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Sökning: WFRF:(Halvarsson Peter)

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1.
  • Baltrusis, Paulius, et al. (författare)
  • Estimation of the impact of three different bioinformatic pipelines on sheep nemabiome analysis
  • 2022
  • Ingår i: Parasites and Vectors. - : Springer Science and Business Media LLC. - 1756-3305. ; 15
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Next-generation sequencing (NGS) has provided an alternative strategy to study the composition of nematode communities with increased resolution and sensitivity. However, the handling and processing of gigabytes worth of amplicon sequence data produced by an NGS platform is still a major hurdle, limiting the use and adoption of faster and more convenient analysis software.Methods: In total 32 paired, fecal samples from Swedish sheep flocks were cultured and the larvae subsequently harvested subjected to internal transcribed spacer 2 (ITS2) amplicon sequencing using the PacBio platform. Samples were analyzed with three different bioinformatic pipelines, i.e. the DADA2, Mothur and SCATA pipelines, to determine species composition and richness.Results: For the the major species tested in this study (Haemonchus contortus, Teladorsagia circumcinta and Trichostrongylus colubriformis) neither relative abundances nor species diversity differed significantly between the three pipelines, effectively showing that all three analysis pipelines, although different in their approaches, yield nearly identical outcomes. In addition, the samples analyzed here had especially high frequencies of H. contortus (90-95% across the three pipelines) both before and after sample treatment, followed by T. circumcinta (3.5-4%). This shows that H. contortus is the parasite of primary importance in contemporary Swedish sheep farms struggling with anthelmintic resistance. Finally, although on average a significant reduction in egg counts was achieved post-treatment, no significant shifts in major species relative frequencies occurred, indicating highly rigid community structures at sheep farms where anthelmintic resistance has been reported.Conclusions: The findings presented here further contribute to the development and application of NGS technology to study nemabiome compositions in sheep, in addition to expanding our understanding about the most recent changes in parasite species abundances from Swedish sheep farms struggling with anthelmintic resistance.
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2.
  • Baltrusis, Paulius, et al. (författare)
  • Exploring benzimidazole resistance in Haemonchus contortus by next generation sequencing and droplet digital PCR
  • 2018
  • Ingår i: International Journal for Parasitology: Drugs and Drug Resistance. - : Elsevier BV. - 2211-3207. ; 8, s. 411-419
  • Tidskriftsartikel (refereegranskat)abstract
    • Anthelmintic resistance in gastrointestinal nematode (GIN) parasites of grazing ruminants is on the rise in countries across the world. Haemonchus contortus is one of most frequently encountered drug-resistant GINs in small ruminants. This blood-sucking abomasal nematode contributes to massive treatment costs and poses a serious threat to farm animal health. To prevent the establishment of resistant strains of this parasite, up-to-date molecular techniques need to be proposed which would allow for quick, cheap and accurate identification of individuals infected with resistant worms. The effort has been made in the previous decade, with the development of the pyrosequencing method to detect resistance-predicting alleles. Here we propose a novel droplet digital PCR (ddPCR) assay for rapid and precise identification of H. contortus strains as being resistant or susceptible to benzimidazole drugs based on the presence or absence of the most common resistance-conferring mutation F200Y (T (A) under barG) in the beta tubulin isotype 1 gene. The newly developed ddPCR assay was first optimized and validated utilizing DNA templates from single-worm samples, which were previously sequenced using the next generation PacBio RSII Sequencing (NGS) platform. Subsequent NGS results for faecal larval cultures were then used as a reference to compare the obtained values for fractional abundances of the resistance-determining mutant allele between ddPCR and NGS techniques in each sample. Both methods managed to produce highly similar results and ddPCR proved to be a reliable tool which, when utilized at full capacity, can be used to create a powerful mutation detection and quantification assay.
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3.
  • Baltrusis, Paulius, et al. (författare)
  • Genome-wide analysis of the response to ivermectin treatment by a Swedish field population of Haemonchus contortus
  • 2022
  • Ingår i: International Journal for Parasitology: Drugs and Drug Resistance. - : Elsevier BV. - 2211-3207. ; 18, s. 12-19
  • Tidskriftsartikel (refereegranskat)abstract
    • Haemonchus contortus is a pathogenic gastrointestinal nematode of small ruminants and, in part due to its capacity to develop resistance to drugs, contributes to significant losses in the animal production sector worldwide. Despite decades of research, comparatively little is known about the specific mechanism(s) driving resistance to drugs such as ivermectin in this species. Here we describe a genome-wide approach to detect evidence of selection by ivermectin treatment in a field population of H. contortus from Sweden, using parasites sampled from the same animals before and seven days after ivermectin exposure followed by whole-genome sequencing. Despite an 89% reduction in parasites recovered after treatment measured by the fecal egg count reduction test, the surviving population was highly genetically similar to the population before treatment, suggesting that resistance has likely evolved over time and that resistance alleles are present on diverse haplotypes. Pairwise gene and SNP frequency comparisons indicated the highest degree of differentiation was found at the terminal end of chromosome 4, whereas the most striking difference in nucleotide diversity was observed in a region on chromosome 5 previously reported to harbor a major quantitative trait locus involved in ivermectin resistance. These data provide novel insight into the genome-wide effect of ivermectin selection in a field population as well as confirm the importance of the previously established quantitative trait locus in the development of resistance to ivermectin.
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4.
  • Baltrusis, Paulius, et al. (författare)
  • Molecular detection of two major gastrointestinal parasite genera in cattle using a novel droplet digital PCR approach
  • 2019
  • Ingår i: Parasitology Research. - : Springer Science and Business Media LLC. - 0932-0113 .- 1432-1955. ; 118, s. 2901-2907
  • Tidskriftsartikel (refereegranskat)abstract
    • Cooperia sp. and Ostertagia sp. are two cosmopolitan parasitic nematodes often found in mixed gastrointestinal infections in cattle across temperate regions. In light of the recent increase in the emergence of anthelmintic resistance in these and other nematodes derived from cattle around the globe, and their negative impact on animal health and productivity, novel molecular assays need to be put forth in order to facilitate the monitoring of parasite burden in infected herds, using pasture and/or fecal samples. Here, we describe a novel droplet digital PCR platform-based concept for precise identification and quantification of the two most abundant and important parasite genera in grazing western European cattle. By exploiting a single nucleotide difference in the two parasites' ITS2 sequence regions, we have developed two specific hydrolysis probes labeled with FAM (TM) or HEX (TM) fluorophores, which can not only distinguish between the DNA sequences of the two, but also quantify them in mixed DNA samples. A third, newly developed universal probe was also tested along the genus-specific probes to provide a robust and accurate reference. It was evident that the universal probe displayed congruent results to those obtained by the genus-specific probes when used with DNA from both parasites in a single sample. All in all, the results of our assay suggest that this novel protocol could be used to distinguish and quantify cattle parasites belonging to the two most important genera (i.e., Cooperia and Ostertagia) in a single mixed DNA sample.
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5.
  • Baltrusis, Paulius, et al. (författare)
  • The presence and relative frequency detection of the levamisole-resistance-associated S168T substitution in hco-acr-8 in Haemonchus contortus
  • 2023
  • Ingår i: International Journal for Parasitology: Drugs and Drug Resistance. - : Elsevier BV. - 2211-3207. ; 21, s. 91-95
  • Tidskriftsartikel (refereegranskat)abstract
    • Parasitic sheep nematodes, among which Haemonchus contortus is often considered to be the most clinically important, exact a significant toll on the animals, not least because of their capacity to evolve drug resistance. Despite decades of research, our understanding of the mechanism of resistance to compounds such as levamisole is fairly limited, which therefore constrains our ability to develop sensitive and efficient molecular diagnostic tools for rapid and accurate resistance detection in field settings. Herein, we investigated the presence and frequency of the newly reported, levamisole-resistance-associated, mutation, yielding a S168T substitution in exon 4 of hco-acr-8, in six different phenotypically described isolates (three susceptible and three resistant), three Swedish field isolates and eight larvae culture samples, the latter two of which originated on farms where le-vamisole showed complete parasite elimination. For this purpose, we created both an allele-specific and droplet digital PCR approaches and found the mutated allele to be present only in the Kokstad isolate, whereas the other five as well as both the Swedish isolates and larvae cultures displayed only the non-mutated, serine-encoding, allele. While the finding of only the non-mutated allele in the phenotypically susceptible and Swedish isolate and larvae culture samples seemed sensible, we speculate that for the other two phenotypically resistant isolates, different (perhaps secondary) variants are responsible for conferring the resistance to levamisole phenotype, given the polygenic nature of levamisole resistance. All in all, despite the limited number of samples tested here, the mutation causing the S168T substitution in hco-acr-8 represents a plausible levamisole resistance-associated variant in, at least, some isolates of H. contortus.
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6.
