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Ilves A, Kaljund K, Sild E, Münzbergová Z. High genetic variation of Trifolium alpestre at the northern margin: but for how long? CONSERV GENET 2022. [DOI: 10.1007/s10592-022-01490-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Genetic diversity of endangered orchid Phaius australis across a fragmented Australian landscape. CONSERV GENET 2017. [DOI: 10.1007/s10592-017-1022-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Pironon S, Papuga G, Villellas J, Angert AL, García MB, Thompson JD. Geographic variation in genetic and demographic performance: new insights from an old biogeographical paradigm. Biol Rev Camb Philos Soc 2016; 92:1877-1909. [DOI: 10.1111/brv.12313] [Citation(s) in RCA: 214] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 10/07/2016] [Accepted: 10/17/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Samuel Pironon
- Instituto Pirenaico de Ecología (IPE-CSIC); Box 1005 avenida Montañana 50059 Zaragoza, Spain
| | - Guillaume Papuga
- UMR 5175 Centre d'Ecologie Fonctionnelle et Evolutive, CNRS; Box 1019 route de Mende 34090 Montpellier France
- Dipartimento di Scienze della Natura e del Territorio; Università degli Studi di Sassari; Box 21 Piazza Universitá 07100 Sassari Italy
| | - Jesús Villellas
- Department of Biology; Duke University; Box 90338 Durham NC 27708-0338 U.S.A
| | - Amy L. Angert
- Departments of Botany and Zoology; University of British Columbia; Box 4200-6270 University Boulevard, Vancouver V6T 1Z4 Canada
| | - María B. García
- Instituto Pirenaico de Ecología (IPE-CSIC); Box 1005 avenida Montañana 50059 Zaragoza, Spain
| | - John D. Thompson
- UMR 5175 Centre d'Ecologie Fonctionnelle et Evolutive, CNRS; Box 1019 route de Mende 34090 Montpellier France
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Phylogeographic pattern of range expansion provides evidence for cryptic species lineages in Silene nutans in Western Europe. Heredity (Edinb) 2015; 116:286-94. [PMID: 26647652 DOI: 10.1038/hdy.2015.100] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 10/05/2015] [Accepted: 10/06/2015] [Indexed: 11/08/2022] Open
Abstract
As a result of recent or past evolutionary processes, a single species might consist of distinct Evolutionary Significant Units (ESUs), even corresponding to cryptic species. Determining the underlying mechanisms of range shifts and the processes at work in the build-up of divergent ESUs requires elucidating the factors that contribute to population genetic divergence across a species' range. We investigated the large-scale patterns of genetic structure in the perennial herbaceous plant species Silene nutans (Caryophyllaceae) in Western Europe. We sampled and genotyped 111 populations using 13 nuclear microsatellite loci and 6 plastid single-nucleotide polymorphisms. Broad-scale spatial population genetic structure was examined using Bayesian clustering, spatial multivariate analyses and measures of hierarchical genetic differentiation. The genotypic structure of S. nutans was typical of a predominantly allogamous mating system. We also identified plastid lineages with no intra-population polymorphism, mirroring two genetically differentiated nuclear lineages. No evidence of admixture was found. Spatial trends in genetic diversity further suggested independent leading-edge expansion associated with founding events and subsequent genetic erosion. Overall, our findings suggested speciation processes in S. nutans and highlighted striking patterns of distinct stepwise recolonisation of Western Europe shaped by Quaternary climate oscillations. Two main potential ESUs can be defined in Western Europe, corresponding to Eastern and Western nuclear-plastid lineages. In situ preservation of populations and genetic rescue implying ex situ conservation techniques should take the lineage identity into account. This is particularly true in Great Britain, northern France and Belgium, where S. nutans is rare and where distinct lineages co-occur in close contact.
