| 1. |
- Hansson, Bengt, et al.
(författare)
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Increase of genetic variation over time in a recently founded population of great reed warblers (Acrocephalus arundinaceus) revealed by microsatellites and DNA fingerprinting
- 2000
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 9:10, s. 1529-1538
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Tidskriftsartikel (refereegranskat)abstract
- Genetic similarity within pairs of individuals was examined using both 10 polymorphic microsatellite loci and multi-locus DNA fingerprinting profiles in a semi-isolated population of great reed warblers at Lake Kvismaren, south Central Sweden, in 1987-1993. The population was founded by a few individuals in 1978, followed by a gradual increase in numbers until 1988, since when the population has remained relatively stable with about 60 breeding birds. We have previously found that high genetic similarity between pairmates in the population during the early part of the study period reduced egg hatching success, and hence reproductive success. The measures of pairwise genetic similarity, microsatellite allele sharing and DNA fingerprinting band sharing, were highly correlated with pedigree-based relatedness. Both microsatellite and DNA fingerprinting similarities between pair-mates declined significantly over the study period, and the pattern was most pronounced in the DNA fingerprinting data. Analyses restricted to the microsatellite data showed that the average annual microsatellite similarity between pairwise combinations of individuals, as well as individual homozygosity in males, declined significantly over the study period, and that several immigrants carrying novel alleles entered the population during the study. Hence, the temporal decline in genetic similarity of mates in the population is probably a consequence of increased immigration, facilitated by the recent expansion of the species in the region. These results suggest that the population has now recovered genetically, or is in the process of recovering, from a recent founder event.
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| 2. |
- Griekspoor, Petra, et al.
(författare)
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Marked host specificity and lack of phylogeographic population structure of Campylobacter jejuni in wild birds
- 2013
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 22:5, s. 1463-1472
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Tidskriftsartikel (refereegranskat)abstract
- Zoonotic pathogens often infect several animal species, and gene flow among populations infecting different host species may affect the biological traits of the pathogen including host specificity, transmissibility and virulence. The bacterium Campylobacter jejuni is a widespread zoonotic multihost pathogen, which frequently causes gastroenteritis in humans. Poultry products are important transmission vehicles to humans, but the bacterium is common in other domestic and wild animals, particularly birds, which are a potential infection source. Population genetic studies of C. jejuni have mainly investigated isolates from humans and domestic animals, so to assess C. jejuni population structure more broadly and investigate host adaptation, 928 wild bird isolates from Europe and Australia were genotyped by multilocus sequencing and compared to the genotypes recovered from 1366 domestic animal and human isolates. Campylobacter jejuni populations from different wild bird species were distinct from each other and from those from domestic animals and humans, and the host species of wild bird was the major determinant of C. jejuni genotype, while geographic origin was of little importance. By comparison, C. jejuni differentiation was restricted between more phylogenetically diverse farm animals, indicating that domesticated animals may represent a novel niche for C. jejuni and thereby driving the evolution of those bacteria as they exploit this niche. Human disease is dominated by isolates from this novel domesticated animal niche.
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| 3. |
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| 4. |
- Tobler, Michael, et al.
(författare)
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Telomeres in ecology and evolution : A review and classification of hypotheses
- 2022
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 31:23, s. 5946-5965
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Forskningsöversikt (refereegranskat)abstract
- Research on telomeres in the fields of ecology and evolution has been rapidly expanding over the last two decades. This has resulted in the formulation of a multitude of, often name-given, hypotheses related to the associations between telomeres and life-history traits or fitness-facilitating processes (and the mechanisms underlying them). However, the differences (or similarities) between the various hypotheses, which can originate from different research fields, are often not obvious. Our aim here is therefore to give an overview of the hypotheses that are of interest in ecology and evolution and to provide two frameworks that help discriminate among them. We group the hypotheses (i) based on their association with different research questions, and (ii) using a hierarchical approach that builds on the assumptions they make, such as about causality of telomere length/shortening and/or the proposed functional consequences of telomere shortening on organism performance. Both our frameworks show that there exist parallel lines of thoughts in different research fields. Moreover, they also clearly illustrate that there are in many cases competing hypotheses within clusters, and that some of these even have contradictory assumptions and/or predictions. We also touch upon two topics in telomere research that would benefit from further conceptualization. This review should help researchers, both those familiar with and those new to the subject, to identify future avenues of research.
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| 5. |
- Hansson, Bengt, et al.
