| 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
-
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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| 11. |
- Liu, Xiaodong, et al.
(författare)
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Evolution of barrier loci at an intermediate stage of speciation with gene flow
- 2024
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding the origin of new species is a central goal in evolutionary biology. Diverging lineages often evolve highly heterogeneous patterns of differentiation; however, the underlying mechanisms are not well understood. We used an integrated approach to investigate evolutionary processes governing genetic differentiation between the hybridizing campions (Silene dioica (L.) Clairv. and S. latifolia Poiret). Demographic modeling indicated that the two species diverged with continuous gene flow. The best-supported scenario with heterogeneity in both migration rate and effective population size suggested that 5% of the loci evolved without gene flow. Differentiation (FST) and sequence divergence (dXY) were correlated and both tended to peak in the middle of most linkage groups, consistent with reduced gene flow at highly differentiated loci. Highly differentiated loci further exhibited signatures of selection and differentiation was significantly elevated around previously identified QTLs associated with assortative mating. In between-species population pairs, isolation by distance was stronger for genomic regions with low between-species differentiation than for highly differentiated regions that may contain barrier loci. Moreover, differentiation landscapes within and between species were only weakly correlated suggesting that the interplay of background selection and conserved genomic features is not the dominant determinant of genetic differentiation in these lineages. Instead, our results suggest that divergent selection drove the evolution of barrier loci played and the genomic landscape of differentiation between the two species, consistent with predictions for speciation in the face of gene flow.
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| 12. |
- Liu, Xiaodong, et al.
(författare)
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Evolution of putative barrier loci at an intermediate stage of speciation with gene flow in campions (Silene)
- 2020
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Ingår i: Molecular Ecology. - : WILEY. - 0962-1083 .- 1365-294X. ; 29:18, s. 3511-3525
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the origin of new species is a central goal in evolutionary biology. Diverging lineages often evolve highly heterogeneous patterns of genetic differentiation; however, the underlying mechanisms are not well understood. We investigated evolutionary processes governing genetic differentiation between the hybridizing campionsSilene dioica(L.) Clairv. andS. latifoliaPoiret. Demographic modelling indicated that the two species diverged with gene flow. The best-supported scenario with heterogeneity in both migration rate and effective population size suggested that a small proportion of the loci evolved without gene flow. Differentiation (F-ST) and sequence divergence (d(XY)) were correlated and both tended to peak in the middle of most linkage groups, consistent with reduced gene flow at highly differentiated loci. Highly differentiated loci further exhibited signatures of selection. In between-species population pairs, isolation by distance was stronger for genomic regions with low between-species differentiation than for highly differentiated regions that may contain barrier loci. Moreover, differentiation landscapes within and between species were only weakly correlated, suggesting that linked selection due to shared recombination and gene density landscapes is not the dominant determinant of genetic differentiation in these lineages. Instead, our results suggest that divergent selection shaped the genomic landscape of differentiation between the twoSilenespecies, consistent with predictions for speciation in the face of gene flow.
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| 13. |
- Liu, Xiaodong, et al.
(författare)
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Genetic architecture of traits associated with reproductive barriers in Silene: : Coupling, sex chromosomes and variation
- 2018
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 27:19, s. 3889-3904
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of reproductive barriers and their underlying genetic architecture is ofcentral importance for the formation of new species. Reproductive barriers can becontrolled either by few large-effect loci suggesting strong selection on key traits,or by many small-effect loci, consistent with gradual divergence or with selection onpolygenic or multiple traits. Genetic coupling between reproductive barrier loci fur-ther promotes divergence, particularly divergence with ongoing gene flow. In thisstudy, we investigated the genetic architectures of ten morphological, phenologicaland life history traits associated with reproductive barriers between the hybridizingsister species Silene dioica and S. latifolia; both are dioecious with XY-sex determina-tion. We used quantitative trait locus (QTL) mapping in two reciprocal F2crosses.One to six QTLs per trait, including nine major QTLs (PVE > 20%), were detectedon 11 of the 12 linkage groups. We found strong evidence for coupling of QTLs foruncorrelated traits and for an important role of sex chromosomes in the geneticarchitectures of reproductive barrier traits. Unexpectedly, QTLs detected in the twoF2crosses differed largely, despite limited phenotypic differences between themand sufficient statistical power. The widely dispersed genetic architectures of traitsassociated with reproductive barriers suggest gradual divergence or multifariousselection. Coupling of the underlying QTLs likely promoted divergence with geneflow in this system. The low congruence of QTLs between the two crosses furtherpoints to variable and possibly redundant genetic architectures of traits associatedwith reproductive barriers, with important implications for the evolutionary dynam-ics of divergence and speciation.
