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Migration Model (migration + model)
Selected AbstractsBehavioural responses to habitat patch boundaries restrict dispersal and generate emigration,patch area relationships in fragmented landscapesJOURNAL OF ANIMAL ECOLOGY, Issue 4 2003Nicolas Schtickzelle Summary 1We studied the consequences of behaviour at habitat patch boundaries on dispersal for the bog fritillary butterfly Proclossiana eunomia Esper in two networks of habitat differing in fragmentation and matrix quality. We tested for differences in responses to patch boundaries according to the fragmentation level of the network by analysing movement paths of adult butterflies. 2Butterflies systematically engaged in U-turns when they reached a boundary in the fragmented network while they crossed over boundaries in more than 40% of boundary encounters in the continuous one. 3We applied the Virtual Migration model (Hanski, Alho & Moilanen 2000) to capture,mark,recapture data collected in both networks. The model indicated (i) a lower dispersal rate and (ii) a lower survival during dispersal in the fragmented network. This latter difference is likely to be the key biological process leading to behavioural avoidance of patch boundary crossings. 4On the basis of this behavioural difference, we designed an individual-based simulation model to explore the relationship between patch area, boundary permeability and emigration rate. 5Predictions of the model fitted observed results of the effect of patch area on emigration rate according to fragmentation: butterflies are more likely to leave small patches than large ones in fragmented landscapes (where patch boundary permeability is low), while this relationship disappears in more continuous landscapes (where patch boundary permeability is high). [source] EFFECTS OF MIGRATION ON THE GENETIC COVARIANCE MATRIXEVOLUTION, Issue 10 2007Frédéric Guillaume In 1996, Schluter showed that the direction of morphological divergence of closely related species is biased toward the line of least genetic resistance, represented by gmax, the leading eigenvector of the matrix of genetic variance,covariance (the G -matrix). G is used to predict the direction of evolutionary change in natural populations. However, this usage requires that G is sufficiently constant over time to have enough predictive significance. Here, we explore the alternative explanation that G can evolve due to gene flow to conform to the direction of divergence between incipient species. We use computer simulations in a mainland,island migration model with stabilizing selection on two quantitative traits. We show that a high level of gene flow from a mainland population is required to significantly affect the orientation of the G -matrix in an island population. The changes caused by the introgression of the mainland alleles into the island population affect all aspects of the shape of G (size, eccentricity, and orientation) and lead to the alignment of gmax with the line of divergence between the two populations' phenotypic optima. Those changes decrease with increased correlation in mutational effects and with a correlated selection. Our results suggest that high migration rates, such as those often seen at the intraspecific level, will substantially affect the shape and orientation of G, whereas low migration (e.g., at the interspecific level) is unlikely to substantially affect the evolution of G. [source] An evaluation of the potential influence of SST and currents on the oceanic migration of juvenile and immature chum salmon (Oncorhynchus keta) by a simulation modelFISHERIES OCEANOGRAPHY, Issue 1 2004Tomonori Azumaya Abstract Using a salmon migration model based on the assumption that swimming orientation is temperature dependent, we investigated the determining factors of the migration of juvenile and immature chum salmon (Oncorhynchus keta) in the North Pacific. We compared the predictions of the model with catch data of immature and juvenile chum salmon collected by Japanese research vessels from 1972 to 1999. The salmon migration model reproduced the observed distributions of immature chum salmon and indicates that passive transport by wind-driven and geostrophic currents plays an important role in the eastward migration of Asian salmon. These factors result in a non-symmetric distribution of Asian and North American chum salmon in the open ocean. The directional swimming component contributes to the northward migration in summer. The model results indicate that during the first winter Asian chum salmon swim northward against the southward wind-driven currents to stay in the western North Pacific. This suggests that Asian chum salmon require more energy to migrate than other stocks during the first winter of their ocean life. [source] Reconstruction of palaeo-burial history and pore fluid pressure in foothill areas: a sensitivity test in the Hammam Zriba (Tunisia) and Koh-i-Maran (Pakistan) ore depositsGEOFLUIDS (ELECTRONIC), Issue 2 2003L. Benchilla Abstract The burial and pore fluid pressure history of fluorite ore deposits is reconstructed: (i) at Hammam Zriba,Djebel Guebli along the eastern margin of the Tunisian Atlas; and (ii) at Koh-i-Maran within the northern part of the Kirthar Range in Pakistan. Both the deposits are hosted by Late Jurassic carbonate reservoirs, unconformably