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Lahiani E, Touzet P, Billard E, Dufay M. When is it worth being a self-compatible hermaphrodite? Context-dependent effects of self-pollination on female advantage in gynodioecious Silene nutans. Ecol Evol 2015; 5:1854-62. [PMID: 26140201 PMCID: PMC4485966 DOI: 10.1002/ece3.1410] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 01/09/2015] [Accepted: 01/09/2015] [Indexed: 11/11/2022] Open
Abstract
In gynodioecious plant species with nuclear-cytoplasmic sex determination, females and hermaphrodites plants can coexist whenever female have higher seed fitness than hermaphrodites. Although the effect of self fertilization on seed fitness in hermaphrodites has been considered theoretically, this effect is far from intuitive, because it can either increase the relative seed fitness of the females (if it leads hermaphrodites to produce inbred, low quality offspring) or decrease it (if it provides reproductive assurance to hermaphrodites). Hence, empirical investigation is needed to document whether relative seed fitness varies with whether pollen is or is not limiting to seed production. In the current study, we measured fruit set and seed production in both females and hermaphrodites and the selfing rate in hermaphrodites in two experimental patches that differed in sex ratios in the gynodioecious plant Silene nutans. We found an impact of plant gender, patch, and their interaction, with females suffering from stronger pollen limitation when locally frequent. In the most pollen-limited situation, the selfing rate of hermaphrodites increased and provided hermaphrodites with a type of reproductive assurance that is not available to females. By integrating both the beneficial (reproductive assurance) and costly effects (through inbreeding depression) of self-pollination, we showed that whether females did or did not exhibit higher seed fitness depended on the degree of pollen limitation on seed production.
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Affiliation(s)
- Emna Lahiani
- Unité Evolution Ecologie Paléontologie, UMR CNRS 8198, Université de Lille 1 - Sciences et Technologies Villeneuve d'Ascq, France
| | - Pascal Touzet
- Unité Evolution Ecologie Paléontologie, UMR CNRS 8198, Université de Lille 1 - Sciences et Technologies Villeneuve d'Ascq, France
| | - Emmanuelle Billard
- Unité Evolution Ecologie Paléontologie, UMR CNRS 8198, Université de Lille 1 - Sciences et Technologies Villeneuve d'Ascq, France
| | - Mathilde Dufay
- Unité Evolution Ecologie Paléontologie, UMR CNRS 8198, Université de Lille 1 - Sciences et Technologies Villeneuve d'Ascq, France
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Kolář F, Píšová S, Záveská E, Fér T, Weiser M, Ehrendorfer F, Suda J. The origin of unique diversity in deglaciated areas: traces of Pleistocene processes in north-European endemics from theGalium pusillumpolyploid complex (Rubiaceae). Mol Ecol 2015; 24:1311-34. [DOI: 10.1111/mec.13110] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Revised: 02/06/2015] [Accepted: 02/09/2015] [Indexed: 01/16/2023]
Affiliation(s)
- Filip Kolář
- National Centre for Biosystematics, Natural History Museum; University of Oslo; Oslo NO-0318 Norway
- Department of Botany; Faculty of Science; Charles University in Prague; Benátská 2 Prague CZ-128 01 Czech Republic
- Institute of Botany; The Czech Academy of Sciences; Průhonice 1 CZ-252 43 Czech Republic
| | - Soňa Píšová
- Department of Botany; Faculty of Science; Charles University in Prague; Benátská 2 Prague CZ-128 01 Czech Republic
- Institute of Botany; The Czech Academy of Sciences; Průhonice 1 CZ-252 43 Czech Republic
| | - Eliška Záveská
- Institute of Botany; University of Innsbruck; Sternwartestraße 15 Innsbruck A-6020 Austria
| | - Tomáš Fér
- Department of Botany; Faculty of Science; Charles University in Prague; Benátská 2 Prague CZ-128 01 Czech Republic
| | - Martin Weiser
- Department of Botany; Faculty of Science; Charles University in Prague; Benátská 2 Prague CZ-128 01 Czech Republic
| | - Friedrich Ehrendorfer
- Department of Systematic and Evolutionary Botany; Faculty Centre for Biodiversity; University of Vienna; Rennweg 14 Vienna A-1030 Austria
| | - Jan Suda
- Department of Botany; Faculty of Science; Charles University in Prague; Benátská 2 Prague CZ-128 01 Czech Republic
- Institute of Botany; The Czech Academy of Sciences; Průhonice 1 CZ-252 43 Czech Republic
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Antiqueira LMOR, Kageyama PY. Genetic diversity of four populations of Qualea grandiflora Mart. in fragments of the Brazilian Cerrado. Genetica 2013; 142:11-21. [PMID: 24352911 DOI: 10.1007/s10709-013-9750-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 12/11/2013] [Indexed: 11/30/2022]
Abstract
We analyzed the genetic structure and diversity of Qualea grandiflora Mart., the most abundant woody species in the Brazilian Cerrado. Eight microsatellite loci were used to analyze samples from four populations subjected to different types of anthropic pressure, distributed throughout the state of São Paulo in the regions of Assis, Brotas, Itirapina and Pedregulho. Results indicated a mean number of 12 alleles per locus, but only six effective alleles. Alleles private to particular populations and rare alleles were also detected. An excess of homozygotes and moderate levels of inbreeding were observed. No clones were identified. All populations departed from Hardy-Weinberg equilibrium (p < 0.05). Spatial structure was observed in the distribution of specimens in distance classes ranging from 30 to 40 km and three genetic clusters were identified, with genotypes in the Pedregulho population differing from the others by up to 90 %. The influence of the Wahlund effect on the studied populations lies between 8.5 and 53.3 %. Estimates of effective population size were low (<10), and the minimum viable area for conservation in the short-, medium- and long-term was estimated to be between 4 and 184 ha. Gene flow was high enough to counter the effects of genetic drift. The genetic diversity and divergence between the studied populations indicated that the Pedregulho population should be considered an Evolutionary Significant Unit and a Management Unit.
