| 1. |
- Bergsten, Anna
(författare)
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Population Differentiation in Solidago virgaurea along Altitudinal Gradients
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Altitudinal gradients offer attractive opportunities for studies of population differentiation in response to environmental heterogeneity. In this thesis, I examined population differentiation along altitudinal gradients by combining common-garden experiments with field studies and experiments in alpine, subalpine and boreal populations of the perennial herb Solidago virgaurea. More specifically, I determined whether leaf physiology in terms of nitrogen concentration and resorption, flowering phenology, flower production and reproductive effort vary along altitudinal gradients. Nitrogen concentration in green leaves were higher in alpine than in subalpine and boreal populations. These differences persisted when plants were grown from seeds in a common-garden experiment at two sites, suggesting that the differences have a genetic component. There was mixed support for a trade-off between maximized carbon gain through the maintenance of high nitrogen concentration, and minimized nitrogen loss through high resorption. In their natural habitats alpine populations began flowering later than subalpine populations, but this difference was reversed when plants were grown in a common environment. This suggests that genetic differences among populations counteract environmental effects and reduce phenotypic variation in flowering time among populations. Flowering time thus shows countergradient genetic variation in S. virgaurea. In a common-garden experiment, boreal populations produced more flowers and had a higher reproductive effort than subalpine and alpine populations indicating habitat-specific genetic differences in reproductive allocation. In a field study, which included three populations, seed set was close to zero in the alpine population, intermediate in the subalpine population, and high in the boreal population. Experimental flower removal showed that seed production was associated with a considerable cost in terms of reduced flowering propensity the following year, but did not support the hypothesis that a large floral display is important for pollination success.
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| 2. |
- Boberg, Elin, 1980-, et al.
(författare)
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Pollinator shifts and the evolution of spur length in the moth-pollinated orchid Platanthera bifolia
- 2014
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 113:2, s. 267-275
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Tidskriftsartikel (refereegranskat)abstract
- Plantpollinator interactions are thought to have shaped much of floral evolution. Yet the relative importance of pollinator shifts and coevolutionary interactions for among-population variation in floral traits in animal-pollinated species is poorly known. This study examined the adaptive significance of spur length in the moth-pollinated orchid Platanthera bifolia. Geographical variation in the length of the floral spur of P. bifolia was documented in relation to variation in the pollinator fauna across Scandinavia, and a reciprocal translocation experiment was conducted in south-east Sweden between a long-spurred woodland population and a short-spurred grassland population. Spur length and pollinator fauna varied among regions and habitats, and spur length was positively correlated with the proboscis length of local pollinators. In the reciprocal translocation experiment, long-spurred woodland plants had higher pollination success than short-spurred grassland plants at the woodland site, while no significant difference was observed at the grassland site. The results are consistent with the hypothesis that optimal floral phenotype varies with the morphology of the local pollinators, and that the evolution of spur length in P. bifolia has been largely driven by pollinator shifts.
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| 3. |
- Huttunen, Piritta, et al.
(författare)
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Leaf trichome production and responses to defoliation and drought in Arabidopsis lyrata (Brassicaceae)
- 2010
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Ingår i: Annales Botanici Fennici. - Helsinki : Finnish Zoological and Botanical Publishing Board. - 0003-3847 .- 1797-2442. ; 47:3, s. 199-207
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Tidskriftsartikel (refereegranskat)abstract
- Leaf trichomes can protect plants against herbivory and drought, but can be costly to produce. Theory suggests that selection for reduced costs of resistance may result in the evolution of inducible defences. We quantified variation in tolerance to drought and defoliation, and tested the hypotheses that (a) tolerance is associated with cost, (b) leaf trichome production increases tolerance to drought, and (c) trichome production is increased in response to defoliation and drought stress in Arabidopsis lyrata (Brassicaceae). Eight maternal half-sib families were exposed to two watering regimes and four defoliation treatments in a factorial design. Tolerance to drought varied among families and was inversely related to leaf size, but was not related to trichome density. Family mean performance in the low-watering treatment tended to correlate negatively with that in the control treatment. Trichome production was not induced by defoliation or drought stress. The results suggest that there is genetic variation in tolerance to drought in the study population, that tolerance to drought is associated with a cost, and that trichome production does not increase tolerance to drought in A. lyrata.
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| 4. |
- Løe, Geir, et al.
