203 research outputs found
The occurrence of haemosporidian parasites in the Fennoscandian bluethroat (Luscinia svecica) population
No full textA total of 86 adult bluethroats (Luscinia svecica) from nine different localities, covering the full length of the Fennoscandian mountain range, were screened for blood parasites of the three genera Haemoproteus, Plasmodium and Leucocytozoon using a recently developed polymerase chain reaction method. The overall occurrence of infection was 59.3%. Prevalence of Leucocytozoon spp. (47.7%), Plasmodium spp. (23.3%) and Haemoproteus spp. (1.2%) was detected. Of the infected birds, 15.1% carried mixed infections. Five different mitochondrial DNA-lineages of Leucocytozoon spp., eight lineages of Plasmodium spp. and one lineage of Haemoproteus spp. were found. Due to large sequence divergence these corresponded to at least five different species, but with the possibility of all 14 being independent evolutionary units with the potential of evolving different effects on the host. Of the lineages of Leucocytozoon spp., the most common was found throughout the range. The occurrence of the second most common lineage of Leucocytozoon spp. showed significant variation in prevalence between sites. The data also showed molecular evidence of one lineage of Leucocytozoon sp. existing in more than one species of avian host, thus challenging the use of host taxon as a taxonomic character when distinguishing between different species leucocytozoids
Avian malaria in the montane tropics
No full textUnderstanding the unequal distribution of life on earth is a fundamental goal of ecology and evolutionary biology. Past efforts to explain large-scale patterns in diversity have tended to focus on two broad classes of explanation, one invoking the importance of abiotic factors (i.e. climate and vegetation) and the other biotic (i.e. competition); but neither has proven entirely adequate. Parasites are a major but poorly understood component of life that may offer some answers. Yet despite widespread theoretical support and some empirical evidence, the role of parasites in explaining patterns in the diversity, distribution, and abundance of species remains largely untested in natural communities. In this thesis I use a mega-diverse elevation gradient of birds as a model system to study the role of avian malaria in explaining these macroecological patterns. In the first data chapter I tested the extent to which patterns of infection across species is predictable. I found that the effects of host ecology and environment were weakly related to infection prevalence and were not consistent across different malaria lineages. Instead, I show that hosts coexisting with many close phylogenetic relatives consistently experience higher infection than evolutionarily distinct host species. In the second chapter I tested if parasite sharing may help explain these observed relationships and show that parasite sharing among host pairs declines with the time since divergence. Spatial contiguity between host pairs was also positively associated with parasite sharing. In the third chapter I tested how infection prevalence varies across species ranges in accordance with expected variation in host abundance. I show that birds are more likely to be infected at the centre of their elevation range, where host abundance is expected to be highest. Intriguingly, I also found that the incidence of host infection is unrelated to the position within the geographic range of the parasite. In the fourth data chapter, I tested whether parasites may regulate diversity by limiting geographic ranges of their hosts through ‘apparent competition’ in which a non-lethal parasite in a primary host, may be lethal in a secondary host. In support of this, I found that more observed bird ranges end at parasite infection zones than would be expected by chance. Taken together, my results suggest that parasites may play a major role in shaping patterns in the distribution and diversity of species, over both ecological and evolutionary scales. This is likely to arise and be maintained by host parasite interactions in which distantly related hosts are less likely to be infected by local parasites than close relatives, thus promoting the build up of diversity locally. On the basis of my analyses, I conclude that across montane elevation gradients in birds, and across diversity gradients more generally, parasites are likely to play a crucial role in the origin and maintenance of high biological diversity
Explaining prevalence, diversity, and host specificity in a community of avian haemosporidian parasites
No full textData from manuscript "Explaining prevalence, diversity, and host specificity in a community of avian haemosporidian parasites" by Vincenzo A. Ellis, Xi Huang, Helena Westerdahl, Jane Jönsson, Dennis Hasselquist, Júlio M. Neto, Jan-Åke Nilsson, Johan Nilsson, Arne Hegemann, Olof Hellgren, Staffan BenschTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Explaining prevalence, diversity, and host specificity in a community of avian haemosporidian parasites
No full textData from manuscript "Explaining prevalence, diversity, and host specificity in a community of avian haemosporidian parasites" by Vincenzo A. Ellis, Xi Huang, Helena Westerdahl, Jane Jönsson, Dennis Hasselquist, Júlio M. Neto, Jan-Åke Nilsson, Johan Nilsson, Arne Hegemann, Olof Hellgren, Staffan BenschTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Allelic variation at innate immune genes (avian beta-defensins), within a natural population of great tits
