| 1. |
- Abbas, Aamer, 1973, et al.
(författare)
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Chemical images of marine bio-active compounds by surface enhanced Raman spectroscopy and transposed orthogonal partial least squares (T-OPLS)
- 2012
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 737, s. 37-44
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Tidskriftsartikel (refereegranskat)abstract
- Surface enhanced Raman spectroscopy combined with transposed Orthogonal Partial Least Squares (T-OPLS) was shown to produce chemical images of the natural antibacterial surface-active compound 1,1,3,3-tetrabromo-2-heptanone (TBH) on Bonnemaisonia hamifera. The use of gold colloids function-alised with the internal standard 4-mercapto-benzonitrile (MBN) made it possible to create images of the relative concentration of TBH over the surfaces. A gradient of TBH could be mapped over and in the close vicinity of the B. hamifera algal vesicles at the attomol/pixel level. T-OPLS produced a measure of the spectral correlation for each pixel of the hyperspectral images whilst not including spectral variation that was linearly independent of the target spectrum. In this paper we show the possibility to retrieve specific spectral information with a low magnitude in a complex matrix.
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| 2. |
- Baumgartner, Finn A., 1982, et al.
(författare)
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Individual Specialization to Non-Optimal Hosts in a Polyphagous Marine Invertebrate Herbivore
- 2014
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Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 9:8
-
Tidskriftsartikel (refereegranskat)abstract
- Factors determining the degree of dietary generalism versus specialism are central in ecology. Species that are generalists at the population level may in fact be composed of specialized individuals. The optimal diet theory assumes that individuals choose diets that maximize fitness, and individual specialization may occur if individuals' ability to locate, recognize, and handle different food types differ. We investigate if individuals of the marine herbivorous slug Elysia viridis, which co-occur at different densities on several green macroalgal species in the field, are specialized to different algal hosts. Individual slugs were collected from three original algal host species (Cladophora sericea, Cladophora rupestris and Codium fragile) in the field, and short-term habitat choice and consumption, as well as long-term growth (proxy for fitness), on four algal diet species (the original algal host species and Chaetomorpha melagonium) were studied in laboratory experiments. Nutritional (protein, nitrogen, and carbon content) and morphological (dry weight, and cell/utricle volume) algal traits were also measured to investigate if they correlated with the growth value of the different algal diets. E. viridis individuals tended to choose and consume algal species that were similar to their original algal host. Long-term growth of E. viridis, however, was mostly independent of original algal host, as all individuals reached a larger size on the non-host C. melagonium. E. viridis growth was positively correlated to algal cell/utricle volume but not to any of the other measured algal traits. Because E. viridis feeds by piercing individual algal cells, the results indicate that slugs may receive more cytoplasm, and thus more energy per unit time, on algal species with large cells/utricles. We conclude that E. viridis individuals are specialized on different hosts, but host choice in natural E. viridis populations is not determined by the energetic value of seaweed diets as predicted by the ODT.
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| 3. |
- Enge, Swantje, 1981, et al.
(författare)
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An exotic chemical weapon explains low herbivore damage in an invasive alga
- 2012
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Ingår i: Ecology. - : Wiley. - 0012-9658. ; 93:12, s. 2736-2745
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Tidskriftsartikel (refereegranskat)abstract
- Invasion success of introduced species is often attributed to a lack of natural enemies as stated by the enemy release hypothesis (ERH). The ERH intuitively makes sense for specialized enemies, but it is less evident why invaders in their new area escape attacks by generalist enemies. A recent hypothesis explains low herbivore damage on invasive plants with plant defense chemicals that are evolutionarily novel to native herbivores. Support for this novel weapon hypothesis (NWH) is so far based on circumstantial evidence. To corroborate the NWH, there is a need for direct evidence through explicit characterizations of the novel chemicals and their effects on native consumers. This study evaluated the NWH using the highly invasive red alga Bonnemaisonia hamifera. In pairwise feeding experiments, preferences between B. hamifera and native competitors were assessed for four common generalist herbivores in the invaded area. Through a bioassay-guided fractionation, we identified the deterrent compound and verified its effect in an experiment with the synthesized compound at natural concentrations. The results showed that native herbivores strongly preferred native algae to B. hamifera. The resistance against herbivores could be tracked down to the algal metabolite 1,1,3,3-tetrabromo-2-heptanone, a compound not known from native algae in the invaded area. The importance of the chemical defense was further underlined by the feeding preference of herbivores for individuals with a depleted content of 1,1,3,3-tetrabromo-2-heptanone. This study thus provides the first conclusive example of a highly successful invader where low consumption in the new range can be directly attributed to a specific chemical defense against evolutionarily naive native generalists. In conclusion, our results support the notion that novel chemical weapons against naive herbivores can provide a mechanistic explanation for plant invasion success.
