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1.
In 1991, the Israeli government responded to severe shortages in the low-wage labour force by developing a Foreign Worker Program. Over the next two decades, hundreds of thousands of labour migrants from the Global South were issued work visas that would allow them to live temporarily in Israel. Migrants have since settled, primarily in Tel Aviv, where some have also overstayed their visas, given birth to children, and established ways of living as undocumented residents of Israel’s largest urban centre. In this article, I describe how undocumented migrant women and their Israeli-born children have had a particularly significant impact on the social and political context in which they live. Specifically, I explore how they have come to constitute a “privileged underclass” within the ethnically, geographically, and socio-economically stratified population of the city. While they share dilapidated public spaces and conditions of poverty with their historically marginalized Mizrahi neighbours in the southern part of the city, undocumented women and their children share special events, interpersonal engagements, and processes of “sentimental civics” with the largely wealthy and politically enfranchised Ashkenazi residents of Tel Aviv’s north who are their employers, financial patrons, and supporters of their campaign for citizenship. The development of a “privileged underclass” has thus exacerbated class conflict in Tel Aviv, bringing to the surface the well-established, but long-ignored Mizrahi struggles for recognition, and sowing the seeds for a sometimes violent, yet politically nuanced, anti-migrant mobilization.  相似文献   

2.
With advances in sequencing technology, research in the field of landscape genetics can now be conducted at unprecedented spatial and genomic scales. This has been especially evident when using sequence data to visualize patterns of genetic differentiation across a landscape due to demographic history, including changes in migration. Two recent model‐based visualization methods that can highlight unusual patterns of genetic differentiation across a landscape, SpaceMix and EEMS, are increasingly used. While SpaceMix's model can infer long‐distance migration, EEMS’ model is more sensitive to short‐distance changes in genetic differentiation, and it is unclear how these differences may affect their results in various situations. Here, we compare SpaceMix and EEMS side by side using landscape genetics simulations representing different migration scenarios. While both methods excel when patterns of simulated migration closely match their underlying models, they can produce either un‐intuitive or misleading results when the simulated migration patterns match their models less well, and this may be difficult to assess in empirical data sets. We also introduce unbundled principal components (un‐PC), a fast, model‐free method to visualize patterns of genetic differentiation by combining principal components analysis (PCA), which is already used in many landscape genetics studies, with the locations of sampled individuals. Un‐PC has characteristics of both SpaceMix and EEMS and works well with simulated and empirical data. Finally, we introduce msLandscape, a collection of tools that streamline the creation of customizable landscape‐scale simulations using the popular coalescent simulator ms and conversion of the simulated data for use with un‐PC, SpaceMix and EEMS.  相似文献   

3.
The narratives and images on websites of US hate groups that oppose undocumented immigrants represent and reproduce discourses that contribute to the subject formation of group members, who feel ethically obliged to counter unauthorized immigration. Left alone by the government, which is seen as unreliable and uncaring of patriotic values, they position themselves as heroic saviours of the nation. We argue that these hate groups’ ‘games of truth’ develop in response to the perception that irregular immigration threatens specific social orders and values, for instance about citizenship, national identity and otherness. This article helps to understand the ways in which anti-immigrant narratives serve the functions of countering these threats and of asserting the group members’ ethical obligation as a form of care of the self. In other words, from a Foucaultian viewpoint, we interpret the problematizations of ‘illegal’ immigration as discursive practices for the subject formation of hate group members.  相似文献   

