| 1. |
- Koch, Kamilla, et al.
(author)
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Morphological differences in the ovary of Libellulidae (Odonata)
- 2009
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In: International Journal of Odonatology. - Oxford : Taylor & Francis. - 1388-7890 .- 2159-6719. ; 12:1, s. 147-156
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Journal article (peer-reviewed)abstract
- All female Odonata have been assumed to produce oocytes continuously during their mature life span. However, a recent study of ovariole orientation and development led to the suggestion that Libellulidae are divided into two groups of species, one with continuous, the other with stepwise oocyte production. To find more evidence of this division, we compared the size variation and growth within the vitellarium of the ovary, studying oocytes, and follicle cells. We found that morphological characters discriminate between the two ovary types in eight of the 10 investigated species. In both types we found an increase in all measurements from the anterior to the posterior end of the vitellarium. The increase in oocyte width and follicle cell length was significantly higher in species with a continuous oocyte production. We also noted that follicle cells may have more than one nucleus and that their number can vary during vitellogenesis. Our study confirmed the hypotheses that two different ovary types exist in Libellulidae. The two species not fitting into this grouping could be an artefact of small samp le size due to intraspecific phenotypic plasticity, or else there might be more than two ovary groups, or even a continuum. We could not offer an explanation as to how the process of stepwise oocyte production differs from continuous based production on morphological characters.
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| 2. |
- Lind, Martin I., et al.
(author)
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Slow development as an evolutionary cost of long life
- 2017
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In: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 31:6, s. 1252-1261
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Journal article (peer-reviewed)abstract
- Life-history theory predicts a trade-off between early-life fitness and life span. While the focus traditionally has been on the fecundity-life span trade-off, there are strong reasons to expect trade-offs with growth rate and/or development time. We investigated the roles of growth rate and development time in the evolution of life span in two independent selection experiments in the outcrossing nematode Caenorhabditis remanei. First, we found that selection under heat-shock leads to the evolution of increased life span without fecundity costs, but at the cost of slower development. Thereafter, the putative evolutionary links between development time, growth rate, fecundity, heat-shock resistance and life span were independently assessed in the second experiment by directly selecting for fast or slow development. This experiment confirmed our initial findings, since selection for slow development resulted in the evolution of long life span and increased heat-shock resistance. Because there were no consistent trade-offs with growth rate or fecundity, our results highlight the key role of development rate - differentiation of the somatic cells per unit of time - in the evolution of life span. Since development time is under strong selection in nature, reduced somatic maintenance resulting in shorter life span may be a widespread cost of rapid development.
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| 3. |
- Bonnot, Nadège, et al.
(author)
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Who’s afraid of the big bad wolf? : Variation in the stress response among personalities and populations in a large wild herbivore
- 2018
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In: Oecologia. - Amsterdam : Springer. - 0029-8549 .- 1432-1939. ; 188:1, s. 85-95
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Journal article (peer-reviewed)abstract
- Faced with rapid environmental changes, individuals may express different magnitude and plasticity in their response to a given stressor. However, little is known about the causes of variation in phenotypic plasticity of the stress response in wild populations. In the present study, we repeatedly captured individual roe deer (Capreolus capreolus) from two wild populations in Sweden exposed to differing levels of predation pressure and measured plasma concentrations of stress-induced cortisol and behavioral docility. While controlling for the marked effects of habituation, we found clear between-population differences in the stress-induced cortisol response. Roe deer living in the area that was recently recolonized by lynx (Lynx lynx) and wolves (Canis lupus) expressed cortisol levels that were around 30% higher than roe deer in the human-dominated landscape free of large carnivores. In addition, for the first time to our knowledge, we investigated the stress-induced cortisol response in free-ranging newborn fawns and found no evidence for hypo-responsiveness during early life in this species. Indeed, stress-induced cortisol levels were of similar magnitude and differed between populations to a similar extent in both neonates and adults. Finally, at an individual level, we found that both cortisol and docility levels were strongly repeatable, and weakly negatively inter-correlated, suggesting that individuals differed consistently in how they respond to a stressor, and supporting the existence of a stress-management syndrome in roe deer. © 2018, The Author(s).
