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| 2. |
- Bengtsson, Bengt Olle, et al.
(författare)
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The effective size of bryophyte populations.
- 2009
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 258:Available online 8 January 2009, s. 121-126
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Tidskriftsartikel (refereegranskat)abstract
- Bryophytes with their dominant haploid stage conform poorly to the life cycles generally treated in population genetical models. Here we make a detailed analysis of what effective sizes bryophyte model populations have as a function of their breeding system. It is found that the effective size is rarely much smaller than the scored number of haploid gametophytic individuals, even when the limited number of diploids (sporophytes) formed is taken into account. The most severe decrease in effective size occurs when unisexual gametophytic females produce only a small number of fertile diploid sporophytes in male biased populations; this effect is due to the restricted sampling of male gametophytic individuals that then occurs. It is shown that the harmonic mean of diploid sporophytes formed per haploid gametophytic individuals is the relevant measure in these calculations and not the standard (and generally larger) arithmetic mean.
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| 3. |
- Bengtsson, Fia, 1986-
(författare)
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Functional Traits in Sphagnum
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Peat mosses (Sphagnum) are ecosystem engineers that largely govern carbon sequestration in northern hemisphere peatlands. I investigated functional traits in Sphagnum species and addressed the questions: (I) Are growth, photosynthesis and decomposition and the trade-offs between these traits related to habitat or phylogeny?, (II) Which are the determinants of decomposition and are there trade-offs between metabolites that affect decomposition?, (III) How do macro-climate and local environment determine growth in Sphagnum across the Holarctic?, (IV) How does N2 fixation vary among different species and habitats?, (V) How do species from different microtopographic niches avoid or tolerate desiccation, and are leaf and structural traits adaptations to growth high above the water table?Photosynthetic rate and decomposition in laboratory conditions (innate growth and decay resistance) were related to growth and decomposition in their natural habitats. We found support for a trade-off between growth and decay resistance, but innate qualities translated differently to field responses in different species. There were no trade-offs between production of different decay-affecting metabolites. Their production is phylogenetically controlled, but their effects on decay are modified by nutrient availability in the habitat. Modelling growth of two species across the Holarctic realm showed that precipitation, temperature and vascular plant cover are the best predictors of performance, but responses were stronger for the wetter growing species. N2 fixation rates were positively related to moss decomposability, field decomposition and tissue phosphorus concentration. Hence, higher decomposition can lead to more nutrients available to N2-fixing microorganisms, while higher concentrations of decomposition-hampering metabolites may impede N2 fixation. A mesocosm experiment, testing effects of water level drawdown on water content and chlorophyll fluorescence, showed that either slow water loss or high maximum water holding capacity can lead to desiccation avoidance. Furthermore, leaf anatomical traits rather than structural traits affected the water economy.This thesis has advanced the emerging field of trait ecology in Sphagnum by comparing many species and revealing novel mechanisms and an ever more complex picture of Sphagnum ecology. In addition, the species-specific trait measurements of this work offers opportunities for improvements of peatland ecosystem models.
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| 4. |
- Bengtsson, Fia, et al.
(författare)
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Mechanisms behind species-specific water economy responses to water level drawdown in peat mosses
- 2020
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 126:2, s. 219-230
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Tidskriftsartikel (refereegranskat)abstract
- Background and AimsThe ecosystem engineers Sphagnum (peat mosses) are responsible for sequestering a large proportion of carbon in northern peatlands. Species may respond differently to hydrological changes, and water level changes may lead to vegetation shifts in peatlands, causing them to revert from sinks to sources of carbon. We aimed to compare species-specific responses to water level drawdown within Sphagnum, and investigate which traits affect water economy in this genus.MethodsIn a mesocosm experiment, we investigated how water level drawdown affected water content (WC) in the photosynthetically active apex of the moss and maximum quantum yield of photosystem II (i.e. Fv/Fm) of 13 Sphagnum species. Structural traits were measured, and eight anatomical traits were quantified from scanning electron microscopy micrographs.Key ResultsMixed-effects models indicated that at high water level, large leaves were the most influential predictor of high WC, and at low water level WC was higher in species growing drier in the field, with larger hyaline cell pore sizes and total pore areas associated with higher WC. Higher stem and peat bulk density increased WC, while capitulum mass per area and numerical shoot density did not. We observed a clear positive relationship between Fv/Fm and WC in wet-growing species.ConclusionsWhile we found that most hummock species had a relatively high water loss resistance, we propose that some species are able to maintain a high WC at drawdown by storing large amounts of water at a high water level. Our result showing that leaf traits are important warrants further research using advanced morphometric methods. As climate change may lead to more frequent droughts and thereby water level drawdowns in peatlands, a mechanistic understanding of species-specific traits and responses is crucial for predicting future changes in these systems.
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| 5. |
- Cheng, Jingmin, et al.