(författare)
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A new approach to study dispersal: immigration of novel alleles reveals female-biased dispersal in great reed warblers
- 2003
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Ingår i: Molecular Ecology. - 0962-1083. ; 12:3, s. 631-637
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Tidskriftsartikel (refereegranskat)abstract
- We use the assignment technique and a new approach, the 'novel allele technique', to detect sex-biased dispersal in great reed warblers Acrocephalus arundinaceus . The data set consisted of immigrants and philopatric birds in a semi-isolated population in Sweden scored at 21 microsatellite loci. Fourteen cohorts were represented of which the four earliest were used to define a reference population. Female immigrants had lower assignment probability than males (i.e. were less likely to have been sampled in the reference population), and carried the majority of 'novel alleles' (i.e. alleles observed in the population for the first time). The difference in number of novel alleles between sexes was caused by a strong over-representation of females among the few individuals that carried several novel alleles, and there was a tendency for a corresponding female bias among individuals with low assignment probabilities. Immigrant males had similar or lower reproductive success than females. These results lead us to conclude that important interregional gene flow in great reed warblers depends on relatively few dispersing females, and that the novel allele technique may be a useful complement to the assignment technique when evaluating dispersal patterns from temporally structured data.
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| 6. |
- Hellgren, Olof, et al.
(författare)
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Detecting shifts of transmission areas in avian blood parasites - a phylogenetic approach
- 2007
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Ingår i: Molecular Ecology. - 0962-1083. ; 16:6, s. 1281-1290
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the degree of geographical shifts of transmission areas of vector-borne avian blood parasites (Plasmodium, Haemoproteus and Leucocytozoon) over ecological and evolutionary timescales. Of 259 different parasite lineages obtained from 5886 screened birds sampled in Europe and Africa, only two lineages were confirmed to have current transmission in resident bird species in both geographical areas. We used a phylogenetic approach to show that parasites belonging to the genera Haemoproteus and Leucocytozoon rarely change transmission area and that these parasites are restricted to one resident bird fauna over a long evolutionary time span and are not freely spread between the continents with the help of migratory birds. Lineages of the genus Plasmodium seem more freely spread between the continents. We suggest that such a reduced transmission barrier of Plasmodium parasites is caused by their higher tendency to infect migratory bird species, which might facilitate shifting of transmission area. Although vector-borne parasites of these genera apparently can shift between a tropical and a temperate transmission area and these areas are linked with an immense amount of annual bird migration, our data suggest that novel introductions of these parasites into resident bird faunas are rather rare evolutionary events.
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| 7. |
- O'Connor, Emily, et al.
(författare)
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The Evolution of Highly Variable Immunity Genes Across a Passerine Bird Radiation
- 2016
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083.
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Tidskriftsartikel (refereegranskat)abstract
- In order to survive, individuals must be able to recognise and eliminate pathogens. The genes of the Major Histocompatibility Complex (MHC) play an essential role in this process in vertebrates as their diversity affects the repertoire of pathogens that can be recognised by the immune system. Emerging evidence suggests that birds within the parvorder Passerida possess an exceptionally high number of MHC genes. However, this has yet to be directly investigated using a consistent framework, and the question of how this MHC diversity has evolved has not been addressed. We used next generation sequencing to investigate how MHC class I gene copy number and sequence diversity varies across the Passerida radiation using twelve species chosen to represent the phylogenetic range of this group. Additionally, we performed phylogenetic analyses on this data to identify, for the first time, the evolutionary model that best describes how MHC class I gene diversity has evolved within Passerida. We found evidence of multiple MHC class I genes in every family tested, with an extremely broad range in gene copy number across Passerida. There was a strong phylogenetic signal in MHC gene copy number and diversity, and these traits appear to have evolved through a process of Brownian Motion in the species studied, i.e. following the pattern of genetic drift or fluctuating selection, as opposed to towards a single optimal value or through evolutionary ‘bursts’. By characterising MHC class I gene diversity across Passerida in a systematic framework, this study provides a first step towards understanding this huge variation.
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| 8. |
- Waldenström, Jonas, et al.