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| 4. |
- Eriksson, Martin, 1970, et al.
(author)
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Community-Level Analysis of psbA Gene Sequences and Irgarol Tolerance in Marine Periphyton
- 2009
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In: Applied and Environmental Microbiology. - Washington, D.C. : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 75:4, s. 897-906
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Journal article (peer-reviewed)abstract
- This study analyzes psbA gene sequences, predicted D1 protein sequences, species relative abundance, and pollution-induced community tolerance in marine periphyton communities exposed to the antifouling compound Irgarol 1051. The mechanism of action of Irgarol is the inhibition of photosynthetic electron transport at photosystem II by binding to the D1 protein. The metagenome of the communities was used to produce clone libraries containing fragments of the psbA gene encoding the D1 protein. Community tolerance was quantified with a short-term test for the inhibition of photosynthesis. The communities were established in a continuous flow of natural seawater through microcosms with or without added Irgarol. The selection pressure from Irgarol resulted in an altered species composition and an inducted community tolerance to Irgarol. Moreover, there was a very high diversity in the psbA gene sequences in the periphyton, and the composition of psbA and D1 fragments within the communities was dramatically altered by increased Irgarol exposure. Even though tolerance to this type of compound in land plants often depends on a single amino acid substitution (Ser(264)-> Gly) in the D1 protein, this was not the case for marine periphyton species. Instead, the tolerance mechanism likely involves increased degradation of D1. When we compared sequences from low and high Irgarol exposure, differences in nonconserved amino acids were found only in the so-called PEST region of D1, which is involved in regulating its degradation. Our results suggest that environmental contamination with Irgarol has led to selection for high-turnover D1 proteins in marine periphyton communities at the west coast of Sweden.
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| 5. |
- Persson, Anders, 1956-, et al.
(author)
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Effects of benthivorous fish on biogeochemical processes in lake sediments
- 2006
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In: Freshwater Biology. - West Sussex, UK : Wiley-Blackwell. - 0046-5070 .- 1365-2427. ; 51:7, s. 1298-1309
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Journal article (peer-reviewed)abstract
- 1. Studies of aquatic environments have shown that community organisation may strongly affect ecosystem functioning. One common phenomenon is a change in nutrient level following a shift in the fish community composition. Although several hypotheses have been suggested, there is no consensus on which mechanisms are involved. Our study evaluated indirect effects of benthivorous fish on the biogeochemical processes at the sediment-water interface separately from direct effects caused by nutrient excretion or sediment resuspension.2. We assigned field enclosures to three treatments representing typical pond communities; without fish, addition of approximately 10 small tench or addition of one large bream. After one summer, we monitored the water chemistry, benthic invertebrates and periphyton in the enclosures and sampled sediment cores for laboratory analysis of biochemical process rates (oxygen, phosphorus and nitrogen exchange between sediment and water, and denitrification rate).3. Fish had strong negative effects on benthic invertebrates, but weaker effects on periphyton, organic content and porosity of the sediment. Moreover, there were significant positive fish effects on both phosphorus and nitrogen concentrations in the water. However, there were no general treatment effects on sediment processes that could explain the treatment effects on water chemistry in the enclosures.4. Hence, overall treatment effects attenuated along the chain of interactions. We conclude that the observed effect of benthic fish on water chemistry was probably because of direct effects on nutrient excretion or resuspension of sediment. The similarity between bream and tench treatments suggests large niche complementarity despite their different habitat preferences.
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| 6. |
- Persson, Anders, 1956-, et al.
