The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Karen D. Mccoy - One of the best experts on this subject based on the ideXlab platform.
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the high diversity and global distribution of the intracellular bacterium rickettsiella in the polar seabird tick Ixodes uriae
Microbial Ecology, 2016Co-Authors: Olivier Duron, Julie Cremaschi, Karen D. MccoyAbstract:Obligate intracellular bacteria of the Rickettsiella genus are emerging as both widespread and biologically diverse in arthropods. Some Rickettsiella strains are highly virulent entomopathogenic agents, whereas others are maternally inherited endosymbionts exerting very subtle manipulations on host phenotype to promote their own spread. Recently, a variety of Rickettsiella strains have been reported from ticks, but their biology is entirely unknown. In the present study, we examined the incidence and diversity of Rickettsiella in 11 geographically distinct populations of the polar seabird tick Ixodes uriae. We found Rickettsiella in most tick populations with a prevalence ranging from 3 to 24 %. 16S ribosomal RNA (rRNA) and GroEL gene sequences revealed an unexpected diversity of Rickettsiella, with 12 genetically distinct Rickettsiella strains present in populations of I. uriae. Phylogenetic investigations further revealed that these Rickettsiella strains do not cluster within a tick-specific clade but rather exhibit distinct evolutionary origins demonstrating frequent horizontal transfers between distantly related arthropod species. Tick rearing further showed that Rickettsiella are present in eggs laid by infected females with no evidence of abortive development. Using this data set, we discuss the potential biological significance of Rickettsiella in seabird ticks. Most notably, we suggest that these organisms may not be pathogenic forms but rather use more subtle adaptive strategies to persist within tick populations.
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tracing the colonization and diversification of the worldwide seabird ectoparasite Ixodes uriae
Molecular Ecology, 2014Co-Authors: Muriel Dietrich, Thierry Boulinier, Florent Kempf, Karen D. MccoyAbstract:Historical patterns of dispersal and population isolation are key components shaping contemporary genetic diversity across landscapes and require explicit consideration when examining the relative role of different factors in driving the evolution of host specificity in parasitic organisms. In this study, we investigate the worldwide colonization history of a common ectoparasite of seabirds, the tick Ixodes uriae. This tick has a circumpolar distribution across both hemispheres but has repeatedly formed host-specific races within different regions. By combining mitochondrial and nuclear data, we infer how this species spread to its present-day distribution and how the colonization process may have affected the geographic and host-associated structure of this tick within regions. We demonstrate that I. uriae is highly structured at a global scale and isolates into four genetic groups that correspond to well-defined geographical regions. Molecular dating suggests that the diversification of I. uriae began in the early Miocene (22 Myr) and that this tick colonized most of the southern hemisphere before moving into northern latitudes via two independent routes. However, no relationship between the degree of host race divergence and colonization history was evident, supporting previous hypotheses that host specialization evolves relatively rapidly in this parasite, but does not typically lead to speciation. We discuss the possible historical and contemporary mechanisms of large-scale dispersal for this ectoparasite and how its biological characteristics may condition current patterns of genetic diversity. More generally, our results illustrate how combining broad-scale sampling and modern molecular tools can help disentangle complex patterns of diversification in widespread parasites.
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Diversity and global distribution of the Coxiella intracellular bacterium in seabird ticks.
Ticks and tick-borne diseases, 2014Co-Authors: Olivier Duron, Elsa Jourdain, Karen D. MccoyAbstract:The obligate intracellular bacterium Coxiella burnetii is the etiological agent of Q fever, a widespread zoonotic disease whose most common animal reservoirs are domestic ruminants. Recently, a variety of Coxiella-like organisms have also been reported from non-mammalian hosts, including pathogenic forms in birds and forms without known effects in ticks, raising questions about the potential importance of non-mammalian hosts as reservoirs of Coxiella in the wild. In the present study, we examined the potential role of globally-distributed seabird ticks as reservoirs of these bacteria. To this aim, we tested for Coxiella infection 11 geographically distinct populations of two tick species frequently found in seabird breeding colonies, the hard tick Ixodes uriae (Ixodidae) and soft ticks of the Ornithodoros (Carios) capensis group (Argasidae). We found Coxiella-like organisms in all O. capensis sensu lato specimens, but only in a few I. uriae specimens of one population. The sequencing of 16S rDNA and GroEL gene sequences further revealed an unexpected Coxiella diversity, with seven genetically distinct Coxiella-like organisms present in seabird tick populations. Phylogenetic analyses show that these Coxiella-like organisms originate from three divergent subclades within the Coxiella genus and that none of the Coxiella strains found in seabird ticks are genetically identical to the forms known to be associated with pathogenicity in vertebrates, including C. burnetii. Using this data set, we discuss the potential epidemiological significance of the presence of Coxiella in seabird ticks. Notably, we suggest that these organisms may not be pathogenic forms, but rather behave as endosymbionts engaged in intricate interactions with their tick hosts.
