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Sökning: WFRF:(Ehrlén Johan) > (2005-2009)

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  • Föregående 12[3]4Nästa
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  • Pico, Xavier, et al. (författare)
  • Modelling the effects of genetics and habitat on the demography of a grassland herb
  • 2009
  • Ingår i: Basic and Applied Ecology. - 1439-1791 .- 1618-0089. ; 10, s. 122-130
  • Tidskriftsartikel (refereegranskat)abstract
    • There is growing evidence that genetic and ecological factors interact in determining population persistence. The demographic effects of inbreeding depression can largely depend on the ecological milieu. We used demographic data of the perennial herb Succisa pratensis from six populations in grazed and ungrazed sites with different soil moisture. We built an individual-based model assessing the demographic consequences of inbreeding depression in populations with different management and habitat. Today this plant has to cope with severe landscape fragmentation, deteriorating habitat conditions in terms of decreasing grazing intensity, and the effects of inbreeding depression. For each population we performed simulations testing two inbreeding depression hypotheses (partial dominance and overdominance) and three epistatic functions among loci. The results indicated stronger inbreeding depression effects for populations in unfavourable sites without grazing or in xeric habitats compared to populations in favourable mesic sites with grazing. Overall, we found stronger effects with overdominance, a result that emphasizes the importance of understanding the genetic mechanisms of inbreeding depression. Hence, management practices can interact with the genetic consequences of inbreeding depression in population dynamics, which may have important implications for plant population ecology and evolutionary dynamics of inbreeding depression.
  • Sandring, Saskia, 1974- (författare)
  • Plant-Animal Interactions and Evolution of Floral Display and Flowering Phenology in Arabidopsis lyrata
  • 2007
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits, and population differentiation in the insect-pollinated, outcrossing, perennial herb Arabidopsis lyrata. More specifically, I (1) determined whether selection on flowering phenology and floral display can be attributed to interactions with pollinators and herbivores, (2) examined whether population differentiation in flowering phenology and floral display is correlated with current selection on these traits, and (3) tested for local adaptation from contrasting environments in Europe.A field experiment conducted in a Swedish population demonstrated, that interactions with pollinators may markedly affect selection on both floral display and phenology of flowering. In an alpine population in Norway, grazing damage to inflorescences strongly influenced selection on floral display. The results suggest that variation in the abundance of pollinators and herbivores should contribute to spatio-temporal variation in selection on flowering phenology and floral display in A. lyrata. A common-garden experiment showed that flowering phenology and floral display vary among Scandinavian populations of A. lyrata. For some traits patterns of population differentiation were consistent with differences in the direction and strength of phenotypic selection determined in comparisons (a) between an alpine population in Norway and a coastal population in Sweden, and (b) among coastal populations in Sweden. This suggests that current selection contributes to the maintenance of genetic differentiation in these traits.Adaptive differentiation among populations was examined in a reciprocal transplant experiment that included populations from three contrasting environments, alpine Norway, coastal Sweden and lowland, continental Germany. The experiment provided evidence for local adaptation, and indicated that populations have diverged in traits affecting plant establishment and early growth.
  • Toräng, Per, et al. (författare)
  • Facilitation in an insect pollinated herb with a floral display dimorphism
  • 2006
  • Ingår i: Ecology. - 0012-9658 .- 1939-9170. ; 87:8, s. 2113-2117
  • Tidskriftsartikel (refereegranskat)abstract
    • Population context should influence pollination success and selection on. oral display in animal-pollinated plants because attraction of pollinators depends not only on the characteristics of individual plants, but also on the attractiveness of co-occurring conspecifics. The insect-pollinated herb Primula farinosa is polymorphic for inflorescence height. Natural populations may include both long-scaped plants, which present their flowers well above the soil surface, and short-scaped plants, with their flowers positioned close to the ground. We experimentally tested whether seed production in short-scaped P. farinosa varied with local morph frequency and surrounding vegetation height. In tall vegetation, short-scaped plants in polymorphic populations produced more fruit and tended to produce more seeds than short-scaped plants did in monomorphic populations. In low vegetation, population composition did not significantly affect fruit and seed output of short-scaped plants. The results suggest that long-scaped plants facilitate short-scaped plants in terms of pollinator attraction and that the facilitation effect is contingent on the height of the surrounding vegetation. The documented facilitation should contribute to the maintenance of the scape length polymorphism in ungrazed areas where litter accumulates and vegetation grows tall.
  • Toräng, Per, et al. (författare)
  • Habitat quality and among-population differentiation in reproductive effort and flowering phenology in the perennial herb Primula farinosa
  • 2009
  • Ingår i: Evolutionary Ecology. - 0269-7653 .- 1573-8477. ; 24:4, s. 715-729
  • Tidskriftsartikel (refereegranskat)abstract
    • In heterogeneous environments, selection on life-history traits and flowering time may vary considerably among populations because of differences in the extent to which mortality is related to age or size, and because of differences in the seasonal patterns of resource availability and intensity of biotic interactions. Spatial variation in optimal reproductive effort and flowering time may result in the evolution of genetic differences in life-history traits, but also in the evolution of adaptive phenotypic plasticity. The perennial herb Primula farinosa occurs at sites that differ widely in soil depth and therefore in water-holding capacity, vegetation cover, and frost-induced soil movement in winter. We used data from eight natural populations and a common-garden experiment to test the predictions that reproductive allocation is negatively correlated with soil depth while age at first reproduction and first flowering date among reproductive individuals are positively correlated with soil depth. In the common-garden experiment, maternal families collected in the field were grown from seed and monitored for 5 years. In the field, reproductive effort (number of flowers in relation to rosette area) varied among populations and was negatively related to soil depth. In the common-garden experiment, among-population differences in age at first reproduction, and reproductive effort were statistically significant, but relatively small and not correlated with soil depth at the site of origin. Flowering time varied considerably among populations, but was not related to soil depth at the site of origin. Taken together, the results suggest that among-population variation in reproductive effort observed in the field largely reflects phenotypic plasticity. They further suggest that among-population differentiation in flowering time cannot be attributed to variation in environmental factors correlated with soil depth.