No full textIn order to fully understand pathogen induced natural variation in fitness in wild animal populations it is important to identify and study the degree of non-synonymous alleles in genes that code for components of the immune system. This study investigates the degree of natural genetic variation at 6 innate immune genes belonging to the -defensin family within a single population of birds, the great tits Parus major. In 40 adult individuals, all belonging to the same local population in Wytham Woods, Oxford, UK, screened across 6 different -defensin genes, all but one individual showed non-synonymous heterozygosity within the exon coding for the mature defensin peptide. The non-synonomous variation was thus associated with the part of the defensin gene that directly interacts with potential pathogens. Within the sample, 31 different genotypes were identified across the 6 different loci. Much of the found allelic variation affected the amino acid composition, which in turn alter the net charge and hydrophilicity of the produced peptide; properties associated with the efficiency of binding to and rupture pathogens. This study demonstrates that non-synonymous genetic variation exists at -defensins genes, a part of the immune system that forms an important first line of defence against various pathogens. Understanding the degree of underlying genetic variation at different parts of the immune system will help achieve a holistic view of the reasons behind individual variation in pathogen susceptibility, as well as why individuals are affected differently once they become infected
Avian Malaria and Related Blood Parasites: Molecular Diversity, Ecology and Evolution
No full textMalaria-like parasites consist of a large group of species that infects primates, rodents, bats, lizard and birds. I have focused on parasites from the genera Haemoproteus, Plasmodium and Leucocytozoon that are infecting birds. By using molecular methods to identify parasites from avian blood samples, I have found a diversity, based on the cytochrome b gene, that greatly exceeds the diversity previously known when identification was based on morphological characters. By phylogenetic analyses we have shown that the morphological identification system of these parasites represent, to a large degree, consists of monophyletic groups and that parasite lineages obtained by molecular identification consists of non-recombining lineages. Using a phylogenetic approach, including ~6000 samples from 139 bird species, we investigated how common it is that parasites are introduced into resident bird faunas in Europe and Africa, two areas linked by an immense amount of migrating birds each year. For Haemoproteus spp. and Leucocytozoon spp. such introductions are rare events that happen over an evolutionary time scale, whereas parasites belonging to the genera Plasmodium seem to be less restricted to a specific transmission area. This might be a consequence of the lower host-specificity of Plasmodium lineages. Detailed analysis of the host specificity of Plasmodium and Haemoproteus showed that lineages that could develop in many different host-species over a large taxonomic range, also exhibited among the highest prevalence in single bird species. Hence, being a generalist did not prevent it to be highly successful in single hosts. A crucial part of the parasite life-cycle takes place inside the blood feeding vector. By using wild-caught and blood-feed blackflies, the main vectors for Leucocytozoon spp., we could successfully determine both which animal they had been feeding on and which parasite each host was carrying and potentially could be transmitted. We found that blackfly species had either a preference for birds or for mammals. Moreover, among blackfly species attacking birds there was also a finer specificity with preferences for e.g. ducks, grouse, passerines, cranes. This host specificity shaped the distribution of the parasites in the different blackfly species such as the same or similar parasite lineages ended up in the same blackfly species or in species with a similar host preference. Hence, the host-preferences of the blackflies could then potentially act as an ecological transmission barrier for parasites between different bird host species
Det machiavellistiska personlighetsdragets förekomst bland fastighetsmäklare: En studie med fokus på försäljningsprestationer
No full textTitle: The occurrence of the Machiavellian personality trait among real estate agents: A study focusing on sales performance Level: Student thesis, final assignment for Bachelor Degrees in Business Administration Author: Jessica Backman & Fanny Hellgren Supervisor: Jonas Kågström Date: 2019 - June Aim: The purpose of this research paper is to analyze the presence of the personality trait Machiavellianism among Swedish real estate agents and its impact on sales performances. Method: The study is based on a quantitative research method with a deductive approach. The primary data of this study is based on a questionnaire. The participants of this questionnaire are 106 registered real estate agents in Sweden. This data was subsequently analyzed in the program jamovi, which resulted in a descriptive analysis, a correlation analysis and a factor analysis. Result & Conclusions: The result shows that the degree of Machiavellianism negatively affects the investigated real estate agents to all sales performance measures. Furthermore, the result shows that people with a high degree of Machiavellianism thinks to a greater extent that it is okay to use cap prices, front man and to withhold information, to the extent that it occurs. Generally speaking, the participating real estate agents consider that it is not okay to use cap prices, front man and to withhold information. Furthermore, the degree of Machiavellianism is relatively low among the investigated real estate agents. Contribution of the thesis: The study has contributed to understanding the occurrence of the Machiavellian personality trait among the investigated real estate brokers and how this personality trait affects their sales performance. Suggestions for future research: In order to gain a deeper understanding of Machiavellianism's influence on sales performance, it would have been interesting to compare how Machiavellianism appears in different cultures in relation to sales performance. To increase the understanding of the subject further, a proposal is to investigate how the degree of Machiavellianism appears in different sales industries. Key words: “Machiavellianism”, “the dark triad”, “real estate”, “sales performance” and “sales