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Affiliation(s)
- Lia Maris Orth Ritter Antiqueira
- Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz (ESALQ), Universidade de São Paulo (USP), Av. Pádua Dias, 11, Piracicaba, São Paulo, 13418-900, Brazil,
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Kolář F, Lučanová M, Vít P, Urfus T, Chrtek J, Fér T, Ehrendorfer F, Suda J. Diversity and endemism in deglaciated areas: ploidy, relative genome size and niche differentiation in the Galium pusillum complex (Rubiaceae) in Northern and Central Europe. ANNALS OF BOTANY 2013; 111:1095-1108. [PMID: 23589633 PMCID: PMC3662515 DOI: 10.1093/aob/mct074] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Accepted: 02/11/2013] [Indexed: 05/29/2023]
Abstract
BACKGROUND AND AIMS Plants endemic to areas covered by ice sheets during the last glaciation represent paradigmatic examples of rapid speciation in changing environments, yet very few systems outside the harsh arctic zone have been comprehensively investigated so far. The Galium pusillum aggregate (Rubiaceae) is a challenging species complex that exhibits a marked differentiation in boreal parts of Northern Europe. As a first step towards understanding its evolutionary history in deglaciated regions, this study assesses cytological variation and ecological preferences of the northern endemics and compares the results with corresponding data for species occurring in neighbouring unglaciated parts of Central and Western Europe. METHODS DNA flow cytometry was used together with confirmatory chromosome counts to determine ploidy levels and relative genome sizes in 1158 individuals from 181 populations. A formalized analysis of habitat preferences was applied to explore niche differentiation among species and ploidy levels. KEY RESULTS The G. pusillum complex evolved at diploid and tetraploid levels in Northern Europe, in contrast to the high-polyploid evolution of most other northern endemics. A high level of eco-geographic segregation was observed between different species (particularly along gradients of soil pH and competition) which is unusual for plants in deglaciated areas and most probably contributes to maintaining species integrity. Relative monoploid DNA contents of the species from previously glaciated regions were significantly lower than those of their counterparts from mostly unglaciated Central Europe, suggesting independent evolutionary histories. CONCLUSIONS The aggregate of G. pusillum in Northern Europe represents an exceptional case with a geographically vicariant and ecologically distinct diploid/tetraploid species endemic to formerly glaciated areas. The high level of interspecific differentiation substantially widens our perception of the evolutionary dynamics and speciation rates in the dramatically changing environments of Northern Europe.