overlain by Late Cretaceous seals. Microthermometric analyses on aqueous and petroleum fluid inclusions with pressure,volume,temperature,composition (PVTX) modeling of hydrocarbon fluid isochores are integrated with kinematics and thermal 2D basin modeling in order to determine the age of mineralization. The results suggest a Cenozoic age for the fluorite mineralization and a dual fluid migration model for both ore deposits. The PVTX modeling indicates that the initial stage of fluorite cementation at Hammam Zriba occurred under fluid pressures of 115 ± 5 bars and at a temperature close to 130°C. At Koh-i-Maran, the F3 geodic fluorite mineralization developed under hydrostatic pressures of 200 ± 10 bars, and at temperatures of 125,130°C. The late increase in temperature recorded in the F3 fluorites can be accounted for by rapid rise of hotter fluids (up to 190°C) along open fractures, resulting from hydraulic fracturing of overpressured sedimentary layers. [source] Evolutionary and statistical properties of three genetic distancesMOLECULAR ECOLOGY, Issue 8 2002Steven T. Kalinowski Abstract Many genetic distances have been developed to summarize allele frequency differences between populations. I review the evolutionary and statistical properties of three popular genetic distances: DS, DA, and ,, using computer simulation of two simple evolutionary histories: an isolation model of population divergence and an equilibrium migration model. The effect of effective population size, mutation rate, and mutation mechanism upon the parametric value between pairs of populations in these models explored, and the unique properties of each distance are described. The effect of these evolutionary parameters on study design is also investigated and similar results are found for each genetic distance in each model of evolution: large sample sizes are warranted when populations are relatively genetically similar; and loci with more alleles produce better estimates of genetic distance. [source] Load Monitoring of Impacted Carbon-Fibre-Reinforced Plastic PlatesPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Andy Ungethuem This work deals with a new wave migration model for the determination of an impact location for non-isotropic plates. The method is based on the wave propagation after the impact. The evaluation and processing of the signals of at least four sensors allow for the calculation of the impact location from the runtime of the signals. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] MIGRATION, MEDICAL AID AND WELFARE*AUSTRALIAN ECONOMIC PAPERS, Issue 4 2007WATARU KUREISHI This paper constructs a simple rural-urban migration model that explicitly incorporates the interactions between the individual's migration decision, the risk of incurring an infectious disease and unemployment. We show that providing a subsidy for health investment in urban regions in the form of medical aid does not improve individual welfare. This is because it induces further urban migration, increases the risk of infection and unemployment, and offsets completely the positive cost-reduction effect. [source] Applicability of Carbazole Migration Indices in Continental Rift Basins: A Case Study of Western Lujiapu Depression in Kailu Basin, NE ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2010Shuqing ZHOU Abstract: Kailu Basin in which the Western Lujiapu Depression is located is a typical continental rift basin. Biomarker parameters of the oils indicate that depositional facies and environments vary between the Bao 1 and Bao 14 fault blocks with a higher saline environment in the Bao 1 fault block, but such difference has no significant impact on carbazole abundance and distribution. Maturity and migration distance are the main controls on carbazole abundance and distribution in the Western Lujiapu Depression. The commonly used migration indices, such as ratios of nitrogen shield isomers to nitrogen exposed isomers (1-/4-methylcarbazole ratio, 1,8-/2,4-dimethylcarbazole (DMC) ratio and half-shield/exposed-DMC ratio), absolute concentrations of alkylated carbazoles and BC ratio (= benzo [a]carbazole/ (benzo[a]carbazole + benzo[c]carbazole)) increase at the low mature range and decrease at a higher mature range with increasing maturity. At relatively low maturity stage (Rc<0.77%), maturation has reversal effects with migration on the ratios of nitrogen shield isomers to nitrogen exposed isomers, which may cover migration influence and makes these parameters fail to indicate migration effects. Valid migration indicators at this maturity stage are concentrations of alkylated carbazoles and BC ratios, which can provide ideal tools for migration direction assessment even within short migration distance. Maturity effects should be taken into account when carbazole compounds are applied to indicate migration direction, and at different maturity stages, these commonly used parameters have different validity in tracing migration direction. Coupled with our previous study in the Eastern Lujiapu Depression, a conceptual model of the variation of nitrogen migration indices can be established for terrestrial rifted basins, that is, strong fractionation lateral migration model through sandy beds, weak fractionation vertical migration model along faults, and maturity impacts on migration assessment. [source] | |||||||||||||