| 1. |
- Broman, Elias, et al.
(författare)
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Oxygenation of anoxic sediments triggers hatching of zooplankton eggs
- 2015
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 282:1817
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Tidskriftsartikel (refereegranskat)abstract
- Many coastal marine systems have extensive areas with anoxic sediments and it is not well known how these conditions affect the benthic-pelagic coupling. Zooplankton lay their eggs in the pelagic zone, and some sink and lie dormant in the sediment, before hatched zooplankton return to the water column. In this study, we investigated how oxygenation of long-term anoxic sediments affects the hatching frequency of dormant zooplankton eggs. Anoxic sediments from the brackish Baltic Sea were sampled and incubated for 26 days with constant aeration whereby, the sediment surface and the overlying water were turned oxic. Newly hatched rotifers and copepod nauplii (juveniles) were observed after 5 and 8 days, respectively. Approximately 1.5 × 105 nauplii per m-2 emerged from sediment turned oxic compared to 0.02 × 105 m-2 from controls maintained anoxic. This study demonstrated that re-oxygenation of anoxic sediments activated a large pool of buried zooplankton eggs, strengthening the benthic-pelagic coupling of the system. Modelling of the studied anoxic zone suggested that a substantial part of the pelagic copepod population can derive from hatching of dormant eggs. We suggest that this process should be included in future studies to understand population dynamics and carbon flows in marine pelagic systems.
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| 2. |
- Broman, Elias, 1985-, et al.
(författare)
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Diatoms dominate the eukaryotic metatranscriptome during spring in coastal 'dead zone' sediments
- 2017
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society Publishing. - 0962-8452 .- 1471-2954. ; 284:1864
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Tidskriftsartikel (refereegranskat)abstract
- An important characteristic of marine sediments is the oxygen concentration that affects many central metabolic processes. There has been a widespread increase in hypoxia in coastal systems (referred to as 'dead zones') mainly caused by eutrophication. Hence, it is central to understand the metabolism and ecology of eukaryotic life in sediments during changing oxygen conditions. Therefore, we sampled coastal 'dead zone' Baltic Sea sediment during autumn and spring, and analysed the eukaryotic metatranscriptome from field samples and after incubation in the dark under oxic or anoxic conditions. Bacillariophyta (diatoms) dominated the eukaryotic metatranscriptome in spring and were also abundant during autumn. A large fraction of the diatom RNA reads was associated with the photosystems suggesting a constitutive expression in darkness. Microscope observation showed intact diatom cells and these would, if hatched, represent a significant part of the pelagic phytoplankton biomass. Oxygenation did not significantly change the relative proportion of diatoms nor resulted in any major shifts in metabolic 'signatures'. By contrast, diatoms rapidly responded when exposed to light suggesting that light is limiting diatom development in hypoxic sediments. Hence, it is suggested that diatoms in hypoxic sediments are on 'standby' to exploit the environment if they reach suitable habitats.
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| 3. |
- Larsson, Kjell, et al.
(författare)
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Intraspecific nest parasitism and adoption of young in the barnacle goose : effects on survival and reproductive performance
- 1995
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Ingår i: Animal Behaviour. - : Elsevier. - 0003-3472 .- 1095-8282. ; 50:5, s. 1349-1360
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Tidskriftsartikel (refereegranskat)abstract
- DNA fingerprinting was used to determine the proportion of extra-pair young in a population of barnacle geese, Branta leticopsis, breeding in the Baltic area, Sweden. Of 137 analysed fledged young 17% were found to be extra-pair young. One or more extra-pair young were found in 27% of the 63 analysed families. The proportion of extra-pair young differed between years. No case of extra-pair fertilization was detected. All extra-pair young at fledgling originated either from intraspecific nest parasitism or from adoptions of foreign hatched young. Broods with extra-pair young at fledgling were significantly larger than broods without extra-pair young. However, the number of within-pair young did not differ significantly in broods with and without extra-pair young. Body mass, survival or subsequent reproductive performance did not differ between parents with and without extra-pair fledged young. Post-fledgling survival and age at first breeding were not significantly different between the three analysed classes of fledged young, i.e., within-pair young in families without extra-pair young, within-pair young in families with at least one extra-pair young, and extra-pair young. It is concluded that possible costs or benefits associated with caring for extra-pair fledged young are small or absent in this population.