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| 4. |
- Enge, Swantje, 1981, et al.
(författare)
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Native generalist herbivores promote invasion of a chemically defended seaweed via refuge-mediated apparent competition
- 2013
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Ingår i: Ecology Letters. - 1461-023X .- 1461-0248. ; 16:4, s. 487-492
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Tidskriftsartikel (refereegranskat)abstract
- Refuge-mediated apparent competition was recently suggested as a mechanism that enables plant invasions. The refuge characteristics of introduced plants are predicted to enhance impacts of generalist herbivores on native competitors and thereby result in an increased abundance of the invader. However, this prediction has so far not been experimentally verified. This study tested if the invasion of a chemically defended seaweed is promoted by native generalist herbivores via refuge-mediated apparent competition. The invader was shown to offer herbivores a significantly better refuge against fish predation compared with native seaweeds. Furthermore, in an experimental community, the presence of herbivores decreased the performance of neighbouring native seaweeds, but increased growth and relative abundance of the invader. These results provides the first experimental evidence that native generalist herbivores can shift a community towards a dominance of a well-defended invader, inferior to native species in direct competitive interactions, by means of refuge-mediated apparent competition.
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| 5. |
- Forslund, Helena, 1978-, et al.
(författare)
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Higher resistance to herbivory in introduced compared to native populations of a seaweed
- 2010
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 164:3, s. 833-840
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Tidskriftsartikel (refereegranskat)abstract
- Non-indigenous species (NIS) are important components of global change, and in order to manage such species it is important to understand which factors affect their success. Interactions with enemies in the new range have been shown to be important for the outcome of introductions, but thus far most studies on NIS-enemy interactions have considered only specialist herbivores in terrestrial systems. Here we present the results from the first biogeographic study that compares herbivore resistance between populations in the native and new region of a non-indigenous seaweed. We show that low consumption of the non-indigenous seaweed by a generalist herbivore is caused by higher chemical defence levels and herbivore resistance in the new range-and not by the failure of the herbivore to recognise the non-indigenous seaweed as a suitable host. Since most seaweed-herbivore interactions are dominated by generalist herbivores, this pattern could be common in marine communities. Our results also reveal that traits used to predict the invasive potential of species, such as their resistance to enemies, can change during the invasion process, but not always in the way predicted by dominant theories.
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| 6. |
- Hanssen, Kine Œ, et al.
(författare)
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The Bromotyrosine derivative Ianthelline isolated from the arctic marine sponge Stryphnus fortis inhibits marine micro- and macrobiofouling
- 2014
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Ingår i: Marine Biotechnology. - : Springer Science and Business Media LLC. - 1436-2228 .- 1436-2236. ; 16:6, s. 684-694
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Tidskriftsartikel (refereegranskat)abstract
- The inhibition of marine biofouling by the bromotyrosine derivative ianthelline, isolated from the Arctic marine sponge Stryphnus fortis, is described. All major stages of the fouling process are investigated. The effect of ianthelline on adhesion and growth of marine bacteria and microalgae is tested to investigate its influence on the initial microfouling process comparing with the known marine antifoulant barettin as a reference. Macrofouling is studied via barnacle (Balanus improvisus) settlement assays and blue mussel (Mytilus edulis) phenoloxidase inhibition. Ianthelline is shown to inhibit both marine micro- and macrofoulers with a pronounced effect on marine bacteria (minimum inhibitory concentration (MIC) values 0.1–10 μg/mL) and barnacle larval settlement (IC50=3.0 μg/mL). Moderate effects are recorded on M. edulis (IC50=45.2 μg/mL) and microalgae, where growth is more affected than surface adhesion. The effect of ianthelline is also investigated against human pathogenic bacteria. Ianthelline displayed low micromolar MIC values against several bacterial strains, both Gram positive and Gram negative, down to 2.5 μg/mL. In summary, the effect of ianthelline on 20 different representative marine antifouling organisms and seven human pathogenic bacterial strains is presented.
