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Auswahl der wissenschaftlichen Literatur zum Thema „Spatial host population structure“
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Zeitschriftenartikel zum Thema "Spatial host population structure"
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Nair, Abhilash, Toby Fountain, Suvi Ikonen, Sami P. Ojanen und 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, Nr. 1831 (25.05.2016): 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 und 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, Nr. 1885 (22.08.2018): 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., und S. Gandon. „Spatial evolutionary epidemiology of spreading epidemics“. Proceedings of the Royal Society B: Biological Sciences 283, Nr. 1841 (26.10.2016): 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 und Noah K. Whiteman. „Birds are islands for parasites“. Biology Letters 10, Nr. 8 (August 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., und H. Charles J. Godfray. „Modelling the spread of Wolbachia in spatially heterogeneous environments“. Journal of The Royal Society Interface 9, Nr. 76 (06.06.2012): 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 und Mike Boots. „Host resistance and coevolution in spatially structured populations“. Proceedings of the Royal Society B: Biological Sciences 278, Nr. 1715 (08.12.2010): 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 und Henrik Glenner. „Comparative population genetics of swimming crab host (Portunus pelagicus) and common symbiotic barnacle (Octolasmis angulata) in Vietnam“. PeerJ 9 (07.07.2021): 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 und Sunetra Gupta. „Host community structure and the maintenance of pathogen diversity“. Proceedings of the Royal Society B: Biological Sciences 274, Nr. 1619 (15.05.2007): 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 und Peter H. Thrall. „Host ecotype generates evolutionary and epidemiological divergence across a pathogen metapopulation“. Proceedings of the Royal Society B: Biological Sciences 281, Nr. 1787 (22.07.2014): 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., und Roman Biek. „Spatial dynamics and genetics of infectious diseases on heterogeneous landscapes“. Journal of The Royal Society Interface 4, Nr. 16 (08.05.2007): 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.
Dissertationen zum Thema "Spatial host population structure"
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Kendrick, Gary. „The epiphyte Microcladia coulteri (Rhodophyta) : changes in population structure with spatial and temporal variation in availablity of host species“. Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25881.
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A comparison of the population structures of the epiphyte, Microcladia coulteri and the three hosts: Prionitis lanceolata, Iridaea cordata and Odonthalia floccosa,
was made at Beaver Point, Saltspring Island, British Columbia. The three host species had distinct seasonal patterns in density and size class distribution. By the use of ANOVA, the partitioning of variation in epiphyte population structure with the seasons, between host species and, within host species variations in size of thalli, reproductive status and spatial distribution was performed. Small percentages of total determined variation were accounted for by seasonality in the abundance of size class and reproductive components of the epiphyte population and distribution of the epiphyte between host species. Larger percentages were due to variations in epiphyte population structure with within host species variations in size and reproductive status and the spatial variation in availability of host substrata. It was concluded that persistence of M. coulteri in relatively stable populations, both temporally and spatially, was due to differential use of available host substrata combined with continuous reproductive output and recruitment of the epiphyte.Science, Faculty of
Botany, Department of
Graduate
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Appelgren, Anais. „Evolutionay consequences of the population structure of an ectoparasite at different spatial scales : an empirical approach of the hen flea-passerines system“. Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10296/document.
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L’évolution divergente est un processus clef générant de la biodiversité. Elle peut avoir lieu entre localités, via la réduction des flux de gènes, et au sein des localités via la spécialisation écologique. Dans le cas des systèmes parasitaires multi-hôtes, l’adaptation dépend des taux relatifs de flux de gènes des hôtes et des parasites entre différentes localités, ainsi que des échanges locaux de parasites entre différents types d’hôtes. En combinant génétique des populations et expérimentations sur le système composé de la puce Ceratophyllus gallinae et deux de ses hôtes, la mésange charbonnière Parus major et le gobe-mouche à collier Ficedula albicollis dans un habitat fragmenté, nous avons examiné comment l’adaptation et l’isolation génétique façonnent l’évolution des parasites. Nous avons aussi testé comment les choix d’habitat des hôtes pouvaient influencer la rencontre avec des populations de parasites spécialisées. Les analyses de microsatellites révèlent que les populations de puce sont différenciées à une échelle spatiale fine, et fréquemment entre espèces hôtes. De plus, des populations de parasites semblent adaptées à chaque type d’hôte. Cependant, aucune variation dans les choix d’habitats par rapport aux parasites n’a été observée chez les hôtes. Enfin, la réponse des hôtes aux parasites variait entre nos deux zones réplica ; l’histoire des populations d’hôtes pourrait donc influer sur la coevolution avec leurs parasites. Ce système semble donc localement façonné à la fois par une isolation génétique et une sélection par différents hôtes. L’étude de nouveaux sites permettraient d’évaluer si cette évolution divergente peut être génératrice de biodiversitéDivergent evolution is a key process generating biodiversity. This can occur between localities, through reduced gene flow followed by local adaptation or genetic drift, and within localities through ecological specialization. In the case of multi-host parasite systems, adaptation can be driven by the relative rate of host-parasite gene flow among spatially isolated populations, and the amount of parasite exchange among local host types. Combining population genetics and field experiments, we examined how adaptation and genetic isolation shape parasite evolution. Focusing on the hen flea Ceratophyllus gallinae, a presumed host generalist, and two of its hosts, the great tit Parus major and the collared flycatcher Ficedula albicollis, we investigated parasite population structure and adaptation within a fragmented landscape. Additionally, we tested how hosts can influence encounter rates with specialized flea populations through their habitat choice. Neutral markers analyses show that flea populations are genetically differentiated at fine spatial scales, and frequently between the two host species. Evidence for parasite adaptation to each host type were also observed. Host specialization may therefore be ongoing in hen fleas. However, birds did not show specific habitat choice strategies regarding flea-infested nests. Host responses differed between two replicate sites, indicating that local population history may impact parasite evolution. Both isolation and host-based selection are therefore acting on hen flea populations at a local scale. Investigations in new localities will help to assess to what extend this divergent evolution may generate biodiversity
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Henri, Dominic Charles. „From individuals to ecosystems : a study of the temporal and spatial variation in ecological network structure“. Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/15726.
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Ecological network theory has developed from studies of static, binary trophic relationships to the analysis of quantitative, dynamic communities consisting of multiple link-types. Particularly, work has focused on the dynamic nature of ecological networks, which maintains stability in complex communities. However, there are few in situ network-level studies of the determinants of temporal and spatial variation in community structure. This thesis utilises data from a 10-year study of a host-parasitoid network and a collaborative study in an applied ecological setting to identify individual level factors important to network structure. The work aims towards an empirical, predictive framework linking adaptive foraging behaviour to ecological network structure. The results show that condition-dependent foraging behaviours structure host-parasitoid networks. The realised niches of the studied parasitoid species were generally biased towards larger host species and condition-dependent sex ratio allocation increased the likelihood that females would eclose from relatively larger hosts and males from relatively smaller hosts, which resulted in sex ratios deviating from Hamiltonian (50:50) predictions. Further, both of these aspects of behaviour are plastic, where parasitoid behaviour responded to environmental heterogeneity. Particularly, host preference behaviour conformed to an egg-/time-limitation framework, where the size dependency of the behaviour is greater when individuals have a greater likelihood of being egg-limited. Both the size-dependency and the plasticity of these behaviours differed significantly between secondary parasitoid species. This species identity effect interacted with landscape heterogeneity, which may explain some inter- and intra-specific variation in network structure. With respect to applied ecology, the results show that the benefits of natural vegetation for pest control are dependent upon the dispersal capabilities and the diet breadth of the pest and its natural enemies. The findings are evaluated towards a predictive framework for understanding the effects of future climate change on community structure and stability. We consider this framework in terms of applied ecology, particularly pest control ecosystem services provided by natural vegetation in an agricultural environment. The synergistic nature of the multiple determinants of network structure found in this thesis suggest that future studies should focus on the whole network, which is not necessarily the sum of its parts.
