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Parasite System (parasite + system)

Distribution by Scientific Domains

Life Sciences	78%

Distribution within Life Sciences

Evolution	39%
Conservation Science	12%

Selected Abstracts

DIRECT AND CORRELATED RESPONSES TO SELECTION IN A HOST,PARASITE SYSTEM: TESTING FOR THE EMERGENCE OF GENOTYPE SPECIFICITY

EVOLUTION, Issue 8 2007
Thibault Nidelet
Genotype × environment interactions can facilitate coexistence of locally adapted specialists. Interactions evolve if adaptation to one environment trades off with performance in others. We investigated whether evolution on one host genotype traded off with performance on others in long-term experimental populations of different genotypes of the protozoan Paramecium caudatum, infected with the bacterial parasite Holospora undulata. A total of nine parasite selection lines evolving on three host genotypes and the ancestral parasite were tested in a cross-infection experiment. We found that evolved parasites produced more infections than did the ancestral parasites, both on host genotypes they had evolved on (positive direct response to selection) and on genotypes they had not evolved on (positive correlated response to selection). On two host genotypes, a negative relationship between direct and correlated responses indicated pleiotropic costs of adaptation. On the third, a positive relationship suggested cost-free adaptation. Nonetheless, on all three hosts, resident parasites tended to be superior to the average nonresident parasite. Thus genotype specificity (i.e., patterns of local adaptation) may evolve without costs of adaptation, as long as direct responses to selection exceed correlated responses. [source]

Effects of Human Exclusion on Parasitism in Intertidal Food Webs of Central Chile

CONSERVATION BIOLOGY, Issue 1 2005
GÉRALDINE LOOT
Fissurella crassa; intermareal rocoso; parasitismo; Proctoeces lintoni; reservas marinas Abstract:,Numerous ecological studies have demonstrated the dramatic effects that humans have on coastal marine ecosystems. Consequently, marine reserves have been established to preserve biodiversity. Recent reviews show that this strategy has paid off because inside reserves, most species have rapidly increased in size and abundance. Even though these studies focused on free-living organisms and paid little attention to parasite populations, numerous authors support the hypothesis that parasitism levels could be good indicators of ecosystem stability. We examined harvesting effects on the dynamics of a parasitic trematode ( Proctoeces lintoni) that completes its life cycle in intertidal mussels ( Perumytilus purpuratus), keyhole limpets (Fissurella crassa), and clingfish ( Sicyases sanguineus). All of these species are directly or indirectly affected by humans. Prevalence and abundance of the trematode P. lintoni in the three host species were compared in four study sites that differed in the intensity of human harvest. Parasitism infection in limpets and mussels was significantly higher in areas protected from human harvesting than in open-access areas, which suggests a significant change in parasite dynamics inside reserves. Yet the average parasitic biomass found in the gonads of F. crassa did not differ between protected and open-access areas. These results show, then, that the parasite system responded by increasing infection rates in marine protected areas without implication for reproductive success of the intermediate host. Our findings show that the indirect effects of harvesting by humans on the embedded parasite communities of littoral ecosystems require further scientific investigation. Resumen:,Numerosos estudios ecológicos han demostrado los efectos dramáticos de la actividad humana sobre ecosistemas marinos costeros. Consecuentemente, se han establecido las reservas marinas para preservar la biodiversidad. Revisiones recientes muestran que esta estrategia es adecuada porque la mayoría de las especies dentro de las reservas han incrementado en tamaño y abundancia rápidamente. Aunque, estos estudios se han concentrado en organismos de vida libre y han puesto poca atención a poblaciones de parásitos, numerosos autores apoyan la hipótesis de que los niveles de parasitismo pueden ser buenos indicadores de la estabilidad del ecosistema. Examinamos los efectos de pesquería artesanal sobre la dinámica de un trematodo parásito ( Proctoeces lintoni) que completa su ciclo de vida en mitíldos intermareales ( Perumytilus purpuratus), lapas ( Fissurella crassa) y Sicyases sanguineus, los cuales son afectados por humanos directa o indirectamente. La prevalencia y abundancia del trematodo P. lintoni en las tres especies de hospedadores fueron comparadas en cuatro sitios de estudio que difieren en la intensidad de recolecta por humanos. La infección parasitaria en lapas y mitíldos fue significativamente mayor en áreas protegidas que en áreas de libre acceso, lo que sugiere un cambio significativo en la dinámica del parásito dentro de las reservas, pero, la biomasa promedio de parásitos en gónadas de F. crassa no fue diferente entre áreas protegidas y de libre acceso. Por lo tanto, los resultados muestran que el sistema parásito respondió incrementando tasas de infección en áreas marinas protegidas sin consecuencias sobre el éxito reproductivo del ho spedador intermediario. Nuestros hallazgos muestran que se requiere más investigación científica de los efectos indirectos de los humanos sobre las comunidades de parásitos en ecosistemas litorales. [source]

