| 1. |
- Cortés, Andrés J., 1989-
(författare)
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On The Big Challenges of a Small Shrub : Ecological Genetics of Salix herbacea L
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The response of plants to climate change is among the main questions in ecology and evolution. Faced with changing conditions, populations may respond by adapting, going extinct or migrating. Fine-scale environmental variation offers a unique mosaic to explore these alternatives. In this thesis, I used ecological surveys, field experiments and molecular methods to study the range of possible responses at a very local scale in the alpine dwarf willow Salix herbacea L. Since gene flow may impact the potential for adaptation and migration, I first explored whether phenological divergence driven by snowmelt patterns impacts gene flow. I found that sites with late snowmelt work as sinks of the genetic diversity, as compared to sites with early snowmelt. I also used a combined approach that looked at the selection, heritability and genomic architecture of ecologically-relevant traits, as well as genomic divergence across the snowmelt mosaic. In this way, I was able to understand which genomic regions may relate to phenological, growth and fitness traits, and which regions in the genome harbor genetic variation associated with late- and early- snowmelt sites. I found that most of the genomic divergence driven by snowmelt is novel and is localized in few regions. Also, Salix herbacea has a strong female bias. Sex bias may matter for adaptation to climate change because different sexes of many dioecious species differ in several functions that may fluctuate with changing conditions. I found that the bias is uniform across environments and is already present at seeds and seedlings. A polygenic sex determination system together with transmission distortion may be maintaining the bias. Overall, fast-evolving microhabitat-driven genomic divergence and, at the same time, genetically-based trait variation at a larger scale may play a role for the ability of S. herbacea to persist in diverse and variable conditions.
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| 2. |
- Cortes, Andres J., et al.
(författare)
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Small-scale patterns in snowmelt timing affect gene flow and the distribution of genetic diversity in the alpine dwarf shrub Salix herbacea
- 2014
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 113:3, s. 233-239
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Tidskriftsartikel (refereegranskat)abstract
- Current threats to biodiversity, such as climate change, are thought to alter the within-species genetic diversity among microhabitats in highly heterogeneous alpine environments. Assessing the spatial organization and dynamics of genetic diversity within species can help to predict the responses of organisms to environmental change. In this study, we evaluated whether small-scale heterogeneity in snowmelt timing restricts gene flow between microhabitats in the common long-lived dwarf shrub Salix herbacea L. We surveyed 273 genets across 12 early-and late-snowmelt sites (that is, ridges and snowbeds) in the Swiss Alps for phenological variation over 2 years and for genetic variation using seven SSR markers. Phenological differentiation triggered by differences in snowmelt timing did not correlate with genetic differentiation between microhabitats. On the contrary, extensive gene flow appeared to occur between microhabitats and slightly less extensively among adjacent mountains. However, ridges exhibited significantly lower levels of genetic diversity than snowbeds, and patterns of effective population size (Ne) and migration (Nem) between microhabitats were strongly asymmetric, with ridges acting as sources and snowbeds as sinks. As no recent genetic bottlenecks were detected in the studied sites, this asymmetry is likely to reflect current metapopulation dynamics of the species dominated by gene flow via seeds rather than ancient re-colonization after the last glacial period. Overall, our results suggest that seed dispersal prevents snowmelt-driven genetic isolation, and snowbeds act as sinks of genetic diversity. We discuss the consequences of such small-scale variation in gene flow and diversity levels for population responses to climate change.
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| 3. |
- Favre, Adrien, et al.
(författare)
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Differential adaptation drives ecological speciation in campions (Silene) : evidence from a multi-site transplant experiment
- 2017
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Ingår i: New Phytologist. - : WILEY-BLACKWELL. - 0028-646X .- 1469-8137. ; 213:3, s. 1487-1499
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the role of differential adaptation for the evolution of reproductive barriers, we conducted a multi-site transplant experiment with the dioecious sister species Silenedioica and S.latifolia and their hybrids. Crosses within species as well as reciprocal first-generation (F-1) and second-generation (F-2) interspecific hybrids were transplanted into six sites, three within each species' habitat. Survival and flowering were recorded over 4yr. At all transplant sites, the local species outperformed the foreign species, reciprocal F-1 hybrids performed intermediately and F-2 hybrids underperformed in comparison to F-1 hybrids (hybrid breakdown). Females generally had slightly higher cumulative fitness than males in both within- and between-species crosses and we thus found little evidence for Haldane's rule acting on field performance. The strength of selection against F-1 and F-2 hybrids as well as hybrid breakdown increased with increasing strength of habitat adaptation (i.e. the relative fitness difference between the local and the foreign species) across sites. Our results suggest that differential habitat adaptation led to ecologically dependent post-zygotic reproductive barriers and drives divergence and speciation in this Silene system.