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Brouard, Vianney. „Cell dynamics of multitype populations in oncology and Invasion probability of cooperative parasites in structured host populations“. Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0037.
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Cette thèse porte sur l'étude de deux modèles stochastiques liés à des problèmes médicaux. Le premier vise à comprendre le processus épidémique généré par des bactériophages coopératifs dans une population de bactéries résistantes aux antibiotiques. Pour cela, nous introduisons un modèle épidémiologique où les infections sont générées par la coopération de parasites dans une population d'hôtes structurée selon un modèle de configuration. Une transition de phase est observée pour la probabilité d'invasion dépendant du degré de connectivité des sommets et du nombre de parasites générés lors d'une infection d'un hôte. Au seuil critique, la probabilité d'invasion est identifiée comme la probabilité de survie d'un processus de Galton-Watson.Dans le but d'obtenir un modèle biologiquement plus pertinent, nous avons analysé un modèle similaire où une structure spatiale est ajoutée à la population d'hôtes en utilisant un "random geometric graph". Nous avons montré qu'une telle structure spatiale facilite la coopération des parasites. Une transition de phase similaire se produit où au seuil critique, des bornes supérieure et inférieure sont obtenues pour la probabilité d'invasion en tant que probabilités de survie de deux processus de branchement avec coopération.La deuxième question médicale concerne la compréhension de l'évolution de la composition génétique d'une tumeur en formation, en utilisant des processus de naissance et de mort multitypes branchants sur un espace de traits fini. Considérant une évolution neutre et délétère, nous fournissons des résultats au premier ordre asymptotique pour toutes les tailles des sous-populations mutantes. En particulier, nous capturons la stochasticité associée aux tailles des sous-populations mutantes lorsqu'une tumeur est observée cliniquement, et surtout nous caractérisons les chemins évolutifs effectifs, fournissant des informations sur le passé, le présent et le futur de l'évolution tumorale.Au-delà de ce cadre restrictif d'évolution neutre et délétère, nous proposons une nouvelle méthode pour comprendre le premier ordre asymptotique du premier trait mutant sélectifThis thesis focuses on the study of two stochastic models related to medical problems. The first one lies on understanding infection spread of cooperating bacteriophages on a structured multi-drug resistant bacterial host population. Motivated by this example, we introduce an epidemiological model where infections are generated by cooperation of parasites in a host population structured on a configuration model. We analysed the invasion probability for which we obtain a phase transition depending on the connectivity degree of the vertices and the offspring number of parasites during an infection of a host. At the critical scaling, the invasion probability is identified as the survival probability of a Galton-Watson process. With the aim to get a biological more relevant model, we analysed a similar model where a spatial structure is added for the host population using a random geometric graph. We have shown that such spatial structure facilitates cooperation of parasites. A similar phase transition occurs where at the same critical scaling the invasion probability is upper and lower bounded by the survival probabilities of two discrete branching processes with cooperation. The second medical question deals with understanding the evolution of the genetic composition of a tumor under carcinogenesis, using multitype birth and death branching process models on a general finite trait space. In the case of neutral and deleterious cancer evolution, we provide first-order asymptotics results on all mutant subpopulation sizes. In particular such results capture the randomness of all cell trait sizes when a tumor is clinically observed, and mostly it allows to characterize the effective evolutionary pathways, providing information on the past, present, and future of tumor evolution.Moving beyond this restrictive neutral and deleterious cancer evolution framework, we provide a new method to understand the first selective mutant trait size
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Vogwill, Tom. „The ecology and evolution of host-parasite interactions in spatially structured populations“. Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533910.
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Purves, Drew William. „Local spatial structure and plant population dynamics“. Thesis, University of York, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251813.
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Hamid, Mohd Norowi. „The analysis of host-parasitoid relationships at various spatial scales“. Thesis, University of Greenwich, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267350.
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Cheshire, J. A. „Population structure and the spatial analysis of surnames“. Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1324522/.
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Geographers have largely overlooked surnames (family names), and their geographic concentrations, as a valuable source of data to indicate the spatial structure of populations. This thesis seeks to provide a substantive contribution to the geographical literature by demonstrating how quantitative spatial analysis of surname data can be used as an aid to understanding population structure at a range of scales from the regional to the continental. The primary purpose of this research is not to develop detailed case studies or to investigate specific examples of population characteristics considered interesting for their novelty: rather, the core concern is to focus on the identification or confirmation of generalised trends. Much of the current research that uses surnames (for example in population genetics) contains a geographical element, yet stops short of exploiting and accommodating the effect of scale, shape and size of spatial units. The application of computationally intensive spatial analysis techniques to a comprehensive and innovative dataset (see worldnames.publicprofiler.org) makes it possible to address these issues for the first time. The thesis develops and applies a robust analytical and methodological framework for the analysis of surnames as a primary data source. Applications of the research are used to demonstrate the utility of surnames in studies of population genetics, in migration research, as well as in the spatial analysis of large datasets more generally.
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Penington, Sarah. „Branching processes with spatial structure in population models“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:361e5c58-e6dd-47a0-9a52-303e897547e8.
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We consider three different settings for branching processes with spatial structure which appear in population models. Firstly, we consider the effect of adding a competitive interaction between nearby individuals in a branching Brownian motion. Each individual has a mass which decays when other individuals are nearby. We study the front location: the location at which the local mass density drops to o(1). We show that there are arbitrarily large times t at which the front location is order of t^(1/3) behind the maximum displacement of a particle from the origin. Secondly, we study the strength of selection in favour of a particular allele in a spatially structured population required to cause a detectable trace in the patterns of genetic variation observed in the contemporary population. We suppose that the effective local population density is small. We show that whereas in dimensions at least three, selection is barely impeded by the spatial structure, in the most relevant dimension, d=2, selection must be stronger (by a factor of log(1/m) where m is the neutral mutation rate) if we are to have a chance of detecting it. Finally, we model the behaviour of what are known in population genetics as hybrid zones. These occur when two genetically distinct groups are able to reproduce, but the hybrid offspring have a lower fitness. We prove that on an appropriate time and space scale, the hybrid zone in our model evolves approximately according to mean curvature flow. We also give a probabilistic proof of a (well-known) analogous result for a special case of the Allen-Cahn equation. In the last two cases, we use the spatial Lambda-Fleming-Viot process to model the population (with different selection mechanisms), and our proofs rely on a duality with a system of branching and coalescing particles.
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Surendran, Anudeep. „Stochastic and continuum descriptions of population dynamics with spatial structure“. Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/207574/1/Anudeep_Surendran_Thesis.pdf.
