Articles de revues : « Spatial host population structure »

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Nair, Abhilash, Toby Fountain, Suvi Ikonen, Sami P. Ojanen et Saskya van Nouhuys. « Spatial and temporal genetic structure at the fourth trophic level in a fragmented landscape ». Proceedings of the Royal Society B : Biological Sciences 283, n^o 1831 (25 mai 2016) : 20160668. http://dx.doi.org/10.1098/rspb.2016.0668.

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A fragmented habitat becomes increasingly fragmented for species at higher trophic levels, such as parasitoids. To persist, these species are expected to possess life-history traits, such as high dispersal, that facilitate their ability to use resources that become scarce in fragmented landscapes. If a specialized parasitoid disperses widely to take advantage of a sparse host, then the parasitoid population should have lower genetic structure than the host. We investigated the temporal and spatial genetic structure of a hyperparasitoid (fourth trophic level) in a fragmented landscape over 50 × 70 km, using microsatellite markers, and compared it with the known structures of its host parasitoid, and the butterfly host which lives as a classic metapopulation. We found that population genetic structure decreases with increasing trophic level. The hyperparasitoid has fewer genetic clusters ( K = 4), than its host parasitoid ( K = 15), which in turn is less structured than the host butterfly ( K = 27). The genetic structure of the hyperparasitoid also shows temporal variation, with genetic differentiation increasing due to reduction of the population size, which reduces the effective population size. Overall, our study confirms the idea that specialized species must be dispersive to use a fragmented host resource, but that this adaptation has limits.

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Nair, Abhilash, Etsuko Nonaka et Saskya van Nouhuys. « Increased fluctuation in a butterfly metapopulation leads to diploid males and decline of a hyperparasitoid ». Proceedings of the Royal Society B : Biological Sciences 285, n^o 1885 (22 août 2018) : 20180372. http://dx.doi.org/10.1098/rspb.2018.0372.

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Climate change can increase spatial synchrony of population dynamics, leading to large-scale fluctuation that destabilizes communities. High trophic level species such as parasitoids are disproportionally affected because they depend on unstable resources. Most parasitoid wasps have complementary sex determination, producing sterile males when inbred, which can theoretically lead to population extinction via the diploid male vortex (DMV). We examined this process empirically using a hyperparasitoid population inhabiting a spatially structured host population in a large fragmented landscape. Over four years of high host butterfly metapopulation fluctuation, diploid male production by the wasp increased, and effective population size declined precipitously. Our multitrophic spatially structured model shows that host population fluctuation can cause local extinctions of the hyperparasitoid because of the DMV. However, regionally it persists because spatial structure allows for efficient local genetic rescue via balancing selection for rare alleles carried by immigrants. This is, to our knowledge, the first empirically based study of the possibility of the DMV in a natural host–parasitoid system.

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Lion, S., et S. Gandon. « Spatial evolutionary epidemiology of spreading epidemics ». Proceedings of the Royal Society B : Biological Sciences 283, n^o 1841 (26 octobre 2016) : 20161170. http://dx.doi.org/10.1098/rspb.2016.1170.

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Most spatial models of host–parasite interactions either neglect the possibility of pathogen evolution or consider that this process is slow enough for epidemiological dynamics to reach an equilibrium on a fast timescale. Here, we propose a novel approach to jointly model the epidemiological and evolutionary dynamics of spatially structured host and pathogen populations. Starting from a multi-strain epidemiological model, we use a combination of spatial moment equations and quantitative genetics to analyse the dynamics of mean transmission and virulence in the population. A key insight of our approach is that, even in the absence of long-term evolutionary consequences, spatial structure can affect the short-term evolution of pathogens because of the build-up of spatial differentiation in mean virulence. We show that spatial differentiation is driven by a balance between epidemiological and genetic effects, and this quantity is related to the effect of kin competition discussed in previous studies of parasite evolution in spatially structured host populations. Our analysis can be used to understand and predict the transient evolutionary dynamics of pathogens and the emergence of spatial patterns of phenotypic variation.

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Koop, Jennifer A. H., Karen E. DeMatteo, Patricia G. Parker et Noah K. Whiteman. « Birds are islands for parasites ». Biology Letters 10, n^o 8 (août 2014) : 20140255. http://dx.doi.org/10.1098/rsbl.2014.0255.

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Understanding the mechanisms driving the extraordinary diversification of parasites is a major challenge in evolutionary biology. Co-speciation, one proposed mechanism that could contribute to this diversity is hypothesized to result from allopatric co-divergence of host–parasite populations. We found that island populations of the Galápagos hawk ( Buteo galapagoensis ) and a parasitic feather louse species ( Degeeriella regalis ) exhibit patterns of co-divergence across variable temporal and spatial scales. Hawks and lice showed nearly identical population genetic structure across the Galápagos Islands. Hawk population genetic structure is explained by isolation by distance among islands. Louse population structure is best explained by hawk population structure, rather than isolation by distance per se , suggesting that lice tightly track the recent population histories of their hosts. Among hawk individuals, louse populations were also highly structured, suggesting that hosts serve as islands for parasites from an evolutionary perspective. Altogether, we found that host and parasite populations may have responded in the same manner to geographical isolation across spatial scales. Allopatric co-divergence is likely one important mechanism driving the diversification of parasites.

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Hancock, Penelope A., et H. Charles J. Godfray. « Modelling the spread of Wolbachia in spatially heterogeneous environments ». Journal of The Royal Society Interface 9, n^o 76 (6 juin 2012) : 3045–54. http://dx.doi.org/10.1098/rsif.2012.0253.

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The endosymbiont Wolbachia infects a large number of insect species and is capable of rapid spread when introduced into a novel host population. The bacteria spread by manipulating their hosts' reproduction, and their dynamics are influenced by the demographic structure of the host population and patterns of contact between individuals. Reaction–diffusion models of the spatial spread of Wolbachia provide a simple analytical description of their spatial dynamics but do not account for significant details of host population dynamics. We develop a metapopulation model describing the spatial dynamics of Wolbachia in an age-structured host insect population regulated by juvenile density-dependent competition. The model produces similar dynamics to the reaction–diffusion model in the limiting case where the host's habitat quality is spatially homogeneous and Wolbachia has a small effect on host fitness. When habitat quality varies spatially, Wolbachia spread is usually much slower, and the conditions necessary for local invasion are strongly affected by immigration of insects from surrounding regions. Spread is most difficult when variation in habitat quality is spatially correlated. The results show that spatial variation in the density-dependent competition experienced by juvenile host insects can strongly affect the spread of Wolbachia infections, which is important to the use of Wolbachia to control insect vectors of human disease and other pests.

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Best, Alex, Steve Webb, Andy White et Mike Boots. « Host resistance and coevolution in spatially structured populations ». Proceedings of the Royal Society B : Biological Sciences 278, n^o 1715 (8 décembre 2010) : 2216–22. http://dx.doi.org/10.1098/rspb.2010.1978.

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Natural, agricultural and human populations are structured, with a proportion of interactions occurring locally or within social groups rather than at random. This within-population spatial and social structure is important to the evolution of parasites but little attention has been paid to how spatial structure affects the evolution of host resistance, and as a consequence the coevolutionary outcome. We examine the evolution of resistance across a range of mixing patterns using an approximate mathematical model and stochastic simulations. As reproduction becomes increasingly local, hosts are always selected to increase resistance. More localized transmission also selects for higher resistance, but only if reproduction is also predominantly local. If the hosts disperse, lower resistance evolves as transmission becomes more local. These effects can be understood as a combination of genetic (kin) and ecological structuring on individual fitness. When hosts and parasites coevolve, local interactions select for hosts with high defence and parasites with low transmissibility and virulence. Crucially, this means that more population mixing may lead to the evolution of both fast-transmitting highly virulent parasites and reduced resistance in the host.

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Dang, Binh Thuy, Oanh Thi Truong, Sang Quang Tran et Henrik Glenner. « Comparative population genetics of swimming crab host (Portunus pelagicus) and common symbiotic barnacle (Octolasmis angulata) in Vietnam ». PeerJ 9 (7 juillet 2021) : e11671. http://dx.doi.org/10.7717/peerj.11671.