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| 4. |
- Larsson, Kjell, et al.
(författare)
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Continuing growth of the Baltic barnacle goose population : Number of individuals and reproductive success in different colonies
- 1997
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Ingår i: Research on arctic geese. - : Norsk Polarinstitutt. - 8276661548 ; , s. 213-219
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Konferensbidrag (refereegranskat)abstract
- The Baltic barnacle goose population increased rapidly after 1971, when the first breeding attempt was observed off the eastern coast of Gotland, Sweden. In 1997, about 3,990 pairs bred along the Baltic coast in Sweden, western Estonia and southern Finland. The majority of these pairs, about 3,490 pairs, were found breeding in colonies along the eastern coasts of Gotland and Oland, Sweden. The total population size at the end of July in 1997 was estimated to be approximately 17,000 individuals. The production of fledged young per breeding pair was negatively related to the size of colonies, although the production varied greatly among different colonies. In 1997, the largest Baltic colony hosted more than 50% of the total number of breeding pairs but produced less than 15% of the total number of fledged young. This finding points out the need to consider different colonies as separate demographic units when studying regulation processes in populations of colonially breeding geese. In the future, we find it most probable that the Baltic population will continue to increase and that new colonies will be established. We also expect that the number of Baltic barnacle geese eventually will be limited by the availability of predator-safe grazing grounds with short, protein rich grass which families with newly hatched goslings are dependent on.
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| 5. |
- Sunde, Johanna, et al.
(författare)
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Mate choice is not consistent with short-term effects of intraspecific admixture in the common rough woodlouse (Porcellio scaber)
- 2016
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 119:2, s. 359-369
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Tidskriftsartikel (refereegranskat)abstract
- Theory posits that individuals should exhibit mate preferences in part based on genetic relatedness such that fitness is maximized. Intraspecific genetic admixture can have different effects depending on the genetic characteristics and evolutionary history of the individuals and populations involved. We investigated whether female mate choice behavior in the common rough woodlouse (Porcellio scaber) matched the fitness consequences of genetic admixture. We found that most females from two populations that were in sequence introduced to one male from each population mated with both males, and further that monandrous females (females that only mated with one male) predominantly mated with males from their own population. To test for effects of genetic admixture, females from four populations were divided into two replicate pairs and assigned to mate either with a male from the same population as the female (pure) or with a male from the other population (admixed). The effect of mating treatment on the proportion of females that produced eggs and hatched young, as well as on the number and viability of offspring depended on female source population. Mating treatment had opposing effects in two of the populations, whereas there were no detectable effects in the other two populations. Contrary to what was expected, the mating patterns did not match the observed effects of genetic admixture. We discuss alternative adaptive and non-adaptive explanations for the observed patterns.
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| 6. |
- Larsson, Kjell, et al.
(författare)
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Population dynamics of the barnacle goose Branta leucopsis in the Baltic area : density-dependent effects on reproduction
- 1994
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Ingår i: Journal of Animal Ecology. - : British Ecological Society. - 0021-8790 .- 1365-2656. ; 63:4, s. 954-962
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Tidskriftsartikel (refereegranskat)abstract
- 1. The three largest breeding colonies of barnacle geese Branta leucopsis in the Baltic area were studied from their natural establishments in 1971, 1982 and 1987, respectively, to 1993. The number of breeding pairs increased from one pair in 1971 to 1550, 225 and 150 pairs in the largest, second largest, and third largest colonies, respectively, in 1993. 2. Data on clutch size and number of hatched and fledged young were collected from the beginning or the middle of the 1980s. In the largest colony most data on reproductive success were obtained from observations of individually marked geese. 3. Mean clutch size differed among years and colonies. However, there was no trend for decreasing mean clutch size with increasing density in any of the colonies. Hatching success did not decrease with increasing density in the largest colony. 4. The production of fledged young per breeding pair declined drastically in the largest colony as numbers of breeding pairs rose. This decline was mainly caused by an increasing proportion of the breeding pairs failing to produce any fledged young at all. 5. The relative contribution of the smaller colonies to the total production of fledged young in the Baltic area increased considerably over the study years. In 1993, colony 2 hosted only about 13% of the number of breeding pairs in colonies 1 and 2 combined, but it produced about 38% of the fledged young. 6. Our results point out the need to study populations of colonially nesting geese on a colony by colony basis in order to detect density-dependent effects on reproduction.