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Spatial structures are ubiquitous in populations of plants, animals and cells, typically occurring as clustering or segregation. These spatial structures influence how individuals interact and the overall population dynamics. Yet, these details are rarely accounted for in classical population dynamics models. Through Individual-based and continuum models, I show that spatial structures can dramatically alter population dynamics. The thesis specifically explores the role of spatial structure in biologically and ecologically relevant scenarios, such as the movement of cells in the presence of biological obstacles, directional movement of animals in response to interaction with others (chase-escape dynamics), predator-prey dynamics, and Allee kinetics.
Bücher zum Thema "Spatial host population structure"
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Miller, Nicholas John. Population structure and gene flow in a host alternating aphid, Pemphigus bursarius. Birmingham: University of Birmingham, 2000.
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Sathāban Khonkhwā Sētthakit hǣng Sāt (Laos). Spatial structure of industries and population in Laos: Current states and future prospects. [Vientiane]: National Economic Research Institute (NERIA), 2008.
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Lindegarth, Mats. Spatial population structure of bivalves in shallow marine sediments: Hydrodynamic effects on recruitment processes. Strömstad: Tjärnö Marine Biological Laboratory, 1996.
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Li, Junfu. Beijing de ren kou, she hui jie ceng yu kong jian jie gou: The spatial structure of population and social strata of Beijing. Beijing Shi: She hui ke xue wen xian chu ban she, 2017.
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M, Dermott Ronald, und Bayfield Institute, Hrsg. Spatial distribution and population structure of the mussels Dreissena polymorpha and Dreissena bugensis in the Bay of Quinte, Lake Ontario, 1998 and 2000. Burlington, Ont: Great Lakes Laboratory for Fisheries and Aquatic Sciences, Bayfield Institute, Fisheries and Oceans Canada, 2003.
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Fahrig, Lenore. Effects of dispersal behaviour on relationships between spatial arrangement of host patches and local population size. 1988.
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Kim, Kyung-Min. Impacts of urban spatial structure on office property values and office workers' commuting. 2008.
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Spatial data analysis in the social and environmental sciences. Cambridge [England]: Cambridge University Press, 1990.
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Furlong, Jamie, und Will Jennings. The Changing Electoral Map of England and Wales. Oxford University PressOxford, 2024. http://dx.doi.org/10.1093/9780191943331.001.0001.
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Abstract This book offers a definitive account of the changing electoral geography of England and Wales over the past half century. Changes in social and economic structure have altered the spatial distribution of voters and combined with changes in the parties’ appeal to those voters (and the behaviour of voters) has led to a gradual, though recently accelerating, realignment in the geographical basis of electoral competition. Constituency-level analysis of voting at general elections between 1979 and 2019 shows a swing from Labour to the Conservatives in demographically left behind areas with largely white, working-class populations and lower levels of educational attainment, while Labour's support has remained stable in places characterized by economic deprivation (economically left behind areas) and insecure employment (precariously left behind areas). Areas with improving socio-economic characteristics—typically cities where Labour have inefficiently stacked up votes—have swung towards Labour, whereas those that have experienced population and economic decline have swung towards the Conservatives. Yet not all areas follow these trends. Spatial analysis reveals clusters of seats where each party has more support than expected based on sociodemographic composition—places where, in short, place matters. In Merseyside, Labour’s vote is much higher than predicted by demographics, while this is likewise the case for the Conservatives in Lincolnshire. Qualitative case studies identify the place-based, contextual factors that help explain the unusual political characteristics in these places. The book argues for the need to recognize the importance of people, places, and parties in shaping the geography of electoral outcomes.
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Dezzani, Raymond J., und Christopher Chase-Dunn. The Geography of World Cities. Oxford University Press, 2018. http://dx.doi.org/10.1093/acrefore/9780190846626.013.423.
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World cities are a product of the globalization of economic activity that has characterized post-World War II capitalism, and exhibit characteristics previously found in primate cities but with influence extending far beyond the range of the metropolitan state. They are the culmination of postwar urbanization mechanisms coupled with the rise of transnational corporations that have served to concentrate unprecedented population and economic power/potential. The potential for both human development advantage and disadvantage is historically unprecedented in these new and highly interconnected urban amalgams. In general, human settlement systems are usually understood to include the systemic (regularized) ways in which settlements (hamlets, villages, towns, cities) are linked with one another by trade and other kinds of human interaction. Geographers, historians, and economists have developed models of urban structure and patterning incorporating population location/movement and the location of economic activity to be able to rationally explain and predict urban growth and allocate resources so as to implement equitable distributions. The resulting models served to illustrate the importance of the interactions between specific geographic location, population concentrations, and economic activity. But given the development of world cities, there is the relationship between the size of settlements and political power in intergroup relations to consider. The spatial aspect of population density is, after all, one of the most fundamental variables for understanding the constraints and possibilities of human social organization.
Buchteile zum Thema "Spatial host population structure"
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Fitzgibbon, W. E., und M. Langlais. „Simple Models for the Transmission of Microparasites Between Host Populations Living on Noncoincident Spatial Domains“. In Structured Population Models in Biology and Epidemiology, 115–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78273-5_3.
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Etheridge, Alison. „Spatial Structure“. In Some Mathematical Models from Population Genetics, 89–107. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-16632-7_6.
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Falińska, Krystyna. „Population Spatial Structure Dynamics During Succession“. In Tasks for vegetation science, 118–37. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3266-4_13.
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Garloff, Alfred, und Duncan Roth. „Regional Population Structure and Young Workers’ Wages“. In Advances in Spatial Science, 261–83. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-68563-2_13.
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Loreau, M., und C. L. Nolf. „Spatial structure and dynamics of a population of Abax ater“. In Carabid Beetles: Ecology and Evolution, 165–69. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-017-0968-2_25.
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He, Dan, und Yuemin Ning. „Evolution of Population Structure and Spatial Distribution in Shanghai Since 2000“. In Urban Development Challenges, Risks and Resilience in Asian Mega Cities, 227–49. Tokyo: Springer Japan, 2014. http://dx.doi.org/10.1007/978-4-431-55043-3_13.
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Chu, Dominique, und Jonathan E. Rowe. „Spread of Vector Borne Diseases in a Population with Spatial Structure“. In Lecture Notes in Computer Science, 222–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-30217-9_23.
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Berenbaum, May R., und Arthur R. Zangerl. „Population-Level Adaptation to Host-Plant Chemicals: The Role of Cytochrome P450 Monooxygenases“. In Genetic Structure and Local Adaptation in Natural Insect Populations, 91–112. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4757-0902-5_5.
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Gourley, S. A., R. Liu und J. Wu. „Spatiotemporal Patterns of Disease Spread: Interaction of Physiological Structure, Spatial Movements, Disease Progression and Human Intervention“. In Structured Population Models in Biology and Epidemiology, 165–208. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-78273-5_4.
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Epping, Lennard, Esther-Maria Antão und Torsten Semmler. „Population Biology and Comparative Genomics of Campylobacter Species“. In Current Topics in Microbiology and Immunology, 59–78. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-65481-8_3.