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Background By comparing spatial geographical structures of host populations with that of their symbionts light can be shed on their biological interactions, and the degree of congruence between host and symbiont phylogeographies should reflect their life histories and especially dispersal mechanisms. Methods Here, we analyzed the genetic diversity and structure of a host, the blue swimming crab, Portunus pelagicus, and its symbiotic pedunculate barnacle Octolasmis angulata from six location sites representing three geographic regions (north, central and south) along the Vietnam coastline. High levels of congruence in their phylogeographic patterns were expected as they both undergo planktonic larval stages. Results Based on the COI mtDNA markers, O. angulata populations showed higher genetic diversity in comparison with their host P. pelagicus (number of haplotype/individuals, haplotype and nucleotide diversity are 119/192, 0.991 ± 0.002 and 0.02; and 89/160, 0.913 ± 0.02 and 0.015, respectively). Pairwise Fst and AMOVA analyses showed a more pronounced population structure in the symbiotic barnacle than in its crab host. The DAPC analyses identified three genetic clusters. However, both haplotype networks and scatter plots supported connectivity of the host and the symbiotic barnacle throughout their distribution range, except for low subdivision of southern population. Isolation by distance were detected only for the symbiont O. angulata (R2 = 0.332, P = 0.05), while dbMEM supported spatial structure of both partners, but only at MEM-1 (Obs. 0.2686, P < 0.01 and Obs. 0.2096, P < 0.01, respectively).

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Buckee, Caroline, Leon Danon et Sunetra Gupta. « Host community structure and the maintenance of pathogen diversity ». Proceedings of the Royal Society B : Biological Sciences 274, n^o 1619 (15 mai 2007) : 1715–21. http://dx.doi.org/10.1098/rspb.2007.0415.

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Community structure has been widely identified as a feature of many real-world networks. It has been shown that the antigenic diversity of a pathogen population can be significantly affected by the contact network of its hosts; however, the effects of community structure have not yet been explored. Here, we examine the congruence between patterns of antigenic diversity in pathogen populations in neighbouring communities, using both a deterministic metapopulation model and individual-based formulations. We show that the spatial differentiation of the pathogen population can only be maintained at levels of coupling far lower than that necessary for the host populations to remain distinct. Therefore, identifiable community structure in host networks may not reflect differentiation of the processes occurring upon them and, conversely, a lack of genetic differentiation between pathogens from different host communities may not reflect strong mixing between them.

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Laine, Anna-Liisa, Jeremy J. Burdon, Adnane Nemri et Peter H. Thrall. « Host ecotype generates evolutionary and epidemiological divergence across a pathogen metapopulation ». Proceedings of the Royal Society B : Biological Sciences 281, n^o 1787 (22 juillet 2014) : 20140522. http://dx.doi.org/10.1098/rspb.2014.0522.

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The extent and speed at which pathogens adapt to host resistance varies considerably. This presents a challenge for predicting when—and where—pathogen evolution may occur. While gene flow and spatially heterogeneous environments are recognized to be critical for the evolutionary potential of pathogen populations, we lack an understanding of how the two jointly shape coevolutionary trajectories between hosts and pathogens. The rust pathogen Melampsora lini infects two ecotypes of its host plant Linum marginale that occur in close proximity yet in distinct populations and habitats. In this study, we found that within-population epidemics were different between the two habitats. We then tested for pathogen local adaptation at host population and ecotype level in a reciprocal inoculation study. Even after controlling for the effect of spatial structure on infection outcome, we found strong evidence of pathogen adaptation at the host ecotype level. Moreover, sequence analysis of two pathogen infectivity loci revealed strong genetic differentiation by host ecotype but not by distance. Hence, environmental variation can be a key determinant of pathogen population genetic structure and coevolutionary dynamics and can generate strong asymmetry in infection risks through space.

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Real, Leslie A., et Roman Biek. « Spatial dynamics and genetics of infectious diseases on heterogeneous landscapes ». Journal of The Royal Society Interface 4, n^o 16 (8 mai 2007) : 935–48. http://dx.doi.org/10.1098/rsif.2007.1041.

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Explicit spatial analysis of infectious disease processes recognizes that host–pathogen interactions occur in specific locations at specific times and that often the nature, direction, intensity and outcome of these interactions depend upon the particular location and identity of both host and pathogen. Spatial context and geographical landscape contribute to the probability of initial disease establishment, direction and velocity of disease spread, the genetic organization of resistance and susceptibility, and the design of appropriate control and management strategies. In this paper, we review the manner in which the physical organization of the landscape has been shown to influence the population dynamics and spatial genetic structure of host–pathogen interactions, and how we might incorporate landscape architecture into spatially explicit population models of the infectious disease process to increase our ability to predict patterns of disease occurrence and optimally design vaccination and control policies.

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Gallagher, Molly, Christopher Brooke, Ruian Ke et Katia Koelle. « Causes and Consequences of Spatial Within-Host Viral Spread ». Viruses 10, n^o 11 (13 novembre 2018) : 627. http://dx.doi.org/10.3390/v10110627.

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The spread of viral pathogens both between and within hosts is inherently a spatial process. While the spatial aspects of viral spread at the epidemiological level have been increasingly well characterized, the spatial aspects of viral spread within infected hosts are still understudied. Here, with a focus on influenza A viruses (IAVs), we first review experimental studies that have shed light on the mechanisms and spatial dynamics of viral spread within hosts. These studies provide strong empirical evidence for highly localized IAV spread within hosts. Since mathematical and computational within-host models have been increasingly used to gain a quantitative understanding of observed viral dynamic patterns, we then review the (relatively few) computational modeling studies that have shed light on possible factors that structure the dynamics of spatial within-host IAV spread. These factors include the dispersal distance of virions, the localization of the immune response, and heterogeneity in host cell phenotypes across the respiratory tract. While informative, we find in these studies a striking absence of theoretical expectations of how spatial dynamics may impact the dynamics of viral populations. To mitigate this, we turn to the extensive ecological and evolutionary literature on range expansions to provide informed theoretical expectations. We find that factors such as the type of density dependence, the frequency of long-distance dispersal, specific life history characteristics, and the extent of spatial heterogeneity are critical factors affecting the speed of population spread and the genetic composition of spatially expanding populations. For each factor that we identified in the theoretical literature, we draw parallels to its analog in viral populations. We end by discussing current knowledge gaps related to the spatial component of within-host IAV spread and the potential for within-host spatial considerations to inform the development of disease control strategies.

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Nyabuga, F. N., H. D. Loxdale, D. G. Heckel et W. W. Weisser. « Coevolutionary fine-tuning : evidence for genetic tracking between a specialist wasp parasitoid and its aphid host in a dual metapopulation interaction ». Bulletin of Entomological Research 102, n^o 2 (27 septembre 2011) : 149–55. http://dx.doi.org/10.1017/s0007485311000496.

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AbstractIn the interaction between two ecologically-associated species, the population structure of one species may affect the population structure of the other. Here, we examine the population structures of the aphidMetopeurum fuscoviride, a specialist on tansyTanacetum vulgare, and its specialist primary hymenopterous parasitoidLysiphlebus hirticornis, both of which are characterized by multivoltine life histories and a classic metapopulation structure. Samples of the aphid host and the parasitoid were collected from eight sites in and around Jena, Germany, where both insect species co-occur, and then were genotyped using suites of polymorphic microsatellite markers. The host aphid was greatly differentiated in terms of its spatial population genetic patterning, while the parasitoid was, in comparison, only moderately differentiated. There was a positive Mantel test correlation between pairwise shared allele distance (DAS) of the host and parasitoid, i.e. if host subpopulation samples were more similar between two particular sites, so were the parasitoid subpopulation samples. We argue that while the differences in the levels of genetic differentiation are due to the differences in the biology of the species, the correlations between host and parasitoid are indicative of dependence of the parasitoid population structure on that of its aphid host. The parasitoid is genetically tracking behind the aphid host, as can be expected in a classic metapopulation structure where host persistence depends on a delay between host and parasitoid colonization of the patch. The results may also have relevance to the Red Queen hypothesis, whereupon in the ‘arms race’ between parasitoid and its host, the latter ‘attempts’ to evolve away from the former.

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St Pierre, Matthew J., Stephen D. Hendrix et Cassandra K. Lewis. « Dispersal ability and host-plant characteristics influence spatial population structure of monophagous beetles ». Ecological Entomology 30, n^o 1 (février 2005) : 105–15. http://dx.doi.org/10.1111/j.0307-6946.2005.00659.x.