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Affiliation(s)
- Filip Kolář
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01 Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice 1, CZ-252 43 Czech Republic
| | - Magdalena Lučanová
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01 Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice 1, CZ-252 43 Czech Republic
| | - Petr Vít
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01 Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice 1, CZ-252 43 Czech Republic
| | - Tomáš Urfus
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01 Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice 1, CZ-252 43 Czech Republic
| | - Jindřich Chrtek
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01 Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice 1, CZ-252 43 Czech Republic
| | - Tomáš Fér
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01 Czech Republic
| | - Friedrich Ehrendorfer
- Department of Systematic and Evolutionary Botany, Faculty Centre for Biodiversity, University of Vienna, Rennweg 14, Vienna, A-1030 Austria
| | - Jan Suda
- Department of Botany, Faculty of Science, Charles University in Prague, Benátská 2, Prague, CZ-128 01 Czech Republic
- Institute of Botany, Academy of Sciences of the Czech Republic, Průhonice 1, CZ-252 43 Czech Republic
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Monitoring reveals two genetically distinct brown trout populations remaining in stable sympatry over 20 years in tiny mountain lakes. CONSERV GENET 2013. [DOI: 10.1007/s10592-013-0475-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Stone JL, Crystal PA, Devlin EE, Downer RHL, Cameron DS. Highest genetic diversity at the northern range limit of the rare orchid Isotria medeoloides. Heredity (Edinb) 2012; 109:215-21. [PMID: 22692268 PMCID: PMC3464020 DOI: 10.1038/hdy.2012.31] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 03/20/2012] [Accepted: 04/16/2012] [Indexed: 11/08/2022] Open
Abstract
Populations in previously glaciated regions are often genetically depauperate in comparison with populations at lower latitudes, due either to bottlenecks experienced in post-glacial colonization or to contemporary genetic drift in small, peripheral populations. Populations of the rare self-fertilizing North American orchid Isotria medeoloides are largest in the previously glaciated region near the northern range limit, allowing us to examine the role of historical versus contemporary processes in determining population genetic diversity and structure. If contemporary processes predominate, genetic diversity should increase with increasing census size. In contrast, if sequential bottlenecks associated with colonization are paramount, diversity should decrease with latitude and be relatively insensitive to census size. We genotyped 299 individuals from 20 populations at four variable microsatellite loci to contrast genetic diversity and structure for populations in previously glaciated regions versus previously unglaciated regions. Populations were highly inbred (F=0.95) and highly differentiated (R(ST)=0.485). Across all sampled populations, genetic diversity decreased and genetic differentiation increased with declining population size. Small southern populations were especially differentiated and genetically depauperate. In the glaciated part of the range, genetic diversity increased as populations approached the northern range limit, demonstrating the centrality of contemporary processes for this post-glacial colonist.
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Affiliation(s)
- J L Stone
- Department of Biology, Colby College, Waterville, ME 04901, USA.
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11
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Population genetic structure of Tunisian Hypericum humifusum assessed by RAPD markers. Biologia (Bratisl) 2011. [DOI: 10.2478/s11756-011-0106-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Genetic and geographic structure of an insect resistant and a susceptible type of Barbarea vulgaris in western Europe. Evol Ecol 2011. [DOI: 10.1007/s10682-011-9515-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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13
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Lauterbach D, Ristow M, Gemeinholzer B. Genetic population structure, fitness variation and the importance of population history in remnant populations of the endangered plant Silene chlorantha (Willd.) Ehrh. (Caryophyllaceae). PLANT BIOLOGY (STUTTGART, GERMANY) 2011; 13:667-777. [PMID: 21668608 DOI: 10.1111/j.1438-8677.2010.00418.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Habitat fragmentation can lead to a decline of genetic diversity, a potential risk for the survival of natural populations. Fragmented populations can become highly differentiated due to reduced gene flow and genetic drift. A decline in number of individuals can result in lower reproductive fitness due to inbreeding effects. We investigated genetic variation within and between 11 populations of the rare and endangered plant Silene chlorantha in northeastern Germany to support conservation strategies. Genetic diversity was evaluated using AFLP techniques and the results were correlated to fitness traits. Fitness evaluation in nature and in a common garden approach was conducted. Our analysis revealed population differentiation was high and within population genetic diversity was intermediate. A clear population structure was supported by a Bayesian approach, AMOVA and neighbour-joining analysis. No correlation between genetic and geographic distance was found. Our results indicate that patterns of population differentiation were mainly caused by temporal and/or spatial isolation and genetic drift. The fitness evaluation revealed that pollinator limitation and habitat quality seem, at present, to be more important to reproductive fitness than genetic diversity by itself. Populations of S. chlorantha with low genetic diversity have the potential to increase in individual number if habitat conditions improve. This was detected in a single large population in the investigation area, which was formerly affected by bottleneck effects.
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Affiliation(s)
- D Lauterbach
- Botanic Garden and Botanical Museum Berlin-Dahlem, Freie Universität Berlin, Königin-Luise-Strasse 6-8, Berlin, Germany.