Associations between host migration and the prevalence of a protozoan parasite in natural populations of adult monarch butterflies

ECOLOGICAL ENTOMOLOGY, Issue 2 2000
Sonia M. Altizer
Summary 1. Monarch butterflies Danaus plexippus (L.) (Lepidoptera: Nymphalidae) are susceptible to infection by the obligate protozoan parasite Ophryocystis elektroscirrha (McLaughlin and Myers) (Apicomplexa: Neogregarinida). Because monarchs form resident and migratory populations in different parts of the world, this host,parasite system provides the opportunity to examine how variation in parasite prevalence relates to host movement patterns. 2. Parasite prevalence was evaluated using 14 790 adult monarchs captured between 1968 and 1997. Comparison of three populations in North America indicated that parasite prevalence is associated negatively with host dispersal distances. A continuously breeding, nonmigratory population in southern Florida showed high prevalence (over 70% heavily infected). The western population migrates moderate distances to overwintering sites on the Pacific Coast and has intermediate prevalence (30% heavily infected). The eastern migratory population, which travels the longest distance to Mexican overwintering sites, has exhibited less than 8% infection throughout the past 30 years. 3. Variation in parasite loads within North American migratory populations was investigated to determine whether the prevalence of heavy infection and average parasite loads declined during migration or overwintering. Average parasite loads of summer-breeding adults in western North America decreased with increasing distance from overwintering sites. This suggests that heavily infected monarchs are less likely to remigrate long distances in spring. No differences in the frequency of heavily infected adults were found among eastern or western North American monarchs throughout the overwintering period, however, suggesting that this parasite does not affect overwintering mortality. 4. Changes in the prevalence of monarchs with low parasite loads demonstrate that spore transfer occurs during migration and overwintering, possibly when adult butterflies contact each other as a result of their clustering behaviour. 5. This study of geographical and temporal variation in O. elektroscirrha among populations of D. plexippus demonstrates the potential role of seasonal migration in mediating interactions between hosts and parasites, and suggests several mechanisms through which migratory behaviour may influence parasite prevalence. [source]

Temperature checks the Red Queen?

ECOLOGY LETTERS, Issue 1 2003
Resistance, virulence in a fluctuating environment
Abstract Numerous studies have revealed genetic variation in resistance and susceptibility in host,parasite interactions and therefore the potential for frequency-dependent selection (Red Queen dynamics). Few studies, if any, have considered the abiotic environment as a mediating factor in these interactions. Using the pea aphid, Acyrthosiphon pisum, and its fungal pathogen, Erynia neoaphidis, as a model host,parasite system, we demonstrate how temperature can mediate the expression of genotypic variation for susceptibility and virulence. Whilst previous studies have revealed among-clone variation in aphid resistance to this pathogen, we show that resistance rankings derived from assessments at one temperature, are not conserved across differing temperature regimes. We suggest that variation in environmental temperature, through its nonlinear impact on parasite virulence and host defence, may contribute to the general lack of evidence for frequency-dependent selection in field systems. [source]

Multiple species of the dinophagous dinoflagellate genus Amoebophrya infect the same host species