  • Toräng, Per, et al. (författare)
  • Mutualists and antagonists mediate frequency-dependent selection on floral display
  • 2008
  • Ingår i: Ecology. - 0012-9658 .- 1939-9170. ; 89:6, s. 1564-1572
  • Tidskriftsartikel (refereegranskat)abstract
    • Theory predicts that, with conflicting selection pressures mediated by mutualists and antagonists, alternative reproductive strategies can be maintained by negative frequency-dependent selection if it results in rare-morph advantage. We combined field experiments and surveys of natural populations to determine whether selection on. oral display is frequency dependent in the self-incompatible herb Primula farinosa, which is polymorphic for inflorescence height and occurs in a short-scaped and a long-scaped morph. Among short-scaped plants, both pollination success, quantified as initiation of fruits and seeds, and seed predation were positively correlated with the relative frequency of the long-scaped morph. The relative strength of these effects and the direction of the resulting frequency-dependent selection on scape morph varied among years and populations. The results suggest that both mutualists and antagonists may mediate frequency-dependent selection and that frequency dependence may vary from positive to negative with rare-morph advantage, depending on the relative strength of these interactions.
  • Toräng, Per, 1978- (författare)
  • Pollinators, Enemies, Drought, and the Evolution of Reproductive Traits in Primula farinosa
  • 2007
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits and population differentiation in the insect-pollinated, self-incompatible, perennial herb Primula farinosa. More specifically, I (1) determined whether the effects of floral display and interactions with pollinators and seed predators, and plant reproductive success were frequency-dependent and affected by surrounding vegetation context, (2) examined the consequences of intermittent drought years on population dynamics using numerical simulations based on demographic data collected over seven years, (3) analyzed among-population differentiation in flowering phenology and reproductive allocation, and its relationship to soil-depth at the site of origin.A field experiment suggested that conspicuous plants facilitate inconspicuous plants in terms of pollinator attraction, and that the facilitation effect is contingent on the height of the surrounding vegetation. Further experiments revealed that both mutualistic and antagonistic interactions can result in frequency-dependent selection on floral display. Among inconspicuous plants, both fruit initiation, and damage from seed predators increased with the proportion of the conspicuous morph. The relative strength of these effects, and therefore their net outcome on the relationship between morph ratio and seed production varied among years.I combined information on vital rates and their relation to environmental conditions in simulations to predict future population viability in changing environments. Simulated stochastic population growth rate decreased with increasing frequency of drought years.Reproductive allocation varied significantly among populations both in the field and in a common-garden experiment, but was correlated with soil depth at the site of origin only in the field. The results suggest that among-population variation in reproductive effort in the field mainly reflects plastic responses to environmental conditions, and that this plasticity may be adaptive. The common-garden experiment suggested that the study populations have diverged genetically in flowering time.
  • Vanhoenacker, Didrik, 1971- (författare)
  • Selection on floral traits in Primula farinosa
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Flowers and inflorescences have evolved in relation to animals for at least 100 million years. Plants attract pollinators with large, conspicuous, bright-coloured or scented flowers. These display attributes, however, also attract herbivores. Optimal conspicuousness may therefore represent a trade-off between attractiveness to pollinators and vulnerability to herbivores. In a heterogenic landscape, the abundances of pollinators and herbivores vary, and this variation should cause the local net selection on floral traits to vary as well. This thesis investigates how pollinators and herbivores select for floral traits, how this selection is linked to interaction intensities, and what factors determine spatial variation in interaction intensity. I have studied the small perennial herb, Primula farinosa, and its interactions with pollinators, a seed predator moth, and grazers. The plant varies in several floral traits; most notably it displays a polymorphism in scape length. Results showed that pollinators selected for long scape, while the seed predator and grazers selected against long scape. Local net selection on scape length depended on interaction intensities of all three interactions. Scape morph also affected selection on number and size of flowers. We hypothesised that intensity of seed predation should depend on local population history of the specialised moth. However, the results from a 5-year survey suggests that patches were recolonized every year, and that the most important patch choice criteria were plant characteristics, such as mean inflorescence size and scape morph frequency. Within a geographic selection mosaic, local hot spots of plant evolution may not be random patches, but patches chosen by the agent of selection based on plant trait values. This thesis shows how spatial population ecology and herbivore dispersal behaviour are linked to mosaic interactions and trait evolution.
  • Vanhoenacker, Didrik, 1971-, et al. (författare)
  • Spatial variability in seed predation in Primula farinosa : local population legacy versus patch selection
  • 2009
  • Ingår i: Oecologia. - 0029-8549 .- 1432-1939. ; 160:1, s. 77-86
  • 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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  • Föregående 12[3]4Nästa
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