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| 7. |
- Long, JD, et al.
(författare)
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Proximate and ultimate causes for transatlantic variation in seaweed defenses
- 2013
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 493, s. 83-89
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Tidskriftsartikel (refereegranskat)abstract
- Previous tests of theories predicting tradeoffs between constitutive and inducible defenses are inconclusive. This may result from focusing on individual traits or using cultivated plants subjected to artificial selection. We examined this tradeoff in the seaweed Ascophyllum nodosum (hereafter Ascophyllum)—one of the best-studied seaweeds with inducible defenses. Although several European populations respond to grazing with induced resistance, a US population failed to express inducible defenses. This variation may be related to corresponding variation in constitutive resistance and consumer pressure. We compared the constitutive resistance of Ascophyllum from an inducing and a non-inducing population (Sweden and USA, respectively). We quantified constitutive resistance by conducting choice feeding assays on seaweed from both populations after inducible defenses had relaxed, rather than focusing on single traits. We measured constitutive phlorotannins to confirm that defenses had relaxed and to compare between-population levels. Periwinkles consistently preferred relaxed Swedish Ascophyllum, suggesting that US Ascophyllum without inducible resistance had higher constitutive resistance. Neither snail source nor experimental arena influenced this result. Phlorotannins were also higher in relaxed US Ascophyllum. To test the hypothesis that defense type may be related to current consumer pressure, we compared per capita grazing rates and average snail densities from both locations. US snails grazed more and were more abundant in the USA, suggesting that current consumer pressure may be higher on US Ascophyllum. Consistent with theory, constitutive and inducible resistance were negatively related between our sites. Inducible resistance may be absent from the US population because these individuals have high constitutive resistance, perhaps because they encounter greater consumer pressure.
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| 8. |
- Nylund, Göran M., 1974, et al.
(författare)
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Costs and Benefits of Chemical Defence in the Red Alga Bonnemaisonia hamifera
- 2013
-
Ingår i: Plos One. - : Public Library of Science (PLoS). - 1932-6203. ; 8:4
-
Tidskriftsartikel (refereegranskat)abstract
- A number of studies have shown that the production of chemical defences is costly in terrestrial vascular plants. However, these studies do not necessarily reflect the costs of defence production in macroalgae, due to structural and functional differences between vascular plants and macroalgae. Using a specific culturing technique, we experimentally manipulated the defence production in the red alga Bonnemaisonia hamifera to examine if the defence is costly in terms of growth. Furthermore, we tested if the defence provides fitness benefits by reducing harmful bacterial colonisation of the alga. Costly defences should provide benefits to the producer in order to be maintained in natural populations, but such benefits through protection against harmful bacterial colonisation have rarely been documented in macroalgae. We found that algae with experimentally impaired defence production, but with an externally controlled epibacterial load, grew significantly better than algae with normal defence production. We also found that undefended algae exposed to a natural epibacterial load experienced a substantial reduction in growth and a 6-fold increase in cell bleaching, compared to controls. Thus, this study provides experimental evidence that chemical defence production in macroalgae is costly, but that the cost is outweighed by fitness benefits provided through protection against harmful bacterial colonisation.
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| 9. |
- Nylund, Göran M., 1974, et al.