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AbstractThe zoonotic pathogen Campylobacter is the leading cause for bacterial foodborne infections in humans. Campylobacters are most commonly transmitted via the consumption of undercooked poultry meat or raw milk products. The decreasing costs of whole genome sequencing enabled large genome-based analyses of the evolution and population structure of this pathogen, as well as the development of novel high-throughput molecular typing methods. Here, we review the evolutionary development and the population diversity of the two most clinically relevant Campylobacter species; C. jejuni and C. coli. The state-of-the-art phylogenetic studies showed clustering of C. jejuni lineages into host specialists and generalists with coexisting lifestyles in chicken and livestock-associated hosts, as well as the separation of C. coli isolates of riparian origin (waterfowl, water) from C. coli isolated from clinical and farm-related samples. We will give an overview of recombination between both species and the potential impact of horizontal gene transfer on host adaptation in Campylobacter. Additionally, this review briefly places the current knowledge of the population structure of other Campylobacter species such as C. lari, C. concisus and C. upsaliensis into perspective. We also provide an overview of how molecular typing methods such as multilocus sequence typing (MLST) and whole genome MLST have been used to detect and trace Campylobacter outbreaks along the food chain.
Konferenzberichte zum Thema "Spatial host population structure"
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spanu, ilaria, cristina vettori, raffaello giannini und donatella paffetti. „Spatial genetic structure of Taxus baccata L. relict population“. In Secondo Congresso Internazionale di Selvicoltura = Second International Congress of Silviculture. Accademia Italiana di Scienze Forestali, 2015. http://dx.doi.org/10.4129/cis-is-str.
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Liu, Yu, Xin Cao, Xihong Cui und Xuehong Chen. „Establishing Shrub Population Structure Using High-Spatial-Resolution Google Earth Imagery“. In IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium. IEEE, 2018. http://dx.doi.org/10.1109/igarss.2018.8519407.
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Messenger, Louisa Alexandra. „Anthroponotic dispersal, ecological host fitting, and mosaic population structure of sylvaticTrypanosoma cruzi: Insights from highland Bolivia“. In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.95416.
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Sains, George, Conor Houghton und Seth Bullock. „Spatial community structure impedes language amalgamation in a population-based iterated learning model“. In The 2023 Conference on Artificial Life. MIT Press, 2023. http://dx.doi.org/10.1162/isal_a_00657.
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Antipova, Ekaterina, Liliya Sushkevich und Anton Tsitou. „SHRINKING CITIES OF BELARUS: DEVELOPMENT FACTORS AND SHIFTS IN THE SPATIAL STRUCTURE“. In Book of Abstracts and Contributed Papers, 96. Geographical Institute "Jovan Cvijić" SASA, 2024. http://dx.doi.org/10.46793/csge5.59ea.
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The article assesses factors, the scale of demographic shrinkage of Belarusian cities and shifts in the spatial structure based on statistical data from three intercensus periods—1989–1999, 1999–2009, and 2009–2019. Using a set of methods of mathematical-statistical, balance, cartographic, typographers, geographic systematization and GIS technologies, for the first time in relation to Belarus, criteria for shrinking cities were determined, calculations of population dynamics for 1989–2019, indicators of natural and migration movements of the population, demographic balance of all cities of Belarus were performed. The analysis established that the main factors of demographic shrinkage are the migration transition of the 1970s, the political and socio-economic transformations of the transition period of the 1990s, and the demographic transition of the 1980–1990s. The authors determined that 46.1% of the country’s cities are classified as shrinking. A distinctive feature of the methodology in comparison with similar studies is the development of a typograph of cities by the nature of shrinkage, distinguishing three types (outpacing shrinkage, catching-up shrinkage and reversible demographic trend). There is a predominance of cities of catching-up shrinkage with negative population dynamics in two intercensus periods (1999–2009–2019) and a predominantly regressive type of demographic balance (68%), which are geographically distributed throughout the country. Every fourth shrinking city in Belarus belongs to the most unfavorable type—outpacing shrinkage with stable negative population dynamics in three intercensus periods (1989–2019) and a regressive type of demographic balance (since 1999), which are represented in the Vitebsk, Gomel, and Mogilev regions. A peculiar phenomenon is represented by shrinking cities of the third type (7.5%), located in the zone of radioactive contamination after the Chernobyl accident and the socio-economic periphery, in which, against the background of negative dynamics, a progressive type of demographic balance began to be observed. The demographic shrinkage of Belarusian cities against the backdrop of the transition to post-industrial development has led to shifts in the spatial and functional structure. This trend manifested itself in a reduction of the area of production functional zones.
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Shpirko, S. „Mathematical modeling of the hierarchical structure of the spatial distribution of the medieval rural population“. In Historical research in the context of data science: Information resources, analytical methods and digital technologies. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1795.978-5-317-06529-4/103-107.
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The subject of paper is the mathematical modeling of the spatial distribution of the medieval rural population. On the basis of the variational approach, two models of the hierarchy of centers are being developed, allowing with a high degree of reliability to identify the factors of the development of the settlement structure and to describe quantitatively the relationship between its most important parameters, such as density, population size and area.
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Shpirko, S. „Mathematical modeling of the hierarchical structure of the spatial distribution of the medieval rural population“. In Historical research in the context of data science: Information resources, analytical methods and digital technologies. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1795.978-5-317-06529-4/103-107.
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The subject of paper is the mathematical modeling of the spatial distribution of the medieval rural population. On the basis of the variational approach, two models of the hierarchy of centers are being developed, allowing with a high degree of reliability to identify the factors of the development of the settlement structure and to describe quantitatively the relationship between its most important parameters, such as density, population size and area.
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Liu, Jiaxin, und Changming Tang. „Chinese nursing home design studies based on changes in design formal language“. In 15th International Conference on Applied Human Factors and Ergonomics (AHFE 2024). AHFE International, 2024. http://dx.doi.org/10.54941/ahfe1004899.
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1 BackgroundBased on the current structural shortage of labor force and serious shortage of caregivers in China's elderly and medical services [1], the future demand for elderly care services for the elderly population is also increasingly strong [2]. At present, the proportion of Chinese elderly people living in elderly care institutions is 0.73%, which reflects that there are still some obstacles to the general acceptance of elderly care institutions by Chinese elderly people. Combined with the theory of environmental psychology, it can be seen that the environment can have an impact on behavior, psychology and other aspects, so the scientific shaping of space is inextricably linked to the enhancement of the user's spatial acceptance. Based on this, this study discusses the development history, development status and future development trend of nursing home design in China, and explores the innovative development path of nursing home design in the future. It aims to improve the acceptance and willingness to use nursing homes by the elderly and their families through optimization at the design level, so as to alleviate the current aging problem in China and the world.2 MethodDesign form language, is a kind of abstract language that can cover the design concept, design strategy, is a logical combination of structure, color, material and other figurative language in design. The change of design form language is often closely related to the change of user needs, the development of the industry now, etc. Citespace can present the structure of knowledge, the situation of information in the form of graphical distribution [3], and combined with the resulting graphs to analyze the disciplinary structure of the field of study related to the discipline structure, the hot frontier and other laws [4]. In view of the fact that the keyword maps that can be directly generated by importing literature data in Citespace cannot accurately represent the design form language explored in this study, this study organizes the design form language of each piece of literature in the valid title data for the titles, keywords, and abstracts of the 253 pieces of literature in the CNKI database, respectively.3 ResultThis study combines the data processing results of the design form language to produce three results related to the development of nursing home design in China. First, the development history of nursing home design in China is divided into three stages: the "starting period", the "high speed development period" and the "innovation enlightenment period", and there is still much room for development. Secondly, from the current development status of Chinese nursing home design, the concentration of current research is high, which also proves that the innovation of Chinese nursing home design is low at this stage. In addition, the research hotspots are mainly "people-oriented" and "integration of medical and nursing care", which reflects the current Chinese nursing home design's emphasis on the physiological and psychological needs of the elderly, and conforms to the current Chinese government's guidelines for nursing homes. Thirdly, "multi-dimensional consideration of user needs", "optimization of nursing home living mode through spatial design", and "exploration of cutting-edge fields" are proposed, The four suggestions on the direction of future development of nursing home design in China are "multi-dimensional consideration of users' needs", "optimization of living mode through spatial design", "exploration of frontier fields", and "in-depth combination of theory and practice".4 ConclusionThis study applies Citespace to analyze the literature about design form language visualization mapping in the field of Chinese nursing home design in the past 15 years, and according to the changing law of design form language, we have launched a study on the development history, development status, and future development trend of China's nursing home design, and obtained four directions of the future of China's nursing home design that are worth developing and studying in depth, which provides a directional guideline for the research of China's nursing home design.References[1] Zuo Meiyun. Meaning and mode of smart aging[J]. China Social Work,2018(32):26-27.[2]Wang Min. Research on nursing home design based on geriatric psychology[D]. Southwest Jiaotong University,2016.[3]Chen Yue,Chen Chaomei,Liu Zeyuan et al. Methodological functions of CiteSpace knowledge graph[J]. Science Research,2015,33(02):242-253.DOI:10.16192/j.cnki.1003-2053.2015.02.009.[4] Du Shuxing,Peng Liping,Lian Lilin. Current status of foreign industrial design research based on CiteSpace econometric analysis[J]. Journal of Graphics,2017,38(06):876-880.