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Fellous, Simon, Elsa Quillery, Alison B. Duncan et Oliver Kaltz. « Parasitic infection reduces dispersal of ciliate host ». Biology Letters 7, n^o 3 (20 octobre 2010) : 327–29. http://dx.doi.org/10.1098/rsbl.2010.0862.

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Parasitic infection can modify host mobility and consequently their dispersal capacity. We experimentally investigated this idea using the ciliate Paramecium caudatum and its bacterial parasite Holospora undulata . We compared the short-distance dispersal of infected and uninfected populations in interconnected microcosms. Infection reduced the proportion of hosts dispersing, with levels differing among host clones. Host populations with higher densities showed lower dispersal, possibly owing to social aggregation behaviour. Parasite isolates that depleted host populations most had the lowest impact on host dispersal. Parasite-induced modification of dispersal may have consequences for the spatial distribution of disease, host and parasite genetic population structure, and coevolution.

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Zhao, Mingli, Louis V. Plough, Donald C. Behringer, Jamie Bojko, Andrew S. Kough, Nathaniel W. Alper, Lan Xu et Eric J. Schott. « Cross-Hemispheric Genetic Diversity and Spatial Genetic Structure of Callinectes sapidus Reovirus 1 (CsRV1) ». Viruses 15, n^o 2 (18 février 2023) : 563. http://dx.doi.org/10.3390/v15020563.

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The movement of viruses in aquatic systems is rarely studied over large geographic scales. Oceanic currents, host migration, latitude-based variation in climate, and resulting changes in host life history are all potential drivers of virus connectivity, adaptation, and genetic structure. To expand our understanding of the genetic diversity of Callinectes sapidus reovirus 1 (CsRV1) across a broad spatial and host life history range of its blue crab host (Callinectes sapidus), we obtained 22 complete and 96 partial genomic sequences for CsRV1 strains from the US Atlantic coast, Gulf of Mexico, Caribbean Sea, and the Atlantic coast of South America. Phylogenetic analyses of CsRV1 genomes revealed that virus genotypes were divided into four major genogroups consistent with their host geographic origins. However, some CsRV1 sequences from the US mid-Atlantic shared high genetic similarity with the Gulf of Mexico genotypes, suggesting potential human-mediated movement of CsRV1 between the US mid-Atlantic and Gulf coasts. This study advances our understanding of how climate, coastal geography, host life history, and human activity drive patterns of genetic structure and diversity of viruses in marine animals and contributes to the capacity to infer broadscale host population connectivity in marine ecosystems from virus population genetic data.

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Latham, A. David M., et Robert Poulin. « Spatiotemporal heterogeneity in recruitment of larval parasites to shore crab intermediate hosts : the influence of shorebird definitive hosts ». Canadian Journal of Zoology 81, n^o 7 (1 juillet 2003) : 1282–91. http://dx.doi.org/10.1139/z03-118.

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Parasitism is a major biotic determinant of animal population dynamics and community structure. Temporal and spatial heterogeneity in parasitism is commonly observed in intermediate host populations. Understanding the causes of temporal and spatial variation in the recruitment of parasites is crucial if we are to manage host populations and animal communities effectively. Here, the temporal and spatial dynamics of Profilicollis antarcticus and Profilicollis novaezelandensis (Acanthocephala) infections in three species of shore crabs (Macrophthalmus hirtipes, Hemigrapsus edwardsii, and Hemigrapsus crenulatus) are examined in relation to the distribution and abundance of shorebird definitive hosts. Temporal patterns of infection were observed in M. hirtipes but not the other two species. Spatial heterogeneity in recruitment of acanthocephalan larvae to M. hirtipes and H. edwardsii populations was found both within and between locations. Weak evidence is found that infection levels in crab populations are related to the distribution and abundance of shorebird hosts both temporally and spatially. In this system, abiotic factors seem to be at least as important in determining how infection levels vary in time and space as the input of parasite eggs from bird definitive hosts.

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Montgomery, S. S. J., et W. I. Montgomery. « Spatial and temporal variation in the infracommunity structure of helminths of Apodemus sylvaticus(Rodentia : Muridae) ». Parasitology 98, n^o 1 (février 1989) : 145–50. http://dx.doi.org/10.1017/s0031182000059783.

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SummaryMean species richness and diversity of the helminth infracommunity of Apodemus sylvaticus in woodland areas of Co. Down, Northern Ireland, varied in time and space. Variation in infracommunity structure among individual hosts, however, always accounted for more than 60% of the variation in the data from different places or different times. Helminth species richness increased with increasing population density, the percentage of the host population 16 weeks old or older, and the proportion of the host population with animal material in their stomachs, at two sites monitored over 33 months. The basis for spatial variation in infracommunity structure is less certain but host dynamics and differences in diet are likely to play some role. It is concluded that analysis at the infracommunity level focuses closely on the potential for species interactions and overlap in resource utilization. Infracommunity structure, at least in the case of A. sylvaticus, varies markedly in time and space and between individual hosts. Such variation should not be ignored in comparative studies.

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Portanier, Elodie, Mathieu Garel, Sébastien Devillard, Jeanne Duhayer, Marie-Thérèse Poirel, Hélène Henri, Corinne Régis et al. « Does host socio-spatial behavior lead to a fine-scale spatial genetic structure in its associated parasites ? » Parasite 26 (2019) : 64. http://dx.doi.org/10.1051/parasite/2019062.

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Gastro-intestinal nematodes, especially Haemonchus contortus, are widespread pathogenic parasites of small ruminants. Studying their spatial genetic structure is as important as studying host genetic structure to fully understand host-parasite interactions and transmission patterns. For parasites having a simple life cycle (e.g., monoxenous parasites), gene flow and spatial genetic structure are expected to strongly rely on the socio-spatial behavior of their hosts. Based on five microsatellite loci, we tested this hypothesis for H. contortus sampled in a wild Mediterranean mouflon population (Ovis gmelini musimon × Ovis sp.) in which species- and environment-related characteristics have been found to generate socio-spatial units. We nevertheless found that their parasites had no spatial genetic structure, suggesting that mouflon behavior was not enough to limit parasite dispersal in this study area and/or that other ecological and biological factors were involved in this process, for example other hosts, the parasite life cycle, or the study area history.

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Andras, Jason P., Peter D. Fields et Dieter Ebert. « Spatial population genetic structure of a bacterial parasite in close coevolution with its host ». Molecular Ecology 27, n^o 6 (mars 2018) : 1371–84. http://dx.doi.org/10.1111/mec.14545.

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Stokke, Bård, Csaba Moskát, Arne Moksnes, Vítezslav Bicík et Eivin Røskaft. « Aggression to dummy cuckoos by potential European cuckoo hosts ». Behaviour 139, n^o 5 (2002) : 613–28. http://dx.doi.org/10.1163/15685390260136735.

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AbstractAggression directed by 53 potential host species towards a dummy of the parasitic common cuckoo, Cuculus canorus, was tested in relation to their breeding habitat, their suitability as a host and whether they were breeding in sympatry or not with the cuckoo. Host habitats were divided into three categories: (1) always breeding near trees, (2) some populations breeding near trees, others in open areas, and (3) always breeding in open areas. Each species was also placed in one of five categories according to their suitability as a cuckoo host. Strong support was found for predictions derived from the 'spatial habitat structure hypothesis', which argues that common cuckoos only breed in areas where they have access to vantage points in trees. Thus, species which have some populations breeding near trees and others breeding further from trees have a different cuckoo-host population dynamics than species that always breed near trees, or always breed in open areas. Aggression levels were highest among species regarded as being always suitable as hosts, and species which always breed near trees. However, populations breeding in sympatry with the cuckoo were more aggressive than allopatric populations, indicating the plasticity of aggressive behaviour. Adaptive behaviour in cuckoo hosts can be predicted from the 'spatial habitat structure hypothesis'.

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Sanchez, Juan Antonio, Michelangelo La-Spina, Pedro Guirao et Fernando Cánovas. « Inferring the population structure of Myzus persicae in diverse agroecosystems using microsatellite markers ». Bulletin of Entomological Research 103, n^o 4 (1 mars 2013) : 473–84. http://dx.doi.org/10.1017/s0007485313000059.