(författare)
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Increased resistance towards generalist herbivory in the new range of a habitat-forming seaweed
- 2012
-
Ingår i: Ecosphere. - 2150-8925. ; 3:12, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between plants and their biotic environment can drastically change during range- expansion and result in rapid adaptive evolution of plant traits. According to the influential evolution of increased competitive ability (EICA) hypothesis escape from specialist natural enemies will lead to a reduction in defense levels, but the way in which generalist consumers in the new ranges affect the evolution of plant defenses remains poorly understood. We conducted a four month controlled environment experiment to examine if the high densities of the generalist herbivore Idotea baltica in the Baltic Sea have selected for increased grazer-resistance in Fucus vesiculosus, a North Atlantic seaweed that has expanded into large parts of the brackish Baltic Sea. Genetic analysis using microsatellites showed that the sampled populations are genetically distinct, which strongly suggests that traits under divergent selection may readily diverge and populations evolve local adaptations. Feeding trials and measurements of defense metabolites, i.e., phlorotannins, showed that F. vesiculosus from the Baltic Sea was least preferred and contained more than 50% higher constitutive levels of phlorotannins than conspecifics in the North Sea (Skagerrak), while algae from the Öresund, one of the sounds connecting the Baltic Sea to the Skagerrak, had intermediate resistance levels both in terms of grazer preference and phlorotannin levels. These results suggest that the higher grazing pressure on F. vesiculosus expanded into the Baltic Sea has resulted in the evolution of increased resistance towards generalist grazing.
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| 10. |
- Nylund, Göran M., 1974, et al.
(författare)
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The red alga Bonnemaisonia asparagoides regulates epiphytic bacterial abundance and community composition by chemical defence
- 2010
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Ingår i: FEMS Microbiology Ecology. - : Oxford University Press (OUP). - 0168-6496 .- 1574-6941. ; 71:1, s. 84-93
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Tidskriftsartikel (refereegranskat)abstract
- Ecological research on algal-derived metabolites with antimicrobial activity has recently received increased attention and is no longer only aimed at identifying novel natural compounds with potential use in applied perspectives. Despite this progress, few studies have so far demonstrated ecologically relevant antimicrobial roles of algal metabolites, and even fewer have utilized molecular tools to investigate the effects of these metabolites on the natural community composition of bacteria. In this study, we investigated whether the red alga Bonnemaisonia asparagoides is chemically defended against bacterial colonization of its surface by extracting surface-associated secondary metabolites and testing their antibacterial effects. Furthermore, we compared the associated bacterial abundance and community composition between B. asparagoides and two coexisting macroalgae. Surface extracts tested at natural concentrations had broad-spectrum effects on the growth of ecologically relevant bacteria, and consistent with this antibacterial activity, natural populations of B. asparagoides had significantly lower densities of epibacteria compared with the coexisting algae. Terminal restriction fragment length polymorphism analysis further showed that B. asparagoides harboured surface-associated bacteria with a community composition that was significantly different from those on coexisting macroalgae. Altogether, these findings demonstrate that B. asparagoides produces surface-bound antibacterial compounds with a significant impact on the abundance and composition of the associated bacterial community.
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| 11. |
- Pavia, Henrik, 1964, et al.
(författare)
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Chemical defences against herbivores
- 2012
-
Ingår i: Chemical ecology in aquatic systems. - New York, US : Oxford University Press. - 9780199583096 ; , s. 210-235
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Bokkapitel (refereegranskat)abstract
- In recent years it has become increasingly clear that chemical interactions play a fundamental role in aquatic habitats and have far-reaching evolutionary and ecological consequences. A plethora of studies have shown that aquatic organisms from most taxa and functional groups respond to minute concentrations of chemical substances released by other organisms. However, our knowledge of this 'chemical network' is still negligible. Chemical interactions can be divided into two larger sub-areas based on the function of the chemical substance. First, there are interactions where chemical substances are toxic to other organisms and are used as a defense against consumers (including both herbivores and predators) or a weapon against competitors (allelopathy). Second, chemical substances mey be used as a source for information of the environment; for example: how can I find the optimal habitat, the best food, the nicest partner, and avoid being eaten? Aquatic organisms are able to detect and respond to extremely low concentrations of chemical cues to answer all these questions. The book aims at connecting these intriguing chemical interactions with traditional knowledge of organism interactions. Chemical ecology in aquatic systems covers a wide range of studies, both plant and animal, from different geographic regions and habitats-pelagic as well as benthic. Most of the chemical interactions are similar in freshwater and marine habitats and this book therefor strives at integrating work on both systems. This accessible, research-level text is aimed at graduate students and professional researchers in the fields of limnology, marine ecology, evolutionary biology, behavioral ecology, and chemical ecology.