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| 14. |
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| 15. |
- Liu, Xiaodong
(författare)
-
Mechanisms of speciation in Silene
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A fundamental question in the field of evolutionary biology is how new species originate. Investigating speciation benefits from an integrated approach, which requires a solid understanding of ecology, reproductive biology, geographical distribution, underlying genetic architecture of reproductive isolation (RI), demographic history and genomic divergence. In this thesis, I studied the evolution of reproductive isolation in the sister species Silene dioica (L.) Clairv. and S. latifolia Poiret. The aims of the thesis are to investigate (1) the individual and cumulative contributions of extrinsic and intrinsic reproductive barriers between S. dioica and S. latifolia, (2) the genetic architecture of traits associated with reproductive barriers (3) the demographic history of lineage-split between the two species, (4) genomic patterns of divergence between the species.I found that multiple extrinsic pre- and postzygotic barriers resulting from ecological differentiation contributed most to total RI, while intrinsic barriers had substantial individual strength but contributed weakly to total RI. QTL mapping revealed evidence for genetic coupling of QTLs controlling traits associated with RI, although QTLs were overall widely distributed. QTLs related to sexually dimorphic traits were located on or near the pseudo-autosomal region of the sex chromosomes. The best-supported demographic model suggests heterogeneous population size and migration rates among genome-wide loci and points to the presence of barrier loci. Genomic divergence (measured using FST and dXY) was commonly accentuated around the middle of linkage groups and near QTLs for traits associated with reproductive barriers.In summary, the results in my thesis indicate that the speciation process is driven by multiple interacting and complex reproductive barriers. The genomic divergence landscape is shaped by interplay of the magnitude of gene flow, the strength and timing of selection, and other confounding factors such as genomic features.
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| 16. |
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| 17. |
- Luo, Yonghai, et al.
(författare)
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A Single Nucleotide Deletion in Gibberellin20-oxidase1 Causes Alpine Dwarfism in Arabidopsis
- 2015
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 168:3, s. 930-937
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Tidskriftsartikel (refereegranskat)abstract
- Alpine dwarfism is widely observed in alpine plant populations and often considered a high-altitude adaptation, yet its molecular basis and ecological relevance remain unclear. In this study, we used map-based cloning and field transplant experiments to investigate dwarfism in natural Arabidopsis (Arabidopsis thaliana) accessions collected from the Swiss Alps. A loss-of-function mutation due to a single nucleotide deletion in gibberellin20-oxidase1 (GA5) was identified as the cause of dwarfism in an alpine accession. The mutated allele, ga5-184, was found in two natural Arabidopsis populations collected from one geographic region at high altitude, but was different from all other reported ga5 null alleles, suggesting that this allele has evolved locally. In field transplant experiments, the dwarf accession with ga5-184 exhibited a fitness pattern consistent with adaptation to high altitude. Across a wider array of accessions from the Swiss Alps, plant height decreased with altitude of origin, but fitness patterns in the transplant experiments were variable and general altitudinal adaptation was not evident. In general, our study provides new insights into molecular basis and possible ecological roles of alpine dwarfism, and demonstrates the importance of the GA-signaling pathway for the generation of ecologically relevant variation in higher plants.