  • Baltrusis, Paulius, et al. (författare)
  • Using droplet digital PCR for the detection of hco-acr-8b levamisole resistance marker in H. contortus
  • 2021
  • Ingår i: International Journal for Parasitology: Drugs and Drug Resistance. - : Elsevier BV. - 2211-3207. ; 15, s. 168-176
  • Tidskriftsartikel (refereegranskat)abstract
    • The nematode Haemonchus contortus is one of the most prevalent and pathogenic parasites in small ruminants. Although usually controlled using anthelmintics, the development of drug resistance by the parasite has become a major issue in livestock production. While the molecular detection of benzimidazole resistance in H. contortus is well developed, the molecular tools and protocols are far less advanced for the detection of levamisole resistance. The hco-acr-8 gene encodes a critical acetylcholine susceptible subunit that confers levamisole-sensitivity to the receptor. Here, we report the development of a droplet digital PCR assay as a molecular tool to detect a 63 bp deletion in the hco-acr-8 that has been previously associated with levamisole resistance. Sanger sequencing of single adult H. contortus yielded 56 high-quality consensus sequences surrounding the region containing the deletion. Based on the sequencing data, new primers and probes were designed and validated with a novel droplet digital PCR assay for the quantification of the deletion containing "resistant" allele in genomic DNA samples. Single adult worms from six phenotypically described isolates (n = 60) and from two Swedish sheep farms (n = 30) where levamisole was effective were tested. Even though a significant difference in genotype frequencies between the resistant and susceptible reference isolates was found (p = 0.01), the homozygous "resistant" genotype was observed to be abundantly present in both the susceptible isolates as well as in some Swedish H. contortus samples. Furthermore, field larval culture samples, collected pre- (n = 7) and post- (n = 6) levamisole treatment on seven Swedish sheep farms where levamisole was fully efficacious according to Fecal Egg Count Reduction Test results, were tested to evaluate the frequency of the "resistant" allele in each. Frequencies of the deletion ranged from 35 to 80% in the pre-treatment samples, whereas no amplifiable H. contortus genomic DNA was detected in the post-treatment samples. Together, these data reveal relatively high frequencies of the 63 bp deletion in the hco-acr-8 both on individual H. contortus and field larval culture scales, and cast doubt on the utility of the deletion in the hco-acr-8 as a molecular marker for levamisole resistance detection on sheep farms.
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7.
  • Baltrusis, Paulius, et al. (författare)
  • Utilization of droplet digital PCR to survey resistance associated polymorphisms in the beta tubulin gene of Haemonchus contortus in sheep flocks in Sweden
  • 2020
  • Ingår i: Veterinary Parasitology. - : Elsevier BV. - 0304-4017 .- 1873-2550. ; 288
  • Tidskriftsartikel (refereegranskat)abstract
    • Infections with gastrointestinal nematodes (GINs) in small ruminants are becoming increasingly harder to treat due to the development of anthelmintic resistance. Across Swedish sheep farms, Haemonchus contortus is one of the more persistent and pathogenic species encountered. Benzimidazole drugs, such as albendazole, are still widely used to control the GIN burden in small ruminants. However, the decline in efficacy of this drug has been observed across the country. In this study, we aimed to continue to investigate the presence of single nucleotide polymorphisms in the beta tubulin gene associated with benzimidazole drug resistance in H. contortus. This was carried out for sheep flocks from 67 farms around Sweden by screening for the two most commonly encountered SNPs at codons 167 and 200 in the isotype 1 beta tubulin gene utilizing the droplet digital PCR technology. We first established a good agreement (Lin's concordance correlation coefficient = 0.987) between the previously widely used pyrosequencing assay for the detection of the SNP at codon 200 (otherwise known as mutation F200Y) and our assay, as well as developed and validated primer-probe pairs for the detection of the mutation at codon 167 (mutation F167Y) in the beta tubulin gene of H. contortus. We then screened 174 pooled larval culture samples, collected either pre- or post-treatment, for the frequencies of the mutations F167Y and F200Y. Not only did we find the latter to be present at much higher frequencies, but the overall levels of this resistance conferring mutation have stayed stable throughout the years 2014-2019 at an average value of 88.5 +/- 20.3% in the pre-treatment samples across the tested farms (p = 0.61, Kruskal-Wallis test). Furthermore, after establishing a mixed model and fitting our data, we found a significant (p < 0.01) difference in the average frequency of the mutation F200Y between paired, pre- and post-treatment with albendazole, samples. Although the frequency difference in samples treated with albendazole was relatively minor (88.5% in pre- and 95.6% in post-treatment), no significant (p = 0.15) change in F200Y mutation frequency was observed between the samples from the flocks treated with ivermectin (90.8% and 92.6 %, respectively).
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8.
  • Cortazar-Chinarro, Maria, et al. (författare)
  • Sign surveys for red fox (Vulpes vulpes) censuses : evaluating different sources of variation in scat detectability
  • 2019
  • Ingår i: Mammal Research. - : Springer Science and Business Media LLC. - 2199-2401 .- 2199-241X. ; 64:2, s. 183-190
  • Tidskriftsartikel (refereegranskat)abstract
    • Wildlife monitoring is essential for assessing the size of species of conservation or management concern. Wildlife monitoring could be undertaken by selected volunteers when limited resources are available. Here, we study the sources of variation in the detectability of red fox scats and to improve the monitoring of the species by means of volunteers who were briefly trained. We selected nine transects to experimentally evaluate the differences in red fox scat detectability between observers, microsite, and scat abundance. Scats were deposited in five microsites, where we simulate low, medium, and high fox scat abundance. We tested the proposed effects by using GLMM analysis incorporating observer effect as a random factor. Our results indicated effects on scat detectability of observer identity and microsite type. We did not observe the effects of scat abundance on detectability of scats. Detectability was lower for scats located in the middle of the transect and on the rocks. We conclude that large-scale red foxes surveys might be conducted using volunteers, but due to the moderate differences detected among observers should be minimized using a training period.
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9.
  • Ejenstam, Jesper, et al. (författare)
  • Oxidation studies of Fe10CrAl-RE alloys exposed to Pb at 550 degrees C for 10,000 h
  • 2013
  • Ingår i: Journal of Nuclear Materials. - : Elsevier BV. - 0022-3115 .- 1873-4820. ; 443:1-3, s. 161-170
  • Tidskriftsartikel (refereegranskat)abstract
    • Five experimental FeCrAl-RE alloys have been exposed up to 10,000 h in stagnant liquid Pb at 550 C. The test matrix consisted of three 10 wt.% Cr alloys, with an Al content ranging from 4 to 8 wt.% (10Cr-4Al, 10Cr-6Al and 10Cr-8Al), one alloy without additions of reactive elements (RE) (10Cr-6Al), and one reference alloy with 21 wt.% Cr and 5 wt.% Al (21Cr-5Al). The evaluation showed a clear difference in oxidation properties, and it was possible to divide the alloys into two distinct groups. A critical Al concentration in the interval of 4-6 wt.% at the given RE content was required to form a thin protective oxide. However, the absence of RE addition in one of the two 10Cr-6Al alloys resulted in a significant reduction in oxidation resistance, comparable with 10Cr-4Al. None of the alloys were severely corroded, however Pb penetrated to a relatively large extent into the porous oxide of the low performing alloys. A 100 nm thick oxide scale, partly consisting of alumina (Al2O3), was observed for the high performing 10Cr-6Al alloy. The Fe10CrAl-RE alloys showed overall very good corrosion resistance and are hence a promising new alloy category for liquid Pb applications. (C) 2013 Elsevier B.V. All rights reserved.
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10.
  • Eklöv, Peter, et al. (författare)
  • The trade-off between foraging activity and predation risk for Rana temporaria in different food environments
  • 2000
  • Ingår i: Canadian Journal of Zoology. - : Canadian Science Publishing. - 0008-4301 .- 1480-3283. ; 78:5, s. 734-739
  • Tidskriftsartikel (refereegranskat)abstract
    •  We evaluated the trade-off between foraging activity and predation risk for larvae of an anuran species presented with different types of food resources. In the laboratory we examined the effects of benthic and phytoplankton resources and the two types combined on the activity and mortality of larvae of the common frog, Rana temporaria, exposed to predatory larva, Dytiscus marginalis.Predation mortality of tadpoles increased with the duration of the experiment and was highest in the presence of the phytoplankton resource alone. This was explained by a decrease in prey activity in the benthic- and combined-resource treatments when the predator was present, whereas in the phytoplankton treatment, the activity of the tadpoles were similar in the presence or absence of the predator.In the presence of the predator, prey mainly used the bottom of the aquarium in the benthic- and combined-resource treatments. In contrast, in the phytoplankton treatment they used the water column more than in the other treatments. In the presence of the predator, the prey had a lower consumption rate in the phytoplankton treatment than in the other treatments.Predator activity did not change among treatments. The results suggest that the trade-off between foraging activity and predation mortality for anuran larvae is strongly affected by the types of food resources present in the environment.  
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11.