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an experimental test of host specialization in a ubiquitous polar ectoparasite a role for adaptation
Journal of Animal Ecology, 2014Co-Authors: Muriel Dietrich, Thierry Boulinier, Elisa Lobato, Karen D. MccoyAbstract:Summary 1. The evolution of host specificity is considered to be an essential mechanism driving parasite diversity. It may be governed by adaptive constraints that lead to host-dependent fitness trade-offs. Alternatively, specificity may arise via transmission constraints that isolate parasite populations, without necessarily involving adaptation per se. 2. Here, we ask whether the repeated observation of host-associated genetic races across the worldwide distribution of the seabird ectoparasite Ixodes uriae is associated with host adaptation. 3. We conducted a field-based experiment to test for adaptive specialisation in host races of I. uriae. We transferred unengorged ticks of two life stages (nymphs and adults) originating from three host species (black-legged kittiwake, common guillemot and Atlantic puffin) onto young kittiwake nestlings and followed attraction and attachment rates, engorgement times and feeding success of the transplanted ticks. All ticks were also typed genetically to match exploitation patterns with genetic differences among races. 4. Ticks from atypical hosts were significantly less attracted to nestlings than ticks from the typical host, and showed lower feeding success and higher mortality. The degree of host specificity matched patterns of neutral genetic variation among races, with puffin ticks being more specific than guillemot ticks. Differences in specificity were also apparent among tick life stages, suggesting that nymphal ticks may be less discriminating of host type than adult ticks. 5. Our results indicate that the genetic divergence previously observed among sympatric I. uriae host races is at least partially linked to adaptive specialisation to the host species and not simply to host-mediated transmission. They also suggest that the adaptation process may evolve differently in different life stages based on trade-offs with physiological constraints. The identification of the selective forces acting in host specialization will now be necessary to better characterize these patterns and to understand how transmission interacts with the adaptation process to generate parasite biodiversity.
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body size and shape evolution in host races of the tick Ixodes uriae
Biological Journal of The Linnean Society, 2013Co-Authors: Muriel Dietrich, Thierry Boulinier, Lorenza Beati, Eric Elguero, Karen D. MccoyAbstract:The tick Ixodes uriae is a common ectoparasite of seabirds, and is widely distributed across the circumpolar regions of both hemispheres. Previous work demonstrated the existence of genetically distinct host races of this ectoparasite, occurring across its current range. The objective of the present study was to examine whether these host races have evolved measurable morphological differences. We measured a set of morphological variables on 255 non-engorged ticks (nymphs and adults) collected from three sympatrically occurring host species in the North Atlantic. Genotyping at eight microsatellite markers enabled us to analyse the relationship between patterns of morphological and neutral genetic variation. Multivariate analyses showed that most morphological variation was associated with size differences among tick individuals. Body size differed among races, but only in adult life stages. A linear discriminant analysis based on shape variation revealed three distinct morphological clusters corresponding to the three tick host races. These results, along with correlated patterns of host-related genetic variation, suggest that differences among host-related groups are not simply the result of phenotypic plasticity or drift, but rather reflect host-associated adaptations. Experimental work and observations across the range of I. uriae will now be required to test the genetic basis and adaptive nature of morphological differences.
Thierry Boulinier - One of the best experts on this subject based on the ideXlab platform.