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| 18. |
- Luo, Y., et al.
(författare)
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The roles of genetic drift and natural selection in quantitative trait divergence along an altitudinal gradient in Arabidopsis thaliana
- 2015
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 114:2, s. 220-228
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Tidskriftsartikel (refereegranskat)abstract
- Understanding how natural selection and genetic drift shape biological variation is a central topic in biology, yet our understanding of the agents of natural selection and their target traits is limited. We investigated to what extent selection along an altitudinal gradient or genetic drift contributed to variation in ecologically relevant traits in Arabidopsis thaliana. We collected seeds from 8 to 14 individuals from each of 14 A. thaliana populations originating from sites between 800 and 2700 m above sea level in the Swiss Alps. Seed families were grown with and without vernalization, corresponding to winter-annual and summer-annual life histories, respectively. We analyzed putatively neutral genetic divergence between these populations using 24 simple sequence repeat markers. We measured seven traits related to growth, phenology and leaf morphology that are rarely reported in A. thaliana and performed analyses of altitudinal clines, as well as overall Q(ST)-F-ST comparisons and correlation analyses among pair-wise Q(ST), F-ST and altitude of origin differences. Multivariate analyses suggested adaptive differentiation along altitude in the entire suite of traits, particularly when expressed in the summer-annual life history. Of the individual traits, a decrease in rosette leaf number in the vegetative state and an increase in leaf succulence with increasing altitude could be attributed to adaptive divergence. Interestingly, these patterns relate well to common within- and between-species trends of smaller plant size and thicker leaves at high altitude. Our results thus offer exciting possibilities to unravel the underlying mechanisms for these conspicuous trends using the model species A. thaliana.
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| 19. |
- Page, Paul, et al.
(författare)
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Do Flower Color and Floral Scent of Silene Species affect Host Preference of Hadena bicruris, a Seed-Eating Pollinator, under Field Conditions?
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:6, s. e98755-
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Tidskriftsartikel (refereegranskat)abstract
- Specialization in plant-insect interactions is an important driver of evolutionary divergence; yet, plant traits mediating such interactions are poorly understood. In this study, we investigated how flower color and floral scent are related to seed predation by a seed-eating pollinator. We used field-transplanted recombinant F-2 hybrids between Silene latifolia and S. dioica that are the preferred and alternative hosts of the moth Hadena bicruris and crosses within these species for comparison. We scored seed predation and flower color and analyzed floral scent. Pinker S. dioica-like flowers and emission of a-pinene decreased the odds of seed predation while emission of benzyl acetate and 6-methyl-5-hepten-2-one increased the odds of seed predation. Emission of these compounds did not differ significantly between the two Silene species. Our results suggest that flower color plays an important role in the specific interaction of H. bicruris with its preferred host S. latifolia. The compounds alpha-pinene, benzyl acetate and 6-methyl-5-hepten-2-one could represent non-specific deterrents and attractants to ovipositing moths. Alternatively, emission of these compounds could be related to herbivory or pathogen attack and act as a signal for host quality. This would weaken the predictability of the plant's costs and benefits of the interaction and act to maintain an imperfect degree of specialization.
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| 20. |
- Rahme, Joelle, et al.