  • Elmahalawy, Safaa, et al. (författare)
  • Droplet digital polymerase chain reaction (ddPCR) as a novel method for absolute quantification of major gastrointestinal nematodes in sheep
  • 2018
  • Ingår i: Veterinary Parasitology. - : Elsevier BV. - 0304-4017 .- 1873-2550. ; 261, s. 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we present for the first time a new tool, based on Droplet Digital (TM) Polymerase Chain Reaction (ddPCR), for absolute quantification of key genera of gastrointestinal (GI) nematode parasites of grazing livestock. Four combinations of primers/probe sets targeting the internal transcribed spacer region 2 (ITS2) of the ribosomal RNA gene array were designed using the Primer3 software, following in silico analysis of nucleotide sequences from nematodes of interest downloaded from common databases. The amplified regions include both a universal region for detection of any strongylid gastrointestinal parasite and three different genus specific regions, making it possible to differentiate between the most important GI nematodes of sheep in Sweden: Haemonchus, Teladorsagia and Trichostrongylus. Analysis of samples containing serial dilutions and different mixtures of genomic DNA extracted from different species of adult worms proved useful in assessment of different threshold settings with the QuantaSoft software. Analysis of template DNA from these worms indicated that ddPCR is a viable choice for detection and absolute quantification of the different genera and also in samples with multiple species. Interpretation of the ddPCR results was straightforward and choice of analytical approach had little influence on the final results. Thus, the results obtained in the different analytical approaches seemed to be robust and the concentrations determined were uniform. Furthermore, the linear range of the Haemonchus ddPCR assay was similar to that of real-time PCR (qPCR). Taken together, our data confirm the suitability of ddPCR for detection and absolute quantification of three major sheep pathogens when tested on larval cultures from pooled ovine faeces. The results also indicate that ddPCR can be a useful complement to applications based on conventional egg counting methods such as the faecal egg reduction test (FECRT).
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12.
  • Elmahalawy, Safaa, et al. (författare)
  • Genetic variants in dyf-7 validated by droplet digital PCR are not drivers for ivermectin resistance in Haemonchus contortus
  • 2018
  • Ingår i: International Journal for Parasitology: Drugs and Drug Resistance. - : Elsevier BV. - 2211-3207. ; 8, s. 278-286
  • Tidskriftsartikel (refereegranskat)abstract
    • Resistance to ivermectin (IVM) in the nematode Haemonchus contortus in small ruminants is an increasing problem throughout the world. Access to molecular diagnostics will allow early detection of IVM resistance, which in turn can limit the spread of resistant isolates. One candidate gene which has recently been suggested as a marker for IVM resistance is that for dye-filling protein (dyf-7). In this study, we critically investigated the suitability of A141G and G153T single nucleotide polymorphisms (SNP) of dyf-7 as a marker in larval cultures collected from sheep farms in Sweden, involving several isolates for which resistance status had been characterised by the faecal egg count reduction test (FECRT). Initially, we designed dyf-7 primers from a worldwide collection of adult Haemonchus contortus DNA. With the sequence data, we created a haplotype network. We then optimised and used the same sets of primers and probes in a droplet digital PCR (ddPCR) assay for precise quantification of dyf-7 allele frequencies in pre-and post-anthelmintic treatment faecal larval cultures. The fractional abundance (FA) of the mutant SNP was within the range 7.8 and 31%. However, the FA was generally stable in samples collected from the same farms, even though they were obtained on different occasions up to 25 months apart. There was also no indication that the level of IVM resistance as measured by the faecal egg count reduction test was higher on farms with high FA. Furthermore, by comparing FA in samples from the same farms pre-and post-IVM treatment, we found no evidence of a correlation between dyf-7 and level of IVM resistance. Based on these results, dyf-7 is not a suitable marker for field testing of IVM resistance in H. contortus.
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13.
  • Griesser, Michael, et al. (författare)
  • Fine-scale kin recognition in the absence of social familiarity in the Siberian jay, a monogamous bird species
  • 2015
  • Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 24:22, s. 5726-5738
  • Tidskriftsartikel (refereegranskat)abstract
    • Kin recognition is a critical element to kin cooperation, and in vertebrates, it is primarily based on associative learning. Recognition of socially unfamiliar kin occurs rarely, and it is reported only in vertebrate species where promiscuity prevents recognition of first-order relatives. However, it is unknown whether the recognition of socially unfamiliar kin can evolve in monogamous species. Here, we investigate whether genetic relatedness modulates aggression among group members in Siberian jays (Perisoreus infaustus). This bird species is genetically and socially monogamous and lives in groups that are formed through the retention of offspring beyond independence, and the immigration of socially unfamiliar nonbreeders. Observations on feeders showed that genetic relatedness modulated aggression of breeders towards immigrants in a graded manner, in that they chased most intensely the immigrant group members that were genetically the least related. However, cross-fostering experiments showed that breeders were equally tolerant towards their own and cross-fostered young swapped as nestlings. Thus, breeders seem to use different mechanisms to recognize socially unfamiliar individuals and own offspring. As Siberian jays show a high degree of nepotism during foraging and predator encounters, inclusive fitness benefits may play a role for the evolution of fine-scale kin recognition. More generally, our results suggest that fine-graded kin recognition can evolve independently of social familiarity, highlighting the evolutionary importance of kin recognition for social species.
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14.
  • Griesser, Michael, et al. (författare)
  • What are the strengths and limitations of direct and indirect assessment of dispersal? : Insights from a long-term field study in a group-living bird species
  • 2014
  • Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 68:3, s. 485-497
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular methods of assessing dispersal have become increasingly powerful and have superseded direct methods of studying dispersal. Although now less popular, direct methods of studying dispersal remain important tools for understanding the evolution of dispersal. Here, we use data from Siberian jays Perisoreus infaustus, a group-living bird species, to compare natal dispersal distances and rates using visual mark-recapture, radio-tracking and microsatellite data. Siberian jays have bimodal natal dispersal timing; socially dominant offspring remain with their parents for up to 5 years (delayed dispersers), while they force their subordinate brood mates to leave the parental territory at independence (early dispersers). Early dispersers moved about 9,000 m (visual mark-recapture, radio-tracking) before settling in a group as a non-breeder. In contrast, delayed dispersers moved about 1,250 m (visual mark-recapture only) and mainly moved to a breeding opening. Dispersal distances were greater in managed habitat compared to natural habitat for both early and delayed dispersers. Molecular estimates based on 23 microsatellite loci and geographical locations supported distance estimates from the direct methods. Our study shows that molecular methods are at least 22 times cheaper than direct methods and match estimates of dispersal distance from direct methods. However, molecular estimates do not give insight into the behavioural mechanisms behind dispersal decisions. Thus, to understand the evolution of dispersal, it is important to combine direct and indirect methods, which will give insights into the behavioural processes affecting dispersal decisions, allowing proximate dispersal decisions to be linked to the ultimate consequences thereof.
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15.
  • Halvarsson, Britta, et al. (författare)
  • Phenotypic heterogeneity in hereditary nonpolyposis colorectal cancer: identical germline mutations associated with variable tumor morphology and immunohistochemical expression.
  • 2007
  • Ingår i: Journal of Clinical Pathology. - : BMJ. - 1472-4146 .- 0021-9746. ; 60:7, s. 781-786
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Hereditary non-polyposis colorectal cancer (HNPCC) is associated with high risks for colorectal and endometrial cancer, young age at onset and an increased risk of multiple primary tumours. Colorectal cancer in HNPCC is characterised by poor tumour differentiation, an expanding growth pattern, and a pronounced lymphocytic reaction with tumour-infiltrating lymphocytes. Aims and METHODS: The mutation spectrum in HNPCC is diverse and in order to clarify whether the HNPCC tumour phenotype is influenced by the underlying genetic alteration, 29 colorectal cancers and 12 adenomas from 24 individuals in two HNPCC families were morphologically and immunohistochemically characterised. RESULTS: The tumour morphology as well as the immunohistochemical expression of beta-catenin varied extensively within the families as well as between synchronous/metachronous colorectal cancers from the same individual. Poor tumour differentiation, an expanding growth pattern, and tumour-infiltrating lymphocytes occurred at higher frequencies in proximal tumours, whereas distal colorectal cancers often lacked distinct HNPCC-associated morphological features. CONCLUSIONS: The clinical, morphological and immunohistochemical variability observed within these families indicates that other mechanisms than the underlying germline mutation influence the HNPCC phenotype. Since morphological features linked to HNPCC are less frequent in distal cancers, it may be particularly relevant to obtain family history and age of onset in these tumours in order to identify individuals with HNPCC.
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16.
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17.