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Savolainen O, Kujala ST, Sokol C, Pyhajarvi T, Avia K, Knurr T, Karkkainen K, Hicks S. Adaptive Potential of Northernmost Tree Populations to Climate Change, with Emphasis on Scots Pine (Pinus sylvestris L.). J Hered 2011; 102:526-36. [DOI: 10.1093/jhered/esr056] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kaljund K, Jaaska V. No loss of genetic diversity in small and isolated populations of Medicago sativa subsp. falcata. BIOCHEM SYST ECOL 2010. [DOI: 10.1016/j.bse.2010.05.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Genetic variation of inbreeding depression among floral and fitness traits in Silene nutans. Heredity (Edinb) 2009; 104:52-60. [DOI: 10.1038/hdy.2009.103] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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Yakimowski SB, Eckert CG. Populations do not become less genetically diverse or more differentiated towards the northern limit of the geographical range in clonal Vaccinium stamineum (Ericaceae). THE NEW PHYTOLOGIST 2008; 180:534-544. [PMID: 18694448 DOI: 10.1111/j.1469-8137.2008.02582.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Geographically peripheral populations are expected to exhibit lower genetic diversity and higher differentiation than central populations because of their smaller size and greater spatial isolation. In plants, a shift from sexual to clonal asexual reproduction may further reduce diversity and increase differentiation. Here, these predictions were tested by assaying 36 inter-simple sequence repeat (ISSR) polymorphisms in 21 populations of the woody, clonal plant Vaccinium stamineum in eastern North America, from the range center to its northern limit where it has 'threatened' status. Populations decline in frequency, but not size or sexual reproductive output, across the range. Within-population diversity did not decline towards range margins. Modest genetic differentiation among populations increased slightly towards range margins and in small populations with high clonal propagation and low seed production, although none of these trends was significant. Low seed production and high clonal propagation were not associated with large-scale clonal spread. By combining demographic and genetic data, this study determined that increased population isolation, rather than reduced population size, can account for the weak increase in genetic differentiation at range margins.
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Affiliation(s)
- Sarah B Yakimowski
- Department of Biology, Queen's University, Kingston, Ontario K7 L 3N6 Canada
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Matern A, Desender K, Drees C, Gaublomme E, Paill W, Assmann T. Genetic diversity and population structure of the endangered insect species Carabus variolosus in its western distribution range: Implications for conservation. CONSERV GENET 2008. [DOI: 10.1007/s10592-008-9606-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Eckert CG, Samis KE, Lougheed SC. Genetic variation across species' geographical ranges: the central-marginal hypothesis and beyond. Mol Ecol 2008; 17:1170-88. [PMID: 18302683 DOI: 10.1111/j.1365-294x.2007.03659.x] [Citation(s) in RCA: 779] [Impact Index Per Article: 48.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
There is growing interest in quantifying genetic population structure across the geographical ranges of species to understand why species might exhibit stable range limits and to assess the conservation value of peripheral populations. However, many assertions regarding peripheral populations rest on the long-standing but poorly tested supposition that peripheral populations exhibit low genetic diversity and greater genetic differentiation as a consequence of smaller effective population size and greater geographical isolation relative to geographically central populations. We reviewed 134 studies representing 115 species that tested for declines in within-population genetic diversity and/or increases in among-population differentiation towards range margins using nuclear molecular genetic markers. On average, 64.2% of studies detected the expected decline in diversity, 70.2% of those that tested for it showed increased differentiation and there was a positive association between these trends. In most cases, however, the difference in genetic diversity between central and peripheral population was not large. Although these results were consistent across plants and animals, strong taxonomic and biogeographical biases in the available studies call for a cautious generalization of these results. Despite the large number of studies testing these simple predictions, very few attempted to test possible mechanisms causing reduced peripheral diversity or increased differentiation. Almost no study incorporated a phylogeographical framework to evaluate historical influences on contemporary genetic patterns. Finally, there has been little effort to test whether these geographical trends in putatively neutral variation at marker loci are reflected by quantitative genetic trait variation, which is likely to influence the adaptive potential of populations across the geographical range.