ENVIRONMENTAL MICROBIOLOGY, Issue 11 2003
Paulo S. Salomon
Summary Populations of the dinoflagellate Dinophysis norvegica in the Baltic Sea and in the adjacent North Sea are infected by the endoparasite Amoebophrya sp. The high diversity recently unveiled within the genus Amoebophrya brings uncertainty about their identities. We applied molecular biology techniques , 18S rDNA sequencing and fluorescent in situ hybridization (FISH) , to compare this host,parasite system from both environments. The North Sea Amoebophrya sp. 18S rDNA sequence was 89% identical to the previously described Baltic Sea Amoebophrya sp. sequence, suggesting they are different species. In spite of that, a phylogenetical analysis placed the North Sea parasite sequence in a well-supported cluster with other Amoebophrya sp. sequences. The D. norvegica 18S rDNA sequences from both environments were 100% identical, indicating that the hosts have not evolved independently. A DNA probe designed for the Baltic Sea Amoebophrya sp. 18S rRNA was used in FISH assays on infected D. norvegica populations from both environments. The probe stained all infected cells from the Baltic sample, whereas none from the North Sea were stained. The results indicate that D. norvegica is released from one parasite when entering the Baltic Sea, and become less infected by an alternative parasite species. [source]

Host sex and ectoparasites choice: preference for, and higher survival on female hosts

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2007
PHILIPPE CHRISTE
Summary 1Sex differences in levels of parasite infection are a common rule in a wide range of mammals, with males usually more susceptible than females. Sex-specific exposure to parasites, e.g. mediated through distinct modes of social aggregation between and within genders, as well as negative relationships between androgen levels and immune defences are thought to play a major role in this pattern. 2Reproductive female bats live in close association within clusters at maternity roosts, whereas nonbreeding females and males generally occupy solitary roosts. Bats represent therefore an ideal model to study the consequences of sex-specific social and spatial aggregation on parasites' infection strategies. 3We first compared prevalence and parasite intensities in a host,parasite system comprising closely related species of ectoparasitic mites (Spinturnix spp.) and their hosts, five European bat species. We then compared the level of parasitism between juvenile males and females in mixed colonies of greater and lesser mouse-eared bats Myotis myotis and M. blythii. Prevalence was higher in adult females than in adult males stemming from colonial aggregations in all five studied species. Parasite intensity was significantly higher in females in three of the five species studied. No difference in prevalence and mite numbers was found between male and female juveniles in colonial roosts. 4To assess whether observed sex-biased parasitism results from differences in host exposure only, or, alternatively, from an active, selected choice made by the parasite, we performed lab experiments on short-term preferences and long-term survival of parasites on male and female Myotis daubentoni. When confronted with adult males and females, parasites preferentially selected female hosts, whereas no choice differences were observed between adult females and subadult males. Finally, we found significantly higher parasite survival on adult females compared with adult males. 5Our study shows that social and spatial aggregation favours sex-biased parasitism that could be a mere consequence of an active and adaptive parasite choice for the more profitable host. [source]

Not everything is everywhere: the distance decay of similarity in a marine host,parasite system

JOURNAL OF BIOGEOGRAPHY, Issue 2 2009
Ana Pérez-del-Olmo
Abstract Aim, We test the similarity,distance decay hypothesis on a marine host,parasite system, inferring the relationships from abundance data gathered at the lowest scale of parasite community organization (i.e. that of the individual host). Location, Twenty-two seasonal samples of the bogue Boops boops (Teleostei: Sparidae) were collected at seven localities along a coastal positional gradient from the northern North-East Atlantic to the northern Mediterranean coast of Spain. Methods, We used our own, taxonomically consistent, data on parasite communities. The variations in parasite composition and structure with geographical and regional distance were examined at two spatial scales, namely local parasite faunas and component communities, using both presence,absence (neighbour joining distance) and abundance (Mahalanobis distance) data. The influence of geographical and regional distance on faunal/community divergence was assessed through the permutation of distance matrices. Results, Our results revealed that: (1) geographical and regional distances do not affect the species composition in the system under study at the higher scales; (2) geographical distance between localities contributes significantly to the decay of similarity estimated from parasite abundance at the lowest scale (i.e. the individual host); (3) the structured spatial patterns are consistent in time but not across seasons; and (4) a restricted clade of species (the ,core' species of the bogue parasite fauna) contributes substantially to the observed patterns of both community homogenization and differentiation owing to the strong relationship between local abundance and regional distribution of species. Main conclusions, The main factors that tend to homogenize the composition of parasite communities of bogue at higher regional scales are related to the dispersal of parasite colonizers across host populations, which we denote as horizontal neighbourhood colonization. In contrast, the spatial structure detectable in quantitative comparisons only, is related to a vertical neighbourhood colonization associated with larval dispersal on a local level. The stronger decline with distance in the spatial synchrony of the assemblages of the ,core' species indicates a close-echoing environmental synchrony that declines with distance. Our results emphasize the importance of the parasite supracommunity (i.e. parasites that exploit all hosts in the ecosystem) to the decay of similarity with distance. [source]

