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Sökning: WFRF:(Ehrlén Johan) > (2010-2014) > (2010)

  • Resultat 1-9 av 9
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1.
  • Arvanitis, Leena, et al. (författare)
  • Novel antagonistic interactions associated with plant polyploidization influence trait selection and habitat preference.
  • 2010
  • Ingår i: Ecology Letters. - 1461-023X .- 1461-0248. ; 13:3, s. 330-7
  • Tidskriftsartikel (refereegranskat)abstract
    • Polyploidization is an important mechanism for sympatric speciation in plants. Still, we know little about whether plant polyploidization leads to insect host shifts, and if novel interactions influence habitat and trait selection in plants. We investigated herbivory by the flower bud gall-forming midge Dasineura cardaminis on tetraploids and octoploids of the herb Cardamine pratensis. Gall midges attacked only octoploid plant populations, and a transplantation experiment confirmed this preference. Attack rates were higher in populations that were shaded, highly connected or occurred along stream margins. Within populations, late-flowering individuals with many flowers were most attacked. Galling reduced seed production and significantly influenced phenotypic selection on flower number. Our results suggest that an increase in ploidy may lead to insect host shifts and that plant ploidy explains insect host use. In newly formed plant polyploids, novel interactions may alter habitat preferences and trait selection, and influence the further evolution of cytotypes.
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2.
  • Kolb, Annette, et al. (författare)
  • Population size affects vital rates but not population growth rate of a perennial plant
  • 2010
  • Ingår i: Ecology. - 0012-9658 .- 1939-9170. ; 91:11, s. 3210-3217
  • Tidskriftsartikel (refereegranskat)abstract
    • Negative effects of habitat fragmentation on individual performance have been widely documented, but relatively little is known about how simultaneous effects on multiple vital rates translate into effects on population viability in long-lived species. In this study, we examined relationships between population size, individual growth, survival and reproduction, and population growth rate in the perennial plant Phyteuma spicatum. Population size positively affected the growth of seedlings, the survival of juveniles, the proportion of adults flowering, and potential seed production. Analyses with integral projection models, however, showed no relationship between population size and population growth rate. This was due to the fact that herbivores and pathogens eliminated the relationship between population size and seed production, and that population growth rate was not sensitive to changes in the vital rates that varied with population size. We conclude that effects of population size on vital rates must not translate into effects on population growth rate, and that populations of long-lived organisms may partly be able to buffer negative effects of small population size on vital rates that have a relatively small influence on population growth rate. Our study illustrates that we need to be cautious when assessing the consequences of habitat fragmentation for population viability based on effects on only one or a few vital rates.
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3.
  • Boalt, Elin, et al. (författare)
  • The association among herbivory tolerance, ploidy level, and herbivory pressure in cardamine pratensis
  • 2010
  • Ingår i: Evolutionary Ecology. - 0269-7653 .- 1573-8477. ; 24:5, s. 1101-1113
  • Tidskriftsartikel (refereegranskat)abstract
    • We tested whether differences in ploidy level and previous exposure to herbivory can affect plant tolerance to herbivory. We conducted a common garden experiment with 12 populations of two ploidy levels of the perennial herb Cardamine pratensis (five populations of tetraploid ssp. pratensis and seven populations of octoploid ssp. paludosa). Earlier studies have shown that attack rates by the main herbivore, the orange tip butterfly Anthocharis cardamines, are lower in populations of octoploids than in populations of tetraploids, and vary among populations. In the common garden experiment, a combination of natural and artificial damage significantly reduced seed and flower production. We measured tolerance based on four plant-performance metrics: survival, growth, seed production and clonal reproduction. For three of these measurements, tolerance of damage did not differ between ploidy levels. For clonal reproduction, the octoploids had a higher tolerance than the tetraploids, although they experience lower herbivore attack rates in natural populations. Populations from sites with high levels of herbivory had higher tolerance, measured by seed production, than populations with low levels of herbivory. We did not detect any significant costs of tolerance. We conclude that high intensity of herbivory has selected for high tolerance measured by seed production in C. pratensis.
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4.