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tracing the colonization and diversification of the worldwide seabird ectoparasite Ixodes uriae
Molecular Ecology, 2014Co-Authors: Muriel Dietrich, Thierry Boulinier, Florent Kempf, Karen D. MccoyAbstract:Historical patterns of dispersal and population isolation are key components shaping contemporary genetic diversity across landscapes and require explicit consideration when examining the relative role of different factors in driving the evolution of host specificity in parasitic organisms. In this study, we investigate the worldwide colonization history of a common ectoparasite of seabirds, the tick Ixodes uriae. This tick has a circumpolar distribution across both hemispheres but has repeatedly formed host-specific races within different regions. By combining mitochondrial and nuclear data, we infer how this species spread to its present-day distribution and how the colonization process may have affected the geographic and host-associated structure of this tick within regions. We demonstrate that I. uriae is highly structured at a global scale and isolates into four genetic groups that correspond to well-defined geographical regions. Molecular dating suggests that the diversification of I. uriae began in the early Miocene (22 Myr) and that this tick colonized most of the southern hemisphere before moving into northern latitudes via two independent routes. However, no relationship between the degree of host race divergence and colonization history was evident, supporting previous hypotheses that host specialization evolves relatively rapidly in this parasite, but does not typically lead to speciation. We discuss the possible historical and contemporary mechanisms of large-scale dispersal for this ectoparasite and how its biological characteristics may condition current patterns of genetic diversity. More generally, our results illustrate how combining broad-scale sampling and modern molecular tools can help disentangle complex patterns of diversification in widespread parasites.
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an experimental test of host specialization in a ubiquitous polar ectoparasite a role for adaptation
Journal of Animal Ecology, 2014Co-Authors: Muriel Dietrich, Thierry Boulinier, Elisa Lobato, Karen D. MccoyAbstract:Summary 1. The evolution of host specificity is considered to be an essential mechanism driving parasite diversity. It may be governed by adaptive constraints that lead to host-dependent fitness trade-offs. Alternatively, specificity may arise via transmission constraints that isolate parasite populations, without necessarily involving adaptation per se. 2. Here, we ask whether the repeated observation of host-associated genetic races across the worldwide distribution of the seabird ectoparasite Ixodes uriae is associated with host adaptation. 3. We conducted a field-based experiment to test for adaptive specialisation in host races of I. uriae. We transferred unengorged ticks of two life stages (nymphs and adults) originating from three host species (black-legged kittiwake, common guillemot and Atlantic puffin) onto young kittiwake nestlings and followed attraction and attachment rates, engorgement times and feeding success of the transplanted ticks. All ticks were also typed genetically to match exploitation patterns with genetic differences among races. 4. Ticks from atypical hosts were significantly less attracted to nestlings than ticks from the typical host, and showed lower feeding success and higher mortality. The degree of host specificity matched patterns of neutral genetic variation among races, with puffin ticks being more specific than guillemot ticks. Differences in specificity were also apparent among tick life stages, suggesting that nymphal ticks may be less discriminating of host type than adult ticks. 5. Our results indicate that the genetic divergence previously observed among sympatric I. uriae host races is at least partially linked to adaptive specialisation to the host species and not simply to host-mediated transmission. They also suggest that the adaptation process may evolve differently in different life stages based on trade-offs with physiological constraints. The identification of the selective forces acting in host specialization will now be necessary to better characterize these patterns and to understand how transmission interacts with the adaptation process to generate parasite biodiversity.
