native Central European range to test for trait differentiation and whether differentiation disappeared when seeds were treated with the demethylation agent zebularine. Microsatellite markers revealed no population structure along the latitudinal gradient in S. canadensis, but three genetic clusters in S. gigantea. Solidago canadensis showed latitudinal clines in flowering phenology and growth. In S. gigantea, the number of clonal offspring decreased with latitude. Although zebularine had a significant effect on early growth, probably through effects on cytosine methylation, latitudinal clines remained (or even got stronger) in plants raised from seeds treated with zebularine. Thus, our experiment provides no evidence that epigenetic mechanisms by selective cytosine methylation contribute to the observed phenotypic differentiation in invasive goldenrods in Central Europe.
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Affiliation(s)
- Silvia Eckert
- Biodiversity Research/Systematic Botany, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Jasmin Herden
- Ecology, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Marc Stift
- Ecology, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Jasmin Joshi
- Biodiversity Research/Systematic Botany, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany.,Institute for Landscape and Open Space, Eastern Switzerland University of Applied Sciences, Rapperswil, Switzerland.,Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB), Berlin, Germany
| | - Mark van Kleunen
- Ecology, Department of Biology, University of Konstanz, Konstanz, Germany.,Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou, China
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Brandenburger CR, Sherwin WB, Creer SM, Buitenwerf R, Poore AGB, Frankham R, Finnerty PB, Moles AT. Rapid reshaping: the evolution of morphological changes in an introduced beach daisy. Proc Biol Sci 2019; 286:20181713. [PMID: 30963824 PMCID: PMC6408894 DOI: 10.1098/rspb.2018.1713] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 02/01/2019] [Indexed: 11/12/2022] Open
Abstract
Thousands of species have been introduced to new ranges worldwide. These introductions provide opportunities for researchers to study evolutionary changes in form and function in response to new environmental conditions. However, almost all previous studies of morphological change in introduced species have compared introduced populations to populations from across the species' native range, so variation within native ranges probably confounds estimates of evolutionary change. In this study, we used microsatellites to locate the source population for the beach daisy Arctotheca populifolia that had been introduced to eastern Australia. We then compared four introduced populations from Australia with their original South African source population in a common-environment experiment. Despite being separated for less than 100 years, source and introduced populations of A. populifolia display substantial heritable morphological differences. Contrary to the evolution of increased competitive ability hypothesis, introduced plants were shorter than source plants, and introduced and source plants did not differ in total biomass. Contrary to predictions based on higher rainfall in the introduced range, introduced plants had smaller, thicker leaves than source plants. Finally, while source plants develop lobed adult leaves, introduced plants retain their spathulate juvenile leaf shape into adulthood. These changes indicate that rapid evolution in introduced species happens, but not always in the direction predicted by theory.
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Affiliation(s)
- Claire R. Brandenburger
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - William B. Sherwin
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Stephanie M. Creer
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Robert Buitenwerf
- Section for Ecoinformatics and Biodiversity, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
- Center for Biodiversity Dynamics in a Changing World (BIOCHANGE), Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark
| | - Alistair G. B. Poore
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Richard Frankham
- Department of Biological Sciences, Macquarie University, North Ryde, New South Wales 2019, Australia
| | - Patrick B. Finnerty
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
- EMM Consulting, 1/20 Chandos St, St Leonard's, New South Wales 2065, Australia
| | - Angela T. Moles
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
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Vedder O, Kürten N, Bouwhuis S. Intraspecific Variation in and Environment-Dependent Resource Allocation to Embryonic Development Time in Common Terns. Physiol Biochem Zool 2017; 90:453-460. [PMID: 28402235 DOI: 10.1086/691690] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Embryonic development time is thought to impact life histories through trade-offs against life-history traits later in life, yet the inference is based on interspecific comparative analyses only. It is largely unclear whether intraspecific variation in embryonic development time that is not caused by environmental differences occurs, which would be required to detect life-history trade-offs. Here we performed a classical common-garden experiment by incubating fresh eggs of free-living common terns (Sterna hirundo) in a controlled incubation environment at two different temperatures. Hatching success was high but was slightly lower at the lower temperature. While correcting for effects of year, incubation temperature, and laying order, we found significant variation in the incubation time embryos required until hatching and in their heart rate. Embryonic heart rate was significantly positively correlated within clutches, and a similar tendency was found for incubation time, suggesting that intrinsic differences in embryonic development rate between offspring of different parents exist. Incubation time and embryonic heart rate were strongly correlated: embryos with faster heart rates required shorter incubation time. However, after correction for heart rate, embryos still required more time for development at the lower incubation temperature. This suggests that processes other than development require a greater share of resources in a suboptimal environment and that relative resource allocation to development is, therefore, environment dependent. We conclude that there is opportunity to detect intraspecific life-history trade-offs with embryonic development time and that the resolution of trade-offs may differ between embryonic environments.