  • Halvarsson, Peter, et al. (författare)
  • Gastrointestinal parasite community structure in horses after the introduction of selective anthelmintic treatment strategies
  • 2024
  • Ingår i: Veterinary Parasitology. - 0304-4017 .- 1873-2550. ; 326
  • Tidskriftsartikel (refereegranskat)abstract
    • A relatively new method to study the species richness and diversity of nematode parasites in grazing animals is to perform deep sequencing on composite samples containing a mixture of parasites. In this work, we compared species composition of strongyles in two groups of horses as a function of egg count and age, based on a DNA barcoding approach. Faecal egg counts and larval cultures were obtained from nearly 300 horses, i.e., domestic horses (n = 167) and trotters (n = 130) sampled nationwide. The second internal transcribed spacer region (ITS2) of strongyle nematodes in the larval cultures was first amplified using barcoded universal primers and then sequenced on the PacBio platform. Subsequently, bioinformatic sequence analysis was performed using SCATA to assign operational taxonomic units (OTU). Finally, species occurrence and composition were assessed using R. ITS2 sequences were found in the majority (89%) of larval samples. Sequencing yielded an average of 140 (26 to 503) reads per sample. The OTUs were assigned to 28 different taxa, of which all but three could be identified as species. The average relative abundance of the seven most abundant species (all Cyathostominae) accounted for 87% of the combined data set. The three species with the highest prevalence in both horse groups were Cyathostomum catinatum, Cylicocyclus nassatus and Cylicostephanus calicatus, and they were frequently found in different combinations with other species regardless of horse group. Interestingly, this result is largely consistent with a previous Swedish study based on morphological analysis of adult worms. In addition, two migratory strongylids (Strongylus vulgaris and S. edentatus) occurred in few domestic horses and trotters. Except for C. minutus and C. nassatus, which decreased with age, and C. catinatum and S. vulgaris, which increased, no specific trends were observed with respect to horse age. Taken together, these results are broadly consistent with data obtained before the introduction of selective targeted treatment in Sweden in 2007. All in all, our results suggest that this treatment strategy has not led to a significant change in strongyle nematode community structure in Swedish horses. The study also confirms that nemabiome analysis in combination with diversity index analysis is an objective method to study strongyle communities in horses.
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18.
  • Halvarsson, Peter (författare)
  • Host-Parasite Interactions in Natural Populations
  • 2016
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Parasitism is one of the most common ways of living and it has arised in many taxa. Parasites feed and live inside or on their hosts resulting in both long and short term consequences for the host. This thesis is exploring the phenotypic and genotypic effects of animals living with parasitic infections. I have been studying three different parasite groups and their associated host species: the great snipe, a lekking freshwater wader bird that migrates between Africa and Northern Europe; the tree sparrow, a stationary passerine found close to human settlements and lastly the water vole, a large rodent living in riparian habitats.Avian malaria is one of the most commonly studied parasites affecting birds. Atoxoplasma, an intestinal protozoan parasite is less studied but is thought to be endemic in free-ranging birds. Given the freshwater habitat great snipes inhabit, a prevalence of 30% avian malaria infections is not high and that the prevalence fluctuated among years. Sequencing of the avian malaria cytochrome b gene revealed that parasites are similar to avian malaria parasites found in African birds suggesting that they were infected on the wintering grounds in Africa. Tree sparrows had few malaria infected individuals, a result that is consistent with other studies of stationary birds at high latitudes. Atoxoplasma infections were common in tree sparrows and capture-recapture analyses show decreased survival in infected compared to uninfected birds and signs of lower mating success among infected.Genetic analyses comparing the transcriptome between mated and unmated great snipe males revealed that the genotype is important for mating success and health status for some of the expressed genes. That variations in some of these genes are involved in maintaining a good health status and mating success supports handicap models for sexual selection in this lek mating system.The major histocompatibility complex (MHC) is a part of the immune system and it contains genes involved in immune response. In water voles, a number of new MHC alleles were identified. Based on their in silico phenotype they were grouped into supertypes to facilitate studies on how helminth infections affect the MHC diversity in the water voles. Some of these MHC supertypes provided resistance to one helminth species, but the same supertype caused the opposite effect for other helminth parasites. Overall, parasites are a driving force for maintaining genetic diversity and parasite infections lowers survival rate, which would lead to a lower lifetime breeding success.
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19.
  • Halvarsson, Peter, 1976- (författare)
  • On the Effects of Blood Parasites in Wild Birds
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Coccidian and haemoatozoan parasites are commonly occurring endo-parasites in wild birds and prevalence can vary among species and populations. In addition to prevalence studies, parasites are often used to investigate effects on life history traits. Findings from these studies are not unambiguous, as correlations with many life history traits are absent, although common findings include negative effects on survival and body condition. In this thesis, coccidian and blood parasite prevalence and their effect on survival were investigated using a PCR approach in eleven popu-lations of great snipes (Gallinago media) and in two populations of tree sparrows (Passer montanus). In great snipes and tree sparrows we investigated the parasites Plasmodium/Haemoproteus (P/H) and Leucocytozoon and in tree sparrows also Atoxoplasma.In Great snipes the overall adult prevalence was 29.9%. At the main study site, Gåvålia, Norway, a decrease in P/H prevalence with age was found and infected birds had a lower mean age. Two not mutually exclusive alternative explanations are that infected young birds may have a higher mortality and/or that individual birds can purge the infection. There was a variation in prevalence among the sample years in Gåvålia and a difference among populations. Finding fluctuations among year demonstrates the need of long term data to study parasite prevalence variation.  In tree sparrows the Haematozoan prevalence was 5.9% in adults and 56.5% in Atoxoplasma. By using recapture models to estimate apparent survival rates with the software MARK 4.2, it was suggested that parasite infections may have an impact on the apparent survival rate in one of the populations. Since condition and breeding performance appeared unaffected, it can be hypothesised that this pattern may indicate that chronic infections generally do not appear to impair birds, although subclinical infections may occasionally develop into disease with fatal outcome.
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20.
  • Halvarsson, Peter, et al. (författare)
  • Parasitic strongyle nemabiome communities in wild ruminants in Sweden
  • 2022
  • Ingår i: Parasites and Vectors. - : Springer Science and Business Media LLC. - 1756-3305. ; 15
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Wildlife hosts may serve as reservoirs for strongyles, which can be transmitted to domestic livestock. Therefore, studies evaluating nemabiome compositions in wildlife ruminants are of great use in assessing the possibility of transmission of important nematode pathogens to domestic sheep in Sweden.Methods: First, fecal samples were collected from roe deer (n = 125), fallow deer (n = 106), red deer (n = 18) and mouflon (n = 13) in south central Sweden during the hunting season in 2019. Second, after fecal examination samples were cultured and the larvae were harvested, followed by DNA extractions. Third, all samples were barcoded and processed for sequence analysis on the PacBio platform. Finally, bioinformatic sequence analysis was conducted with DADA2, while species diversity and richness, as well as interactions between the different hosts, were calculated and analyzed in R.Results: Nematode ITS2 sequences were found in 225 of 262 (86%) samples. In total, 31 taxa were identified, among which 26 (86%) to the species level. These were found in different combinations, among which 24 (77%) occurred in roe deer, 19 (61%) in fallow deer, 20 (65%) in red deer and 10 (32%) in mouflon. Five of the species found are known to be associated with livestock (Chabertia ovina, Haemonchus contortus, Oesophagostomum venulosum, Teladorsagia circumcincta and Trichostrongylus axei). However, in the present study the relative abundance and prevalence of most of these species were low. The most striking exception was T axei, which was relatively abundant in all wildlife hosts. Mostly a wide range of wildlife specific nematodes such as Ostertagia leptospicularis and Spiculopteragia spp. were identified including the invasive nematode Spiculopteragia houdemeri, which was found for the first time in red deer, fallow deer, and mouflon in Sweden. The difference in the number of shared species between mouflon and all cervids (n = 6) was less than among all three cervids (n= 8).Conclusion: In this study, we investigated the community structure of parasitic intestinal nematodes in four wildlife hosts, and we found that the majority of the parasite species identified were wildlife specific. We also found a new, potentially invasive species not reported before. After comparing the nemabiome of the wildlife hosts in this study with a previous study in sheep from the same geographical region, we conclude that the horizontal transmission potential appears to be relatively low. Still, cross-infections of nematodes between game and sheep cannot be completely ignored.
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21.
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22.
  • Halvarsson, Peter, et al. (författare)
  • Sheep nemabiome diversity and its response to anthelmintic treatment in Swedish sheep herds
  • 2021
  • Ingår i: Parasites and Vectors. - : Springer Science and Business Media LLC. - 1756-3305. ; 14
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: A novel way to study the species composition and diversity of nematode parasites in livestock is to perform deep sequencing on composite samples containing a mixture of different species. Herein we describe for the first time the nematode community structures (nemabiomes) inhabiting Swedish sheep and how these are/were affected by host age and recent anthelmintic treatments.Methods: A total of 158 fecal samples were collected (n = 35 in 2007 and n = 123 in 2013-2016) and cultured from groups of sheep on 61 commercial farms in the south-central part of the country where most animals are grazed. Among the samples, 2 x 44 (56%) were paired collections from the same groups pre- and post-treatment with anthelmintics such as macrocyclic lactones, benzimidazoles or levamisole. Samples were analyzed for their nemabiome using the PacBio platform followed by bioinformatic sequence analysis with SCATA. Species richness and diversity were calculated and analyzed in R.Results: Nematode ITS2 sequences were found in all larval culture samples except two, even though the fecal egg counts were below the McMaster threshold in 20 samples. Sequencing yielded, on average, 1008 sequences per sample. In total, 16 operational taxonomical units (OTU), all with >= 98 % identity to sequences in the NCBI database, were recognized. The OTUs found represented nematode species of which ten are commonly associated with sheep. Multiple species were identified in all pre-anthelmintic treatment larval culture samples. No effects on nematode diversity were found in relation to host age. On the other hand, recent anthelmintic treatment lowered species richness, especially after use of ivermectin and albendazole. Interestingly, despite zero egg counts after use of levamisole, these samples still contained nematode DNA and especially H. contortus.Conclusions: Our findings provide evidence that nemabiome analysis combined with diversity index analysis provides an objective methodology in the study of the efficacy of anthelmintic treatment as both high and low abundant species were detected.