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| 12. |
- Persson, Frank, 1970, et al.
(författare)
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Ecological role of a seaweed secondary metabolite for a colonizing bacterial community
- 2011
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Ingår i: Biofouling. - : Informa UK Limited. - 0892-7014 .- 1029-2454. ; 27:6, s. 579-588
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Tidskriftsartikel (refereegranskat)abstract
- Bacteria associated with seaweeds can both harm and benefit their hosts. Many seaweed species are known to produce compounds that inhibit growth of bacterial isolates, but the ecological role of seaweed metabolites for the associated bacterial community structure is not well understood. In this study the response of a colonizing bacterial community to the secondary metabolite (1,1,3,3-tetrabromo-2-heptanone) from the red alga Bonnemaisonia hamifera was investigated by using field panels coated with the metabolite at a range of concentrations covering those measured at the algal surface. The seaweed metabolite has previously been shown to have antibacterial effects. The metabolite significantly affected the natural fouling community by (i) altering the composition, (ii) altering the diversity by increasing the evenness and (iii) decreasing the density, as measured by terminal restriction fragment length polymorphism in conjunction with clone libraries of the 16S rRNA genes and by bacterial enumeration. No single major bacterial taxon (phylum, class) was particularly affected by the metabolite. Instead changes in community composition were observed at a more detailed phylogenetic level. This indicates a broad specificity of the seaweed metabolite against bacterial colonization, which is supported by the observation that the bacterial density was significantly affected at a lower concentration (0.02 μg cm -2) than the composition (1-2.5 μg cm -2) and the evenness (5 μg cm -2) of the bacterial communities. Altogether, the results emphasize the role of secondary metabolites for control of the density and structure of seaweed-associated bacterial communities.
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| 13. |
- Sagerman, Josefin, et al.
(författare)
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Divergent ecological strategies determine different impacts on community production by two successful non-native seaweeds
- 2014
-
Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 175:3, s. 937-946
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Tidskriftsartikel (refereegranskat)abstract
- The consequences of plant introductions into ecosystems are frequently reported from terrestrial environments, but little is known about the effects on ecosystem functioning caused by non-native primary producers in marine systems. In this study we explored the effects of the invasion by the two filamentous red algae Heterosiphonia japonica and Bonnemaisonia hamifera on the primary production of seaweed communities by using single and mixed cultures of non-native and native red algae. The experiments were conducted both in the presence and absence of herbivores. Biomass production of the invaded community increased more than four times in mixed cultures with H. japonica, while introduction by B. hamifera had no significant effect. The different impact on community production could be explained by differences in life history strategies between the invaders; H. japonica grew considerably faster than the native seaweeds which directly increased the community production, while B. hamifera showed a relatively slow growth rate and therefore had no effect. From previous studies it is known that B. hamifera produces a highly deterrent, but also costly, chemical defence. The assessment of survival and growth of a native generalist herbivore further corroborated that the biomass produced by B. hamifera constitutes a very low-quality food, whereas the performance of herbivores on a diet of H. japonica was comparable to that on native algal diets. In summary, this study demonstrates that successful invaders belonging to the same functional group (filamentous red algae) may have distinctly different impacts on productivity in the recipient community, depending on their specific life history traits.
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| 14. |
- Selander, Erik, 1973, et al.
