| 1. |
- Bargholtz, Chr., et al.
(författare)
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Measurement of the eta -> pi(+)pi(-)e(+)e(-) decay branching ratio
- 2007
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 644:5-6, s. 299-303
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Tidskriftsartikel (refereegranskat)abstract
- The reaction pd -> He-3 eta at threshold was used to provide a clean source of eta mesons for decay studies with the WASA detector at CELSIUS. The branching ratio of the decay eta -> pi(+)pi(-)e(+)e(-) is measured to be (4.3 +/- 1.3 +/- 0.4) x 10(-4).
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| 2. |
- Rogell, Björn, et al.
(författare)
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Fitness costs associated with low genetic variation are reduced in a harsher environment in amphibian island populations
- 2010
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Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 11:2, s. 489-496
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- A basic premise of conservation geneticists is that low levels of genetic variation are associated with fitness costs in terms of reduced survival and fecundity. These fitness costs may frequently vary with environmental factors and should increase under more stressful conditions. However, there is no consensus on how fitness costs associated with low genetic variation change under natural conditions in relation to the stressfulness of the environment. On the Swedish west coast, natterjack toad Bufo calamita populations show a strong population genetic structure and large variation in the amount of within-population genetic variation. We experimentally examined the survival of natterjack larvae from six populations with different genetic variation in three thermal environments corresponding to (a) the mean temperature of natural ponds (stable, laboratory), (b) a high temperature environment occurring in desiccating ponds (stable, laboratory) and (c) an outdoor treatment mimicking the natural, variable thermal conditions (fluctuating, semi-natural). We found that larvae in the outdoor treatment had poorer survival than larvae in the stable environments suggesting that the outdoor treatment was more stressful. Overall, populations with higher genetic variation had higher larval survival. However, a significant interaction between treatments and genetic variation indicated that fitness costs associated with low genetic variation were less severe in the outdoor treatment. Thus, we found no support for the hypothesis that fitness costs associated with low genetic variation increase under more stressful conditions. Our results suggest that natural thermal stress may mask fitness losses associated with low genetic variation in these populations.
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| 3. |
- Rogell, Björn, 1979-, et al.
(författare)
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Genetic structure in peripheral populations of the natterjack toad, Bufo calamita, as revealed by AFLP
- 2010
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Ingår i: Conservation Genetics. - : Springer Science and Business Media LLC. - 1566-0621 .- 1572-9737. ; 11:1, s. 173-181
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Tidskriftsartikel (refereegranskat)abstract
- Decreased fitness due to loss of genetic variation is a well recognised issue in conservation biology. Along the Swedish west coast, the endangered natterjack toad (Bufo calamita) occurs on, for the species, highly unusual habitat of rocky islands. Although the toads inhabit a restricted geographical area (maximum distance between the populations is 71 km), the fragmented nature of the landscape makes the genetic properties of the populations of conservation interest. However, lack of genetic variation found using conventional methods (microsatellites) has impeded genetic studies within these peripheral populations so far. In this study we assess population structure and genetic variation among seven of these fringe populations using 105 polymorphic Amplified Fragment Length Polymorphism (AFLP) loci. We found a well-defined population structure without evidence for isolation by distance, implying restricted gene flow between populations. Additionally, the populations differed in their amount of genetic variation, emphasizing the need to monitor genetically impoverished populations for possible declines mediated by inbreeding depression and reduced adaptive potential. Conservation implications for these unique populations are discussed in the light of our results.
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| 4. |
- Rogell, Björn, 1979-, et al.
(författare)
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The effects of selection, drift and genetic variation on life-history trait divergence among insular populations of natterjack toad, Bufo calamita
- 2010
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 19:11, s. 2229-2240
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Tidskriftsartikel (refereegranskat)abstract
- Although loss of genetic variation is frequently assumed to be associated with loss of adaptive potential, only few studies have examined adaptation in populations with little genetic variation. On the Swedish west coast, the northern fringe populations of the natterjack toad Bufo calamita inhabit an atypical habitat consisting of offshore rock islands. There are strong among-population differences in the amount of neutral genetic variation, making this system suitable for studies on mechanisms of trait divergence along a gradient of within-population genetic variation. In this study, we examined the mechanisms of population divergence using Q(ST)-F-ST comparisons and correlations between quantitative and neutral genetic variation. Our results suggest drift or weak stabilizing selection across the six populations included in this study, as indicated by low Q(ST)-F-ST values, lack of significant population x temperature interactions and lack of significant differences among the islands in breeding pond size. The six populations included in this study differed in both neutral and quantitative genetic variation. Also, the correlations between neutral and quantitative genetic variation tended to be positive, however, the relatively small number of populations prevents any strong conclusions based on these correlations. Contrary to the majority of Q(ST)-F-ST comparisons, our results suggest drift or weak stabilizing selection across the examined populations. Furthermore, the low heritability of fitness-related traits may limit evolutionary responses in some of the populations.
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| 5. |
- Sahlsten, Jonas, et al.
(författare)
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Inference of hazel grouse population structure using multilocus data : a landscape genetic approach
- 2008
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 101:6, s. 475-482
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- In conservation and management of species it is important to make inferences about gene flow, dispersal and population structure. In this study, we used 613 georeferenced tissue samples from hazel grouse (Bonasa bonasia) where each individual was genotyped at 12 microsatellite loci to make inference on population genetic structure, gene flow and dispersal in northern Sweden. Observed levels of genetic diversity suggest that Swedish hazel grouse do not suffer loss of genetic diversity compared with other grouse species. We found significant F-IS (deviation from Hardy-Weinberg expectations) over the entire sample using jack-knifed estimators over loci, which is most likely explained by a Wahlund effect. With the use of spatial autocorrelation methods, we detected significant isolation by distance among individuals. Neighbourhood size was estimated in the order of 62-158 individuals corresponding to a dispersal distance of 950-1500 m. Using a spatial statistical model for landscape genetics to infer the number of populations and the spatial location of genetic discontinuities between these populations we found indications that Swedish hazel grouse are divided into a northern and a southern population. We could not find a sharp border between these two populations and none of the observed borders appeared to coincide with any potential geographical barriers. These results imply that gene flow appears somewhat unrestricted in the boreal taiga forests of northern Sweden and that the two populations of hazel grouse in Sweden may be explained by the post-glacial reinvasion history of the Scandinavian Peninsula. Heredity (2008) 101, 475-482; doi: 10.1038/hdy.2008.94; published online 1 October 2008
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| 6. |
- Thörngren Engblom, Pia, et al.
(författare)
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Anisotropy in the pion angular distribution of the reaction pp -> pp pi(0) at 400 MeV
- 2007
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 76:1, s. 011602-
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Tidskriftsartikel (refereegranskat)abstract
- The reaction pp -> pp pi(0) was studied with the WASA detector at the CELSIUS storage ring. The center of mass angular distribution of the pi(0) was obtained by detection of the gamma decay products together with the two outgoing protons and found to be anisotropic with a negative second derivative slope, in agreement with the theoretical predictions from a microscopic calculation.
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