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Poleganova, Dessislava, Desislava Varadzhakova und Marina Raykova. „Spatial polarization and urban ghettoization of the Roma population in Bulgaria“. In International Scientific-Practical Conference "Economic growth in the conditions of globalization". National Institute for Economic Research, 2023. http://dx.doi.org/10.36004/nier.cdr.v.2023.17.7.
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The current urban development in Europe faces many complex problems, mainly related to the deepening of socio-economic inequalities, spatial polarization and ghettoization, the increasing share of marginalized populations and those at risk of poverty, and school segregation. These issues are particularly acute in countries with a heterogeneous ethnic structure, and the Roma population has emerged as the most vulnerable group within Europe, particularly in Bulgaria. Roma ethnical group constituted 4.4% of the total Bulgarian population in 2021 and shows a high territorial concentration in several well-delineated areas, namely North-Western, North-Eastern, Maritsa, Trans-Balkan, and Burgas regions. In addition, more than half of them live in cities and possess the most favorable demographic features and the highest migration mobility compared to other ethnic groups. So far, despite the long-standing efforts of the Bulgarian state for Roma's successful integration, there are continuous and unfavorable trends of deepening processes of social exclusion, intolerance manifestations, spatial segregation, poor housing conditions, and lack of employment. The paper explores the current spatial polarization and urban ghettoization of the Roma population in Bulgaria. The spatial segregation of Roma urban communities is a significant issue in Bulgaria, and efforts to address their integration through national and regional strategies have not yet yielded substantial improvements. The extensive knowledge of the Roma population's cultural and other inherent peculiarities and the involvement of Roma stakeholders in policy discussions and implementations are crucial for achieving sustainable change in Bulgarian society.
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Ma, Guoqiang, und Zhenlong Zhang. „The change of urban population spatial structure of Nanjing, 1982–2007: Based on ESDA, density function and GIS“. In 2010 18th International Conference on Geoinformatics. IEEE, 2010. http://dx.doi.org/10.1109/geoinformatics.2010.5567737.
Der volle Inhalt der QuelleBerichte der Organisationen zum Thema "Spatial host population structure"
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Boyle, Maxwell, Mallorie Davis, Maxwell Boyle und Mallorie Davis. Terrestrial vegetation monitoring at Horseshoe Bend National Military Park: 2022 data summary. National Park Service, 2024. http://dx.doi.org/10.36967/2305166.
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Parks within the Southeast Coast Network (SECN) host a diverse assemblage of plants and terrestrial vegetation communities. Vegetation communities are dynamic entities whose species composition, abundance, distribution, and structure are influenced by environmental factors and impacted over time by natural and anthropogenic disturbances. Determining trends in vegetation communities over time and identifying plant stressors is vital to understanding the ecological health of terrestrial ecosystems within SECN parks. Horseshoe Bend National Military Park lies within the Southern Inner Piedmont ecoregion of Alabama. The distribution and composition of forested habitats within the park are largely determined by former land-use patterns (including clearing land for agriculture and timber removal), as well as by localized edaphic conditions. Stressors and threats to vegetation resources are present within the park, many of which are related to large-scale land-use changes of the 19th and 20th centuries, current impacts from upstream and downstream dams along the Tallapoosa River, and adjacent land use. Other threats to the vegetation resources of Horseshoe Bend National Military Park include over-population of white-tailed deer (Odocoileus virginianus), outbreaks of southern pine beetle (Dendroctonus frontalis), and competition from invasive non-native vegetation. 2022 marked the first year of conducting this monitoring effort at Horseshoe Bend National Military Park. Ten vegetation plots were established throughout the park in August. Data collected in each plot included species richness across multiple spatial scales, species-specific cover and constancy, species-specific woody stem seedling/sapling counts and adult tree diameter at breast height (DBH), overall tree health, landform, soil, observed disturbance, and woody biomass estimates. Data were stratified across two dominant broadly defined habitats within the park: Piedmont Alluvial Wetlands and Piedmont Upland Forests. One hundred ninety-nine vascular plant taxa were detected during this monitoring effort, including 54 taxa not detected in previous lists.
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Poos, Jan Jaap, Timo Staeudle, Eleanor Greenway und Jurgen Batsleer. Spatial distribution, migration, and population structure of North Sea rays. Wageningen: Wageningen University & Research, 2023. http://dx.doi.org/10.18174/632935.
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Ansari, S. M., E. M. Schetselaar und J. A. Craven. Three-dimensional magnetotelluric modelling of the Lalor volcanogenic massive-sulfide deposit, Manitoba. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/328003.
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Unconstrained magnetotelluric inversion commonly produces insufficient inherent resolution to image ore-system fluid pathways that were structurally thinned during post-emplacement tectonic activity. To improve the resolution in these complex environments, we synthesized the 3-D magnetotelluric (MT) response for geologically realistic models using a finite-element-based forward-modelling tool with unstructured meshes and applied it to the Lalor volcanogenic massive-sulfide deposit in the Snow Lake mining camp, Manitoba. This new tool is based on mapping interpolated or simulated resistivity values from wireline logs onto unstructured tetrahedral meshes to reflect, with the help of 3-D models obtained from lithostratigraphic and lithofacies drillhole logs, the complexity of the host-rock geological structure. The resulting stochastic model provides a more realistic representation of the heterogeneous spatial distribution of the electric resistivity values around the massive, stringer, and disseminated sulfide ore zones. Both models were combined into one seamless tetrahedral mesh of the resistivity field. To capture the complex resistivity distribution in the geophysical forward model, a finite-element code was developed. Comparative analyses of the forward models with MT data acquired at the Earth's surface show a reasonable agreement that explains the regional variations associated with the host rock geological structure and detects the local anomalies associated with the MT response of the ore zones.