(författare)
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Inheritance and Reproductive Consequences of Floral Anthocyanin Deficiency in Silene Dioica (Caryophyllaceae)
- 2014
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Ingår i: American Journal of Botany. - : Wiley. - 0002-9122 .- 1537-2197. ; 101:8, s. 1388-1392
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Tidskriftsartikel (refereegranskat)abstract
- Premise of the study: Flower color is one of the most important traits for pollinator attraction. However, natural plant populations often harbor rare flower color variants resulting from mutations in biochemical pathways for floral pigment production. It is unclear how such mutations can persist because they can affect not only pollinator visitation but also plant fertility and performance. Methods: We collected rare white-flowered (anthocyanin-deficient) and common pink-flowered morphs of Silene dioica from natural populations in Switzerland. First-and second-generation hybrids between pink and white morphs, as well as back-crosses toward white morphs were produced, and the proportion of white-flowered offspring was determined. We compared seed siring ability and seed production between morphs using hand pollination experiments. Moreover, we scored the transfer of pollen analogues (fluorescent dyes) in a 50: 50 array of the two morphs. Key results: The proportions of white-flowered plants in the offspring of our crosses were consistent with more than one recessive mutation as the cause of floral anthocyanin deficiency and further suggested a role of maternal effects for flower color. Seed siring ability and seed set did not differ significantly between pink and white morphs. Pollen transfer occurred preferentially within morphs. Conclusions: Overall, our results imply that the white morph of S. dioica likely is caused by recessive mutations that do not impair reproduction. However, as this flower color polymorphism led to assortative mating in our experiment, it may represent standing genetic variation with the potential to contribute to evolutionary divergence.
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| 21. |
- Sedlacek, Janosch, et al.
(författare)
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Evolutionary potential in the Alpine: trait heritabilities and performance variation of the dwarf willow Salix herbacea from different elevations and microhabitats
- 2016
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 6:12, s. 3940-3952
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Tidskriftsartikel (refereegranskat)abstract
- Alpine ecosystems are seriously threatened by climate change. One of the key mechanisms by which plants can adapt to changing environmental conditions is through evolutionary change. However, we still know little about the evolutionary potential in wild populations of long-lived alpine plants. Here, we investigated heritabilities of phenological traits, leaf size, and performance traits in natural populations of the long-lived alpine dwarf shrub Salix herbacea using relatedness estimates inferred from SSR (Simple Sequence Repeat) markers. Salix herbacea occurs in early-and late-snowmelt microhabitats (ridges and snowbeds), and we assessed how performance consequences of phenological traits and leaf size differ between these microhabitats in order to infer potential for evolutionary responses. Salix herbacea showed low, but significant, heritabilities of leaf size, clonal and sexual reproduction, and moderate heritabilities of phenological traits. In both microhabitats, we found that larger leaves, longer intervals between snowmelt and leaf expansion, and longer GDD (growing-degree days) until leaf expansion resulted in a stronger increase in the number of stems (clonal reproduction). In snowbeds, clonal reproduction increased with a shorter GDD until flowering, while the opposite was found on ridges. Furthermore, the proportion of flowering stems increased with GDD until flowering in both microhabitats. Our results suggest that the presence of significant heritable variation in morphology and phenology might help S. herbacea to adapt to changing environmental conditions. However, it remains to be seen if the rate of such an evolutionary response can keep pace with the rapid rate of climate change.
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| 22. |
- Sedlacek, Janosch, et al.
(författare)
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The Response of the Alpine Dwarf Shrub Salix herbacea to Altered Snowmelt Timing : Lessons from a Multi-Site Transplant Experiment
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is altering spring snowmelt patterns in alpine and arctic ecosystems, and these changes may alter plant phenology, growth and reproduction. To predict how alpine plants respond to shifts in snowmelt timing, we need to understand trait plasticity, its effects on growth and reproduction, and the degree to which plants experience a home-site advantage. We tested how the common, long-lived dwarf shrub Salix herbacea responded to changing spring snowmelt time by reciprocally transplanting turfs of S. herbacea between early-exposure ridge and late-exposure snowbed microhabitats. After the transplant, we monitored phenological, morphological and fitness traits, as well as leaf damage, during two growing seasons. Salix herbacea leafed out earlier, but had a longer development time and produced smaller leaves on ridges relative to snowbeds. Longer phenological development times and smaller leaves were associated with reduced sexual reproduction on ridges. On snowbeds, larger leaves and intermediate development times were associated with increased clonal reproduction. Clonal and sexual reproduction showed no response to altered snowmelt time. We found no home-site advantage in terms of sexual and clonal reproduction. Leaf damage probability depended on snowmelt and thus exposure period, but had no short-term effect on fitness traits. We conclude that the studied populations of S. herbacea can respond to shifts in snowmelt by plastic changes in phenology and leaf size, while maintaining levels of clonal and sexual reproduction. The lack of a home-site advantage suggests that S. herbacea may not be adapted to different microhabitats. The studied populations are thus unlikely to react to climate change by rapid adaptation, but their responses will also not be constrained by small-scale local adaptation. In the short term, snowbed plants may persist due to high stem densities. However, in the long term, reduction in leaf size and flowering, a longer phenological development time and increased exposure to damage may decrease overall performance of S. herbacea under earlier snowmelt.