(author)
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Vertical distribution of benthic community responses to fish predators, and effects on algae and suspended material
- 2006
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In: Aquatic Ecology. - Dordrecht, Netherlands : Springer Netherlands. - 1386-2588 .- 1573-5125. ; 40:1, s. 85-95
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Journal article (peer-reviewed)abstract
- The vertical positioning of benthic invertebrates should be a trade-off between the risky, but productive, sediment surface and the safer, but physiologically harsher, conditions deeper down in the sediment. This is because the foraging efficiency of benthic fish decreases with sediment depth, whereas the sediment surface is generally better oxygenated and has a higher resource quality than lower layers. We studied how two benthic fish predators, bream (Abramis brama) and ruffe (Gymnocephalus cernuus), affected the community composition and vertical distribution of benthos, and their indirect effects on algae and suspended material, in field enclosures. Whereas bream had significant effects on the density, composition and distribution of the benthos, ruffe had no such effects. The total benthos biomass in bream treatments was an-order of magnitude lower in the upper sediment layer (0-1 cm) and three times lower in the middle layer (1-3 cm) than in the controls, whereas there were no significant effects in the deepest layer (3-10 cm). Bivalves persisted in the deepest layer although their density was reduced in shallow sediment, whereas gastropods faced the risk of local extinction in the presence of bream. As indirect effects, small-bodied cladocerans, phytoplankton, periphyton and both organic and inorganic suspended material were higher in the bream treatments. We conclude that the impact of bream diminished substantially with increasing sediment depth, enabling invertebrates to survive in the sediment and to persist in the presence of bream. However, there were no indications of any group adjusting their vertical position behaviourally as a response to predation threat.
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| 7. |
- Rowiński, Piotr K., et al.
(author)
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Parental effects influence life history traits and covary with an environmental cline in common frog populations
- 2020
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In: Oecologia. - : Springer Nature. - 0029-8549 .- 1432-1939. ; 192:4, s. 1013-1022
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Journal article (peer-reviewed)abstract
- Across latitudinal clines, the juvenile developmental rates of ectotherms often covary with the length of the growing season, due to life-history trade-offs imposed by the time-constrained environments. However, as the start of the growing season often varies substantially across years, adaptive parental effects on juvenile developmental rates may mediate the costs of a delayed season. By employing a meta-analysis, we tested whether larval developmental rates across a latitudinal cline of the common frog (Rana temporaria) are affected by fluctuating onsets of breeding, across years. We predicted that larval developmental rate will be inversely related to the onset of breeding, and that northern populations will be more prone to shorten their developmental rate in response to late breeding, as the costs of delayed metamorphosis should be highest in areas with a shorter growing season. We found that the larval period of both northern and southern populations responded to parental environmental conditions to a similar degree in absolute terms, but in different directions. In northern populations, a late season start correlated with decreased development time, suggesting that the evolution of parental effects aids population persistence in time-constrained environments. In southern populations, late season start correlated with increased development time, which could potentially be explained as a predator avoidance strategy. Our findings suggest that local ecological variables can induce adaptive parental effects, but responses are complex, and likely trade-off with other ecological factors.
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| 8. |
- Woin, Per, 1958-, et al.