Local co-adaptation leading to a geographical mosaic of coevolution in a social parasite system

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2004
B. Fischer
Abstract The geographical mosaic theory of coevolution predicts differences in the advance or trajectory of the coevolutionary process between local communities due to their composition and the strength of ecological selection pressures through competition and resource availability. In this study, we investigate local co-adaptation in different populations of a social parasite. We conducted cross-fostering experiments to test for interpopulational differences in raiding efficiency between various populations of a slave-making ant and the defence abilities of local hosts. Here, we demonstrate that the success of raids strongly depends on the combination of populations of the parasite Harpagoxenus sublaevis and its host Leptothorax acervorum, indicating very localized coevolution. We found no absolute differences between slave-maker populations; the outcome of an encounter depended more on whether the two opponents occur in sympatry or allopatry. Furthermore, this study supports the results of our earlier work, that the unparasitized English L. acervorum population is most aggressive against the parasite. [source]

Risk of ectoparasitism and genetic diversity in a wild lesser kestrel population

MOLECULAR ECOLOGY, Issue 17 2007
JOAQUÍN ORTEGO
Abstract Parasites and infectious diseases are major determinants of population dynamics and adaptive processes, imposing fitness costs to their hosts and promoting genetic variation in natural populations. In the present study, we evaluate the role of individual genetic diversity on risk of parasitism by feather lice Degeeriella rufa in a wild lesser kestrel population (Falco naumanni). Genetic diversity at 11 microsatellite loci was associated with risk of parasitism by feather lice, with more heterozygous individuals being less likely to be parasitized, and this effect was statistically independent of other nongenetic parameters (colony size, sex, location, and year) which were also associated with lice prevalence. This relationship was nonlinear, with low and consistent prevalences among individuals showing high levels of genetic diversity that increased markedly at low levels of individual heterozygosity. This result appeared to reflect a genome-wide effect, with no single locus contributing disproportionably to the observed effect. Thus, overall genetic variation, rather than linkage of markers to genes experiencing single-locus heterosis, seems to be the underlying mechanism determining the association between risk of parasitism and individual genetic diversity in the study host,parasite system. However, feather lice burden was not affected by individual heterozygosity; what suggest that differences in susceptibility, rather than variation in defences once the parasite has been established, may shape the observed pattern. Overall, our results highlight the role of individual genetic diversity on risk of parasitism in wild populations, what has both important evolutionary implications and major consequences for conservation research on the light of emerging infectious diseases that may endanger genetically depauperated populations. [source]

Coevolution of daily activity timing in a host,parasite system

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009
IRENE ORTOLANI
Coevolutionary theories applied in the study of host,parasite systems indicate that lineages exhibit progressive trends in response to reciprocal selective pressures. Avian brood parasites have generated intense interest as models for coevolutionary processes. Similar to avian cuckoos, Polistes wasp social parasites usurp a nest and exploit the parental care of a congeneric species to rear their own brood. In the present study, we show a coevolutionary arms race in the daily activity pattern in a Polistes host,parasite pair. We measured the daily activity rate, in constant laboratory conditions, of both host and parasite females during the period in which nest usurpations occur. The parasites showed a hyperkinesis in the middle of the day. As the field observations suggested, this mid-day activity is used to perform host nest usurpation attempts. Timing the usurpations allows the parasite to maximize its usurpation attempts during daytime when the host defence is lower. A field comparison of host presence on the nest in two populations with different parasitism rates showed that populations under strong parasitic pressure exhibit timing counteradaptations to optimize nest defence. This study provides the first example of a mutual coadaptation in timing activity in a parasite,host system. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 399,405. [source]

Are there general rules governing parasite diversity?