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Host speci®city of a generalist parasite: genetic evidence of sympatric host races in the seabird tick Ixodes uriae
2014Co-Authors: K. D. Mccoy, Claire Tirard, Thierry Boulinier, Yanis MichalakisAbstract:colonial seabirds; host speci®city; host±parasite interactions; Ixodes; microsatellites; speciation. Due to the close association between parasites and their hosts, many `generalist ' parasites have a high potential to become specialized on different host species. We investigated this hypothesis for a common ectoparasite of seabirds, the tick Ixodes uriae that is often found in mixed host sites. We examined patterns of neutral genetic variation between ticks collected from Black-legged kittiwakes (Rissa tridactyla) and Atlantic puf®ns (Fratercula arctica) in sympatry. To control for a potential distance effect, values were compared to differences among ticks from the same host in nearby monospeci®c sites. As predicted, there was higher genetic differentiation between ticks from different sympatric host species than between ticks from nearby allopatric populations of the same host species. Patterns suggesting isolation by distance were found among tick populations of each host group, but no such patterns existed between tick populations of different hosts. Overall, results suggest that hostrelated selection pressures have led to the specialization of I. uriae and that host race formation may be an important diversifying mechanism in parasites
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body size and shape evolution in host races of the tick Ixodes uriae
Biological Journal of The Linnean Society, 2013Co-Authors: Muriel Dietrich, Thierry Boulinier, Lorenza Beati, Eric Elguero, Karen D. MccoyAbstract:The tick Ixodes uriae is a common ectoparasite of seabirds, and is widely distributed across the circumpolar regions of both hemispheres. Previous work demonstrated the existence of genetically distinct host races of this ectoparasite, occurring across its current range. The objective of the present study was to examine whether these host races have evolved measurable morphological differences. We measured a set of morphological variables on 255 non-engorged ticks (nymphs and adults) collected from three sympatrically occurring host species in the North Atlantic. Genotyping at eight microsatellite markers enabled us to analyse the relationship between patterns of morphological and neutral genetic variation. Multivariate analyses showed that most morphological variation was associated with size differences among tick individuals. Body size differed among races, but only in adult life stages. A linear discriminant analysis based on shape variation revealed three distinct morphological clusters corresponding to the three tick host races. These results, along with correlated patterns of host-related genetic variation, suggest that differences among host-related groups are not simply the result of phenotypic plasticity or drift, but rather reflect host-associated adaptations. Experimental work and observations across the range of I. uriae will now be required to test the genetic basis and adaptive nature of morphological differences.
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recent evolution of host associated divergence in the seabird tick Ixodes uriae
Molecular Ecology, 2009Co-Authors: Florent Kempf, Thierry Boulinier, Thierry De Meeus, Celine Arnathau, Karen D. MccoyAbstract:Ecological interactions are an important source of rapid evolutionary change and thus may generate a significant portion of novel biodiversity. Such changes may be particularly prevalent in parasites, where hosts can induce strong selection for adaptation. To understand the relative frequency at which host-associated divergences occur, it is essential to examine the evolutionary history of the divergence process, particularly when it is occurring over large geographical scales where both geographical and host-associated isolation may playa part. In this study, we use population genetics and phylogeography to study the evolutionary history of host-associated divergence in the seabird tick Ixodes uriae (Acari, Ixodidae). We compare results from microsatellite markers that reflect more ecological timescales with a conserved mitochondrial gene (COIII) that reflects more ancient divergence events. Population structure based on microsatellites showed clear evidence of host-associated divergence in all colonies examined. However, isolated populations of the same host type did not always group together in overall analyses and the genetic differentiation among sympatric host races was highly variable. In contrast, little host or geographical structure was found for the mitochondrial gene fragment. These results suggest that host race formation in I. uriae is a recent phenomenon, that it may have occurred several times and that local interactions are at different points in the divergence process. Rapid divergence in I. uriae implies a strong interaction with its local host species, an interaction that will alter the ecological dynamics of the system and modify the epidemiological landscape of circulating micropathogens.
Sven Bergström - One of the best experts on this subject based on the ideXlab platform.
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circumpolar diversification of the Ixodes uriae tick virome
PLOS Pathogens, 2020Co-Authors: Sven Bergström, Daniel Gonzalezacuna, John H O Pettersson, Patrik Ellstrom, Jiaxin Ling, Ingela Nilsson, Bjorn Olsen, Edward C HolmesAbstract:Ticks (order: Ixodida) are a highly diverse and ecologically important group of ectoparasitic blood-feeding organisms. One such species, the seabird tick (Ixodes uriae), is widely distributed around the circumpolar regions of the northern and southern hemispheres. It has been suggested that Ix. uriae spread from the southern to the northern circumpolar region millions of years ago and has remained isolated in these regions ever since. Such a profound biographic subdivision provides a unique opportunity to determine whether viruses associated with ticks exhibit the same evolutionary patterns as their hosts. To test this, we collected Ix. uriae specimens near a Gentoo penguin (Pygoscelis papua) colony at Neko harbour, Antarctica, and from migratory birds—the Razorbill (Alca torda) and the Common murre (Uria aalge)—on Bonden island, northern Sweden. Through meta-transcriptomic next-generation sequencing we identified 16 RNA viruses, seven of which were novel. Notably, we detected the same species, Ronne virus, and two closely related species, Bonden virus and Piguzov virus, in both hemispheres indicating that there have been at least two cross-circumpolar dispersal events. Similarly, we identified viruses discovered previously in other locations several decades ago, including Gadgets Gully virus, Taggert virus and Okhotskiy virus. By identifying the same or closely related viruses in geographically disjunct sampling locations we provide evidence for virus dispersal within and between the circumpolar regions. In marked contrast, our phylogenetic analysis revealed no movement of the Ix. uriae tick hosts between the same locations. Combined, these data suggest that migratory birds are responsible for the movement of viruses at both local and global scales.