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23.
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24.
  • Halvarsson, Peter, et al. (författare)
  • The complete ITS2 barcoding region for Strongylus vulgaris and Strongylus edentatus
  • 2023
  • Ingår i: Veterinary Research Communications. - : Springer Science and Business Media LLC. - 0165-7380 .- 1573-7446. ; 47, s. 1767-1771
  • Tidskriftsartikel (refereegranskat)abstract
    • Gastrointestinal nematode parasites are of major concern for horses, where Strongylus vulgaris is considered the most pathogenic among the Strongylus species. Diagnosis of S. vulgaris infections can be determined with next generation sequencing techniques, which are inherently dependent on reference sequences. The best marker for parasitic nematodes is internal transcribed spacer 2 (ITS2) and we provide the first complete ITS2 sequences from five morphologically identified S. vulgaris and additional sequences from two S. edentatus. These sequences have high similarity to already published partial sequences and amplicon sequence variants (ASV) based on next generation sequencing (NGS). The ITS2 sequences from S. vulgaris matched available partial ITS2 sequences and the full ASVs, whereas the S. edentatus sequence matched another complete sequence. We also compare Sanger sequencing and NGS methods and conclude that the ITS2 variation is better represented with NGS methods. Based on this, we recommend that further sequencing of morphologically identified specimens of various species should be performed with NGS cover the intraspecific variation in the ITS2.
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25.
  • Hedberg Alm, Ylva, et al. (författare)
  • Demonstration of reduced efficacy against cyathostomins without change in species composition after pyrantel embonate treatment in Swedish equine establishments
  • 2023
  • Ingår i: International Journal for Parasitology: Drugs and Drug Resistance. - 2211-3207. ; 23, s. 78-86
  • Tidskriftsartikel (refereegranskat)abstract
    • Consisting of approximately 50 different species, the cyathostomin parasites are ubiquitous in grazing horses. Coinfection with several species is common, and large burdens can cause the fatal disease of larval cyathostominosis. Due to intense anthelmintic drug use, cyathostomin resistance has developed to all available anthelmintic drug groups. Resistance to the anthelmintic drug pyrantel (PYR) has been documented in over 90% of studies published over the past two decades. In Sweden, a study performed in the early 2000s only confirmed resistance in 4.5% of farms. Further, prescription-only administration of equine anthelmintic drugs was enforced in Sweden in 2007. However, it is unknown if this conservative drug use has maintained PYR efficacy in cyathostomins. The aim of the present study was to investigate the effect of PYR on cyathostomin infection in Sweden using fecal egg count reduction tests (FECRTs). Further, the effect of PYR treatment on cyathostomin species composition was studied using metabarcoding. Sixteen farms with at least six horses excreting a minimum of 100 eggs per gram feces were included. Using the current World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines, PYR resistance was demonstrated in nine of farms, with seven farms showing full susceptibility. Farms with low biosecurity measures had significantly lower efficacy of PYR treatment. The most common cyathostomin species were Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cys. calicatus, Cys. goldi, Cys. minutus, Coronocyclus coronatus and Cya. pateratum, accounting for 97% of all sequence reads prior to treatment. Of these, Cyc. nassatus and Cya. catinatum had the highest occurrence, accounting for 68% of all sequence reads prior to PYR treatment. Treatment did not significantly affect the species composition. The results highlight the importance of drug efficacy testing when using PYR to treat cyathostomin infection, even when selective anthelmintic treatment and thus low treatment intensity, is used on the farm.
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26.
  • Hesson, Jenny C., 1980-, et al. (författare)
  • A sensitive and reliable restriction enzyme assay to distinguish between the mosquitoes Culex torrentium and Culex pipiens
  • 2010
  • Ingår i: Medical and Veterinary Entomology. - : Wiley. - 0269-283X .- 1365-2915. ; 24:2, s. 142-149
  • Tidskriftsartikel (refereegranskat)abstract
    • Culex pipiens pipiens Linnaeus and Culex torrentium Martini (Diptera: Culicidae) are closely related vector species that exist sympatrically in Europe. The two species are morphologically almost identical and can only be distinguished with certainty by characters of the male genitalia. Hence, correct species identification and conclusions on distribution and vector status are very difficult and often neglected. Therefore, we developed a reliable and simple mitochondrial cytochrome c oxidase subunit I (COI) gene restriction enzyme assay to discriminate between Cx. pipiens and Cx. torrentium, based on the analysis of morphologically identified male specimens. We sequenced approximately 830 bp in the 3′ region of the mitochondrial COI gene of 18 morphologically identified males of Cx. pipiens and Cx. torrentium. Two restriction enzymes (FspBI and SspI) that could distinguish between the two species according to species-specific differences in these sequences were chosen. The restriction enzymes were tested on 227 samples from Sweden and verified by sequencing 44 of them. The enzyme FspBI correctly identified all investigated samples; the enzyme SspI identified all samples except one Cx. torrentium. We hope the method and the findings presented here will help to shed light on the true distribution and relative proportions of the two species in Europe.
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27.
  • Höglund, Jacob, et al. (författare)
  • Blood transcriptomes and de novo identification of candidate loci for mating success in lekking great snipe (Gallinago media)
  • 2017
  • Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 26:13, s. 3458-3471
  • Tidskriftsartikel (refereegranskat)abstract
    • We assembled the great snipe blood transcriptome using data from fourteen lekking males, in order to de novo identify candidate genes related to sexual selection, and determined the expression profiles in relation to mating success. The three most highly transcribed genes were encoding different haemoglobin subunits. All tended to be overexpressed in males with high mating success. We also called single nucleotide polymorphisms (SNPs) from the transcriptome data and found considerable genetic variation for many genes expressed during lekking. Among these, we identified 14 polymorphic candidate SNPs that had a significant genotypic association with mating success (number of females mated with) and/or mating status (mated or not). Four of the candidate SNPs were found in HBAA (encoding the haemoglobin a-chain). Heterozygotes for one of these and one SNP in the gene PABPC1 appeared to enjoy higher mating success compared to males homozygous for either of the alleles. In a larger data set of individuals, we genotyped 38 of the identified SNPs but found low support for consistent selection as only one of the zygosities of previously identified candidate SNPs and none of their genotypes were associated with mating status. However, candidate SNPs generally showed lower levels of spatial genetic structure compared to noncandidate markers. We also scored the prevalence of avian malaria in a subsample of birds. Males infected with avian malaria parasites had lower mating success in the year of sampling than noninfected males. Parasite infection and its interaction with specific genes may thus affect performance on the lek.
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28.
  • Höglund, Johan, et al. (författare)
  • Detection of Haemonchus contortus on sheep farms increases using an enhanced sampling protocol combined with PCR based diagnostics
  • 2019
  • Ingår i: Veterinary Parasitology. - : Elsevier BV. - 0304-4017 .- 1873-2550. ; 276
  • Tidskriftsartikel (refereegranskat)abstract
    • An enhanced sampling strategy for detection of gastrointestinal parasites of sheep based on faecal sampling covering approximately 10% of the animals in the flock was evaluated with focus on the major sheep pathogen Haemonchus contortus. We also compared traditional diagnostics based on faecal eggs counts (FEC) by microscopy with DNA detection on frozen faeces samples using a droplet digital (dd) PCR assay. The investigation was carried out in 2018 in 20 conventional and 19 organic sheep flocks in Sweden with between 70 and 250 production ewes. On 76 different sampling occasions a total of 810 individual faecal samples were collected. Samples were pooled in the laboratory into 270 triplets which were examined both by microscopy and a ddPCR assay. On most farms (95%) a minimum of three triplets were investigated, first from the ewes prior to turn-out and later from the lambs after they had been grazing for at least six weeks. Extra information about the Haemonchus status was provided on 48% of the 76 sampling occasions by including more triplets compared with the old sampling strategy applied in Sweden before 2015 based on two triplets per sampling occasion irrespective of flock size. At a farmlevel H. contortus was identified by microscopy in 22 (56%) of the 39 flocks and by ddPCR it was found in 28 (72%) flocks with the enhanced protocol. There was a substantial agreement between the two diagnostic tests (Cohens kappa = 0.70 +/- 0.087). No significant differences in infection levels were observed between the two production systems (conventional and organic) irrespective of the diagnostic method used. However, samples from the ewes were more often Haemonchus positive than those from the lambs indicating that the level of parasite control was in general acceptable. Combined, our results show that Haemonchus infection is widespread throughout Sweden. In conclusion, we have validated a practical tool for sheep producers to assess Haemonchus infection with high precision.
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29.