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| 4. |
- Favre, Adrien, et al.
(författare)
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Stress tolerance in closely related species and their first-generation hybrids : a case study of Silene
- 2011
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 99:6, s. 1415-1423
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Tidskriftsartikel (refereegranskat)abstract
- 1. Hybridization is common in natural plant populations. Trait expression and ecological performance of hybrids determine the consequences of hybridization such as the degree and direction of gene flow or the generation of phenotypic novelty. 2. We investigated responses to shade and drought stress in crosses within the naturally hybridizing campions Silene dioica and S. latifolia and reciprocal crosses between them. We collected data on fitness proxies and on leaf and root traits in a 2-year greenhouse experiment. 3. Responses to drought stress did not differ between cross types. Shade stress, in contrast, led to a reduced flowering incidence in S. dioica but not in S. latifolia. Rapid flowering under stress conditions in S. latifolia could be an adaptation to disturbance in its habitat, whereas a delay of reproduction might be adaptive in the more predictable environment of S. dioica. 4. Hybrids exhibited intermediate, parental-like and transgressive trait expression. Both hybrid cross types were similar to S. latifolia in terms of biomass production possibly because of dominance of S. latifolia alleles or heterosis. Hybrids further had a strongly reduced flowering incidence under shade stress as did S. dioica, suggesting dominance of S. dioica alleles for flower induction. Under shade stress, both hybrid cross types produced much larger leaves than either of the two species suggesting that epigenetic interactions are disturbed. Reciprocal hybrids did not differ in fitness; however, maternal effects were observed for root cross-sectional area and mass per male flower, possibly supporting asymmetric gene flow in natural populations. 5. Synthesis. Silene latifolia and S. dioica responded to stress with differences in life history rather than in growth. Our results further suggest that different modes of gene action are responsible for the specific combination of intermediate, parental-like and transgressive traits observed in first-generation hybrids that may limit their performance and thus gene flow between the species.
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| 5. |
- Gramlich, Susanne, et al.
(författare)
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A polygenic architecture with habitat-dependent effects underlies ecological differentiation in Silene
- 2022
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Ingår i: New Phytologist. - : John Wiley & Sons. - 0028-646X .- 1469-8137. ; 235:4, s. 1641-1652
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Tidskriftsartikel (refereegranskat)abstract
- Ecological differentiation can drive speciation but it is unclear how the genetic architecture of habitat-dependent fitness contributes to lineage divergence. We investigated the genetic architecture of cumulative flowering, a fitness component, in second-generation hybrids between Silene dioica and Silene latifolia transplanted into the natural habitat of each species.We used reduced-representation sequencing and Bayesian sparse linear mixed models (BSLMMs) to analyze the genetic control of cumulative flowering in each habitat.Our results point to a polygenic architecture of cumulative flowering. Allelic effects were mostly beneficial or deleterious in one habitat and neutral in the other. Positive-effect alleles often were derived from the native species, whereas negative-effect alleles, at other loci, tended to originate from the non-native species.We conclude that ecological differentiation is governed and maintained by many loci with small, habitat-dependent effects consistent with conditional neutrality. This pattern may result from differences in selection targets in the two habitats and from environmentally dependent deleterious load. Our results further suggest that selection for native alleles and against non-native alleles acts as a barrier to gene flow between species.
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| 6. |
- Halbritter, Aud H., et al.