(författare)
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Interspecific competition affects spore germination and gametophore development of mosses
- 2023
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Ingår i: Open Research Europe. - 2732-5121. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Background: Interactions between moss species in their earliest growth stages have received little attention. To what extent interspecific competition or priority effects influence spore germination, protonemal development and gametophore emergence is unknown. We evaluated such effects in pairwise interaction between six common bryophyte species: Atrichum undulatum, Bryum argenteum, Ceratodon purpureus, Funaria hygrometrica, Hypnum cupressiforme, Leptobryum pyriforme Methods: Interspecific interactions were assessed in vitro. Spores were sterilized and sown on agar plates in three treatments: 1) as single species cultures (controls), 2) as pairwise species cultures inoculated simultaneously, and 3) with a time lag of 20 days between species. Data on the time needed for spore germination, germination rate, the time needed for gametophore differentiation, number of gametophores per germinated spore and average diameter of colonies were collected. We also performed spore germination tests in single-species cultures at the start and end of the study, as well as tests for density-dependency at spore germination and gametophore formation. Results: We observed strong pairwise interactive effects when sowing spores of different species simultaneously or with a delay of 20 days. The results indicate that spore germination is often inhibited by interspecific competition. The first species has an advantage as compared to the later colonizing species, i.e., an apparent priority effect. Interspecific interactions were also evident during gametophore development and included both inhibition and facilitation. Conclusion: We found pronounced differences in the relative performance of species in interaction with other species during spore germination and gametophore formation. Allelopathic effects are the most probable explanation for these observations. Our results under sterile lab conditions are likely to reflect processes that occur in the wild, governing biotic filtering and bryophyte community assembly during primary and secondary colonization.
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| 6. |
- Cronberg, Nils
(författare)
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Absence of genetic variation in populations of the liverwort Plagiochila porelloides from northern Greece and southern Scandinavia
- 2000
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Ingår i: Lindbergia. - 0105-0761. ; 25:1, s. 20-24
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Populations of the leafy liverwort Plagiochila porelloides from lowland southern Scandinavia and mountain peaks on mainland Greece were screened for polymorphisms at 16 putative isozyme loci. The study areas were chosen to represent regions severely and mildly affected by the Pleistocene glaciations, respectively. As in an earlier study from Poland, total absence of variability was recorded. It is concluded that a population ancestral to the present-day populations may have passed through a severe bottleneck. The data are uninformative regarding the circumstances of this event.
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| 7. |
- Cronberg, Nils, et al.
(författare)
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Alger och blågröna bakterier
- 2008
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Ingår i: Botanik – systematik, evolution och mångfald. - 9789144043043 ; , s. 77-121
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 8. |
- Cronberg, Nils, et al.
(författare)
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Allelopathy in bryophytes - a review
- 2018
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Ingår i: Lindbergia. - : Dutch Bryological and Lichenological Society and Nordic Bryological Society. - 0105-0761. ; 41, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Allelopathy in bryophytes shapes ecosystems by influencing the species composition of both vascular plants and other bryophytes. Several allelopathically active chemicals in bryophytes have been discovered since the latter half of the 20th century and laboratory studies have showed their inhibiting impact on germination, growth and establishment of surrounding plants. However, other studies failed to demonstrate these effects. In the field, other properties of bryophytes might have stronger impacts, such as mechanical obstruction or alterations in temperature. In laboratory studies, water might not be an adequate extractant for active substances, since all of the chemicals claimed to be allelopathic are lipophilic with potentially longer retention times of the active substances in the soil when compared to water-soluble substances.
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| 9. |
- Cronberg, Nils
(författare)
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Animal-mediated fertilization in bryophytes – parallel or precursor to insect pollination in angiosperms?
- 2012
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Ingår i: Lindbergia. - 0105-0761. ; 35, s. 76-85
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Tidskriftsartikel (refereegranskat)abstract
- Bryophytes have until now been absent from all hypotheses regarding the origin of insect pollination of seed plants. The discovery that both springtails and mites are able to transfer sperm in mosses makes it possible to suggest a ’Bryophyte precursor hypothesis of plant pollination’ stating that animal-mediated fertilization in mosses and insect pollination in seed plants is historically linked by homologous or analogous evolution of structures responsible for attraction and reward aimed at a pool of fertilization vectors originally co-evolved with bryophytes and subsequently co-opted by seed plants. The earliest point in time when animal-mediated fertilization of bryophytes, involving springtails and mites, could have arisen is Late Silurian/Early Devonian, ca 280 Myr before the evolutionary radiation of angiosperms. Soil-dwelling microarthropods and wingless insects are assumed to have been the primary vectors transporting sperm in ancient mosses and possibly other groups of bryophytes. These animals may later have secondarily expanded to transfer pollen in gymnosperms and angiosperms, similar to the frequent pollinator shifts observed among angiosperm groups. Several ancestral traits pointed out by recent studies of early angiosperms are in favour of this hypothesis, such as small size of flowers, small and non-sticky pollen, adaptations for growth in moist and shaded habitats close to running water, and weedy growth forms with rapid life-cycles in disturbed habitats. It is also possible to envisage a link from sexual attractants excreted by oogonia in charophyte algae and archegonia in bryophytes to guide sperm, via sugar released to attract insects in pollination drop mechanisms in gymnosperms to more advanced structures specialized for insect attraction such as nectaries and nectar discs in angiosperms.
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| 10. |
- Cronberg, Nils, et al.
(författare)
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Biogeografi
- 2008
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Ingår i: Botanik – systematik, evolution och mångfald. - 9789144043043 ; , s. 387-407
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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