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Affiliation(s)
- Oscar Vedder
- 1 Groningen Institute for Evolutionary Life Sciences, University of Groningen, PO Box 11103, 9700 CC Groningen, The Netherlands.,2 Institute of Avian Research "Vogelwarte Helgoland," An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany
| | - Nathalie Kürten
- 2 Institute of Avian Research "Vogelwarte Helgoland," An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany.,3 University of Oldenburg, D-26111 Oldenburg, Germany
| | - Sandra Bouwhuis
- 2 Institute of Avian Research "Vogelwarte Helgoland," An der Vogelwarte 21, D-26386 Wilhelmshaven, Germany
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von Wettberg EJB, Marques E, Murren CJ. Local adaptation or foreign advantage? Effective use of a single-test site common garden to evaluate adaptation across ecological scales. New Phytol 2016; 211:8-10. [PMID: 27240708 DOI: 10.1111/nph.14029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 04/28/2016] [Indexed: 06/05/2023]
Affiliation(s)
- Eric J B von Wettberg
- Department of Biological Sciences and International Center for Tropical Botany, Florida International University, Miami, FL, 33199, USA
| | - Edward Marques
- Department of Biological Sciences and International Center for Tropical Botany, Florida International University, Miami, FL, 33199, USA
| | - Courtney J Murren
- Department of Biology, College of Charleston, Charleston, SC, 29424, USA
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Oomen RA, Hutchings JA. Variation in spawning time promotes genetic variability in population responses to environmental change in a marine fish. Conserv Physiol 2015; 3:cov027. [PMID: 27293712 PMCID: PMC4778481 DOI: 10.1093/conphys/cov027] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Revised: 05/03/2015] [Accepted: 05/09/2015] [Indexed: 05/29/2023]
Abstract
The level of phenotypic plasticity displayed within a population (i.e. the slope of the reaction norm) reflects the short-term response of a population to environmental change, while variation in reaction norm slopes among populations reflects spatial variation in these responses. Thus far, studies of thermal reaction norm variation have focused on geographically driven adaptation among different latitudes, altitudes or habitats. Yet, thermal variability is a function of both space and time. For organisms that reproduce at different times of year, such variation has the potential to promote adaptive variability in thermal responses for critical early life stages. Using common-garden experiments, we examined the spatial scale of genetic variation in thermal plasticity for early life-history traits among five populations of endangered Atlantic cod (Gadus morhua) that spawn at different times of year. Patterns of plasticity for larval growth and survival suggest that population responses to climate change will differ substantially, with increasing water temperatures posing a considerably greater threat to autumn-spawning cod than to those that spawn in winter or spring. Adaptation to seasonal cooling or warming experienced during the larval stage is suggested as a possible cause. Furthermore, populations that experience relatively cold temperatures during early life might be more sensitive to changes in temperature. Substantial divergence in adaptive traits was evident at a smaller spatial scale than has previously been shown for a marine fish with no apparent physical barriers to gene flow (∼200 km). Our findings highlight the need to consider the impact of intraspecific variation in reproductive timing on thermal adaptation when forecasting the effects of climate change on animal populations.
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Affiliation(s)
- Rebekah A Oomen
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo 0371, Norway
| | - Jeffrey A Hutchings
- Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo 0371, Norway
- Department of Natural Sciences, University of Agder, Kristiansand 4630, Norway
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Van Dijk H, Hautekèete NC. Evidence of genetic change in the flowering phenology of sea beets along a latitudinal cline within two decades. J Evol Biol 2014; 27:1572-81. [PMID: 24835689 DOI: 10.1111/jeb.12410] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 04/08/2014] [Accepted: 04/10/2014] [Indexed: 01/15/2023]
Abstract
Sea beets grown from seeds collected in 1989 and 2009 along the coasts of France and adjacent regions were compared for flowering date under controlled conditions. Seeds from both collection years were sown simultaneously and cultivated under the same glasshouse conditions. Date of flowering onset and year of first flowering were recorded. There was an overall northward shift in flowering time of about 0.35° latitude (i.e. 39 km) over the 20-year period. The southern portion of the latitudinal gradient--that is, from 44.7°N to 47.28°N--flowered significantly later by a mean of 1.78 days, equivalent to a 43.2-km northward shift of phenotypes. In the northern latitudes between 48.6°N and 52°N, flowering date was significantly earlier by a mean of 4.04 days, corresponding to a mean northward shift of 104.9 km, and this shift was apparently due to a diminished requirement of exposure to cold temperatures (i.e. vernalization), for which we found direct and indirect evidence. As all plants were grown from seed under identical conditions, we conclude that genetic changes occurred in the sensitivity to environmental cues that mediate the onset of flowering in both the northern and the southern latitudes of the gradient. Microevolution and gene flow may have contributed to this change. There was no significant change in the frequency of plants that flowered without vernalization. The lack of vernalization requirement may be associated with environmental instability rather than with climate conditions.
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Affiliation(s)
- H Van Dijk
- Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8198, Université des Sciences et Technologies de Lille - Lille 1, Villeneuve d'Ascq, France
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