(författare)
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Trichome production and spatiotemporal variation in herbivory in the perennial herb Arabidopsis lyrata
- 2007
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 116:1, s. 134-142
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Tidskriftsartikel (refereegranskat)abstract
- Allocation theory suggests that the optimal level of resistance against herbivores should vary with the risk of herbivory if allocation to resistance is costly. The perennial herb Arabidopsis lyrata has a genetically based polymorphism for- trichome production and occurs in a glabrous and a trichome-producing form. Leaf trichomes (hairs) can protect plants against insect herbivores, and may increase tolerance to drought and UV-radiation. To examine the functional significance of trichome production, we documented the frequency of glabrous plants and damage by insect herbivores in 30 A. lyrata populations in Sweden and Norway. The proportion of glabrous plants ranged from 0.10 to 0.71 (median = 0.44) in polymorphic populations; 7 of 12 populations in Norway and 14 of 18 populations in Sweden were monomorphic glabrous, i.e. with fewer than 5% trichome-producing plants. The mean proportion of the leaf area removed by herbivores varied substantially among populations and years. With few exceptions, glabrous plants were more damaged than trichome-producing plants in polymorphic populations. The intensity of herbivory quantified as the mean damage to glabrous plants tended to be higher in polymorphic populations than in populations monomorphic for the glabrous morph and was higher in Sweden than in Norway. In Norway, both the magnitude of herbivore damage and the frequency of trichome-producing plants tended to decrease with increasing altitude. The results indicate that leaf trichomes contribute to resistance against herbivorous insects in A. lyrata, and suggest that herbivore-mediated selection contributes to the maintenance of the polymorphism in trichome production.
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| 5. |
- Vanhoenacker, Didrik, 1971-, et al.
(författare)
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Spatial variability in seed predation in Primula farinosa: local population legacy vs. patch selection
- 2009
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 160:1, s. 77-86
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Tidskriftsartikel (refereegranskat)abstract
- Spatio-temporal variation in seed predation may strongly influence both plant population dynamics and selection on plant traits. The intensity of seed predation may depend on a number of factors, but the relative importance of previous predator abundance (“local legacy”), spatial distribution of the host plant, environmental factors and plant characteristics has been explored in few species. We monitored seed predation in the perennial herb Primula farinosa, which is dimorphic for scape length, during 5 consecutive years, in a 10-km × 4-km area comprising 79 P. farinosa populations. A transplant experiment showed that the seed predator, the oligophagous tortricid moth Falseuncaria ruficiliana, was not dispersal limited at the spatial scale corresponding to typical distances between P. farinosa populations. Correlations between population characteristics and incidence and intensity of seed predation varied among years. The incidence of the seed predator was positively correlated with host population size and mean number of flowers, while intensity of seed predation in occupied patches was positively related to the frequency of the long-scaped morph in 2 years and negatively related to host population size in 1 year. In both scape morphs, predation tended to increase with increasing frequency of the long morph. There was no evidence of a local legacy; incidence and intensity of seed predation were not related to the abundance of the seed predator in the population in the previous year. Taken together, the results indicate that among-population variation in seed predation intensity is determined largely by patch selection and that the seed predator’s preference for tall and many-flowered inflorescences may not only affect selection on plant traits within host plant populations, but also the overall intensity of seed predation.
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| 6. |
- Price, Nicholas, et al.
(författare)
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Combining population genomics and fitness QTLs to identify the genetics of local adaptation in Arabidopsis thaliana
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 115:19, s. 5028-5033
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Tidskriftsartikel (refereegranskat)abstract
- Evidence for adaptation to different climates in the model species Arabidopsis thaliana is seen in reciprocal transplant experiments, but the genetic basis of this adaptation remains poorly understood. Field-based quantitative trait locus (QTL) studies provide direct but low-resolution evidence for the genetic basis of local adaptation. Using high-resolution population genomic approaches, we examine local adaptation along previously identified genetic trade-off (GT) and conditionally neutral (CN) QTLs for fitness between locally adapted Italian and Swedish A. thaliana populations [angstrom gren J, et al. (2013) Proc Natl Acad Sci USA 110: 21077-21082]. We find that genomic regions enriched in high F-ST SNPs colocalize with GT QTL peaks. Many of these high F-ST regions also colocalize with regions enriched for SNPs significantly correlated to climate in Eurasia and evidence of recent selective sweeps in Sweden. Examining unfolded site frequency spectra across genes containing high F-ST SNPs suggests GTs may be due to more recent adaptation in Sweden than Italy. Finally, we collapse a list of thousands of genes spanning GT QTLs to 42 genes that likely underlie the observed GTs and explore potential biological processes driving these trade-offs, from protein phosphorylation, to seed dormancy and longevity. Our analyses link population genomic analyses and field-based QTL studies of local adaptation, and emphasize that GTs play an important role in the process of local adaptation.
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| 7. |
- Akiyama, Reiko, et al.