  • Buckley, Yvonne M., et al. (författare)
  • Causes and consequences of variation in plant population growth rate : a synthesis of matrix population models in a phylogenetic context
  • 2010
  • Ingår i: Ecology Letters. - 1461-023X .- 1461-0248. ; 13:9, s. 1182-1197
  • Forskningsöversikt (refereegranskat)abstract
    • Explaining variation in population growth rates is fundamental to predicting population dynamics and population responses to environmental change. In this study, we used matrix population models, which link birth, growth and survival to population growth rate, to examine how and why population growth rates vary within and among 50 terrestrial plant species. Population growth rates were more similar within species than among species; with phylogeny having a minimal influence on among-species variation. Most population growth rates decreased over the observation period and were negatively autocorrelated between years; that is, higher than average population growth rates tended to be followed by lower than average population growth rates. Population growth rates varied more through time than space; this temporal variation was due mostly to variation in post-seedling survival and for a subset of species was partly explained by response to environmental factors, such as fire and herbivory. Stochastic population growth rates departed from mean matrix population growth rate for temporally autocorrelated environments. Our findings indicate that demographic data and models of closely related plant species cannot necessarily be used to make recommendations for conservation or control, and that post-seedling survival and the sequence of environmental conditions are critical for determining plant population growth rate.
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5.
  • Burns, Jean H., et al. (författare)
  • Empirical tests of life-history evolution theory using phylogenetic analysis of plant demography
  • 2010
  • Ingår i: Journal of Ecology. - 0022-0477 .- 1365-2745. ; 98:2, s. 334-344
  • Tidskriftsartikel (refereegranskat)abstract
    • 1. A primary goal of evolutionary ecology is to understand factors selecting for the diversity of life histories. Life-history components, such as time-to-reproduction, adult survivorship and fecundity, might differ among species because of variation in direct and indirect benefits of these life histories in different environments or might have lower-than-expected variability because of phylogenetic constraints. Here, we present a phylogenetic examination of demography and life histories using a data base of 204 terrestrial plant species. 2. Overall, statistical models without phylogeny were preferred to models with phylogeny for vital rates and elasticities, suggesting that they lacked phylogenetic signal and are evolutionarily labile. However, the effect of phylogeny was significant in models including sensitivities, suggesting that sensitivities exhibit greater phylogenetic signal than vital rates or elasticities. 3. Species with a greater age at first reproduction had lower fecundity, consistent with a cost of delayed reproduction, but only in some habitats (e.g. grassland). We found no evidence for an indirect benefit of delayed reproduction via a decrease in variation in fecundity with age to first reproduction. 4. The greater sensitivity and lower variation in survival than in fecundity was consistent with buffering of more important vital rates, as others have also found. This suggests that studies of life-history evolution should include survival, rather than only fecundity, for the majority of species. 5. Synthesis. Demographic matrix models can provide informative tests of life-history theory because of their shared construction and outputs and their widespread use among plant ecologists. Our comparative analysis suggested that there is a cost of delayed reproduction and that more important vital rates exhibit lower variability. The absolute importance of vital rates to population growth rates (sensitivities) exhibited phylogenetic signal, suggesting that a thorough understanding of life-history evolution might require an understanding of the importance of vital rates, not just their means, and the role of phylogenetic history.
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6.
  • Horvitz, Carol C., et al. (författare)
  • Context-dependent pollinator limitation in stochastic environments : can increased seed set overpower the cost of reproduction in an understorey herb?
  • 2010
  • Ingår i: Journal of Ecology. - 0022-0477 .- 1365-2745. ; 98:2, s. 268-278
  • Tidskriftsartikel (refereegranskat)abstract
    • 1. In the understorey herb Lathyrus vernus seed production is pollen limited, but increased reproduction results in a lower probability of remaining reproductive. Putting these two results together, previous research reported that population growth rate lambda was negatively impacted by high pollination. 2. Thus, costs and benefits have to be translated into the common currency of their respective effects on population dynamics to determine whether populations are truly pollen limited or whether they are already at an optimal level of pollination. 3. Also, when pollinators and demography vary from year to year we require a framework that examines reproductive benefits and demographic costs in the context of a variable environment. Whether or not additional pollination will increase the stochastic population growth rate lambda(S) depends upon the balance of stochastic elasticities of the costs and benefits. 4. In constant environment models, where seed survival, germination and seedling survival were increased, we found that the high cost of reproduction could be offset by improvements in seed survival and germination, but not by improvements of seedling survival. 5. In variable environment models, where changes in the sequence and frequencies of high- and low-pollination years mixed with occasional high-germination years were modelled, we found that increasing the frequency of high-germination conditions could offset the cost of reproduction, and the offset was even greater if high-germination years occurred after a high-pollination year or if high pollination was accompanied by high-germination conditions in the same year. 6. Both deterministic lambda and stochastic lambda(S) were less sensitive to perturbation of reproduction than to perturbation of the probability for flowering plants to remain reproductive. In other words, a small change in the parameter which is related to the 'cost' of reproduction had a bigger effect than a small change in the parameter which is related to the 'benefit' of increased pollination for Lathyrus. 7.Synthesis. Stochastic environment-specific elasticities for reproduction and stasis of flowering plants differ in their response to environmental context. The cost-benefit relationships, the ultimate fitness consequences of supplemental pollen, are influenced by the frequency and sequence of years differing in pollen availability and recruitment conditions.