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Thiemermann, Andre, und Florian Groß. Identification of logistics land and examination of location patterns – the Rhineland metropolitan region case. Preprint, 2024. http://dx.doi.org/10.26128/2024.18.
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In Germany identification of logistics land is done rarely, among other things due to anonymization of employment and building data. The paper at hands presents a method for identifying logistics land based on publicly available data, in order to present an image of the existing spatial structure of logistics land. Identified spatial hotspots are mostly located in Metropolises/Regiopolises and their suburbs, along highways in areas with flat relief and in vicinity to large inland teminals/inland harbours. Correlation analyses show, that the area of identified logistics land shows only weak but significant correlations with other variables. In order to identify possible existing types of logistics hotspots, a cluster analysis is carried out for the identified logistics hotspots. The formation of the resulting three clusters is mainly driven by the existing logistics employment and company structure, the accessibility (e. g. of inland terminals) and population density. A comparison of the identified clusters with the remaining potential logistics land shows that extensive land reserves are only available in the low-density sururbs and rural areas cluster. Thus, the appearance of logistics sprawl is therefore to be expected solely due this reason.
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Crowley, David E., Dror Minz und Yitzhak Hadar. Shaping Plant Beneficial Rhizosphere Communities. United States Department of Agriculture, Juli 2013. http://dx.doi.org/10.32747/2013.7594387.bard.
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PGPR bacteria include taxonomically diverse bacterial species that function for improving plant mineral nutrition, stress tolerance, and disease suppression. A number of PGPR are being developed and commercialized as soil and seed inoculants, but to date, their interactions with resident bacterial populations are still poorly understood, and-almost nothing is known about the effects of soil management practices on their population size and activities. To this end, the original objectives of this research project were: 1) To examine microbial community interactions with plant-growth-promoting rhizobacteria (PGPR) and their plant hosts. 2) To explore the factors that affect PGPR population size and activity on plant root surfaces. In our original proposal, we initially prqposed the use oflow-resolution methods mainly involving the use of PCR-DGGE and PLFA profiles of community structure. However, early in the project we recognized that the methods for studying soil microbial communities were undergoing an exponential leap forward to much more high resolution methods using high-throughput sequencing. The application of these methods for studies on rhizosphere ecology thus became a central theme in these research project. Other related research by the US team focused on identifying PGPR bacterial strains and examining their effective population si~es that are required to enhance plant growth and on developing a simulation model that examines the process of root colonization. As summarized in the following report, we characterized the rhizosphere microbiome of four host plant species to determine the impact of the host (host signature effect) on resident versus active communities. Results of our studies showed a distinct plant host specific signature among wheat, maize, tomato and cucumber, based on the following three parameters: (I) each plant promoted the activity of a unique suite of soil bacterial populations; (2) significant variations were observed in the number and the degree of dominance of active populations; and (3)the level of contribution of active (rRNA-based) populations to the resident (DNA-based) community profiles. In the rhizoplane of all four plants a significant reduction of diversity was observed, relative to the bulk soil. Moreover, an increase in DNA-RNA correspondence indicated higher representation of active bacterial populations in the residing rhizoplane community. This research demonstrates that the host plant determines the bacterial community composition in its immediate vicinity, especially with respect to the active populations. Based on the studies from the US team, we suggest that the effective population size PGPR should be maintained at approximately 105 cells per gram of rhizosphere soil in the zone of elongation to obtain plant growth promotion effects, but emphasize that it is critical to also consider differences in the activity based on DNA-RNA correspondence. The results ofthis research provide fundamental new insight into the composition ofthe bacterial communities associated with plant roots, and the factors that affect their abundance and activity on root surfaces. Virtually all PGPR are multifunctional and may be expected to have diverse levels of activity with respect to production of plant growth hormones (regulation of root growth and architecture), suppression of stress ethylene (increased tolerance to drought and salinity), production of siderophores and antibiotics (disease suppression), and solubilization of phosphorus. The application of transcriptome methods pioneered in our research will ultimately lead to better understanding of how management practices such as use of compost and soil inoculants can be used to improve plant yields, stress tolerance, and disease resistance. As we look to the future, the use of metagenomic techniques combined with quantitative methods including microarrays, and quantitative peR methods that target specific genes should allow us to better classify, monitor, and manage the plant rhizosphere to improve crop yields in agricultural ecosystems. In addition, expression of several genes in rhizospheres of both cucumber and whet roots were identified, including mostly housekeeping genes. Denitrification, chemotaxis and motility genes were preferentially expressed in wheat while in cucumber roots bacterial genes involved in catalase, a large set of polysaccharide degradation and assimilatory sulfate reduction genes were preferentially expressed.
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Raikow, David, Jacob Gross, Amanda McCutcheon und Anne Farahi. Trends in water quality and assessment of vegetation community structure in association with declining mangroves: A condition assessment of American Memorial Park. National Park Service, 2023. http://dx.doi.org/10.36967/2301598.
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American Memorial Park (AMME) in Saipan contains a rare mangrove wetland that is known to support several endangered species. Through monitoring water quality and vegetation characteristics of the wetland for >10 years we documented a declining mangrove population, an increase in invasive plant species, and declining surface water salinity. Comprehensive surveys conducted in 2014 and 2019 quantified declines in the plant community observed by park staff. Surface water salinity declined from 2009 to 2018 and no other trend in surface water quality was observed. Over the time period of the present study, AMME experienced shifts in annual rainfall conditions that could be associated with ENSO cycles. Dry conditions beginning in late 2016 and continuing through mid-2018 resulted in some surface water sampling sites completely drying. Several stressors may have contributed to declines in mangroves adapted to saturated soils directly and allowed competing plants to proliferate, including disruption of hydrologic connectivity with marine waters resulting in reduced surface water salinity, reduced rainfall causing dry soil conditions, and physical storm damage to canopies. Recommendations include study of groundwater salinity, maintaining or modifying a culvert subject to filling with sediment or other excavation work to improve saline water flow to the wetland at high tides, the establishment of a new groundwater monitoring well, adding a surface water monitoring station near the culvert, conducting a spatial assessment of the mangrove habitat suitability within the mangrove wetland, and developing or assisting with mangrove interpretive and outreach programs.
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Boyle, M., und M. Boyle. Terrestrial vegetation monitoring at Canaveral National Seashore: 2022 data summary?version 1.1. National Park Service, 2024. http://dx.doi.org/10.36967/2305810.
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Parks within the Southeast Coast Network (SECN) host a diverse assemblage of plants and terrestrial vegetation communities. Vegetation communities are dynamic entities whose species composition, abundance, distribution, and structure are influenced by environmental factors and impacted over time by natural and anthropogenic disturbances. Determining trends in vegetation communities over time and identifying plant stressors is vital to understanding the ecological health of terrestrial ecosystems within SECN parks. Canaveral National Seashore lies within the Southern Coastal Plain ecoregion of Florida. The distribution and composition of vegetation communities within the park are largely determined by former land-use patterns, climate influences, as well as by localized edaphic conditions. Stressors and threats to vegetation resources are present within the park, many of which are related to large-scale land-use changes of the 19th and 20th centuries and rapidly changing climate patterns and sea-level rise. Other threats to the vegetation resources of Canaveral National Seashore include fire exclusion, feral hogs, and competition from invasive non-native vegetation. 2022 marked the first year of conducting this monitoring effort at Canaveral National Seashore. Fourteen vegetation plots were established throughout the park in April. Data collected in each plot included species richness across multiple spatial scales, species-specific cover and constancy, species-specific woody stem seedling/sapling counts and adult tree diameter at breast height (DBH), overall tree health, landform, soil, observed disturbance, and woody biomass estimates. Plot locations were stratified across two land parcels of the park (Apollo Beach and Oak Hill) and across two dominant broadly defined habitats: Maritime Upland Forests and Shrublands and Coastal Plain Upland Open Woodlands. One hundred seventy-six vascular plant taxa were detected during this monitoring effort, including eight taxa not detected in previous lists.