(författare)
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Trait differentiation and adaptation of plants along elevation gradients
- 2018
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 31:6, s. 784-800
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Forskningsöversikt (refereegranskat)abstract
- Studies of genetic adaptation in plant populations along elevation gradients in mountains have a long history, but there has until now been neither a synthesis of how frequently plant populations exhibit adaptation to elevation nor an evaluation of how consistent underlying trait differences across species are. We reviewed studies of adaptation along elevation gradients (i) from a meta-analysis of phenotypic differentiation of three traits (height, biomass and phenology) from plants growing in 70 common garden experiments; (ii) by testing elevation adaptation using three fitness proxies (survival, reproductive output and biomass) from 14 reciprocal transplant experiments; (iii) by qualitatively assessing information at the molecular level, from 10 genomewide surveys and candidate gene approaches. We found that plants originating from high elevations were generally shorter and produced less biomass, but phenology did not vary consistently. We found significant evidence for elevation adaptation in terms of survival and biomass, but not for reproductive output. Variation in phenotypic and fitness responses to elevation across species was not related to life history traits or to environmental conditions. Molecular studies, which have focussed mainly on loci related to plant physiology and phenology, also provide evidence for adaptation along elevation gradients. Together, these studies indicate that genetically based trait differentiation and adaptation to elevation are widespread in plants. We conclude that a better understanding of the mechanisms underlying adaptation, not only to elevation but also to environmental change, will require more studies combining the ecological and molecular approaches.
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| 7. |
- Karrenberg, Sophie, et al.
(författare)
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Dedication : Christian Lexer (1971-2019)
- 2020
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : Royal Society. - 0962-8436 .- 1471-2970. ; 375:1806
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 8. |
- Karrenberg, Sophie, et al.
(författare)
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Ecological divergence plays an important role in strong but complex reproductive isolation in campions (Silene)
- 2019
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Ingår i: Evolution. - : Wiley-Blackwell. - 0014-3820 .- 1558-5646. ; 73:2, s. 245-261
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Tidskriftsartikel (refereegranskat)abstract
- New species arise through the evolution of reproductive barriers between formerly interbreeding lineages. Yet, comprehensive assessments of potential reproductive barriers, which are needed to make inferences on processes driving speciation, are only available for a limited number of systems. In this study, we estimated individual and cumulative strengths of seven prezygotic and six postzygotic reproductive barriers between the recently diverged taxa Silene dioica (L.) Clairv. and S. latifolia Poiret using both published and new data. A combination of multiple partial reproductive barriers resulted in near-complete reproductive isolation between S. dioica and S. latifolia, consistent with earlier estimates of gene flow between the taxa. Extrinsic barriers associated with adaptive ecological divergence were most important, while intrinsic postzygotic barriers had moderate individual strength but contributed only little to total reproductive isolation. These findings are in line with ecological divergence as driver of speciation. We further found extensive variation in extrinsic reproductive isolation, ranging from sites with very strong selection against migrants and hybrids to intermediate sites where substantial hybridization is possible. This situation may allow for, or even promote, heterogeneous genetic divergence.
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| 9. |
- Karrenberg, Sophie
(författare)
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Speciation genetics : Limits and promises
- 2010
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Ingår i: Taxon. - 0040-0262 .- 1996-8175. ; 59:5, s. 1404-1412
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Tidskriftsartikel (refereegranskat)abstract
- Many central questions on speciation genetics such as the nature of genetic changes involved and the role of selection in speciation have been under prolonged and intense debate. The development of massively parallel sequencing and increased cooperation among ecological, population and molecular geneticists, offer the promise to find answers to these questions. However, there currently is evidence for the involvement of many different factors and processes in speciation, with their relative importance unresolved. Processes implicated in speciation include not only geographic isolation and structural change through small-effect mutations, but also regulatory mutations, copy number variation and chromosomal rearrangements, as well as scenarios of divergence-with-gene-flow and evolution through genetic conflict. In this review, I summarize current views and persistent limitations in speciation genetics, explore two promising research approaches in this field and end with an overview on current and expected progress in plant speciation genetics.
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| 10. |
- Kokko, Hanna, et al.
(författare)
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Can Evolution Supply What Ecology Demands?
- 2017
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Ingår i: Trends in Ecology & Evolution. - : ELSEVIER SCIENCE. - 0169-5347 .- 1872-8383. ; 32:3, s. 187-197
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Forskningsöversikt (refereegranskat)abstract
- A simplistic view of the adaptive process pictures a hillside along which a population can climb: when ecological 'demands' change, evolution 'supplies' the variation needed for the population to climb to a new peak. Evolutionary ecologists point out that this simplistic view can be incomplete because the fitness landscape changes dynamically as the population evolves. Geneticists meanwhile have identified complexities relating to the nature of genetic varia-tion and its architecture, and the importance of epigenetic variation is under debate. In this review, we highlight how complexity in both ecological 'demands' and the evolutionary 'supply' influences organisms' ability to climb fitness landscapes that themselves change dynamically as evolution proceeds, and encourage new synthetic effort across research disciplines towards eco-logically realistic studies of adaptation.
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