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circumpolar diversification of the Ixodes uriae tick virome
bioRxiv, 2020Co-Authors: John H O Pettersson, Sven Bergström, Daniel Gonzalezacuna, Patrik Ellstrom, Jiaxin Ling, Ingela Nilsson, Bjorn Olsen, Edward C HolmesAbstract:Ticks (order: Ixodida) are a highly diverse and ecologically important group of ectoparasitic blood-feeding organisms. One such species, the seabird tick (Ixodes uriae), is widely distributed around the circumpolar regions of the northern and southern hemispheres. It has been suggested that Ix. uriae spread from the southern to the northern circumpolar region millions of years ago and has remained isolated in these regions ever since. Such a profound biographic subdivision provides a unique opportunity to determine whether viruses associated with ticks exhibit the same evolutionary patterns as their hosts. To test this, we collected Ix. uriae specimens near a Gentoo penguin (Pygoscelis papua) colony at Neko harbour, Antarctica, and from migratory birds - the Razorbill (Alca torda) and the Common murre (Uria aalge) - on Bonden island, northern Sweden. Through meta-transcriptomic next-generation sequencing we identified 16 RNA viruses, seven of which were novel. Notably, we detected the same species, Ronne virus, and two closely related species, Bonden virus and Piguzov virus, in both hemispheres indicating that there have been at least two cross-circumpolar dispersal events. Similarly, we identified viruses discovered previously in other locations several decades ago, including Gadgets Gully virus, Taggert virus and Okhotskiy virus. By identifying the same or closely related viruses in geographically disjunct sampling locations we therefore provide evidence for virus dispersal within and between the circumpolar regions. In marked contrast, our phylogenetic analysis revealed no movement of the Ix. uriae hosts between the same locations. Combined, these data suggest that migratory birds are responsible for the movement of viruses at both the local and global scales.
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increased mortality of black browed albatross chicks at a colony heavily infested with the tick Ixodes uriae
International Journal for Parasitology, 1999Co-Authors: Sven Bergström, Paul D Haemig, Bjorn R OlsenAbstract:At Bird Island, South Georgia, we studied the effects of the tick Ixodes uriae on survival of chicks at two colonies of the black-browed albatross Diomedea melanophrys, one where most chicks were infested with ticks, the other where most chicks were tick-free. When the two colonies were compared, it was found that the colony heavily-infested with ticks had significantly greater chick mortality than the colony lightly-infested with ticks. However, within each of the two colonies, there was no significant difference in survival between chicks with ticks and those without ticks.
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distribution and abundance of the tick Ixodes uriae in a diverse subantarctic seabird community
Journal of Parasitology, 1999Co-Authors: Sven Bergström, Paul D Haemig, Bjorn R OlsenAbstract:At Bird Island, South Georgia, we surveyed the distribution and abundance of ticks on the vertebrate fauna and found only 1 species Ixodes uriae. We classified all seabird species into 3 groups: (1) seabirds nesting on the surface of the ground solitarily, in dispersed groups of a few nests, or in colonies with well-spaced nests; (2) seabirds nesting on the surface of the ground in dense colonies; and (3) seabirds nesting in dense colonies in burrows or rock crevices. We detected I. uriae only on 3 species of the second group that nested in large, dense, persistent colonies, i.e., black-browed albatross (Diomedea melanophrys), gray-headed albatross (Diomedea chrysostoma), and macaroni penguin (Eudyptes chrysolophus). Ticks were found on the undersides of the feet on albatrosses but not on the undersides of the feet on penguins. We hypothesize that the coarse pebble nests of penguins, combined with the fact that their young walk around more than albatross young, make the environment on the underside of penguin feet more harsh and hostile for ticks than the underside of albatross feet. Despite the great abundance of Antarctic fur seals (Arctocephalus gazella) on the island, we found no ticks on them.