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AbstractDiverse agroecosystems offer phytophagous insects a wide choice of host plants. Myzus persicae is a polyphagous aphid common in moderate climates. During its life cycle it alternates between primary and secondary hosts. A spatial genetic population structure may arise due to environmental factors and reproduction modes. The aim of this work was to determine the spatial and temporal genetic population structure of M. persicae in relation to host plants and climatic conditions. For this, 923 individuals of M. persicae collected from six plant families between 2005 and 2008 in south-eastern Spain were genotyped for eight microsatellite loci. The population structure was inferred by neighbour-joining, analysis of molecular variance (AMOVA) and Bayesian analyses. Moderate polymorphism was observed for the eight loci in almost all the samples. No differences in the number of alleles were observed between primary and secondary hosts or between geographical areas. The proportion of unique genotypes found in the primary host was similar in the north (0.961 ± 0.036) and the south (0.987 ± 0.013), while in the secondary host it was higher in the north (0.801 ± 0.159) than in the south (0.318 ± 0.063). Heterozygosity excess and linkage disequilibrium suggest a high representation of obligate parthenogens in areas with warmer climate and in the secondary hosts. The FST-values pointed to no genetic differentiation of M. persicae on the different plant families. FST-values, AMOVA and Bayesian model-based cluster analyses pointed to a significant population structure that was related to primary and secondary hosts. Differences between primary and secondary hosts could be due to the overrepresentation of parthenogens on herbaceous plants.

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Roychoudhury, Pavitra, Neelima Shrestha, Valorie R. Wiss et Stephen M. Krone. « Fitness benefits of low infectivity in a spatially structured population of bacteriophages ». Proceedings of the Royal Society B : Biological Sciences 281, n^o 1774 (7 janvier 2014) : 20132563. http://dx.doi.org/10.1098/rspb.2013.2563.

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For a parasite evolving in a spatially structured environment, an evolutionarily advantageous strategy may be to reduce its transmission rate or infectivity. We demonstrate this empirically using bacteriophage (phage) from an evolution experiment where spatial structure was maintained over 550 phage generations on agar plates. We found that a single substitution in the major capsid protein led to slower adsorption of phage to host cells with no change in lysis time or burst size. Plaques formed by phage isolates containing this mutation were not only larger but also contained more phage per unit area. Using a spatially explicit, individual-based model, we showed that when there is a trade-off between adsorption and diffusion (i.e. less ‘sticky’ phage diffuse further), slow adsorption can maximize plaque size, plaque density and overall productivity. These findings suggest that less infective pathogens may have an advantage in spatially structured populations, even when well-mixed models predict that they will not.

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Eliopoulos, P. A., A. Kapranas, E. G. Givropoulou et I. C. W. Hardy. « Reproductive efficiency of the bethylid waspCephalonomia tarsalis:the influences of spatial structure and host density ». Bulletin of Entomological Research 107, n^o 2 (3 octobre 2016) : 139–47. http://dx.doi.org/10.1017/s0007485316000651.

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AbstractThe parasitoid waspCephalonomia tarsalis(Ashmead) (Hymenoptera: Bethylidae) is commonly present in stored product facilities. While beneficial, it does not provide a high degree of biological pest control against its host, the saw-toothed beetleOryzaephilus surinamensis(L.) (Coleoptera: Silvanidae). A candidate explanation for poor host population suppression is that adult females interfere with each other's foraging and reproductive behavior. We used simple laboratory microcosms to evaluate such mutual interference in terms of its overall effects on offspring production. We varied the density of the hosts and also the spatial structure of the environment, via the extent of population sub-division and the provision of different substrates. Production ofC. tarsalisoffspring was positively influenced by host density and by the isolation of females. With incomplete sub-division within microcosms offspring production was, in contrast, low and even zero. The provision of corrugated paper as a substrate enhanced offspring production and partially mitigated the effects of mutual interference. We recommend simple improvements to mass rearing practice and identify promising areas for further behavioral and chemical studies towards a better understanding of the mechanisms of mutual interference.

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Urabe, M., et M. Hinoue. « Component community dynamics of larval trematodes in the freshwater snail Semisulcospira nakasekoae in the Uji River, central Japan ». Journal of Helminthology 78, n^o 4 (décembre 2004) : 361–70. http://dx.doi.org/10.1079/joh2004250.

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AbstractThe component community of larval trematodes in the freshwater snail Semisulcospira nakasekoae (Caenogastropoda: Sorbeoconcha: Pleuroceridae) was surveyed over 13 months from April 1996 to April 1997 inclusive. Temporal and spatial fluctuation of trematode prevalence, the frequency of multiple infections, and the duration of cercarial shedding were examined as factors that might affect trematode community structure. The spatial prevalence of some species varied significantly, but the dynamics were too small to allow an explanation of the overall pattern. The prevalence of sanguinicolids fluctuated temporally, despite a stable size distribution in the host populations (> 6.0 mm shell width), suggesting the life-cycle phenology of this species. Some pairs of species had statistically positive associations, but no pairs had negative associations. This shows the importance of positive association possibly as a result of suppression of the host defensive response on trematode community structures in molluscan hosts. The length of the patent period, which is part of the persistent period, varied among trematode species, suggesting it to be one of the factors determining prevalence in the host population.

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DAVIDSON, R. S., G. MARION, P. C. L. WHITE et M. R. HUTCHINGS. « Use of host population reduction to control wildlife infection : rabbits and paratuberculosis ». Epidemiology and Infection 137, n^o 1 (18 avril 2008) : 131–38. http://dx.doi.org/10.1017/s0950268808000642.

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SUMMARYReduction in wildlife populations is a common method for the control of livestock infections which have wildlife hosts, but its success is dependent on the characteristics of the infection itself, as well as on the spatial and social structure of the wildlife host. Paratuberculosis (Mycobacterium avium subsp. paratuberculosis; Map) is a widespread and difficult infection to control in livestock populations and also has possible links to Crohn's disease in humans. Rabbits have recently been identified as a key wildlife species in terms of paratuberculosis persistence in the environment and risk to the wider host community, including cattle. Here we use a spatially explicit stochastic simulation model of Map dynamics in rabbit populations to quantify the effects of rabbit population control on infection persistence. The model parameters were estimated from empirical studies of rabbit population dynamics and rabbit-to-rabbit routes of Map transmission. Three rabbit control strategies were compared: single unrepeated population reductions based on removing individual animals; single unrepeated population reductions based on removal of entire social groups; and repeated annual population reductions based on removing individual animals. Unrealistically high rabbit culls (>95% population reduction) are needed if infection is to be eradicated from local rabbit populations with a single one-off population reduction event, either of individuals or social groups. Repeated annual culls are more effective at reducing the prevalence of infection in rabbit populations and eradicating infection. However, annual population reductions of >40% are required over extended periods of time (many years). Thus, using an approach which is both highly conservative and parsimonious with respect to estimating lower bounds on the time to eradicate the infection, we find that Map is extremely persistent in rabbit populations and requires significant and prolonged effort to achieve control.

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Garrett, K. A., et C. C. Mundt. « Epidemiology in Mixed Host Populations ». Phytopathology® 89, n^o 11 (novembre 1999) : 984–90. http://dx.doi.org/10.1094/phyto.1999.89.11.984.

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Although plant disease epidemiology has focused on populations in which all host plants have the same genotype, mixtures of host genotypes are more typical of natural populations and offer promising options for deployment of resistance genes in agriculture. In this review, we discuss Leonard's classic model of the effects of host genotype diversity on disease and its predictions of disease level based on the proportion of susceptible host tissue. As a refinement to Leonard's model, the spatial structure of host and pathogen population can be taken into account by considering factors such as autoinfection, interaction between host size and pathogen dispersal gradients, lesion expansion, and host carrying capacity for disease. The genetic composition of the host population also can be taken into account by considering differences in race-specific resistance among host genotypes, compensation, plant competition, and competitive interactions among pathogen genotypes. The magnitude of host-diversity effects for particular host-pathogen systems can be predicted by considering how the inherent characteristics of a system causes it to differ from the assumptions of the classic model. Because of the limited number of studies comparing host-diversity effects in different systems, it is difficult at this point to make more than qualitative predictions. Environmental conditions and management decisions also influence host-diversity effects on disease through their effect on factors such as host density and epidemic length and intensity.