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Affiliation(s)
- C G Eckert
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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Abstract
SummaryOne of the long-standing mysteries in genomic evolution is the observation that much of the genome is composed of repetitive DNA, resulting in inter- and intraspecific variation in nuclear DNA content. Our discovery of a negative correlation between nuclear DNA content and flower size inSilene latifoliahas been supported by our subsequent investigation of changes in DNA content as a correlated response to selection on flower size. Moreover, we have observed a similar trend across a range of related dioecious species inSilenesect.Elisanthe. Given the presence of sex chromosomes in dioeciousSilenespecies, and the tendency of sex chromosomes to accumulate repetitive DNA, it seems plausible that dioecious species undergo genomic evolution in ways that differ from what one might expect in hermaphroditic species. Specifically, we query whether the observed relationship between nuclear DNA content and flower size observed in dioeciousSileneis a peculiarity of sex chromosome evolution. In the present study we investigated nuclear DNA content and flower size variation in hermaphroditic species ofSilenesect.Siphonomorpha, as close relatives of the dioecious species studied previously. Although the nuclear DNA contents of these species were lower than those for species in sect.Elisanthe, there was still significant intra- as well as interspecific variation in nuclear DNA content. Flower size variation was found among species of sect.Siphonomorphafor petal claw and petal limb lengths, but not for calyx diameter. This last trait varies extensively in sect.Elisanthe, in part due to sex-specific selection. A negative correlation with nuclear DNA content was found across populations for petal limb length, but not for other floral dimensions. We conclude that impacts of nuclear DNA content on phenotypic evolution do manifest themselves in hermaphroditic species, so that the effects observed in sect.Elisanthe, and particularly inS. latifolia, while perhaps amplified by the genomic impacts of sex chromosomes, are not limited to dioecious taxa.
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Pyhäjärvi T, García-Gil MR, Knürr T, Mikkonen M, Wachowiak W, Savolainen O. Demographic history has influenced nucleotide diversity in European Pinus sylvestris populations. Genetics 2007; 177:1713-24. [PMID: 18039881 PMCID: PMC2147978 DOI: 10.1534/genetics.107.077099] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 08/28/2007] [Indexed: 11/18/2022] Open
Abstract
To infer the role of natural selection in shaping standing genetic diversity, it is necessary to assess the genomewide impact of demographic history on nucleotide diversity. In this study we analyzed sequence diversity of 16 nuclear loci in eight Pinus sylvestris populations. Populations were divided into four geographical groups on the basis of their current location and the geographical history of the region: northern Europe, central Europe, Spain, and Turkey. There were no among-group differences in the level of silent nucleotide diversity, which was approximately 0.005/bp in all groups. There was some evidence that linkage disequilibrium extended further in northern Europe than in central Europe: the estimates of the population recombination rate parameter, rho, were 0.0064 and 0.0294, respectively. The summary statistics of nucleotide diversity in central and northern European populations were compatible with an ancient bottleneck rather than the standard neutral model.
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Affiliation(s)
- Tanja Pyhäjärvi
- Department of Biology, University of Oulu, 90014 Oulu, Finland.
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Honnay O, Jacquemyn H. Susceptibility of common and rare plant species to the genetic consequences of habitat fragmentation. CONSERVATION BIOLOGY : THE JOURNAL OF THE SOCIETY FOR CONSERVATION BIOLOGY 2007; 21:823-31. [PMID: 17531059 DOI: 10.1111/j.1523-1739.2006.00646.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Small plant populations are more prone to extinction due to the loss of genetic variation through random genetic drift, increased selfing, and mating among related individuals. To date, most researchers dealing with genetic erosion in fragmented plant populations have focused on threatened or rare species. We raise the question whether common plant species are as susceptible to habitat fragmentation as rare species. We conducted a formal meta-analysis of habitat fragmentation studies that reported both population size and population genetic diversity. We estimated the overall weighted mean and variance of the correlation coefficients among four different measures of genetic diversity and plant population size. We then tested whether rarity, mating system, and plant longevity are potential moderators of the relationship between population size and genetic diversity. Mean gene diversity, percent polymorphic loci, and allelic richness across studies were positively and highly significantly correlated with population size, whereas no significant relationship was found between population size and the inbreeding coefficient. Genetic diversity of self-compatible species was less affected by decreasing population size than that of obligate outcrossing and self-compatible but mainly outcrossing species. Longevity did not affect the population genetic response to fragmentation. Our most important finding, however, was that common species were as, or more, susceptible to the population genetic consequences of habitat fragmentation than rare species, even when historically or naturally rare species were excluded from the analysis. These results are dramatic in that many more plant species than previously assumed may be vulnerable to genetic erosion and loss of genetic diversity as a result of ongoing fragmentation processes. This implies that many fragmented habitats have become unable to support plant populations that are large enough to maintain a mutation-drift balance and that occupied habitat fragments have become too isolated to allow sufficient gene flow to enable replenishment of lost alleles.