(författare)
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Conflicting selection on the timing of germination in a natural population of Arabidopsis thaliana
- 2014
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 27:1, s. 193-199
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Tidskriftsartikel (refereegranskat)abstract
- The timing of germination is a key life-history trait that may strongly influence plant fitness and that sets the stage for selection on traits expressed later in the life cycle. In seasonal environments, the period favourable for germination and the total length of the growing season are limited. The optimal timing of germination may therefore be governed by conflicting selection through survival and fecundity. We conducted a field experiment to examine the effects of timing of germination on survival, fecundity and overall fitness in a natural population of the annual herb Arabidopsis thaliana in north-central Sweden. Seedlings were transplanted at three different times in late summer and in autumn covering the period of seed germination in the study population. Early germination was associated with low seedling survival, but also with high survival and fecundity among established plants. The advantages of germinating early more than balanced the disadvantage and selection favoured early germination. The results suggest that low survival among early germinating seeds is the main force opposing the evolution of earlier germination and that the optimal timing of germination should vary in space and time as a function of the direction and strength of selection acting during different life-history stages.
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| 8. |
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| 9. |
- Akiyama, Reiko, 1981-
(författare)
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Life History and Tolerance and Resistance against Herbivores in Natural Populations of Arabidopsis thaliana
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I combined observational studies with field and greenhouse experiments to examine selection on life history traits and variation in tolerance and resistance against herbivores in natural populations of the annual herb Arabidopsis thaliana in its native range. I investigated (1) phenotypic selection on flowering time and plant size, (2) the effects of timing of germination on plant fitness, (3) the effect of leaf damage on seed production, and (4) correlations between resistance against a specialist and a generalist insect herbivore. In all three study populations, flowering time was negatively related to plant fitness, but in only one of the populations, significant selection on flowering time was detected when controlling for size prior to the flowering season. The results show that correlations between flowering time and plant fecundity may be confounded by variation in plant size prior to the reproductive season. A field experiment detected conflicting selection on germination time: Early germination was associated with low seedling survival, but also with large leaf rosette before winter and high survival and fecundity among established plants. The results suggest that low survival among early germinating seeds is the main force opposing the evolution of earlier germination, and that the optimal timing of germination should vary in space and time as a function of the relative strength of selection acting during different life-history stages. Experimental leaf damage demonstrated that tolerance to damage was lowest among vegetative plants early in the season, and highest among flowering plants later in the season. Given similar damage levels, leaf herbivores feeding on plants before flowering should thus exert stronger selection on defence traits than those feeding on plants during flowering. Resistance against larval feeding by the specialist Plutella xylostella was negatively correlated with resistance against larval feeding by the generalist Mamestra brassicae and with resistance against oviposition by P. xylostella when variation in resistance was examined within and among two Swedish and two Italian A. thaliana populations. The results suggest that negative correlations between resistance against different herbivores and different life-history stages of herbivores may contribute to the maintenance of genetic variation in resistance.
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| 10. |
- Akiyama, Reiko, et al.
(författare)
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Magnitude and timing of leaf damage affect seed production in a natural population of Arabidopsis thaliana (Brassicaceae)
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:1, s. e30015-
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Tidskriftsartikel (refereegranskat)abstract
- Background: The effect of herbivory on plant fitness varies widely. Understanding the causes of this variation is of considerable interest because of its implications for plant population dynamics and trait evolution. We experimentally defoliated the annual herb Arabidopsis thaliana in a natural population in Sweden to test the hypotheses that (a) plant fitness decreases with increasing damage, (b) tolerance to defoliation is lower before flowering than during flowering, and (c) defoliation before flowering reduces number of seeds more strongly than defoliation during flowering, but the opposite is true for effects on seed size. Methodology/Principal Findings: In a first experiment, between 0 and 75% of the leaf area was removed in May from plants that flowered or were about to start flowering. In a second experiment, 0, 25%, or 50% of the leaf area was removed from plants on one of two occasions, in mid April when plants were either in the vegetative rosette or bolting stage, or in mid May when plants were flowering. In the first experiment, seed production was negatively related to leaf area removed, and at the highest damage level, also mean seed size was reduced. In the second experiment, removal of 50% of the leaf area reduced seed production by 60% among plants defoliated early in the season at the vegetative rosettes, and by 22% among plants defoliated early in the season at the bolting stage, but did not reduce seed output of plants defoliated one month later. No seasonal shift in the effect of defoliation on seed size was detected. Conclusions/Significance: The results show that leaf damage may reduce the fitness of A. thaliana, and suggest that in this population leaf herbivores feeding on plants before flowering should exert stronger selection on defence traits than those feeding on plants during flowering, given similar damage levels.
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