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| 23. |
- Söderquist, Linus, et al.
(författare)
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Genetic differentiation and diversity do not explain variation in heterosis or inbreeding depression
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Assisted gene flow can restore genetic diversity when genetic drift has driven deleterious alleles to high frequencies in small, isolated populations. Previous crosses among 20 populations of Gymnadenia conopsea documented the strongest heterosis and the weakest inbreeding depression in sparse and small populations, consistent with fixation of mildly deleterious alleles by genetic drift. We genotyped the populations used for crosses for 1,728 SNPs and tested the following predictions: 1) heterosis increases with genetic differentiation (FST) to donor populations and decreases with genetic diversity in the recipient population, 2) inbreeding depression increases with genetic diversity, and 3) genetic diversity increases, and mean FST to other populations decreases, with population size and density. Pairwise FST ranged from very low to moderate (0.005-0.20) and genetic diversity varied moderately among populations (proportion of polymorphic loci=0.52-0.75). However, neither FST between populations, nor genetic diversity in the recipient population, was related to the strength of heterosis. There was also no association between genetic diversity and the strength of inbreeding depression. Genetic diversity increased and mean FST decreased with population size, consistent with reduced diversity and increased differentiation of small populations by genetic drift. The results indicate that the loci conferring heterosis are not mirrored by overall population differentiation, and limited additional information on potential source populations for genetic rescue is gained by the genetic data. Instead, controlled crosses can directly reveal positive effects of introducing new genetic material, and is a simple method with high potential in conservation.
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| 24. |
- Söderquist, Linus, et al.
(författare)
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Genetic structure and diversity of the declining orchid Gymnadenia conopsea in Scandinavia: implications for conservation and management
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding how historical versus contemporary processes shape population genetic structure and variation is important to design effective management actions for threatened species. To unravel population structure, connectivity, and genetic variation in the declining Gymnadenia conopsea, we genotyped 1,834 SNPs in 1,120 individuals in 110 populations, in three different habitats (fen, meadow, coastal) across Scandinavia. We further tested if genetic diversity increases with census population size, and is higher in core habitats (fen and meadow) than in marginal, coastal habitats. We identified three main genetic clusters and pronounced isolation by distance, consistent with two independent colonization routes after last glacial maximum, followed by admixture. Estimates of effective migration using EEMS indicated reduced gene flow between coastal and inland populations, suggesting that the complex topography of the fjord landscape constitutes a dispersal barrier. Genetic diversity increased with census population size. The highest genetic diversity was found in core habitats, in meadows in southern Sweden and in inland fens along the Scandes mountains, while the lowest genetic diversity was found on the Atlantic coast and in a few populations scattered across Scandinavia. Genetic diversity did not vary significantly among habitat types. In conclusion, current genetic structure suggests a strong legacy of historical events, and the high genetic diversity documented in the main Scandinavian range indicates that both current viability and future adaptation potential is high. To maintain genetic diversity and connectivity, it is particularly important to preserve southern meadow populations, which depend on traditional land use, along with central fen populations.