  • Jing, Chun-lei, et al. (författare)
  • Avian malaria parasite infections do not affect personality in the chestnut thrush (Turdus rubrocanus) on the Qinghai-Tibet Plateau
  • 2023
  • Ingår i: Heliyon. - : Cell Press. - 2405-8440. ; 9:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Personality traits, the consistent individual behavioral differences, are currently gaining much attention in studies of natural bird populations. However, associations between personality traits and parasite infections are not often investigated. Even less attention has been given to studies of birds in the high-elevation region such as the Tibetan plateau. This research aims to examine the relationship between avian malaria parasites and two personality traits in a population of the Chestnut Thrush (Turdus rubrocanus) breed in the Tibetan plateau. Our results revealed no evidence of sex bias in malaria parasite prevalence. Furthermore, we found no effect of infection status on two personality scores: activity and boldness. Additionally, no effects on the activity level or boldness were observed for different parasite lineages of Haemoproteus, Leucocytozoon, the sex of the birds, or their interactions. Similarly, we did not find any relationship between activity level and boldness with nestling numbers, sex, or their interactions. Notably, individuals with a larger number of offspring tended to display greater boldness. Our findings indicate that blood parasite infections are common in this population but do not significantly impact the personality of the birds.
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30.
  • Johansson, Frank, et al. (författare)
  • Genetic differentiation in the boreal dragonfly Leucorrhinia dubia in the Palearctic region
  • 2017
  • Ingår i: Biological Journal of the Linnean Society. - : OXFORD UNIV PRESS. - 0024-4066 .- 1095-8312. ; 121:2, s. 294-304
  • Tidskriftsartikel (refereegranskat)abstract
    • The last glacial period had a strong influence on the population genetic structure of boreal species in southern and central Europe. In addition, recent and current human impact on the boreal environment has led to habitat loss, which also has a large influence on population genetic structure of species. Here we present the spatial genetic structure of the boreal dragonfly Leucorrhinia dubia using ddRAD sequencing. We sampled individuals from nine locations in Europe, three in Asia (Russia and Japan) and one location of L. intermedia in Japan. Results showed three distinct genetic clusters in Europe. One genetic cluster consisted of individuals sampled from the locations in the Swiss Alps, a second consisted of individuals sampled in the United Kingdom, and a third cluster consisted of individuals from the rest of the seven sampled locations in Europe covering a latitudinal gradient from the French Pyrenees to the north of Finland. There was also a week support that the French Pyrenees and Austrian Alps samples differentiated from the cluster of the five samples from central and north Europe. We suggest that these clusters reflect historical recolonization patterns since the last glaciation. The L. dubia individuals sampled from locations in Asia formed one cluster referring to L. dubia orientalis separated from the individuals sampled in European and from the L. intermedia locality sampled. Our result suggests that aquatic insects in the fragmented boreal landscape in south central Europe and United Kingdom need conservation consideration.
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31.
  • Johansson, Frank, et al. (författare)
  • Phylogeography and larval spine length of the dragonfly Leucorhinia dubia in Europe
  • 2017
  • Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 12:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Presence or absence of predators selects for different kind of morphologies. Hence, we expect variation in traits that protect against predators to vary over geographical areas where predators vary in past and present abundance. Abdominal larval spines in dragonfly larvae provide protection against fish predators. We studied geographical variation in larval spine length of the dragonfly Leucorrhinia dubia across Western Europe using a phylogenetic approach. Larvae were raised in a common garden laboratory experiment in the absence of fish predators. Results show that larvae from northern Europe (Sweden and Finland) had significantly longer larval spines compared to larvae from western and central Europe. A phylogeny based on SNP data suggests that short larval spines is the ancestral stage in the localities sampled in this study, and that long spines have evolved in the Fenno-Scandian clade. The role of predators in shaping the morphological differences among the sampled localities is discussed.
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32.
  • Johansson, Ulf S., 1970-, et al. (författare)
  • A complete multilocus species phylogeny of the tits and chickadees (Aves:Paridae)
  • 2013
  • Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 69:3, s. 852-860
  • Tidskriftsartikel (refereegranskat)abstract
    • The avian family Paridae (tits and chickadees) contains c. 55 species distributed in the Palearctic, Nearctic, Afrotropics and Indomalaya. The group includes some of the most well-known and extensively studied avian species, and the evolutionary history, in particular the post-glacial colonization of the northern latitudes, has been comparably well-studied for several species. Yet a comprehensive phylogeny of the whole clade is lacking. Here, we present the first complete species phylogeny for the group based on sequence data front two nuclear introns and one mitochondrial gene for 67 taxa of parids. Our results strongly support the inclusion of the Fire-capped Tit (Cephalopyrus flammiceps), currently placed in the Remizidae, as the most basal member of the Paridae. The Yellow-browed Tit (Sylviparus modestus) and the Sultan Tit (Melanochlora sultanea) constitute the next two sequential branches whereas the remaining tits fall into two large clades, one of which contains the seed hoarding and nest excavating species. The indicated clades within these two groups are largely congruent with recent classifications, but with several unforeseen relationships, such as non-monophyly of the Sombre Tit (Poecile lugubris) and the Marsh Tit (Poecile palustris), as well as non-monophyly of both the African gray and the African black tits. Further, our results support a close relationship between the White-fronted Tit (Parus semilarvatus) and the varied Tit (Poecile varius) as well as a close relationship between the White-naped Tit (Parus nuchalis) and the Yellow-cheeked and Black-bred tits (Parus spilonotus and P. xanthogenys). Finally, Hume's Ground-tit (Pseudopodoces humilis) is found to be closely related to the Green-backed Tit (Parus monticolus) and the Great Tit (Parus major). We propose a new classification that is in accordance with this phylogeny. 
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33.
  • Liu, Yang, et al. (författare)
  • Environmental factors influence both abundance and genetic diversity in a widespread bird species
  • 2013
  • Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 3:14, s. 4683-4695
  • Tidskriftsartikel (refereegranskat)abstract
    • Genetic diversity is one of the key evolutionary variables that correlate with population size, being of critical importance for population viability and the persistence of species. Genetic diversity can also have important ecological consequences within populations, and in turn, ecological factors may drive patterns of genetic diversity. However, the relationship between the genetic diversity of a population and how this interacts with ecological processes has so far only been investigated in a few studies. Here, we investigate the link between ecological factors, local population size, and allelic diversity, using a field study of a common bird species, the house sparrow (Passer domesticus). We studied sparrows outside the breeding season in a confined small valley dominated by dispersed farms and small-scale agriculture in southern France. Population surveys at 36 locations revealed that sparrows were more abundant in locations with high food availability. We then captured and genotyped 891 house sparrows at 10 microsatellite loci from a subset of these locations (N=12). Population genetic analyses revealed weak genetic structure, where each locality represented a distinct substructure within the study area. We found that food availability was the main factor among others tested to influence the genetic structure between locations. These results suggest that ecological factors can have strong impacts on both population size per se and intrapopulation genetic variation even at a small scale. On a more general level, our data indicate that a patchy environment and low dispersal rate can result in fine-scale patterns of genetic diversity. Given the importance of genetic diversity for population viability, combining ecological and genetic data can help to identify factors limiting population size and determine the conservation potential of populations.
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34.
  • Maganira, Justine, et al. (författare)
  • Soil contamination by Taenia solium egg DNA in rural villages in Kongwa district, Tanzania
  • 2020
  • Ingår i: Infection Ecology & Epidemiology. - : Informa UK Limited. - 2000-8686. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • The presence ofTaenia solium DNA from eggs in soils around the households in four Tanzanian villages in Kongwa district were analysed in relation to seasonal fluctuations and infection risk implications. A total of 192 pooled soil samples from five sampling points per household were examined by droplet digital Polymerase Chain Reaction (ddPCR) from 96 pig-keeping households both during the dry and rainy seasons. The pooled samples were first processed by a flotation-double sieving technique, followed by screening for worm DNA employing universal primers targeting the mitochondrial cytochrome c oxidase subunit I (cox1) gene of human taeniid species and some other helminths. All DNA positive samples were later confirmed by a specific ddPCR probe assay targeting the mitochondrial cox1 gene of T. solium. A total of 17.2% (n = 33) samples were positive with the universal ddPCR, whereas T. solium DNA was confirmed by the specific ddPCR only in 3.1% (n = 3) of the surveyed households. The detection of T. solium DNA in this study spells out a low risk of exposure to T. solium eggs from contaminated household soil. Based on our results, ddPCR seems to be a promising technology for screening T. solium eggs in soil.
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35.
  • Martin, Frida, et al. (författare)
  • Exploring the beta-tubulin gene family in a benzimidazole-resistant Parascaris univalens population
  • 2021
  • Ingår i: International Journal for Parasitology: Drugs and Drug Resistance. - : Elsevier BV. - 2211-3207. ; 17, s. 84-91
  • Tidskriftsartikel (refereegranskat)abstract
    • Benzimidazole (BZ) drugs are frequently used to treat infections with the equine ascarid Parascaris univalens due to increasing resistance to macrocyclic lactones and pyrantel. Benzimidazole resistance is rare in ascarids in contrast to strongyle parasites where this resistance is widespread. In strongyles, single nucleotide polymorphisms (SNPs) at codons 167, 198 and 200 in a 13-tubulin gene have been correlated to BZ resistance, but little is known about the 13-tubulin genes and their possible involvement in BZ resistance in P. univalens and other ascarids. Previously two 13-tubulin genes have been identified in P. univalens. In this study, we present five additional 13-tubulin genes as well as the phylogenetic relationship of all seven genes to 13-tubulins of other clade III and V nematodes. In addition, the efficacy of fenbendazole for treatment of P. univalens on a Swedish stud farm was studied in 2019 and 2020 using faecal egg count reduction test. Reductions varied from 73% to 88%, indicating the presence of a resistant P. univalens population on the farm. The emergence of BZ resistance emphasizes the need for development of molecular markers for rapid and more sensitive detection of resistant populations. We therefore investigated whether possible SNPs at positions 167, 198 or 200 in any of the 13-tubulin genes could be used to distinguish between resistant and susceptible P. univalens populations. Amplicon sequencing covering the mutation sites 167, 198 and 200 in all seven 13-tubulin genes revealed an absence of SNPs in both resistant and susceptible populations, suggesting that the mechanism behind BZ resistance in ascarids is different from that in strongyle nematodes and the search for a molecular marker for BZ resistance in P. univalens needs to continue.