(författare)
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Fight and flight in dinoflagellates? Kinetics of simultaneous grazer-induced responses in Alexandrium tamarense
- 2012
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 57:1, s. 58-64
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Tidskriftsartikel (refereegranskat)abstract
- We monitored the kinetics of grazer-induced responses in the marine dinoflagellate Alexandrium tamarense. Chemical cues from each of three calanoid copepods (Calanus sp., Centropages typicus, and Acartia tonsa) induced increased toxicity and suppressed chain formation in A. tamarense. Both chemical and morphological responses augmented over 3 d. Toxicity subsequently averaged 299% higher than controls, and average biovolume 24% lower than controls because of suppression of chain formation in grazed treatments. Grazer-induced toxicity returned to control levels after approximately 11 d, equivalent to five cell divisions, and average biovolume returned to control levels within 1 to 4 d (one to two cell divisions). This suggests that dinoflagellates simultaneously reduce grazer encounter rates and increase chemical defense levels in the presence of copepod grazers. Media replacement experiments showed that the inducing cue(s) attenuate rapidly in seawater, which allows A. tamarense to adjust resource allocation to grazer-induced responses to follow fluctuations in grazer density. Grazer-induced responses, however, develop too slowly to be accounted for in short-term grazing experiments with laboratory cultures.
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| 15. |
- Svensson, J. Robin, 1979, et al.
(författare)
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Disturbance-diversity models: what do they really predict and how are they tested?
- 2012
-
Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 279:1736, s. 2163-2170
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Tidskriftsartikel (refereegranskat)abstract
- The intermediate disturbance hypothesis (IDH) and the dynamic equilibrium model (DEM) are influential theories in ecology. The IDH predicts large species numbers at intermediate levels of disturbance and the DEM predicts that the effect of disturbance depends on the level of productivity. However, various indices of diversity are considered more commonly than the predicted number of species in tests of the hypotheses. This issue reaches beyond the scientific community as the predictions of the IDH and the DEM are used in the management of national parks and reserves. In order to compare responses with disturbance among measures of biodiversity, we used two different approaches of mathematical modelling and conducted an extensive meta-analysis. Two-thirds of the surveyed studies present different results for different diversity measures. Accordingly, the meta-analysis showed a narrow range of negative quadratic regression components for richness, but not evenness. Also, the two models support the IDH and the DEM, respectively, when biodiversity is measured as species richness, but predict evenness to increase with increasing disturbance, for all levels of productivity. Consequently, studies that use compound indices of diversity should present logical arguments, a priori, to why a specific index of diversity should peak in response to disturbance.
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| 16. |
- Svensson, J. Robin, 1979, et al.
(författare)
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Novel chemical weapon of an exotic macroalga inhibits recruitment of native competitors in the invaded range
- 2013
-
Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 101:1, s. 140-148
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Tidskriftsartikel (refereegranskat)abstract
- 1. Allelopathy is an important non-resource interaction in terrestrial plant communities that may affect invasions by non-indigenous plants. The ‘novel weapons hypothesis’ (NWH) predicts that non-indigenous plants will become invasive if they have allelopathic compounds that assem- blages in the new range are not adapted to. Recently, the non-indigenous, chemically rich macroalga Bonnemaisonia hamifera (Hariot) has become one of the most abundant filamentous red algae in Scandinavian waters. 2. We used B. hamifera to specifically test the aspect of the NWH that concerns invasion success based on novel allelochemicals in the invaded range. Allelopathic interactions were tested through effects on the growth rate of adult native macroalgae in co-cultures with B. hamifera and through the settlement success of native macroalgal propagules and microalgae on surfaces coated with 1,1,3,3-tetrabromo-2-heptanone. We also investigated whether 1,1,3,3-tetrabromo-2-heptanone can be transferred from B. hamifera to its native host algae, as a means of pre-emptive competition. 3. The settlement of native macroalgal propagules and microalgae was strongly inhibited on surfaces coated with 1,1,3,3-tetrabromo-2-heptanone at ecologically relevant concentrations, but there were no effects of adult B. hamifera on growth rates of adults of the six native naturally co-occurring spe- cies. The compound was shown to be transferred from B. hamifera to the surface of its native host algae at inhibitory concentrations in both laboratory and field experiments. 4. By inhibiting the settlement of propagules on its thallus and on surrounding surfaces, B. hamifera achieves a competitive advantage over native macroalgae, a finding that parallels previous reports on soil- and litter-mediated allelopathic interactions among vascular plants. Because competition for available substrata in marine benthic systems is intense, the ability to reserve space may be vital for B. hamifera’s successful invasion. This is the first example of an allelopathic compound that can be transferred by direct contact from an exotic to a native species, with an active and unaltered func- tion. 5. Synthesis. Our results clearly show that the main secondary metabolite of the invasive red alga B. hamifera has strong allelopathic effects towards native competitors, suggesting that its novel chemical weapon is important for the highly successful invasion of new ranges.