DIVERSITY AND DISTRIBUTIONS, Issue 3 2007
Small mammalian hosts, gamasid mite assemblages
ABSTRACT Parasite biodiversity varies on several scales, and in particular among different host species. Previous attempts at finding relationships between host features and the diversity of the parasite assemblages they harbour have yielded inconsistent results, suggesting strongly that any patterns might be taxon-specific. Here, we examined the potential of three host characteristics (host body mass, basal metabolic rate, and area of the geographical range) as determinants of parasite diversity in one group of ectoparasites, gamasid mites (superfamily Dermanyssoidea), using data from 63 species of small mammalian hosts. Our analyses used three measures of parasite diversity (species richness, the Shannon diversity index, and average taxonomic distinctness), and controlled for sampling effort and phylogenetic influences. Although several significant relationships were observed, they depended entirely on which diversity measure was used, or on which host taxon was investigated (insectivores vs. rodents and lagomorphs). In addition, the present results on patterns of mite diversity were not consistent with those of an earlier study involving roughly the same host taxa and the same biogeographical area, but a different group of ectoparasites, i.e. fleas. Thus, there appears to be no universal determinant of parasite diversity, and associations between host features and parasite diversity probably evolve independently in different host,parasite systems. [source]

Low level of cuticular hydrocarbons in a parasitoid of a solitary digger wasp and its potential for concealment

ENTOMOLOGICAL SCIENCE, Issue 1 2009
Johannes KROISS
Abstract Insect cuticular hydrocarbons (CHC) play a role as semiochemicals in many host,parasite systems and chemical mimicry or camouflage is a well-known mechanism of parasites to evade detection by the host. The cuckoo wasp Hedychrum rutilans (Hymenoptera, Chrysididae) is a parasitoid of larvae of the European beewolf Philanthus triangulum (Hymenoptera, Crabronidae). Females chemically mimic the cuticular hydrocarbons of their hosts to avoid detection and countermeasures when entering the host nest for oviposition. Here we report on a possible second mechanism of the chrysidid wasp H. rutilans to evade detection: the amount of CHC/mm2 of cuticle is only approximately one-fifth compared to its beewolf host. Furthermore, we show that surprisingly large amounts of CHC of beewolf females can be found on the walls of the underground nest. Potentially, these hydrocarbons might constitute a background odor against which the cuckoo wasps or their chemical traces have to be perceived by the beewolf. The reduction in the amount of CHC of the cuckoo wasps might be equivalent to a dilution of recognition cues, especially against the background odor of the nest walls, and might provide a means to escape detection within the nest due to "chemical insignificance". [source]

Can vertebrate predation alter aggregation of risk in an insect host,parasitoid system?

JOURNAL OF ANIMAL ECOLOGY, Issue 3 2002
William F. Fagan
Summary 1,Insect host,parasite systems allow investigations of the trophodynamics of ecological communities within a well-formed theoretical context. A little explored feature of such systems involves the interplay between generalized consumers and host,parasitoid dynamics. I report a study investigating how the impacts of generalized consumers, viewed here as interaction modifications, may influence the stability of a particular interspecific interaction. 2,In a study involving overwintering oothecae of the praying mantis Stagmomantis limbata (Hahn), birds damaged 36% of oothecae, 85% of which had also been parasitized by winter-active, multivoltine torymid wasps of the genus Podagrion. Birds preferentially preyed upon oothecae oviposited high on trees, but such predation was often incomplete, leaving both viable and parasitized mantid eggs inside damaged oothecae. 3,Two factors allowed bird damage to influence the distribution of risk of parasitism among oothecae and among hosts. These were (1) that some parasites , but no mantids , emerged successfully prior to bird predation and (2) that extensive post-damage foraging by parasitoids occurred, but that the nature of this foraging was altered little by oothecal damage. 4,In all, bird damage engendered a fourfold increase (from 1·5 to 6·5) in the CV2 of parasitism risk among hosts (a stability criterion that has been proposed for host,parasitoid interactions) and increased the relative importance of host-density-dependent parasitism. The role of timing of the two natural enemy impacts for stability of the host,parasitoid interaction is discussed. [source]