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7.
  • Kolb, Annette, et al. (författare)
  • Environmental context drives seed predator-mediated selection on a floral display trait
  • 2010
  • Ingår i: Evolutionary Ecology. - 0269-7653 .- 1573-8477. ; 24:2, s. 433-445
  • Tidskriftsartikel (refereegranskat)abstract
    • Linking trait selection to environmental context is necessary to move beyond the simple recognition that selection is spatially variable and to understand what ultimately drives this variation. Natural selection acts through differences among individuals in lifetime fitness and information about effects on fitness components is therefore often not sufficient to gain such an understanding. We investigated how environmental context influenced intensity of seed predation, flower abortion and selection on floral display traits in 44-52 populations of the perennial herb Primula veris over 2 years. Phenotypic selection on both inflorescence height and flower number varied among populations and was mediated partly by pre-dispersal seed predation and flower abortion in one of the years. Among-population variation in selection on inflorescence height, but not flower number, was linked to variation in canopy cover via its effects on seed predation. Lifetime fitness was less sensitive to seed predator damage in shaded environments but estimates of selection based on lifetime fitness agreed qualitatively with those based on seed output. Our results demonstrate that seed predators constitute an important link between environmental conditions and trait evolution in plants, and that selection on plant traits by seed predators can depend on environmental context.
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8.
  • Torang, Per, et al. (författare)
  • Linking environmental and demographic data to predict future population viability of a perennial herb
  • 2010
  • Ingår i: Oecologia. - 0029-8549 .- 1432-1939. ; 163:1, s. 99-109
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent advances in stochastic demography provide tools to examine the importance of random and periodic variation in vital rates for population dynamics. In this study, we explore with simulations the effect of disturbance regime on population dynamics and viability. We collected 7 years of demographic data in three populations of the perennial herb Primula farinosa, and used these data to examine how variation in vital rates affected population viability parameters (stochastic growth rate, lambda(S)), and how vital rates were related to weather conditions. Elasticity analysis indicated that the stochastic growth rate was very sensitive to changes in regeneration, quantified as the production, survival, and germination of seeds. In one of the study years, all seedlings and mature plants in the demography plots died. This extinction coincided with the driest summer during the study period. Simulations suggested that a future increase in the frequency of high-mortality years due to climate change would result in reduced population growth rate, and an increased importance of survival in the seed bank for population viability. The results illustrate how the limited demographic data typically available for many natural systems can be used in simulation models to assess how environmental change will affect population viability.
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9.
  • Vanhoenacker, Didrik, et al. (författare)
  • Morph-specific selection on floral traits in a polymorphic plant
  • 2010
  • Ingår i: Journal of Evolutionary Biology. - 1010-061X .- 1420-9101. ; 23:6, s. 1251-1260
  • Tidskriftsartikel (refereegranskat)abstract
    • Correlations between phenotypic traits are common in many organisms, but the relative importance of nonadaptive mechanisms and selection for the evolution and maintenance of such correlations are poorly understood. In polymorphic species, morphs may evolve quantitative differences in additional characters as a result of morph-specific selection. The perennial rosette herb Primula farinosa is polymorphic for scape length. The short-scaped morph is less damaged by grazers and seed predators but is more strongly pollen limited than the long-scaped morph. We examined whether morph-specific differences in biotic interactions are associated with differences in selection on two other traits affecting floral display (number of flowers and petal size) and on one trait likely to affect pollination efficiency (corolla tube width) in three P. farinosa populations. Differences in selection between morphs were detected in one population. In this population, selection for more flowers and larger petals was stronger in the short-scaped than in the long-scaped morph, and although there was selection for narrower corolla tubes in the short-scaped morph, no statistically significant selection on corolla tube width could be detected in the long-scaped morph. In the study populations, the short-scaped morph produced more and larger flowers and wider corolla tubes. Current morph-specific selection was thus only partly consistent with trait differences between morphs. The results provide evidence of morph-specific selection on traits associated with floral display and pollination efficiency, respectively.
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