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Cornwell, Brendan H., et Luis Hernández. « Genetic structure in the endosymbiont Breviolum ‘muscatinei’ is correlated with geographical location, environment and host species ». Proceedings of the Royal Society B : Biological Sciences 288, n^o 1946 (10 mars 2021) : 20202896. http://dx.doi.org/10.1098/rspb.2020.2896.

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Corals and cnidarians form symbioses with dinoflagellates across a wide range of habitats from the tropics to temperate zones. Notably, these partnerships create the foundation of coral reef ecosystems and are at risk of breaking down due to climate change. This symbiosis couples the fitness of the partners, where adaptations in one species can benefit the holobiont. However, the scales over which each partner can match their current—and future—environment are largely unknown. We investigated population genetic patterns of temperate anemones ( Anthopleura spp.) and their endosymbiont Breviolum ‘muscatinei’ , across an extensive geographical range to identify the spatial scales over which local adaptation is possible. Similar to previously published results, two solitary host species exhibited isolation by distance across hundreds of kilometres. However, symbionts exhibited genetic structure across multiple spatial scales, from geographical location to depth in the intertidal zone, and host species, suggesting that symbiont populations are more likely than their hosts to adaptively mitigate the impact of increasing temperatures.

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TULLY, O., et D. T. NOLAN. « A review of the population biology and host–parasite interactions of the sea louse Lepeophtheirus salmonis (Copepoda : Caligidae) ». Parasitology 124, n^o 7 (24 septembre 2002) : 165–82. http://dx.doi.org/10.1017/s0031182002001889.

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Lepeophtheirus salmonis is a specific parasite of salmonids that occurs in the Atlantic and Pacific Oceans. When infestations are heavy fish mortality can occur although the factors that are responsible for causing epizootics, especially in wild salmonid populations are still largely unknown. Over the past 20 years this parasite has caused significant economic losses in farmed salmon production and possibly in wild salmonid populations locally. Understanding the connectivity between populations is crucial to an understanding of the epidemiology of infections and for management of infections in aquaculture. Data from genetics, pesticide resistance, larval dispersal models and spatial and temporal patterns of infestation in wild and farmed hosts suggests a spatially highly structured metapopulation the components of which have different levels of connectivity, probabilities of extinction and influence on the development of local infestations. The population structure is defined mainly by the dispersal dynamics of the planktonic stages and the behaviour of the host.Until recently virtually nothing was known about the relationship between the parasite and the host, or how the host may influence lice at local or population level. Typically, impacts on the host have usually been reported in terms of pathological lesions caused by attachment and feeding of the adult stages, as well as localised mild epithelial responses to juvenile attachment. However many studies report pathology associated with severe infestation. Recent new studies on the host–parasite interactions of L. salmonis have shown that this parasite induces stress-related responses systemically in the host skin and gills and that the stress response and immune systems are modulated. In the second part of this review, these new studies are presented, together with results from other host–parasite model systems where data for caligid sea lice are missing. One of the most revealing methods reported recently is the application of a net confinement stressor to examine modulation of the stress response and immune system of the host fish. This approach has shown that although until now, infective stages of L. salmonis were not thought to affect the host, they do induce systematic effects in the host that result in a stress response and modulated immune system. Host–parasite interactions affecting these stress responses and the immune system may be key factors in facilitating epizootics by reducing the host's ability to reject the parasites, as well as reducing disease resistance under some environmental conditions. The host–parasite interaction therefore needs to be incorporated into any model of population structure and dynamics.

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Dawson, Daniel, David Rasmussen, Xinxia Peng et Cristina Lanzas. « Inferring environmental transmission using phylodynamics : a case-study using simulated evolution of an enteric pathogen ». Journal of The Royal Society Interface 18, n^o 179 (juin 2021) : 20210041. http://dx.doi.org/10.1098/rsif.2021.0041.

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Indirect (environmental) and direct (host–host) transmission pathways cannot easily be distinguished when they co-occur in epidemics, particularly when they occur on similar time scales. Phylodynamic reconstruction is a potential approach to this problem that combines epidemiological information (temporal, spatial information) with pathogen whole-genome sequencing data to infer transmission trees of epidemics. However, factors such as differences in mutation and transmission rates between host and non-host environments may obscure phylogenetic inference from these methods. In this study, we used a network-based transmission model that explicitly models pathogen evolution to simulate epidemics with both direct and indirect transmission. Epidemics were simulated according to factorial combinations of direct/indirect transmission proportions, host mutation rates and conditions of environmental pathogen growth. Transmission trees were then reconstructed using the phylodynamic approach SCOTTI (structured coalescent transmission tree inference) and evaluated. We found that although insufficient diversity sets a lower bound on when accurate phylodynamic inferences can be made, transmission routes and assumed pathogen lifestyle affected pathogen population structure and subsequently influenced both reconstruction success and the likelihood of direct versus indirect pathways being reconstructed. We conclude that prior knowledge of the likely ecology and population structure of pathogens in host and non-host environments is critical to fully using phylodynamic techniques.

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Laurin-Lemay, S., B. Angers, B. Benrey et J. Brodeur. « Inconsistent genetic structure among members of a multitrophic system : did bruchid parasitoids (Horismenusspp.) escape the effects of bean domestication ? » Bulletin of Entomological Research 103, n^o 2 (4 octobre 2012) : 182–92. http://dx.doi.org/10.1017/s000748531200051x.

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AbstractAnthropogenic range expansion and cultural practices have modified the distribution, abundance and genetic diversity of domesticated organisms, thereby altering multitrophic assemblages through space and time. The putative Mesoamerican domestication centre of the common bean,Phaseolus vulgarisL., in Mexico allows investigating the effects of plant domestication on the genetic structure of members of a multitrophic system. The aim of this study was to compare the evolutionary history ofHorismenusparasitoids (Hymenoptera: Eulophidae) to those of their bruchid beetle hosts (Coleoptera: Bruchidae) and their domesticated host plant (P. vulgaris), in the context of traditional agriculture in Mexico. We analyzed the population genetic structure of fourHorismenusspecies in Mexico using mitochondrialCOIhaplotype data. The two most abundant parasitoid species wereHorismenus depressusandHorismenus missouriensis. Horismenus missouriensiswere infected byWolbachiaendosymbionts and had little to no population differentiation (FST = 0.06). We suspect the mitochondrial history ofH. missouriensisto be blurred byWolbachia, because differentiation among infected vs. non-infected individuals exists (FST = 0.11). Populations ofH. depressuswere found to be highly differentiated (FST = 0.34), but the genetic structuring could not be explained by tested spatial components. We then compared the genetic structure observed in this parasitoid species to previously published studies on bruchid beetles and their host plants. Despite extensive human-mediated migration and likely population homogenization of its twoAcanthoscelidesbruchid beetle hosts,H. depressuspopulations are structured like its host plant, by a recent dispersal from a diverse ancestral gene pool. Distinct evolutionary dynamics may explain inconsistent patterns among trophic levels. Parasitoids likely migrate from wild bean populations and are poorly adapted to bean storage conditions similar to their bruchid beetle hosts. Integrating several trophic levels to the study of evolutionary history has proven to be fruitful in detecting different ecological responses to human-mediated disturbances and host parasite interactions.

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Duncan, Alison B., Andrew Gonzalez et Oliver Kaltz. « Stochastic environmental fluctuations drive epidemiology in experimental host–parasite metapopulations ». Proceedings of the Royal Society B : Biological Sciences 280, n^o 1769 (22 octobre 2013) : 20131747. http://dx.doi.org/10.1098/rspb.2013.1747.

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Environmental fluctuations are important for parasite spread and persistence. However, the effects of the spatial and temporal structure of environmental fluctuations on host–parasite dynamics are not well understood. Temporal fluctuations can be random but positively autocorrelated, such that the environment is similar to the recent past (red noise), or random and uncorrelated with the past (white noise). We imposed red or white temporal temperature fluctuations on experimental metapopulations of Paramecium caudatum , experiencing an epidemic of the bacterial parasite Holospora undulata . Metapopulations (two subpopulations linked by migration) experienced fluctuations between stressful (5°C) and permissive (23°C) conditions following red or white temporal sequences. Spatial variation in temperature fluctuations was implemented by exposing subpopulations to the same (synchronous temperatures) or different (asynchronous temperatures) temporal sequences. Red noise, compared with white noise, enhanced parasite persistence. Despite this, red noise coupled with asynchronous temperatures allowed infected host populations to maintain sizes equivalent to uninfected populations. It is likely that this occurs because subpopulations in permissive conditions rescue declining subpopulations in stressful conditions. We show how patterns of temporal and spatial environmental fluctuations can impact parasite spread and host population abundance. We conclude that accurate prediction of parasite epidemics may require realistic models of environmental noise.