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Minz, Dror, Stefan J. Green, Noa Sela, Yitzhak Hadar, Janet Jansson und Steven Lindow. Soil and rhizosphere microbiome response to treated waste water irrigation. United States Department of Agriculture, Januar 2013. http://dx.doi.org/10.32747/2013.7598153.bard.
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Research objectives : Identify genetic potential and community structure of soil and rhizosphere microbial community structure as affected by treated wastewater (TWW) irrigation. This objective was achieved through the examination soil and rhizosphere microbial communities of plants irrigated with fresh water (FW) and TWW. Genomic DNA extracted from soil and rhizosphere samples (Minz laboratory) was processed for DNA-based shotgun metagenome sequencing (Green laboratory). High-throughput bioinformatics was performed to compare both taxonomic and functional gene (and pathway) differences between sample types (treatment and location). Identify metabolic pathways induced or repressed by TWW irrigation. To accomplish this objective, shotgun metatranscriptome (RNA-based) sequencing was performed. Expressed genes and pathways were compared to identify significantly differentially expressed features between rhizosphere communities of plants irrigated with FW and TWW. Identify microbial gene functions and pathways affected by TWW irrigation*. To accomplish this objective, we will perform a metaproteome comparison between rhizosphere communities of plants irrigated with FW and TWW and selected soil microbial activities. Integration and evaluation of microbial community function in relation to its structure and genetic potential, and to infer the in situ physiology and function of microbial communities in soil and rhizospere under FW and TWW irrigation regimes. This objective is ongoing due to the need for extensive bioinformatics analysis. As a result of the capabilities of the new PI, we have also been characterizing the transcriptome of the plant roots as affected by the TWW irrigation and comparing the function of the plants to that of the microbiome. *This original objective was not achieved in the course of this study due to technical issues, especially the need to replace the American PIs during the project. However, the fact we were able to analyze more than one plant system as a result of the abilities of the new American PI strengthened the power of the conclusions derived from studies for the 1ˢᵗ and 2ⁿᵈ objectives. Background: As the world population grows, more urban waste is discharged to the environment, and fresh water sources are being polluted. Developing and industrial countries are increasing the use of wastewater and treated wastewater (TWW) for agriculture practice, thus turning the waste product into a valuable resource. Wastewater supplies a year- round reliable source of nutrient-rich water. Despite continuing enhancements in TWW quality, TWW irrigation can still result in unexplained and undesirable effects on crops. In part, these undesirable effects may be attributed to, among other factors, to the effects of TWW on the plant microbiome. Previous studies, including our own, have presented the TWW effect on soil microbial activity and community composition. To the best of our knowledge, however, no comprehensive study yet has been conducted on the microbial population associated BARD Report - Project 4662 Page 2 of 16 BARD Report - Project 4662 Page 3 of 16 with plant roots irrigated with TWW – a critical information gap. In this work, we characterize the effect of TWW irrigation on root-associated microbial community structure and function by using the most innovative tools available in analyzing bacterial community- a combination of microbial marker gene amplicon sequencing, microbial shotunmetagenomics (DNA-based total community and gene content characterization), microbial metatranscriptomics (RNA-based total community and gene content characterization), and plant host transcriptome response. At the core of this research, a mesocosm experiment was conducted to study and characterize the effect of TWW irrigation on tomato and lettuce plants. A focus of this study was on the plant roots, their associated microbial communities, and on the functional activities of plant root-associated microbial communities. We have found that TWW irrigation changes both the soil and root microbial community composition, and that the shift in the plant root microbiome associated with different irrigation was as significant as the changes caused by the plant host or soil type. The change in microbial community structure was accompanied by changes in the microbial community-wide functional potential (i.e., gene content of the entire microbial community, as determined through shotgun metagenome sequencing). The relative abundance of many genes was significantly different in TWW irrigated root microbiome relative to FW-irrigated root microbial communities. For example, the relative abundance of genes encoding for transporters increased in TWW-irrigated roots increased relative to FW-irrigated roots. Similarly, the relative abundance of genes linked to potassium efflux, respiratory systems and nitrogen metabolism were elevated in TWW irrigated roots when compared to FW-irrigated roots. The increased relative abundance of denitrifying genes in TWW systems relative FW systems, suggests that TWW-irrigated roots are more anaerobic compare to FW irrigated root. These gene functional data are consistent with geochemical measurements made from these systems. Specifically, the TWW irrigated soils had higher pH, total organic compound (TOC), sodium, potassium and electric conductivity values in comparison to FW soils. Thus, the root microbiome genetic functional potential can be correlated with pH, TOC and EC values and these factors must take part in the shaping the root microbiome. The expressed functions, as found by the metatranscriptome analysis, revealed many genes that increase in TWW-irrigated plant root microbial population relative to those in the FW-irrigated plants. The most substantial (and significant) were sodium-proton antiporters and Na(+)-translocatingNADH-quinoneoxidoreductase (NQR). The latter protein uses the cell respiratory machinery to harness redox force and convert the energy for efflux of sodium. As the roots and their microbiomes are exposed to the same environmental conditions, it was previously hypothesized that understanding the soil and rhizospheremicrobiome response will shed light on natural processes in these niches. This study demonstrate how newly available tools can better define complex processes and their downstream consequences, such as irrigation with water from different qualities, and to identify primary cues sensed by the plant host irrigated with TWW. From an agricultural perspective, many common practices are complicated processes with many ‘moving parts’, and are hard to characterize and predict. Multiple edaphic and microbial factors are involved, and these can react to many environmental cues. These complex systems are in turn affected by plant growth and exudation, and associated features such as irrigation, fertilization and use of pesticides. However, the combination of shotgun metagenomics, microbial shotgun metatranscriptomics, plant transcriptomics, and physical measurement of soil characteristics provides a mechanism for integrating data from highly complex agricultural systems to eventually provide for plant physiological response prediction and monitoring. BARD Report
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Boyle, Maxwell. Terrestrial vegetation monitoring at Cape Lookout National Seashore: 2022 data summary. National Park Service, 2024. http://dx.doi.org/10.36967/2303636.