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| 25. |
- Söderquist, Linus
(författare)
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Population size, viability and genetic diversity in the orchid Gymnadenia conopsea
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I combined controlled crosses with genetic and demographic data to examine how a main conservation value indicator, population size, was associated with estimates of population viability. I focused on the still common, but decreasing, perennial orchid Gymnadenia conopsea at two spatial scales—locally on the island Öland, in SE Sweden, and regionally across Scandinavia. I aimed to determine whether: (1) population size or density could predict the strength of heterosis and inbreeding depression, (2) local density variation within populations affected self-pollen transfer and relatedness of individuals, (3) genetic diversity increased with population size or density, and genetic differentiation and diversity predicted the strength of heterosis, (4) population growth rate increased with population size and genetic diversity, and (5) large-scale genetic structure indicated several independent colonization events in Scandinavia, with clear genetic groups and genetic diversity hotspots.I found heterosis to decrease and inbreeding depression to increase with local density in Öland populations. The proportion of deposited self-pollen decreased with local density, but established individuals located in sparse patches were not more related than those in dense ones, possibly due to high inbreeding depression at early life stages. Genetic diversity increased with population size, but neither population genetic differentiation or within population genetic diversity was related to the strength of heterosis or inbreeding depression. I found the majority of Öland populations to be declining, and population growth rate to increase with population size. This relationship was driven by higher survival in large populations, and most likely reflects that population size was positively associated with local habitat quality and stability. Population growth rate was not related to the amount of genetic diversity within the population, suggesting declines are not driven by genetic erosion. At the Scandinavian scale, I identified three genetic groups, consistent with two independent post-glacial colonizations followed by admixture. High genetic diversity was found in southern and central populations, while low diversity was seen in marginal populations along the Atlantic coast.In conclusion, population size was associated with both genetic diversity and population viability at the Öland scale. Genetic diversity was not related to the strength of heterosis or population viability, suggesting that demographic metrics can be more informative than genetic metrics, regarding conservation priority.
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| 26. |
- Wheeler, Julia A., et al.
(författare)
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The snow and the willows : earlier spring snowmelt reduces performance in the low-lying alpine shrub Salix herbacea
- 2016
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 104:4, s. 1041-1050
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Tidskriftsartikel (refereegranskat)abstract
- Current changes in shrub abundance in alpine and arctic tundra ecosystems are primarily driven by climate change. However, while taller shrub communities are expanding, dwarf shrub communities show reductions under climate warming, and the mechanisms driving the latter (such as warming temperatures or accelerated spring snowmelt) may be complex. To determine and disentangle the response of a widespread arctic-alpine prostrate dwarf shrub to both climate warming and changes in snowmelt time, we investigated phenology, clonal and sexual reproduction, leaf size, wood tissue carbon balance and leaf damage in 480 patches of Salix herbacea, along its elevational and snowmelt microhabitat range over 3years in a space-for-time substitution. Earlier snowmelt was associated with longer phenological development periods, an increased likelihood of herbivory and fungal damage, lower stem density, smaller leaves and lower end-of-season wood reserve carbohydrates. Furthermore, while early snowmelt was associated with an increased proportion of flowering stems, the proportion of fruiting stems was not, as fruit set decreased significantly with earlier snowmelt. Warmer temperatures at lower elevations were associated with lower stem numbers and larger leaves.Synthesis. Our study indicates that phenology, fitness proxies and fungal/insect damage of the dwarf shrub S.herbacea are strongly influenced by snowmelt timing, and that earlier spring snowmelt reduced performance in S.herbacea. The likely mechanisms for many of the observed patterns are related to adverse temperature conditions in the early growing season. Reductions in clonal (stem number) and sexual reproduction (reduced fruit set) under earlier snowmelt, in addition to increasing damage probability, will likely lead to lower fitness and poorer performance, particularly in shrubs growing in early-exposure microhabitats. Further, we saw few concurrent benefits of higher temperatures for S.herbacea, particularly as warming was associated with lower clonal growth. As growing seasons become warmer and longer in arctic and alpine tundra ecosystems, early snowmelt is a critical mechanism reducing fitness and performance in a widespread dwarf shrub and may ultimately reduce dwarf shrub communities in tundra biomes.
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