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BLASCO-COSTA, ISABEL, et ROBERT POULIN. « Host traits explain the genetic structure of parasites : a meta-analysis ». Parasitology 140, n^o 10 (18 juillet 2013) : 1316–22. http://dx.doi.org/10.1017/s0031182013000784.

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SUMMARYGene flow maintains the genetic integrity of species over large spatial scales, and dispersal maintains gene flow among separate populations. However, body size is a strong correlate of dispersal ability, with small-bodied organisms being poor dispersers. For parasites, small size may be compensated by using their hosts for indirect dispersal. In trematodes, some species use only aquatic hosts to complete their life cycle, whereas others use birds or mammals as final hosts, allowing dispersal among separate aquatic habitats. We performed the first test of the universality of the type of life cycle as a driver of parasite dispersal, using a meta-analysis of 16 studies of population genetic structure in 16 trematode species. After accounting for the geographic scale of a study, the number of populations sampled, and the genetic marker used, we found the type of life cycle to be the best predictor of genetic structure (Fst): trematode species bound to complete their life cycle within water showed significantly more pronounced genetic structuring than those leaving water through a bird or mammal host. This finding highlights the dependence of parasites on host traits for their dispersal, suggesting that genetic differentiation of parasites reflects the mobility of their hosts.

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Salje, Henrik, Justin Lessler, Irina Maljkovic Berry, Melanie C. Melendrez, Timothy Endy, Siripen Kalayanarooj, Atchareeya A-Nuegoonpipat et al. « Dengue diversity across spatial and temporal scales : Local structure and the effect of host population size ». Science 355, n^o 6331 (23 mars 2017) : 1302–6. http://dx.doi.org/10.1126/science.aaj9384.

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Atkinson, Stephen D., et Jerri L. Bartholomew. « Spatial, temporal and host factors structure the Ceratomyxa shasta (Myxozoa) population in the Klamath River basin ». Infection, Genetics and Evolution 10, n^o 7 (octobre 2010) : 1019–26. http://dx.doi.org/10.1016/j.meegid.2010.06.013.

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Vögeli, Matthias, Jesús A. Lemus, David Serrano, Guillermo Blanco et José L. Tella. « An island paradigm on the mainland : host population fragmentation impairs the community of avian pathogens ». Proceedings of the Royal Society B : Biological Sciences 278, n^o 1718 (26 janvier 2011) : 2668–76. http://dx.doi.org/10.1098/rspb.2010.1227.

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Emergent infectious diseases represent a major threat for biodiversity in fragmented habitat networks, but their dynamics in host metapopulations remain largely unexplored. We studied a large community of pathogens (including 26 haematozoans, bacteria and viruses as determined through polymerase chain reaction assays) in a highly fragmented mainland bird metapopulation. Contrary to recent studies, which have established that the prevalence of pathogens increase with habitat fragmentation owing to crowding and habitat-edge effects, the analysed pathogen parameters were neither dependent on host densities nor related to the spatial structure of the metapopulation. We provide, to our knowledge, the first empirical evidence for a positive effect of host population size on pathogen prevalence, richness and diversity. These new insights into the interplay between habitat fragmentation and pathogens reveal properties of a host–pathogen system resembling island environments, suggesting that severe habitat loss and fragmentation could lower pathogen pressure in small populations.

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Fiebig, Aretha, Catherine E. Vrentas, Thien Le, Marianne Huebner, Paola M. Boggiatto, Steven C. Olsen et Sean Crosson. « Quantification of Brucella abortus population structure in a natural host ». Proceedings of the National Academy of Sciences 118, n^o 11 (9 mars 2021) : e2023500118. http://dx.doi.org/10.1073/pnas.2023500118.

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Cattle are natural hosts of the intracellular pathogen Brucella abortus, which inflicts a significant burden on the health and reproduction of these important livestock. The primary routes of infection in field settings have been described, but it is not known how the bovine host shapes the structure of B. abortus populations during infection. We utilized a library of uniquely barcoded B. abortus strains to temporally and spatially quantify population structure during colonization of cattle through a natural route of infection. Introducing 108 bacteria from this barcoded library to the conjunctival mucosa resulted in expected levels of local lymph node colonization at a 1-wk time point. We leveraged variance in strain abundance in the library to demonstrate that only 1 in 10,000 brucellae introduced at the site of infection reached a parotid lymph node. Thus, cattle restrict the overwhelming majority of B. abortus introduced via the ocular conjunctiva at this dose. Individual strains were spatially restricted within the host tissue, and the total B. abortus census was dominated by a small number of distinct strains in each lymph node. These results define a bottleneck that B. abortus must traverse to colonize local lymph nodes from the conjunctival mucosa. The data further support a model in which a small number of spatially isolated granulomas founded by unique strains are present at 1 wk postinfection. These experiments demonstrate the power of barcoded transposon tools to quantify infection bottlenecks and to define pathogen population structure in host tissues.

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Chen, Fajun, Paul H. Goodwin, Adalat Khan et Tom Hsiang. « Population structure and mating-type genes ofColletotrichum graminicolafromAgrostis palustris ». Canadian Journal of Microbiology 48, n^o 5 (1 mai 2002) : 427–36. http://dx.doi.org/10.1139/w02-034.

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Eighty-seven isolates of Colletotrichum graminicola, mostly from Agrostis palustris, were collected in grass fields, most of which were in Ontario, Canada. Specific primers were designed to amplify the mating-type (MAT) genes and, among 35 isolates tested, all yielded a band of the expected size for MAT2. For six isolates, the MAT2 PCR products were sequenced and found to be similar to that reported for MAT2 of C. graminicola from maize. Based on 119 polymorphic bands from 10 random amplified polymorphic DNA primers, analyses of genetic distances were found to generally cluster isolates by host and geographic origin. Among 42 isolates from a grass field in Ontario, significant spatial autocorrelation was found to occur within a 20-m distance, implying that this is the effective propagule dispersal distance. Although clonal propagation was observed in the 87 isolates with 67 unique genotypes, the extent of genetic variation in local populations implies some occurrence of sexual or asexual recombination.Key words: anthracnose, turfgrass, RAPD, MAT, reproduction, fungi.

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Zhang, Li, Fuping Wang, Jiaxi Wu, Sicheng Ye, Ye Xu et Yanan Liu. « Fine-Scale Genetic Structure of Curculio chinensis (Coleoptera : Curculionidae) Based on Mitochondrial COI : The Role of Host Specificity and Spatial Distance ». Insects 15, n^o 2 (6 février 2024) : 116. http://dx.doi.org/10.3390/insects15020116.

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The Camellia weevil, Curculio chinensis (Chevrolat, 1978), is a dominant oligophagous pest that bores into the fruit of oil-tea Camellia. Genetic differentiation among populations in various hosts can easily occur, which hinders research on pest management. In this study, the genetic structure, genetic diversity, and phylogenetic structure of local C. chinensis populations were examined using 147 individuals (from 6 localities in Jiangxi), based on 2 mitochondrial COI markers. Results indicated that the C. chinensis population in Jiangxi exhibits a high haplotype diversity, especially for the populations from Cam. meiocarpa plantations. Structural differentiation was observed between Haplogroup 1 (73 individuals from Ganzhou, Jian, and Pingxiang) in the monoculture plantations of Cam. meiocarpa and Haplogroup 2 (75 individuals from Pingxiang and Jiujiang) in Cam. oleifera. Two haplogroups have recently undergone a demographic expansion, and Haplogroup 1 has shown a higher number of effective migrants than Haplogroup 2. This suggests that C. chinensis has been spreading from Cam. meiocarpa plantations to other oil-tea Camellia, such as Cam. oleifera. The increased cultivation of oil-tea Camellia in Jiangxi has contributed to a unique genetic structure within the C. chinensis population. This has, in turn, expanded the distribution of C. chinensis and increased migration between populations.