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Isolation of Lyme Disease Borrelia from Puffins (Fratercula arctica) and Seabird Ticks (Ixodes uriae) on the Faeroe Islands
Journal of Clinical Microbiology, 1999Co-Authors: Åsa Gylfe, Laila Noppa, Bjorn Olsen, Darius Strasevicius, Nuria Marti Ras, Pál Weihe, Yngve Östberg, Guy Baranton, Sven BergströmAbstract:This is the first report on the isolation of Lyme disease Borrelia from seabirds on the Faeroe Islands and the characteristics of its enzootic cycle. The major components of the Borrelia cycle include the puffin (Fratercula arctica) as the reservoir and Ixodes uriae as the vector. The importance of this cycle and its impact on the spread of human Lyme borreliosis have not yet been established. Borrelia spirochetes isolated from 2 of 102 sampled puffins were compared to the borreliae previously obtained from seabird ticks, I. uriae. The rrf-rrl intergenic spacer and the rrs and the ospC genes were sequenced and a series of phylogenetic trees were constructed. Sequence data and restriction fragment length polymorphism analysis grouped the strains together with Borrelia garinii. In a seroepidemiological survey performed with residents involved in puffin hunting on the Faeroe Islands, 3 of 81 serum samples were found to be positive by two commonly used clinical tests: a flagellin-based enzyme-linked immunosorbent assay (ELISA) and Western blotting. These three positive serum samples also had high optical density values in a whole-cell ELISA. The finding of seropositive Faeroe Islanders who are regularly exposed to I. uriae indicate that there may be a transfer of B. garinii by this tick species to humans.
Yanis Michalakis - One of the best experts on this subject based on the ideXlab platform.
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Host speci®city of a generalist parasite: genetic evidence of sympatric host races in the seabird tick Ixodes uriae
2014Co-Authors: K. D. Mccoy, Claire Tirard, Thierry Boulinier, Yanis MichalakisAbstract:colonial seabirds; host speci®city; host±parasite interactions; Ixodes; microsatellites; speciation. Due to the close association between parasites and their hosts, many `generalist ' parasites have a high potential to become specialized on different host species. We investigated this hypothesis for a common ectoparasite of seabirds, the tick Ixodes uriae that is often found in mixed host sites. We examined patterns of neutral genetic variation between ticks collected from Black-legged kittiwakes (Rissa tridactyla) and Atlantic puf®ns (Fratercula arctica) in sympatry. To control for a potential distance effect, values were compared to differences among ticks from the same host in nearby monospeci®c sites. As predicted, there was higher genetic differentiation between ticks from different sympatric host species than between ticks from nearby allopatric populations of the same host species. Patterns suggesting isolation by distance were found among tick populations of each host group, but no such patterns existed between tick populations of different hosts. Overall, results suggest that hostrelated selection pressures have led to the specialization of I. uriae and that host race formation may be an important diversifying mechanism in parasites
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Spatial genetic structure of the ectoparasite Ixodes uriae within breeding cliffs of its colonial seabird host
Heredity, 2003Co-Authors: Karen D. Mccoy, Claire Tirard, Yanis MichalakisAbstract:To examine the potential importance of the spatial subdivision of hosts for the functioning of parasite populations, we analysed patterns of local genetic structure within natural populations of the seabird ectoparasite, Ixodes uriae, at the scale of the host breeding cliff. The seabird hosts of this parasite nest in dense colonies with a hierarchical spatial organisation (individual nests-breeding cliffs-colony). Using eight microsatellite markers and samples from three breeding cliffs of the Black-legged kittiwake (Rissa tridactyla), we found that tick populations were indeed genetically structured at this spatial scale. However, the nature of this structuring depended on the characteristics of the cliffs considered. Both the host nest and cliff topography seemed to be important factors in the isolation of tick groups, but their relative roles may depend on the size of the local parasite population. We found no evidence of isolation by distance within a cliff suggesting that independent tick dispersal may not be a significant force influencing population structure in highly infested cliffs. However, genetic structure seemed to decrease with tick life stage, nymphal ticks being more strongly structured than adult ticks. These results may be related to the clustering of tick progeny combined with differential mortality and dispersal probabilities of each life stage. Overall, results indicate that the spatial organisation of hosts can indeed have important consequences for the population genetic structure of their parasites and, thus, may modify parasite dynamics and the scale at which local coevolutionary processes occur.