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Affiliation(s)
- Olivier Honnay
- University of Leuven, Biology Department, Laboratory of Plant Ecology, Kasteelpark Arenberg 31, B-3001 Heverlee, Belgium.
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Hamilton JA, Eckert CG. Population genetic consequences of geographic disjunction: a prairie plant isolated on Great Lakes alvars. Mol Ecol 2007; 16:1649-60. [PMID: 17402980 DOI: 10.1111/j.1365-294x.2007.03241.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Species may often exhibit geographic variation in population genetic structure due to contemporary and historical variation in population size and gene flow. Here, we test the predictions that populations on the margins of a species' distribution contain less genetic variation and are more differentiated than populations towards the core of the range by comparing patterns of genetic variation at five microsatellite loci between disjunct and core populations of the perennial, allohexaploid herb Geum triflorum. We sampled nine populations isolated on alvar habitat within the eastern Great Lakes region in North America, habitats that include disjunct populations of several plant species, and compared these to 16 populations sampled from prairie habitat throughout the core of the species' distribution in midwestern Canada and the USA. Alvar populations exhibited much lower within-population diversity and contained only a subset of alleles found in prairie populations. We detected isolation by distance across the species' range and within alvar and prairie regions separately. As predicted, genetic differentiation was higher among alvar populations than among prairie populations, even after controlling for the geographic distance between sampled populations. Low diversity and high differentiation can be accounted for by the greater contemporary spatial isolation of alvar populations. However, the genetic structure of alvar populations may also have been influenced by postglacial range expansion and contraction. Our results are consistent with alvar populations being founded during an expansion of prairie habitat during the warmer, hypsithermal period approximately 5000 bp and subsequently becoming stranded on isolated alvar habitat as the climate grew cooler and wetter.
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Affiliation(s)
- J A Hamilton
- Department of Biology, Queen's University, Kingston, Ontario, Canada.
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Can the preservation of historical relicts permit the conservation of endangered plant species? The case of Silene sennenii (Caryophyllaceae). CONSERV GENET 2006. [DOI: 10.1007/s10592-006-9245-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
The contemporary pattern of intraspecific genetic variation can indicate the relative role of gene flow and local differentiation in shaping the evolutionary history and future trajectory of a species. To assess the recent influence of contrasting life history and demographic characteristics on genetic structure within a group of closely related species, patterns of genetic differentiation (F(ST) and related statistics) and isolation by distance (IBD) were compared among 17 congeneric herbaceous plant species. Data came from 35 published studies of 16 species, and a previously unpublished analysis of chloroplast genetic variation in the rare endemic Silene rotundifolia. Among-population genetic variance was most strongly influenced by the type of genetic marker used; cytoplasmic markers showed larger values than allozyme and anonymous nuclear markers. Other independently significant factors were geographical range size and, for allozyme studies, reproductive system; in particular, endemism and hermaphroditism were associated with higher among-population genetic variance, whereas large native geographical range and dioecy were associated with lower among-population variance. Over equivalent spatial scales, dioecious populations also showed weaker IBD than hermaphrodites, perhaps because increased population transience and/or variance in the spatial pattern of gene flow are more closely associated with dioecy in this genus. Invasive populations had both highly variable among-population genetic variance, and no evidence for IBD, consistent with nonequilibrium conditions. Other analysed factors including predominant pollinator had no discernable influence on genetic structure or patterns of IBD. In general, this comparative approach appears to be valuable for synthesizing the complementary information provided by F-statistics and IBD, and for indicating the relative importance of particular biological factors in shaping genetic variation within different species of a closely related plant group.
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Affiliation(s)
- Leonie C Moyle
- Center for Population Biology, Section of Evolution and Ecology, 2320 Storer Hall, University of California, Davis CA 95616, USA.
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