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Leggett, Helen C., Geoff Wild, Stuart A. West et Angus Buckling. « Fast-killing parasites can be favoured in spatially structured populations ». Philosophical Transactions of the Royal Society B : Biological Sciences 372, n^o 1719 (13 mars 2017) : 20160096. http://dx.doi.org/10.1098/rstb.2016.0096.

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It is becoming increasingly clear that the evolution of infectious disease is influenced by host population structure. Theory predicts that parasites should be more ‘prudent’—less transmissible—in spatially structured host populations. However, here we (i) highlight how low transmission, the phenotype being selected for in this in context, may also be achieved by rapacious host exploitation, if fast host exploitation confers a local, within-host competitive advantage and (ii) test this novel concept in a bacteria–virus system. We found that limited host availability and, to a lesser extent, low relatedness favour faster-killing parasites with reduced transmission. By contrast, high host availability and high relatedness favour slower-killing, more transmissible parasites. Our results suggest high, rather than low, virulence may be selected in spatially structured host–parasite communities where local competition and hence selection for a within-host fitness advantage is high. This article is part of the themed issue ‘Opening the black box: re-examining the ecology and evolution of parasite transmission’.

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Parsons, Sandra K., C. Michael Bull et David M. Gordon. « Spatial Variation and Survival of Salmonella enterica Subspecies in a Population of Australian Sleepy Lizards (Tiliqua rugosa) ». Applied and Environmental Microbiology 81, n^o 17 (19 juin 2015) : 5804–11. http://dx.doi.org/10.1128/aem.00997-15.

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ABSTRACTThe life cycles of many enteric bacterial species require a transition between two very distinct environments. Their primary habitat is the gastrointestinal tract of the host, while their secondary habitat, during transmission from one host to another, consists of environments external to the host, such as soil, water, and sediments. Consequently, both host and environmental factors shape the genetic structure of enteric bacterial populations. This study examined the distribution of fourSalmonella entericasubspecies in a population of sleepy lizards,Tiliqua rugosa, in a semiarid region of South Australia. The lizards living within the 1,920-m by 720-m study site were radio tracked, and their enteric bacteria were sampled at regular intervals throughout their active seasons in the years 2001, 2002, and 2006. Four of the six subspecies ofS. entericawere present in this population and were nonrandomly distributed among the lizards. In particular,S. entericasubsp.diarizonaewas restricted to lizards living in the most shaded parts of the study site with an overstorey ofCasuarinatrees. Experiments undertaken to investigate the survival ofS. entericacells under seminatural conditions revealed that cell survival decreased with increased exposure to elevated temperatures and UV light. Among the threeS. entericasubspecies tested,S. entericasubsp.diarizonaeconsistently had an average expected life span that was shorter than that observed for the other two subspecies. There was no indication in the data that there was any competitive dominance hierarchy among theS. entericasubspecies within individual hosts. Thus, the nonrandom distribution ofS. entericasubspecies in this population of lizards appears to be driven by their different survival characteristics in the external environment.

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Petermann, Sarah, Sabine Otto, Gerrit Eichner et Marc F. Schetelig. « Spatial and temporal genetic variation of Drosophila suzukii in Germany ». Journal of Pest Science 94, n^o 4 (12 mars 2021) : 1291–305. http://dx.doi.org/10.1007/s10340-021-01356-5.

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AbstractNative to Southeast Asia, the spotted wing drosophila (SWD), Drosophila suzukii Matsumura, rapidly invaded America and Europe in the past 20 years. As a crop pest of soft-skinned fruits with a wide range of host plants, it threatens the fruit industry worldwide, causing enormous economic losses. To control this invasive pest species, an understanding of its population dynamics and structure is necessary. Here, we report the population genetics and development of SWD in Germany from 2017–19 using microsatellite markers over 11 different sample sites. It is the first study that examines SWD’s genetic changes over 3 years compared to multiple international SWD laboratory strains. Results show that SWD populations in Germany are highly homogenous without differences between populations or years, which indicates that populations are well adapted, migrate freely, and multiple invasions from outside Germany either did not take place or are negligible. Such high genetic variability and migration between populations could allow for a fast establishment of the pest species. This is especially problematic with regard to the ongoing spread of this invasive species and could bear a potential for developing pesticide resistance, which could increase the impact of the SWD further in the future.

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Cullingham, C. I., S. M. Nakada, E. H. Merrill, T. K. Bollinger, M. J. Pybus et D. W. Coltman. « Multiscale population genetic analysis of mule deer (Odocoileus hemionus hemionus) in western Canada sheds new light on the spread of chronic wasting disease ». Canadian Journal of Zoology 89, n^o 2 (février 2011) : 134–47. http://dx.doi.org/10.1139/z10-104.

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To successfully manage wildlife diseases, it is necessary to understand factors that influence spread. One approach is to analyze host movement and social structure, as these behaviors can be associated with the probability of transmission. Some populations of mule deer ( Odocoileus hemionus hemionus (Rafinesque, 1817)) in western Canada are infected with chronic wasting disease (CWD), a transmissible and fatal neurodegenerative disease. We used population analysis of spatial genetic structure of mule deer at broad and local scales to understand factors that influence spread. We genotyped 2535 mule deer sampled from Alberta, Saskatchewan, and portions of British Columbia using 16 microsatellite loci. We found weak genetic structure at broad spatial scales (overall FST = 0.008) that was well defined by geographic distance, indicating the risk of CWD spread from the focus of infection will decline gradually with increasing distance, but there are no barriers to the spread over time. At the local scale of approximately 2 km, elevated relatedness among CWD-infected individuals suggests transmission rates within social groups. Sex-biased spatial autocorrelation in genetic relatedness also indicates that female philopatry underlies the social structure, and therefore transmission among relatives is potentially driving local disease persistence.

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Dong, J. J., B. Skinner, N. Breecher, B. Schmittmann et R. K. P. Zia. « Spatial structures in a simple model of population dynamics for parasite-host interactions ». EPL (Europhysics Letters) 111, n^o 4 (1 août 2015) : 48001. http://dx.doi.org/10.1209/0295-5075/111/48001.

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Fromont, Emmanuelle, Dominique Pontier et Michel Langlais. « Dynamics of a feline retrovirus (FeLV) in host populations with variable spatial structure ». Proceedings of the Royal Society of London. Series B : Biological Sciences 265, n^o 1401 (22 juin 1998) : 1097–104. http://dx.doi.org/10.1098/rspb.1998.0404.

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Francisco, Carolina S., Paulo C. Ceresini, Rodrigo P. P. Almeida et Helvécio D. Coletta-Filho. « Spatial Genetic Structure of Coffee-Associated Xylella fastidiosa Populations Indicates that Cross Infection Does Not Occur with Sympatric Citrus Orchards ». Phytopathology® 107, n^o 4 (avril 2017) : 395–402. http://dx.doi.org/10.1094/phyto-08-16-0300-r.

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Xylella fastidiosa, an economically important plant-pathogenic bacterium, infects both coffee and citrus trees in Brazil. Although X. fastidiosa in citrus is well studied, knowledge about the population structure of this bacterium infecting coffee remains unknown. Here, we studied the population structure of X. fastidiosa infecting coffee trees in São Paulo State, Brazil, in four regions where citrus is also widely cultivated. Genotyping of over 500 isolates from coffee plants using 14 genomic microsatellite markers indicated that populations were largely geographically isolated, as previously found with populations of X. fastidiosa infecting citrus. These results were supported by a clustering analysis, which indicated three major genetic groups among the four sampled regions. Overall, approximately 38% of isolates showed significant membership coefficients not related to their original geographical populations (i.e., migrants), characterizing a significant degree of genotype flow among populations. To determine whether admixture occurred between isolates infecting citrus and coffee plants, one site with citrus and coffee orchards adjacent to each other was selected; over 100 isolates were typed from each host plant. No signal of natural admixture between citrus- and coffee-infecting isolates was found; artificial cross-infection assays with representative isolates also yielded no successful cross infection. A comparison determined that X. fastidiosa populations from coffee have higher genetic diversity and allelic richness compared with citrus. The results showed that coffee and citrus X. fastidiosa populations are effectively isolated from each other and, although coffee populations are spatially structured, migration has an important role in shaping diversity.