A macroevolutionary mosaic: episodic host-switching, geographical colonization and diversification in complex host,parasite systems

JOURNAL OF BIOGEOGRAPHY, Issue 9 2008
Eric P. Hoberg
Abstract Aim, To integrate ecological fitting, the oscillation hypothesis and the taxon pulse hypothesis into a coherent null model for the evolution of complex host,parasite associations. Location, Global. Methods, This paper reviews and synthesizes literature that focuses on phylogenetic analyses and reciprocal mapping of a model system of hosts and their parasites to determine patterns of host,parasite associations and geographical distributions through time. Results, Host-switching and geographical dispersal of parasites are common phenomena, occurring on many temporal and spatial scales. Diversification involving both co-evolution and colonization explains complex host,parasite associations. Across the expanse of Earth history, the major radiations in host,parasite assemblages have been preceded by ecological disruption, ecological breakdown and host-switching in a context that can be defined by the concept of ecological fitting. This cyclical process sets the stage for co-diversification during periods of relative stability, punctuated by host-switching during episodes of regional to global environmental disruption and climatological change. Main conclusions, Most observed host,parasite associations can be explained by an historical interaction between ecological fitting, oscillation (episodes of increasing host range alternating with isolation on particular hosts) and taxon pulses (cyclical episodes of expansion and isolation in geographical range). Major episodes of environmental change appear to be the main drivers for both the persistence and diversification of host,parasite systems, creating opportunities for host-switching during periods of geographical expansion and allowing for co-evolution and co-speciation during periods of geographical isolation. [source]

Alternative parasite development in transmission strategies: how time flies!

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 10 2010
M. BADETS
Abstract Among parasitic platyhelminths with complex life cycles, it has been well documented that transmission opportunities are the main forces shaping the diversity of life-history traits and parasite developmental strategies. While deviations in the development pathway usually involve shortening of life cycles, their extension may also occur following perception of remaining time by parasites. Polystoma gallieni, the monogenean parasite of Hyla meridionalis, is able to trigger two alternative developmental strategies depending on the physiological stage of the tadpoles upon which larvae attach. The distribution and reproductive outputs of both resulting phenotypes were surveyed to address questions about the dynamics of transmission in natural environments. Because modifications in the completion of life cycles can have drawbacks which may perturb the dynamic equilibrium of the resulting host,parasite systems, experimental infestations were also performed to assess parasite,parasite interactions. Our results suggest that the bladder adult phenotype, which involves transmission between frogs and tadpoles, is supplied secondarily by the branchial phenotype which involves transmission between tadpoles and metamorphs. They also support the occurrence of finely tuned trade-offs between hosts and parasites and highlight positive trends behind the extension of direct life cycles, in which host-derived signals account for the remaining time to achieve parasitic transmission. [source]

Begging call matching between a specialist brood parasite and its host: a comparative approach to detect coevolution

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009
MICHAEL G. ANDERSON
Studies of avian brood parasite systems have typically investigated the mimicry of host eggs by specialist parasites. Yet, several examples of similarity between host and parasite chick appearance or begging calls suggest that the escalation of host,parasite arms races may also lead to visual or vocal mimicry at the nestling stage. Despite this, there have been no large-scale comparative studies of begging calls to test whether the similarity of host and parasite is greater than predicted by chance or phylogenetic distance within a geographically distinct species assemblage. Using a survey of the begging calls of all native forest passerines in New Zealand, we show that the begging call of the host-specialist shining cuckoo (Chrysococcyx lucidus) is most similar to that of its grey warbler (Gerygone igata) host compared to any of the other species, and that this is unlikely to have occurred by chance. Randomization tests revealed that the incorporation of the shining cuckoo's begging calls into our species-set consistently reduced the phylogenetic signal within cluster trees based on begging call similarity. By contrast, the removal of the grey warbler calls did not reduce the phylogenetic signal in the begging call similarity trees. These two results support a scenario in which coevolution of begging calls has not taken place: the begging call of the host retains its phylogenetic signal, whereas that of the parasite has changed to match that of its host. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 208,216. [source]