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local adaptation of the ectoparasite Ixodes uriae to its seabird host
Evolutionary Ecology Research, 2002Co-Authors: Karen D. Mccoy, Thierry Boulinier, Solveig Schjorring, Yanis MichalakisAbstract:In addition to reproductive rates and generation times, local parasite adaptation is predicted to be associated with relative host/parasite migration rates, parasite virulence and local resource levels. We tested for local parasite adaptation in a spatially structured natural host-parasite system with fluctuating host resources. Using a cross-fostering design replicated over 2 years, we exchanged chicks of the Black-legged kittiwake (Rissa tridactyla) between subpopulations of its ectoparasite, the tick Ixodes uriae. We found evidence that ticks were adapted to their local hosts; ticks had higher success (capacity to continue to the next life stage) and shorter engorgement times on sympatric birds than on allopatric birds. However, infestation levels were similar between the resident and non-resident chicks in a nest, implying that ticks are unable to distinguish between good and bad hosts and that selection acts during tick engorgement. Hosts appeared to be locally maladapted to their parasites; growth rates tended to be lower for sympatric birds in the presence of parasites. However, we found no effect of host group on the T-cell immune response of chicks. Overall, the results seemed to depend on the environmental quality. When resources were low, local maladaptation was expressed in the host, but adaptation was not shown by the parasite. In the higher quality year, evidence for local parasite adaptation was found, but the host seemed to be able to compensate for the pathogenic effects of ticks. This suggests that virulence (pathogenic effect on host) and the reciprocal effects of the interaction can fluctuate depending on host environmental conditions.
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host specificity of a generalist parasite genetic evidence of sympatric host races in the seabird tick Ixodes uriae
Journal of Evolutionary Biology, 2001Co-Authors: Karen D. Mccoy, Claire Tirard, Thierry Boulinier, Yanis MichalakisAbstract:Due to the close association between parasites and their hosts, many ‘generalist’ parasites have a high potential to become specialized on different host species. We investigated this hypothesis for a common ectoparasite of seabirds, the tick Ixodes uriae that is often found in mixed host sites. We examined patterns of neutral genetic variation between ticks collected from Black-legged kittiwakes (Rissa tridactyla) and Atlantic puffins (Fratercula arctica) in sympatry. To control for a potential distance effect, values were compared to differences among ticks from the same host in nearby monospecific sites. As predicted, there was higher genetic differentiation between ticks from different sympatric host species than between ticks from nearby allopatric populations of the same host species. Patterns suggesting isolation by distance were found among tick populations of each host group, but no such patterns existed between tick populations of different hosts. Overall, results suggest that host-related selection pressures have led to the specialization of I. uriae and that host race formation may be an important diversifying mechanism in parasites.
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dispersal and distribution of the tick Ixodes uriae within and among seabird host populations the need for a population genetic approach
Journal of Parasitology, 1999Co-Authors: Karen D. Mccoy, Thierry Boulinier, John W Chardine, Etienne Danchin, Yanis MichalakisAbstract:The aim of this study was to characterize the spatial distribution of the tick Ixodes uriae within and among populations of its seabird hosts and to consider the potential insight that could be gained by a population genetic approach to the issue of dispersal of this tick. Analyses of data collected around the Avalon Peninsula, Newfoundland, indicated that both the prevalence and mean abundance of ticks varied significantly among sample locations. Whereas ticks were found on all 4 host species examined (Rissa tridactyla, Uria aalge, Alca torda, Fratercula arctica), infestation prevalence and mean abundance differed among the species. On R. tridactyla, ticks were significantly aggregated at the among-nest scale and nestling infestation was spatially autocorrelated. Conversely, ticks were not aggregated among chicks within nests. These results enabled us to make a priori predictions regarding tick dispersal and host specificity and suggest there may be spatial structure of Ixodes uriae populations at both macro- and microgeographic scales. Investigating the population genetic structure of ticks within and among populations of hosts with different breeding biologies should provide direct insight into the metapopulation dynamics of such a spatially structured system.
Bjorn R Olsen - One of the best experts on this subject based on the ideXlab platform.