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36.
  • Mitchell, Jonathan S., et al. (författare)
  • Genome-wide association study identifies multiple susceptibility loci for multiple myeloma
  • 2016
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiple myeloma (MM) is a plasma cell malignancy with a significant heritable basis. Genome-wide association studies have transformed our understanding of MM predisposition, but individual studies have had limited power to discover risk loci. Here we perform a meta-analysis of these GWAS, add a new GWAS and perform replication analyses resulting in 9,866 cases and 239,188 controls. We confirm all nine known risk loci and discover eight new loci at 6p22.3 (rs34229995, P = 1.31 x 10(-8)), 6q21 (rs9372120, P = 9.09 x 10(-15)), 7q36.1 (rs7781265, P = 9.71 x 10(-9)), 8q24.21 (rs1948915, P = 4.20 x 10(-11)), 9p21.3 (rs2811710, P = 1.72 x 10(-13)), 10p12.1 (rs2790457, P = 1.77 x 10(-8)), 16q23.1 (rs7193541, P = 5.00 x 10(-12)) and 20q13.13 (rs6066835, P = 1.36 x 10(-13)), which localize in or near to JARID2, ATG5, SMARCD3, CCAT1, CDKN2A, WAC, RFWD3 and PREX1. These findings provide additional support for a polygenic model of MM and insight into the biological basis of tumour development.
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37.
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38.
  • Song, Kai, 1988-, et al. (författare)
  • Conservation genomics in the boreal forest : Population structure and local adaptation in the sibling species Chinese Grouse and Hazel Grouse
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The climate of the world’s arctic regions, including the poles and the Tibetan plateau region, act as a bellwether for global change. On the Tibetan plateau, there are numerous species well adapted to cold environments. The Chinese Grouse and Hazel Grouse are sibling species distributed in the Eurasian subarctic forests of the Tibetan plateau respectively. Conservation genomics are transforming our understanding of organismal responses in a changing Arctic boreal forest. In this study, we used 29 individuals from the sister species Chinese Grouse and Hazel Grouse from the boreal forest in Eurasia.  Our results provide insights into the genetic diversity and differentiation in to different geographic populations of the two species. Full genome sequencing of samples covering the distribution area of grouse species throughout the Eurasian boreal forest has enabled us to provide the first analysis of the population structure and introgression. Through selective sweep analysis, we detected that the Chinese Grouse inhabiting the QTP high altitude environment show evidence of having evolved adaptations to hypobaric hypoxia and high ultraviolet radiation.
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39.
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  • Song, Kai, 1988-, et al. (författare)
  • Demographic history and divergence of sibling grouse species inferred from whole genome sequencing reveal past effects of climate change
  • 2021
  • Ingår i: BMC Ecology and Evolution. - : BioMed Central (BMC). - 2730-7182. ; 21:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background The boreal forest is one of the largest biomes on earth, supporting thousands of species. The global climate fluctuations in the Quaternary, especially the ice ages, had a significant influence on the distribution of boreal forest, as well as the divergence and evolution of species inhabiting this biome. To understand the possible effects of on-going and future climate change it would be useful to reconstruct past population size changes and relate such to climatic events in the past. We sequenced the genomes of 32 individuals from two forest inhabiting bird species, Hazel Grouse (Tetrastes bonasia) and Chinese Grouse (T. sewerzowi) and three representatives of two outgroup species from Europe and China. Results We estimated the divergence time of Chinese Grouse and Hazel Grouse to 1.76 (0.46-3.37) MYA. The demographic history of different populations in these two sibling species was reconstructed, and showed that peaks and bottlenecks of effective population size occurred at different times for the two species. The northern Qilian population of Chinese Grouse became separated from the rest of the species residing in the south approximately 250,000 years ago and have since then showed consistently lower effective population size than the southern population. The Chinese Hazel Grouse population had a higher effective population size at the peak of the Last Glacial Period (approx. 300,000 years ago) than the European population. Both species have decreased recently and now have low effective population sizes. Conclusions Combined with the uplift history and reconstructed climate change during the Quaternary, our results support that cold-adapted grouse species diverged in response to changes in the distribution of palaeo-boreal forest and the formation of the Loess Plateau. The combined effects of climate change and an increased human pressure impose major threats to the survival and conservation of both species.
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41.
  • Song, Kai, 1988-, et al. (författare)
  • Demographics and divergence of the sibling species Chinese Grouse and Hazel Grouse inferred from whole genome sequencing
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The boreal forest is one of the largest biomes on earth, supporting thousands of species. The global climate fluctuations in the Quaternary, especially the ice ages, had a significant influence on the distribution of boreal forest, as well as the divergence and evolution of species inhabiting this biome. To provide insights into the role of recent ice ages in species divergence and population history in southern Eurasian boreal forests, we sequenced the genomes of 32 individuals from the sister species Hazel Grouse (Tetrastes bonasia) and Chinese Grouse (T. sewerzowi) and three representatives of outgroup species from Europe and China. Our results show very different population demographic histories between the sibling species. Using PSMC we show that the peak and bottleneck of effective population size (Ne) occurred at different times; the Hazel Grouse had a peak in the Mid-Pleistocene and a bottleneck during the Last Glacial Period, in contrast to the Chinese Grouse, which peaked with a larger population size after the Hazel Grouse. In addition, the northern population of Chinese Grouse inhabiting the Qilian Mountains became separated from the main population residing in the south and since then consistently showed lower effective population size than the southern population. The Hazel Grouse population in northern China had a higher effective population size at the peak of the Last Glacial Period compared to the European population, which appeared to have gone through a severe bottleneck. As revealed by MSMC modelling, both species have recently decreased and now have low effective population sizes. The results of this study, suggest that differences in the demographic processes that shaped the evolutionary history and distribution for both species, will contribute to the understanding of the biological processes affecting the fauna in boreal forests in Eurasia.
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42.
  • Song, Kai, 1988- (författare)
  • Divergence, selection, demographic history and conservation genomics of sibling bird species in boreal forest in Northern Eurasia and the Qinghai-Tibetan Plateau
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • I used two pairs of sibling boreal forest bird species to study divergence, selection, demographics, and conservation in northern Eurasia and the Qinghai-Tibetan Plateau at the microsatellite level (chapter 1) and whole genome level (chapters 2, 3, 4 and 5). In chapter 1, which is the first study to describe genetic diversity of the Sichuan Jay, I used microsatellite markers to estimate genetic differentiation in Sichuan Jay and Siberian Jay populations. The results showed similar levels of genetic variability, strong population structure, and high genetic differentiation between the two species and among different populations. In chapter 2, I used demographic analyses, and found that the Chinese Grouse has experienced substantial changes in population size from the beginning of the last interglacial, with a peak just before the last glacial maximum. The results inferred from the whole genome sequencing and species distribution models support a history of population size fluctuations. In chapter 3 to 5, I used population genomic methods to explore genomic variation, demographic divergence, local adaptation, and inbreeding from 29 whole genome re-sequenced individuals of Chinese Grouse and Hazel Grouse. I found strong evidence for population structure, changing demographic histories, and varying inbreeding levels and genetic load within both species. In Chinese Grouse, an isolated population in the northern part of the species range showed the lowest genetic diversity, high pairwise FST, high LD decay, higher inbreeding and genetic load compared to two other populations. In Hazel Grouse, there were strong population differences and inbreeding levels among the three populations, especially among the Swedish and German populations. The Swedish population likely lost genetic diversity during the re-colonization of the boreal forests in Scandinavia after the last glaciation. Analyses of genetic load showed that purifying selection of mildly deleterious mutations has been more efficient in Hazel Grouse, a species with a larger population size and range compared to Chinese Grouse. However, when I compared the genetic load as the ratio between highly deleterious loss-of-function mutations and synonymous mutations for Chinese Grouse and Hazel Grouse, purifying selection did not seem to have a large effect. My findings show that small, isolated and fragmented populations of forests birds loose genetic variation and may thereby become vulnerable to future challenges and also that populations may track past habitat changes and adapt to local conditions.
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43.