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Gunasekara, Umanga, Miranda R. Bertram, Nguyen Van Long, Phan Quang Minh, Vo Dinh Chuong, Andres Perez, Jonathan Arzt et Kimberly VanderWaal. « Phylogeography as a Proxy for Population Connectivity for Spatial Modeling of Foot-and-Mouth Disease Outbreaks in Vietnam ». Viruses 15, n^o 2 (29 janvier 2023) : 388. http://dx.doi.org/10.3390/v15020388.

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Bayesian space–time regression models are helpful tools to describe and predict the distribution of infectious disease outbreaks and to delineate high-risk areas for disease control. In these models, structured and unstructured spatial and temporal effects account for various forms of non-independence amongst case counts across spatial units. Structured spatial effects capture correlations in case counts amongst neighboring provinces arising from shared risk factors or population connectivity. For highly mobile populations, spatial adjacency is an imperfect measure of connectivity due to long-distance movement, but we often lack data on host movements. Phylogeographic models inferring routes of viral dissemination across a region could serve as a proxy for patterns of population connectivity. The objective of this study was to investigate whether the effects of population connectivity in space–time regressions of case counts were better captured by spatial adjacency or by inferences from phylogeographic analyses. To compare these two approaches, we used foot-and-mouth disease virus (FMDV) outbreak data from across Vietnam as an example. We identified that accounting for virus movement through phylogeographic analysis serves as a better proxy for population connectivity than spatial adjacency in spatial–temporal risk models. This approach may contribute to design surveillance activities in countries lacking movement data.

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CALVETE, C., J. A. BLANCO-AGUIAR, E. VIRGÓS, S. CABEZAS-DÍAZ et R. VILLAFUERTE. « Spatial variation in helminth community structure in the red-legged partridge (Alectoris rufaL.) : effects of definitive host density ». Parasitology 129, n^o 1 (10 juin 2004) : 101–13. http://dx.doi.org/10.1017/s0031182004005165.

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Parasite community ecology has recently focused on understanding the forces structuring these communities. There are few surveys, however, designed to study the spatial repeatability and predictability of parasite communities at the local scale in one host. The purpose of our study was to address the relationship between infracommunity and component community richness, and to describe spatial variations on the local scale, of helminth parasite communities in an avian host, the red-legged partridge (Alectoris rufa). We sampled 235 wild partridges from 8 separate localities, with different partridge population densities, in the Ciudad Real and Toledo provinces of central Spain, and we determined their overall and intestinal helminth species. We found that habitat variables (mean temperature and land use) were not significantly associated with any component community. The partridge population abundance index was directly correlated with the prevalence and mean intensity of infection but not with component community species richness. There was a curvilinear relationship between infracommunity and component community species richness, as well as negative interspecific associations, for the helminth species assemblage parasitizing the intestine. A nestedness/anti-nestedness pattern, considered as part of a continuum, was associated with prevalence, mean intensity and partridge population abundance index, but not with component community richness. Increases in the partridge population abundance index and the prevalence and mean intensity of infection were associated with increases in helminth community nestedness. Although negative interactions between helminth species could not be ruled out as forces structuring helminth communities, our results suggest that parasite community structure in the red-legged partridge was primarily determined by the extrinsic influence of parasite habitat heterogeneity and its amplification of the differing probabilities of colonization of parasite species.

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Hosseinalizadeh Nobarinezhad, Mahboubeh, et Lisa E. Wallace. « Fine-Scale Patterns of Genetic Structure in the Host Plant Chamaecrista fasciculata (Fabaceae) and Its Nodulating Rhizobia Symbionts ». Plants 9, n^o 12 (7 décembre 2020) : 1719. http://dx.doi.org/10.3390/plants9121719.

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In natural plant populations, a fine-scale spatial genetic structure (SGS) can result from limited gene flow, selection pressures or spatial autocorrelation. However, limited gene flow is considered the predominant determinant in the establishment of SGS. With limited dispersal ability of bacterial cells in soil and host influence on their variety and abundance, spatial autocorrelation of bacterial communities associated with plants is expected. For this study, we collected genetic data from legume host plants, Chamaecrista fasciculata, their Bradyrhizobium symbionts and rhizosphere free-living bacteria at a small spatial scale to evaluate the extent to which symbiotic partners will have similar SGS and to understand how plant hosts choose among nodulating symbionts. We found SGS across all sampled plants for both the host plants and nodulating rhizobia, suggesting that both organisms are influenced by similar mechanisms structuring genetic diversity or shared habitat preferences by both plants and microbes. We also found that plant genetic identity and geographic distance might serve as predictors of nodulating rhizobia genetic identity. Bradyrhizobium elkanii was the only type of rhizobia found in nodules, which suggests some level of selection by the host plant.

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Silva, Claudia, Pablo Vinuesa, Luis E. Eguiarte, Esperanza Martínez-Romero et Valeria Souza. « Rhizobium etli and Rhizobium gallicum Nodulate Common Bean (Phaseolus vulgaris) in a Traditionally Managed Milpa Plot in Mexico : Population Genetics and Biogeographic Implications ». Applied and Environmental Microbiology 69, n^o 2 (février 2003) : 884–93. http://dx.doi.org/10.1128/aem.69.2.884-893.2003.

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ABSTRACT The stability of the genetic structure of rhizobial populations nodulating Phaseolus vulgaris cultivated in a traditionally managed milpa plot in Mexico was studied over three consecutive years. The set of molecular markers analyzed (including partial rrs, glnII, nifH, and nodB sequences), along with host range experiments, placed the isolates examined in Rhizobium etli bv. phaseoli and Rhizobium gallicum bv. gallicum. Cluster analysis of multilocus enzyme electrophoresis and plasmid profile data separated the two species and identified numerically dominant clones within each of them. Population genetic analyses showed that there was high genetic differentiation between the two species and that there was low intrapopulation differentiation of the species over the 3 years. The results of linkage disequilibrium analyses are consistent with an epidemic genetic structure for both species, with frequent genetic exchange taking place within conspecific populations but not between the R. etli and R. gallicum populations. A subsample of isolates was selected and used for 16S ribosomal DNA PCR-restriction fragment length polymorphism analysis, nifH copy number determination, and host range experiments. Plasmid profiles and nifH hybridization patterns also revealed the occurrence of lateral plasmid transfer among distinct multilocus genotypes within species but not between species. Both species were recovered from nodules of the same plants, indicating that mechanisms other than host, spatial, or temporal isolation may account for the genetic barrier between the species. The biogeographic implications of finding an R. gallicum bv. gallicum population nodulating common bean in America are discussed.

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Milne, Georgina, Adrian Allen, Jordon Graham, Raymond Kirke, Carl McCormick, Eleanor Presho, Robin Skuce et Andrew W. Byrne. « Mycobacterium bovis Population Structure in Cattle and Local Badgers : Co-Localisation and Variation by Farm Type ». Pathogens 9, n^o 7 (21 juillet 2020) : 592. http://dx.doi.org/10.3390/pathogens9070592.

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Bovine tuberculosis surveillance in Northern Ireland includes Multiple-Locus Variable number tandem repeat Analysis (MLVA) to determine the Mycobacterium bovis genetic type present in both cattle and the predominant wildlife host, the European badger (Meles meles). These data are useful for investigating clusters of infection and understanding the scale at which interspecific transmission may occur. We utilised a comprehensive dataset of routinely sampled isolates from infected cattle and from badgers killed in road-traffic accidents to investigate the spatial co-location of MLVA types in, and between, the badger and cattle populations. Furthermore, we investigated the hypothesis that the type of farming enterprise might explain some variation in this relationship. MLVA types were spatially co-localised in cattle and road-traffic accident (RTA) badger hosts, indicative of a shared epidemic. Dairy herds were more likely to have at least one MLVA type in common with nearby RTA badgers, compared to non-dairy herd types. Marginally more MLVA spatial clustering was observed in non-dairy herds, which may be a consequence of relatively more between-herd movements. For the cattle population, local transmission mechanisms such as infection from contiguous herds, infectious wildlife and short-range between-herd cattle movements appear primarily to drive the epidemic: there appears to be a more limited role for long-range movements. Animal management practices are likely to be the driving force behind this observation, as beef rearing is associated with elevated numbers of animal movements compared to dairy herds.

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