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increased mortality of black browed albatross chicks at a colony heavily infested with the tick Ixodes uriae
International Journal for Parasitology, 1999Co-Authors: Sven Bergström, Paul D Haemig, Bjorn R OlsenAbstract:At Bird Island, South Georgia, we studied the effects of the tick Ixodes uriae on survival of chicks at two colonies of the black-browed albatross Diomedea melanophrys, one where most chicks were infested with ticks, the other where most chicks were tick-free. When the two colonies were compared, it was found that the colony heavily-infested with ticks had significantly greater chick mortality than the colony lightly-infested with ticks. However, within each of the two colonies, there was no significant difference in survival between chicks with ticks and those without ticks.
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distribution and abundance of the tick Ixodes uriae in a diverse subantarctic seabird community
Journal of Parasitology, 1999Co-Authors: Sven Bergström, Paul D Haemig, Bjorn R OlsenAbstract:At Bird Island, South Georgia, we surveyed the distribution and abundance of ticks on the vertebrate fauna and found only 1 species Ixodes uriae. We classified all seabird species into 3 groups: (1) seabirds nesting on the surface of the ground solitarily, in dispersed groups of a few nests, or in colonies with well-spaced nests; (2) seabirds nesting on the surface of the ground in dense colonies; and (3) seabirds nesting in dense colonies in burrows or rock crevices. We detected I. uriae only on 3 species of the second group that nested in large, dense, persistent colonies, i.e., black-browed albatross (Diomedea melanophrys), gray-headed albatross (Diomedea chrysostoma), and macaroni penguin (Eudyptes chrysolophus). Ticks were found on the undersides of the feet on albatrosses but not on the undersides of the feet on penguins. We hypothesize that the coarse pebble nests of penguins, combined with the fact that their young walk around more than albatross young, make the environment on the underside of penguin feet more harsh and hostile for ticks than the underside of albatross feet. Despite the great abundance of Antarctic fur seals (Arctocephalus gazella) on the island, we found no ticks on them.
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research note increased mortality of black browed albatross chicks at a colony heavily infested with the tick Ixodes uriae
1999Co-Authors: Paul D Haemig, Bjorn R OlsenAbstract:At Bird Island, South Georgia, we studied the eAects of the tick Ixodes uriae on survival of chicks at two colonies of the black-browed albatross Diomedea melanophrys, one where most chicks were infested with ticks, the other where most chicks were tick-free. When the two colonies were compared, it was found that the colony heavilyinfested with ticks had significantly greater chick mortality than the colony lightly-infested with ticks. However, within each of the two colonies, there was no significant diAerence in survival between chicks with ticks and those without ticks. # 1999 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.
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survival and mortality of grey headed albatross chicks in relation to infestation by the tick Ixodes uriae
Colonial Waterbirds, 1998Co-Authors: Paul D Haemig, Sven Bergström, Bjorn R OlsenAbstract:On Bird Island, South Georgia, we studied infestation by the tick Ixodes uriae on chicks of the Grey-headed Albatross (Diomedea chrysostoma). Our investigation found no significant difference in survival between infested and uninfested chicks.
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a lyme borreliosis cycle in seabirds and Ixodes uriae ticks
Nature, 1993Co-Authors: Bjorn R Olsen, Jonas Bunikis, Thomas G T Jaenson, Laila Noppa, Sven BergströmAbstract:The Lyme disease spirochaete, Borrelia burgdorferi s.l., is the only Borrelia known to infect both mammals and birds. The main vertebrate reservoirs of B. burgdorferi are thought to be various small and intermediate size mammals, but the importance of birds as a reservoir has not been thoroughly explored. In the Northern and Southern Hemispheres the seabird tick, Ixodes uriae, is prevalent and closely associated with many species of colony-nesting marine birds. Here we report the presence of spirochaetes, demonstrated by immunofluorescent assay, by polymerase chain reaction and in culture, in I. uriae infesting razorbills on an island in the Baltic Sea. This island is free from mammals. The protein profile of the spirochaetes and the sequences of their flagellin and ospA genes are identical to those of the Lyme disease spirochaete, Borrelia burgdorferi s.l., previously isolated from I. ricinus on a nearby island. In biopsies from the foot web of razorbills, B. burgdorferi-specific DNA was detected after amplification by polymerase chain reaction. Our results suggest that birds play an important part in the maintenance of B. burgdorferi and that mammals may not be a prerequisite for its life cycle.