  • Song, Kai, 1988-, et al. (författare)
  • Genetic differentiation in Sichuan jay (Perisoreus internigrans) and itssibling species Siberian jay (P. infaustus)
  • 2020
  • Ingår i: Conservation Genetics. - : Springer Nature. - 1566-0621 .- 1572-9737. ; 21:2, s. 319-327
  • Tidskriftsartikel (refereegranskat)abstract
    • The Pleistocene ice age and recent forest fragmentation have both played a significant role in shaping the population geneticvariation of boreal coniferous species in the Qinghai-Tibet Plateau (QTP) and Eurasian coniferous forests. The Sichuan jay isone of the least know endemic bird species in QTP coniferous forests in western China while its sibling species, the SiberianJay, is widespread within the coniferous forests in northern Eurasia. Here we used 11 microsatellite markers to assay geneticdiversity across 58 Sichuan jay samples from China and 205 Siberian jay samples from Sweden and Russia. Results showedthree distinct genetic clusters from the Sichuan jay sampling. Furthermore, the pair-wise FST values indicated high geneticdifferentiation not only among the two species but also between Swedish and Russian Siberian jay populations. What ismore, a pattern of isolation by distance was found among the analyzed populations. Our study suggests that targeted
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44.
  • Song, Kai, 1988-, et al. (författare)
  • Genomic analysis of demographic history and ecological niche modeling in the endangered Chinese Grouse Tetrastes sewerzowi
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Background: The Quaternary is characterized by marked climatic oscillations between glacial and interglacial periods that had worldwide consequences in forming the contemporary diversity of many populations, species and communities. The origin and evolution of biodiversity in mountainous areas are highly dependent on historical orogenesis and associated climatic changes. The Chinese grouse Tetrastes sewerzowi is a forest-dwelling species endemic to the mountains to the east of the Qinghai–Tibet Plateau, which has been listed as Near Threatened with a decreasing trend by the IUCN because of ongoing deforestation and fragmentation of coniferous forests. Understanding demographic history is important in placing current population status into a broader ecological and evolutionary context.Results: Analysis of the Chinese Grouse genome reveals fluctuation in effective population size throughout the Pleistocene. Populations decreased during early to middle Pleistocene but showed an expansion during late Pleistocene then followed a sharp decline during the last glacial maximum (LGM). Ecological niche modeling indicated that suitable habitat shift between high altitude regions to low altitude regions were due to a changing climate. The result parallels patterns of population size change in Chinese Grouse estimated from PSMC modelling, which suggested an expansion in population size from the last interglacial period and then a peak and a bottleneck occurring at the LGM. Furthermore, the present-day distribution of Chinese Grouse is greatly reduced and will become highly fragmented if boreal forest cover restricts the ecological niche.Conclusions: The Chinese Grouse have experienced substantial population size changes from the beginning to the LIG and reached a peak before the LGM. A sharp decrease and bottleneck happened during the LGM, when the conifer forests were subjected to extensive loss. The results inferred from the whole genome sequencing and species distribution models both support the historical population fluctuation. The distribution of the Chinese Grouse was strongly dependent on the boreal forest cover. To protect the fragmented boreal forest is an essential action to protect the Chinese Grouse.
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45.
  • Song, Kai, 1988-, et al. (författare)
  • Genomic analysis of demographic history and ecological niche modeling in the endangered Chinese GrouseTetrastes sewerzowi
  • 2020
  • Ingår i: BMC Genomics. - : BMC. - 1471-2164. ; 21:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background The Quaternary had worldwide consequences in forming the contemporary diversity of many populations, species and communities, which is characterized by marked climatic oscillations between glacial and interglacial periods. The origin and evolution of biodiversity in mountainous areas are highly dependent on historical orogenesis and associated climatic changes. The Chinese grouseTetrastes sewerzowiis a forest-dwelling species endemic to the mountains to the east of the Qinghai-TibetPlateau, which has been listed as Near Threatened with a decreasing trend by the IUCN because of ongoing deforestation and fragmentation of coniferous forests. It is important to place current population status into a broader ecological and evolutionary context to understand their demographic history. Results Analyses of the Chinese Grouse genome revealed fluctuations throughout the Pleistocene in effective population size. Populations decreased during early to middle Pleistocene but showed an expansion during late Pleistocene which was then followed by a sharp decline during the last glacial maximum (LGM). Ecological niche modeling indicated that a suitable habitat shift between high altitude regions to low altitude regions was due to a changing climate. This result parallels patterns of population size change in Chinese Grouse estimated from PSMC modelling, which suggested an expansion in population size from the last interglacial period (LIG) and then a peak and a bottleneck occurring at the last glacial maximum (LGM). Furthermore, the present-day distribution of Chinese Grouse is greatly reduced and fragmented. It will likely become even more fragmented in the future since coniferous forest cover is threatened in the region of their distribution and the availability of such habitat restricts their ecological niche. Conclusions The Chinese Grouse have experienced substantial population size changes from the beginning to the LIG and reached a peak before the LGM. A sharp decrease and bottleneck occurred during the LGM, when the coniferous forests were subjected to extensive loss. The results inferred from the whole genome sequencing and species distribution models both support historical population fluctuations. The distribution of the Chinese Grouse is strongly dependent on the coniferous forest cover. To protect the fragmented coniferous forests is an essential action to protect the Chinese Grouse.
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46.
  • Song, Kai, 1988-, et al. (författare)
  • Inbreeding and genetic load in a pair of sibling grouse species : Tetrastes sewersowi and T. bonasia
  • 2024
  • Ingår i: Avian Research. - : Elsevier. - 2053-7166. ; 15
  • Tidskriftsartikel (refereegranskat)abstract
    • Genetic load and inbreeding are recognized as important factors to be considered in conservation programs. Elevated levels of both can increase the risk of population extinction by negatively impacting fitness-related characters in many species of plants and animals, including humans (inbreeding depression). Genomic techniques are increasingly used in measuring and understanding genetic load and inbreeding and their importance in evolution and conservation. We used whole genome resequencing data from two sibling grouse species in subarctic Eurasia to quantify both. We found a large range of inbreeding measured as FROH (fraction of runs of homozygosity) in individuals from different populations of Chinese Grouse (Tetrastes sewerzowi) and Hazel Grouse (T. bonasia). FROH estimated from genome-wide runs of homozygosity (ROH) ranged from 0.02 to 0.24 among Chinese Grouse populations and from 0.01 to 0.44 in Hazel Grouse. Individuals from a population of Chinese Grouse residing in the Qilian mountains and from the European populations of Hazel Grouse (including samples from Sweden, Germany and Northeast Poland) were the most inbred (FROH ranged from 0.10 to 0.23 and 0.11 to 0.44, respectively). These levels are comparable to other highly inbred populations of birds. Hazel Grouse from northern China and Chinese Grouse residing in the Qinghai-Tibetan Plateau showed relatively lower inbreeding levels. Comparisons of the ratio between deleterious missense mutations and synonymous mutations revealed higher levels in Chinese Grouse as compared to Hazel Grouse. These results are possibly explained by higher fixation rates, mutational melt down, in the range-restricted Chinese Grouse compared to the wide-ranging Hazel Grouse. However, when we compared the relatively more severe class of loss-of-function mutations, Hazel Grouse had slightly higher levels than Chinese Grouse, a result which may indicate that purifying selection (purging) has been more efficient in Chinese Grouse on this class of mutations.
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47.
  • Song, Kai, 1988-, et al. (författare)
  • Purifying selection in Grouse is more efficient in large populations
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Inbreeding depression and purging are recognized as essential factors to be considered in conservation programs. Elevated levels of both can increase the risk of population extinction by negatively impacting fitness-related characters in many species of plants and animals, including humans. Genomic techniques are increasingly used in measuring and understanding inbreeding and inbreeding depression and their importance in evolution and conservation. We use whole genome resequencing data from isolated, bottlenecked, and outbred Tetrastes and Lagopus populations in subarctic Eurasia to quantify inbreeding depression and purifying selection. We found a large range of inbreeding measured as FROH in populations of Chinese Grouse (Tetrastes sewerzowi) and Hazel Grouse (T. bonasia). FROH estimated from genome-wide runs of homozygosity (ROH) ranged from 0.02 to 0.24 among Chinese Grouse populations and 0.01 to 0.44 in Hazel grouse. A population of Chinese Grouse residing in the Qilian mountains and the European populations of Hazel Grouse (including samples from Sweden, Germany and North East Poland) were both highly inbred (FROH ranged from 0.10 to 0.23 and 0.11 to 0.44, respectively). Hazel grouse from northern China and Chinese grouse residing in the Qinghai-Tibetan Plateau showed relatively lower inbreeding levels. In addition, through comparison of the ratio between deleterious missense mutations and synonymous mutations, purifying selection was found to be more efficient in Hazel grouse and ptarmigan populations which hold larger population sizes than Chinese grouse. However, when we compared the ratio between loss-of-function and synonymous mutations, Hazel Grouse had slightly higher levels than Chinese Grouse while Willow Ptarmigan and Rock Ptarmigan had lower levels of genetic load. These results indicate that purifying selection has been more efficient in the wide ranging hazel grouse which thereby can sustain higher levels of inbreeding compared to Chinese grouse. Our study provides the first genetic evidence of inbreeding depression and purging patterns in boreal forest species in Eurasia from the respective sibling species and provide relevant information for future conservation and management of the species.
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