(författare)
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Cross-species infection of blood parasites between resident and migratory songbirds in Africa
- 2002
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Ingår i: Molecular Ecology. - 0962-1083. ; 11:8, s. 1545-1554
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Tidskriftsartikel (refereegranskat)abstract
- We studied the phylogeny of avian haemosporidian parasites, Haemoproteus and Plasmodium, in a number of African resident and European migratory songbird species sampled during spring and autumn in northern Nigeria. The phylogeny of the parasites was constructed through sequencing part of their mitochondrial cytochrome b gene. We found eight parasite lineages, five Haemoproteus and three Plasmodium, infecting multiple host species. Thus, 44% of the 18 haemospiridian lineages found in this study were detected in more than one host species, indicating that host sharing is a more common feature than previously thought. Furthermore, one of the Plasmodium lineages infected species from different host families, Sylviidae and Ploceidae, expressing exceptionally large host range. We mapped transmission events, e.g. the occurrence of the parasite lineages in resident bird species in Europe or Africa, onto a phylogenetic tree. This yielded three clades, two Plasmodium and one Haemoproteus, in which transmission seems to occur solely in Africa. One Plasmodium clade showed European transmission, whereas the remaining two Haemoproteus clades contained mixes of lineages of African, European or unknown transmission. The mix of areas of transmission in several branches of the phylogenetic tree suggests that transmission of haemosporidian parasites to songbirds has arisen repeatedly in Africa and Europe. Blood parasites could be viewed as a cost of migration, as migratory species in several cases were infected with parasite lineages from African resident species. This cost of migration could have considerable impact on the evolution of migration and patterns of winter distribution in migrating birds.
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| 9. |
- Westerdahl, Helena, et al.
(författare)
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Sex ratio variation among broods of great reed warblers Acrocephalus arundinaceus
- 1997
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Ingår i: Molecular Ecology. - 0962-1083. ; 6:6, s. 543-548
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Tidskriftsartikel (refereegranskat)abstract
- The sex of 746 great reed warbler fledglings (from 175 broods) was determined by the use of single primer polymerase-chain reaction. The reliability of the technique was confirmed as 104 of the fledglings were subsequently recorded as adults of known sex. The overall sex ratio did not differ from unity. Variation in sex ratios between broods was larger than expected from a binomial distribution. Female identity explained some of the variation of brood sex ratio indicating that certain females consistently produced sex ratios that departed from the average value in the population. The theory of sex allocation predicts that parents should adjust the sex ratio of their brood to the relative value of sons and daughters and this may vary in relation to the quality of the parents or to the time of breeding. In the great reed warbler, the proportion of sons was not related to time of breeding, or to any of five female variables. Of five male variables, males with early arrival date tended to produce more daughters. The sex ratio of fledglings that were a result of extra-pair fertilizations did not differ from that of legitimate fledglings. Hence, there is currently no evidence of that female great reed warblers invest in a higher proportion of sons when mated with attractive males.
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| 10. |
- Åkesson, Mikael, et al.
(författare)
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Linkage mapping of AFLP markers in a wild population of great reed warblers: importance of heterozygosity and number of genotyped individuals
- 2007
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Ingår i: Molecular Ecology. - 0962-1083. ; 16:11, s. 2189-2202
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Tidskriftsartikel (refereegranskat)abstract
- Amplified fragment length polymorphisms (AFLP) are dominant markers frequently used to build linkage maps where heterozygosity could be inferred by a backcross breeding strategy. In the present study, we describe the utilization of an unmanipulated great reed warbler, Acrocephalus arundinaceus pedigree to infer heterozygous genotypes of AFLP markers in order to map these markers to a partial linkage map previously based on microsatellites. In total, 50 of the 83 autosomal AFLPs (60%) and 4 of 5 Z-linked AFLPs (80%) were mapped. For each marker, on average, 88% of the expected number of heterozygote parents was detected. The likelihood of map assignment was to a large extent due to the number and density of microsatellite markers already in the map. The 'parsimonious linkage map', that is the map based on the most parsimonious location of all significantly linked markers, consisted of 21 autosomal linkage groups with 2 to 15 markers and had a total map size of 552 cM in males and 858 cM in females. The Z-chromosome linkage group with 12 markers had a size of 155 cM. The autosomal 'framework linkage map', that is the map based only on markers with an unambiguous position, had a total size of 237 cM in males and 440 cM in females, respectively. The inclusion of AFLPs enlarged the previous map substantially (e.g. the autosomal parsimonious linkage map became 441 cM and 621 cM larger for male and female recombination, respectively). The probability that an AFLP became mapped increased with increasing level of heterozygosity, whereas the probability of mapping into a framework position increased with both heterozygosity and number of genotyped individuals. Our results suggest that AFLP provides a fast and inexpensive means of enlarging genetic maps already composed of markers with high polymorphism, also in wild populations with unmanipulated pedigrees.
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