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Parks within the Southeast Coast Network (SECN) host a diverse assemblage of plants and terrestrial vegetation communities. Vegetation communities are dynamic entities whose species composition, abundance, distribution, and structure are influenced by environmental factors and impacted over time by natural and anthropogenic disturbances. Determining trends in vegetation communities over time and identifying plant stressors is vital to understanding the ecological health of terrestrial ecosystems within SECN parks. Like most barrier islands along the southeastern coast, the vegetation communities along Cape Lookout National Seashore range from open beach and foredune grasslands on the ocean-facing side to tidal marshes on the sound-facing side. Between is a mixture of interdune swales, backdunes, and enclosed wetlands. Open upland vegetation is found on foredunes and occasional backdunes within the seashore. Cape Lookout National Seashore ecosystems are subjected to high frequencies of storm-, wind-, tide-, and wave-driven processes. Historic and current vegetation composition and structure are largely a result of these highly dynamic processes. Current vegetation patterns and processes across the Outer Banks are impacted and will continue to be impacted by rising sea-levels. Vegetation communities are vulnerable to overwash, which moves sand from the island?s ocean-side to the sound-side, brought on by more frequent and higher intensity storms. In 2019, Hurricane Dorian produced significant storm surge from the sound-side that overwashed the island and deposited sand into the ocean. Sand was scoured out from over 54 major cuts in the island, creating current ponds that are in various stages of succession. 2022 marked the first year of conducting this monitoring effort at Cape Lookout National Seashore. Forty-nine vegetation plots were established throughout the park in May and June. Data collected in each plot included species richness across multiple spatial scales, species-specific cover and constancy, species-specific woody stem seedling/sapling counts and adult tree diameter at breast height (DBH), overall tree health, landform, soil, observed disturbance, and woody biomass estimates. Data were stratified across four dominant broadly defined habitats within four park subunits: North Core Banks, South Core Banks, Cape Lookout, and Shackleford Banks. Broadly defined habitats monitored included: Open Upland Vegetation, Upland Forests and Shrublands, Nontidal Wetland Vegetation and Tidal Wetlands. One hundred and eighty-six vascular plant taxa were detected during this monitoring effort, including 11 taxa not detected in previous lists. Human-caused disturbances (e.g., historical plowing, shifting fire regimes, and altered hydrology) affecting plant communities within other SECN parks were not observed within these plots during this survey effort. Stunted plant growth was observed on several plots of Shackleford Banks and is likely caused by feral horse grazing. It is unclear from these data if grazing has impacted overall vegetation diversity and structure patterns across the island.
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Jones, David, Roy Cook, John Sovell, Matt Ley, Hannah Shepler, David Weinzimmer und Carlos Linares. Natural resource condition assessment: Lincoln Boyhood National Memorial. National Park Service, 2024. http://dx.doi.org/10.36967/2301822.
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The National Park Service (NPS) Natural Resource Condition Assessment (NRCA) Program administered by the NPS Water Resources Division evaluates current conditions for important natural resources and resource indicators using primarily existing information and data. NRCAs also report on trends in resource condition, when possible, identify critical data gaps, and characterize a general level of confidence for study findings. This NRCA complements previous scientific endeavors, is multi-disciplinary in scope, employs a hierarchical indicator framework, identifies and develops reference conditions/values for comparison against current conditions, and emphasizes spatial evaluation of conditions where possible. Lincoln Boyhood National Memorial (LIBO) was authorized by an act of Congress on February 19, 1962, (Public Law 87-407) to preserve the site associated with the boyhood and family of President Abraham Lincoln, including a portion of the original Tom Lincoln farm and the nearby gravesite of Nancy Hanks Lincoln. The 200-acre memorial commemorates the pioneer farm where Abraham Lincoln lived from the age of 7 to 21. The NRCA for LIBO employed a scoping process involving Colorado State University, LIBO and other NPS staffs to establish the NRCA framework, identify important park resources, and gather existing information and data. Indicators and measures for each resource were then identified and evaluated. Data and information were analyzed and synthesized to provide summaries and address condition, trend and confidence using a standardized but flexible framework. A total of nine focal resources were examined: four addressing system and human dimensions, one addressing chemical and physical attributes, and four addressing biological attributes. The quality and currentness of data used for the evaluation varied by resource. Landscape context ? system and human dimensions included land cover and land use, natural night skies, soundscape, and climate change. Climate change and land cover/land use were not assigned a condition or trend?they provide important context to the memorial and many natural resources and can be stressors. Some of the land cover and land use-related stressors at LIBO and in the larger region are related to the development of rural land and increases in population/housing over time. The trend in land development, coupled with the lack of significantly sized and linked protected areas, presents significant challenges to the conservation of natural resources of LIBO to also include natural night skies, natural sounds and scenery. Climate change is happening and is affecting resources, but is not considered good or bad per se. The information synthesized in that section is useful in examining potential trends in the vulnerability of sensitive resources and broad habitat types such as forests. Night skies and soundscapes, significantly altered by disturbance due to traffic, development and urbanization, warrant significant and moderate concern, respectively, and appear to be in decline. Air quality was the sole resource supporting chemical and physical environment at the memorial. The condition of air quality can affect human dimensions of the park such as visibility and scenery as well as biological components such as the effect of ozone levels on vegetation health. Air quality warrants significant concern and is largely impacted by historical and current land uses outside the memorial boundary. The floral biological component was examined by assessing native species composition, Mean Coefficient of Conservation, Floristic Quality Assessment Index, invasive exotic plants, forest pests and disease, and forest vulnerability to climate change. Vegetation resources at LIBO have been influenced by historical land uses that have changed the species composition and age structure of these communities. Although large tracts of forests can be found surrounding the park, the majority of forested areas are fragmented, and few areas within and around LIBO exhibit late-successional or old-growth characteristics. Vegetation communities at LIBO have a long history of being impacted by a variety of stressors and threats including noxious and invasive weeds, diseases and insect pests; compounding effects of climate change, air pollution, acid rain/atmospheric chemistry, and past land uses; and impacts associated with overabundant white-tail deer populations. These stressors and threats have collectively shaped and continue to impact plant community condition and ecological succession. The sole metric in good condition was native species composition, while all other indicators and metrics warranted either moderate or significant concern. The faunal biological components examined included birds, herptiles, and mammals. Birds (unchanging trend) and herptiles (no trend determined) warrant moderate concern, while mammal populations warrant significant concern (no trend determined). The confidence of both herptiles and mammals was low due to length of time since data were last collected. Current forest structure within and surrounding LIBO generally reflects the historical overstory composition but changes in the hardwood forest at LIBO and the surrounding area have resulted in declines in the avian fauna of the region since the 1970s. The decline in woodland bird populations has been caused by multiple factors including the conversion of hardwood forest to other land cover types, habitat fragmentation, and increasing human population growth. The identification of data gaps during the course of the assessment is an important NRCA outcome. Resource-specific details are presented in each resource section. In some cases, significant data gaps contributed to the resource not being evaluated or low confidence in the condition or trend being assigned to a resource. Primary data gaps and uncertainties encountered were lack of recent survey data, uncertainties regarding reference conditions, availability of consistent long-term data, and the need for more robust or sensitive sampling designs. Impacts associated with development outside the park will continue to stress some resources. Regionally, the direct and indirect effects of climate change are likely but specific outcomes are uncertain. Nonetheless, within the past several decades, some progress has been made toward restoring the quality of natural resources within the park, most notably the forested environments. Regional and park-specific mitigation and adaptation strategies are needed to maintain or improve the condition of some resources over time. Success will require acknowledging a ?dynamic change context? that manages widespread and volatile problems while confronting uncertainties, managing natural and cultural resources simultaneously and interdependently, developing disciplinary and interdisciplinary knowledge, and establishing connectivity across broad landscapes beyond park borders.