(author)
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Effects of metsulfuron methyl and cypermethrin exposure on freshwater model ecosystems
- 2003
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In: Aquatic Toxicology. - Amsterdam : Elsevier. - 0166-445X .- 1879-1514. ; 63:3, s. 243-256
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Journal article (peer-reviewed)abstract
- The aim of this study was to investigate the short-term (2 weeks) effects of the herbicide metsulfuron methyl alone and in combination with the insecticide cypermethrin in freshwater enclosures (80 l). We used a factorial design with four levels of herbicide (0, 1, 5, 20 mg/l) and two levels of insecticide (0 and 0.05 mg/l). The root growth of the macrophyte species Elodea canadensis and Myriophyllum spicatum decreased following exposure to the lowest concentration of metsulfuron methyl tested. Metsulfuron methyl exposure resulted in a decreased pH in the aquatic enclosure at the lowest concentration tested, which is most likely a further indication of decreased macrophyte primary production. The biomass of periphytic algae growing on the leaves of M. spicatum increased in the enclosures exposed to metsulfuron methyl. The species composition of the periphytic algae differed significantly from the controls in the enclosures exposed to 20 mg/l of the herbicide. The increased biomass of periphytic algae on the leaves of the macrophytes is probably an indirect effect of the herbicide exposure. The exposure to metsulfuron methyl possibly induced a leakage of nutrients from the macrophyte leaves, which promoted an increased algal growth. The exposure to metsulfuron methyl did not alter the biomass or the species composition of the phytoplankton community. The zooplankton communities in the enclosures were dominated by rotifers, which were not affected by the exposure to cypermethrin. However, a cypermethrin exposure of 0.05 mg/l initially decreased the abundance of copepod nauplii. Ten days after exposure, the abundance of nauplii was significantly higher in the insecticide-exposed enclosures compared with the non-exposed enclosures. This might be an indication of a sub-lethal stress response, which either increased the number of offspring produced or induced an increased hatching of copepod resting stages. No combined effects of the herbicide and insecticide exposure, either direct or indirect, were observed in the enclosure study. Significant effects on the macrophytes were observed following exposure to 1 mg metsulfuron methyl per litre in the enclosure study. Furthermore, a single species laboratory assay indicated that the shoot elongation of E. canadensis decreased following exposure to ]/0.1 mg metsulfuron methyl per litre. These concentrations are well within the range of expected environmental concentrations, thus this study shows that aquatic ecosystems, in particular those which are macrophyte- dominated, may be affected by metsulfuron methyl at concentrations that may well occur in water bodies adjacent to agricultural land.
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| 9. |
- You, Liwen, 1976-
(author)
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Detection of cleavage sites for HIV-1 protease in native proteins
- 2006
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In: Proceedings of LSS Computational Systems Bioinformatics Conference. - : Imperial College Press. ; , s. 249-256
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Conference paper (peer-reviewed)abstract
- Predicting novel cleavage sites for HIV-1 protease in non-viral proteins is a difficult task because of the scarcity of previous cleavage data on proteins in a native state. We introduce a three-level hierarchical classifier which combines information from experimentally verified short oligopeptides, secondary structure and solvent accessibility information from prediction servers to predict potential cleavage sites in non-viral proteins. The best classifier using secondary structure information on the second level classification of the hierarchical classifier is the one using logistic regression. By using this level of classification, the false positive ratio was reduced by more than half compared to the first level classifier using only the oligopeptide cleavage information. The method can be applied on other protease specificity problems too, to combine information from oligopeptides and structure from native proteins.
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| 10. |
- Renes, Sophia Elise, et al.
(author)
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Disturbance history can increase functional stability in the face of both repeated disturbances of the same type and novel disturbances - dataset
- 2020
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Other publicationabstract
- Climate change is expected to increase the incidences of extremes in environmental conditions. To investigate how repeated disturbances affect microbial ecosystem resistance, natural lake bacterioplankton communities were subjected to repeated temperature disturbances of two intensities (25 °C and 35 °C), and subsequently to an acidification event. We measured functional parameters (bacterial production, abundance, extracellular enzyme activities) and community composition parameters (richness, evenness, niche width) and found that, compared to undisturbed control communities, the 35 °C treatment was strongly affected in all parameters, while the 25 °C treatment did not significantly differ from the control. Interestingly, exposure to multiple temperature disturbances caused gradually increasing stability in the 35 °C treatment in some parameters, while others parameters showed the opposite, indicating that the choice of parameters can strongly affect the outcome of a study. The acidification event did not lead to stronger changes in community structure, but functional resistance of bacterial production towards acidification in the 35 °C treatments increased. This indicates that functional resistance in response to a novel disturbance can be increased by previous exposure to another disturbance, suggesting similarity in stress tolerance mechanisms for both disturbances. These results highlight the need for understanding function- and disturbance-specific responses, since general responses are likely to be unpredictable.
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