The Use of Molecular Methods in Studies of Avian Haemosporidians
No full textDuring the last two decades, molecular methods to study mitochondrial DNA sequence variation have become an important part in the studies of avian haemosporidians. Up until recently, these methods have primarily been used for identification of the parasites and for tentative phylogenetic reconstructions, allowing researchers not trained in traditional parasitology to compare data across the globe. However, with the introduction of genome and transcriptome sequencing, studies are emerging that go deeper into the genetics and molecular biology of the parasites. In this chapter, we describe and summarize the common methods used for genetic barcoding of the parasites and give an introduction of what to take into account when designing a molecular study of avian haemosporidians. This chapter further discusses why nuclear genetic data are needed in order to answer several important ecological and evolutionary questions and which methods to use in order to overcome the obstacles of obtaining nuclear data of the parasites. Finally, this chapter highlights the challenges and opportunities that come with the use of molecular methods, such as how to study and interpret prevalence, the challenge of aborted developments, and how to obtain data for more robust phylogenies and population structure studies of the parasites
Evolution of a cluster of innate immune genes(beta-defensins) along the ancestral lines of chicken and zebra finch
No full textBACKGROUND:Avian beta-defensins (AvBDs) represent a group of innate immune genes with broad antimicrobial activity. Within the chicken genome, previous work identified 14 AvBDs in a cluster on chromosome three. The release of a second bird genome, the zebra finch, allows us to study the comparative evolutionary history of these gene clusters between from two species that shared a common ancestor about 100 million years ago. RESULTS:A phylogenetic analysis of the beta-defensin gene clusters in the chicken and the zebra finch identified several cases of gene duplication and gene loss along their ancestral lines. In the zebra finch genome a cluster of 22 AvBD genes were identified, all located within 125Kbp on chromosome three. Ten of the 22 genes were found to be highly conserved with orthologous genes in the chicken genome. The remaining 12 genes were all located within a cluster of 58 Kbp and are suggested to be a result of recent gene duplication events that occurred after the galliformes- passeriformes split (G-P split) and where no duplications have happened along the chicken line. Within the chicken genome, AvBD6 was found to be a duplication of AvBD7, whereas the gene AvDB14 seems to have been lost along the ancestral line of the zebra finch. The duplicated beta-defensin genes have had a significantly higher accumulation of non-synonymous over synonymous substitutions compared to the genes that have not undergone duplication since the G-P split. The expression patterns of avian beta-defensin genes seem to be well conserved between chicken and zebra finch.CONCLUSION:The genomic comparisons of the beta-defensins gene clusters of the chicken and zebra finch illuminate the evolutionary history of this gene complex. Along their ancestral lines, several gene duplication events have occurred in the passerine line after the galliformes-passeriformes split giving rise to 12 novel genes compared to a single duplication event in the galliformes line. After the duplication events, the duplicated genes have been subject to a relaxed selection pressure compared to the non-duplicated genes, thus supporting models of evolution by gene duplication
Allelic variation at innate immune genes (avian beta-defensins), within a natural population of great tits
No full textIn order to fully understand pathogen induced natural variation in fitness in wild animal populations it is important to identify and study the degree of non-synonymous alleles in genes that code for components of the immune system. This study investigates the degree of natural genetic variation at 6 innate immune genes belonging to the -defensin family within a single population of birds, the great tits Parus major. In 40 adult individuals, all belonging to the same local population in Wytham Woods, Oxford, UK, screened across 6 different -defensin genes, all but one individual showed non-synonymous heterozygosity within the exon coding for the mature defensin peptide. The non-synonomous variation was thus associated with the part of the defensin gene that directly interacts with potential pathogens. Within the sample, 31 different genotypes were identified across the 6 different loci. Much of the found allelic variation affected the amino acid composition, which in turn alter the net charge and hydrophilicity of the produced peptide; properties associated with the efficiency of binding to and rupture pathogens. This study demonstrates that non-synonymous genetic variation exists at -defensins genes, a part of the immune system that forms an important first line of defence against various pathogens. Understanding the degree of underlying genetic variation at different parts of the immune system will help achieve a holistic view of the reasons behind individual variation in pathogen susceptibility, as well as why individuals are affected differently once they become infected
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