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| 7. |
- Larsson, Kjell, et al.
(författare)
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Body size declines despite positive directional selection on heritable size traits in a barnacle goose population
- 1998
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Ingår i: Evolution. - : Society for the Study of Evolution. - 0014-3820 .- 1558-5646. ; 52:4, s. 1169-1184
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Tidskriftsartikel (refereegranskat)abstract
- Analyses of more than 2000 marked barnacle geese (Branta leucopsis) in the largest Baltic colony, Sweden, showed that structurally large females generally produced larger clutches and larger eggs, hatched their broods earlier in the season, and produced more and heavier young than smaller females. In males, the corresponding relationships between reproductive parameters and structural body size were weaker or nonsignificant. Because structural body size traits have previously been found to be significantly heritable and positively genetically correlated, an increase in mean structural body size of individuals as a response to selection might have been expected. By contrast, we found that the mean adult head length and mean adult tarsus length decreased significantly in the largest colony by approximately 0.7 and 0.5 standard deviations, respectively, in both males and females during the 13-year study period. Environmental factors, such as the amount of rain in different years, were found to affect the availability of high-quality food for growing geese. As a consequence of this temporal variability in the availability of high-quality food, the mean adult structural body size of different cohorts differed by up to 1.3 standard deviations. Comparisons of mean body size of cohorts born in different colonies suggest that the most likely explanation for the body-size decline in the main study colony is that a density-dependent process, which mainly was in effect during the very early phase of colony growth, negatively affected juvenile growth and final size. We conclude that large environmental effects on growth and final structural body size easily can mask microevolutionary responses to selection. Analyses of environmental causes underlying temporal and spatial body size variation should always be considered in the reconstruction and prediction of evolutionary changes in natural populations.
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| 8. |
- Forslund, Pär, et al.
(författare)
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Age-related reproductive success in the barnacle goose
- 1992
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Ingår i: Journal of Animal Ecology. - : British Ecological Society. - 0021-8790 .- 1365-2656. ; 61, s. 195-204
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Tidskriftsartikel (refereegranskat)abstract
- 1. We studied age-related reproductive success in a recently established breeding colony of barnacle goose Branta leucopsis on the island of Gotland, Sweden.2. Associations of age and breeding experience with several reproductive parameters were investigated by comparing the success of individuals of 2, 3, 4 and >=5 years of age. Also, we measured the within-individual changes in reproductive parameters as the individuals grew older.3. Associations between survival and reproductive success were investigated by comparing the reproductive success of 2, 3 and 4-year-old birds that returned or did not return, respectively, in the subsequent breeding season.4. The reproductive success increased up to an age of 4-5 years. Thus, clutch size, number of hatched young and number of fledged young increased, and hatching date was advanced with increasing age. This was due to the fact that individuals increased in reproductive success as they grew older.5. A possibly higher probability of survival among individuals that perform well in reproduction could not explain the higher reproductive success in older age-classes as compared to young age-classes of geese, because there were no associations between survival and reproductive success, and very few individuals did actually disappear between any two breeding seasons.6. Path analysis suggested age effects only at earlier stages of reproduction, i. e. timing of breeding and clutch size. These characters, in turn, were associated with number of fledged young. These findings were further supported by measurements of hatching success and rearing success, which did not seem to increase with age.7. Increased breeding experience was associated with early hatching date and larger clutch size in males, and with larger clutch size in females. This was concluded from path analysis and from comparisons of individuals of the same age but with different breeding experience.8. The increase in reproductive success with age in the barnacle goose is probably a result of age-related skills in individuals and the direct effects of these skills on reproductive success, but possibly also because of increased reproductive effort with age owing to these age-related skills.
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