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| 17. |
- Svensson, J. Robin, 1979, et al.
(författare)
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Physical and biological disturbance interacts differently with productivity: divergence in effects on floral and faunal richness
- 2010
-
Ingår i: Ecology. - 0012-9658. ; 91:10, s. 3069-3080
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Tidskriftsartikel (refereegranskat)abstract
- Physical and biological disturbance are ecological processes affecting patterns in biodiversity at a range of scales in a variety of terrestrial and aquatic systems. Theoretical and empirical evidence suggest that effects of disturbance on diversity differ qualitatively and quantitatively depending on levels of productivity (e.g. the dynamic equilibrium model). In this study we contrasted the interactive effects between physical disturbance and productivity to those between biological disturbance and productivity. Furthermore, to evaluate how these effects varied among different components of marine hard-substratum assemblages, analyses were done separately on algal and invertebrate richness, as well as richness of the whole assemblage. Physical disturbance (wave action) was simulated at five distinct frequencies, while biological disturbance (grazing periwinkles) was manipulated as present or absent, and productivity as high or ambient. Uni- and multivariate analyses both showed significant effects of physical disturbance and interactive effects between biological disturbance and productivity on the composition of assemblages and the total species richness. The algal richness was significantly affected by productivity and biological disturbance, whereas the invertebrate richness was affected by physical disturbance only. Thus, we show, for the first time, that biological disturbance and physical disturbance interact differently with productivity, because these two types of disturbance affect different components of assemblages. These patterns might be explained by differences in the distribution (i.e. press vs. pulse) and degree of selectivity between disturbances. Because different types of disturbance can affect different components of assemblages, general ecological models will benefit from using natural diverse communities and studies concerned with particular subsets of assemblages may be misleading. In conclusion, this study shows that the outcome of experiments on effects of disturbance and productivity on diversity is greatly influenced by the composition of the assemblage under study, as well as on the type of disturbance that is used as an experimental treatment.
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| 18. |
- Trepos, Rozenn, et al.
(författare)
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Antifouling compounds from the Sub-Arctic ascidian Synoicum pulmonaria: Synoxazolidinones A and C, Pulmonarins A and B, and synthetic analogues.
- 2014
-
Ingår i: Journal of natural products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 77:9, s. 2105-2113
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Tidskriftsartikel (refereegranskat)abstract
- The current study describes the antifouling properties of four members belonging to the recently discovered synoxazolidinone and pulmonarin families, isolated from the sub-Arctic sessile ascidian Synoicum pulmonaria collected off the Norwegian coast. Four simplified synthetic analogues were also prepared and included in the study. Several of the studied compounds displayed MIC values in the micro-nanomolar range against 16 relevant marine species involved in both the micro- and macrofouling process. Settlement studies on Balanus improvisus cyprids indicated a deterrent effect and a low toxicity for selected compounds. The two synoxazolidinones displayed broad activity and are shown to be among the most active natural antifouling bromotyrosine derivatives described. Synoxazolidinone C displayed selected antifouling properties comparable to the commercial antifouling product Sea-Nine-211. The pulmonarins prevented the growth of several bacterial strains at nanomolar concentrations but displayed a lower activity toward microalgae and no effect on barnacles. The linear and cyclic synthetic peptidic mimics also displayed potent antifouling activities mainly directed against bacterial adhesion and growth.
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| 19. |
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