4.
Abstract:  The process of invasion of the fruit surface by three species of armored scale insects [ Lepidosaphes beckii (Newman), Parlatoria pergandii Comstock and Aonidiella aurantii (Maskell)], was studied in citrus orchards in València, Spain. Three periods of intense crawler migration were detected annually for L. beckii and P. pergandii . Abundance of crawlers increased throughout the year and they moved outwards in the tree canopy. The fruit was continuously invaded during the period of fruit growth, starting at a very early stage of fruit development, by crawlers of the first generation of all the three species. Differences in fruit invasion and settling behaviour were found between the three species. First-generation crawlers tended to settle under the fruit calyx in L. beckii and P. pergandii , and on the exposed fruit surface in A. aurantii . During the second generation, most A. aurantii scales originated from reproducing females already settled on the fruit, whereas in L. beckii and P. pergandii new scales came preferentially from other tree substrates or from females settled under the fruit calyx. These findings suggest changes to optimize the timing of chemical sprays for controlling the scales.  相似文献   

5.
In this article, we develop population game theory, a theory that combines the dynamics of animal behavior with population dynamics. In particular, we study interaction and distribution of two species in a two-patch environment assuming that individuals behave adaptively (i.e., they maximize Darwinian fitness). Either the two species are competing for resources or they are in a predator-prey relationship. Using some recent advances in evolutionary game theory, we extend the classical ideal free distribution (IFD) concept for single species to two interacting species. We study population dynamical consequences of two-species IFD by comparing two systems: one where individuals cannot migrate between habitats and one where migration is possible. For single species, predator-prey interactions, and competing species, we show that these two types of behavior lead to the same population equilibria and corresponding species spatial distributions, provided interspecific competition is patch independent. However, if differences between patches are such that competition is patch dependent, then our predictions strongly depend on whether animals can migrate or not. In particular, we show that when species are settled at their equilibrium population densities in both habitats in the environment where migration between habitats is blocked, then the corresponding species spatial distribution need not be an IFD. Thus, when species are given the opportunity to migrate, they will redistribute to reach an IFD (e.g., under which the two species can completely segregate), and this redistribution will also influence species population equilibrial densities. Alternatively, we also show that when two species are distributed according to the IFD, the corresponding population equilibrium can be unstable.  相似文献   

6.

Drawing on fieldwork and interviews in Oslo and Bergen, Norway, this article discusses irregular migrants’ experiences of existential displacement and the tactics they use to try to re-establish a sense of emplacement and belonging. More specifically, it argues that irregular migrants’ experiences of embodied unbelonging are a consequence of a violent form of governmentality that includes specific laws, healthcare structures, and migration management rationalities. The article makes this argument by tracing how these experiences translate into embodied effects that feature prominently in migrants’ narratives of suffering while living in a country that purports to provide welfare services to all. The narratives of their state of being-in-the-world are ways through which migrants both experience and express the violence and deprivation they face. I argue that these narratives are instances of structures of feeling (Williams 1973), which are shaped by modes of governmentality. The article shows that irregular migrants’ coping strategies centrally involve faith, religious communities and friends. Irregular migrants draw on these relationships to get by, access healthcare, and to resist the (health) effects of social deprivation and political violence. These relationships allow irregular migrants to find meaningful ways of being-in-the-world and rebuilding, to some extent, a sense of entitlement and belonging.

  相似文献   

7.
Decision-making animals can use slow-but-accurate strategies, such as making multiple comparisons, or opt for simpler, faster strategies to find a 'good enough' option. Social animals make collective decisions about many group behaviours including foraging and migration. The key to the collective choice lies with individual behaviour. We present a case study of a collective decision-making process (house-hunting ants, Temnothorax albipennis), in which a previously proposed decision strategy involved both quality-dependent hesitancy and direct comparisons of nests by scouts. An alternative possible decision strategy is that scouting ants use a very simple quality-dependent threshold rule to decide whether to recruit nest-mates to a new site or search for alternatives. We use analytical and simulation modelling to demonstrate that this simple rule is sufficient to explain empirical patterns from three studies of collective decision-making in ants, and can account parsimoniously for apparent comparison by individuals and apparent hesitancy (recruitment latency) effects, when available nests differ strongly in quality. This highlights the need to carefully design experiments to detect individual comparison. We present empirical data strongly suggesting that best-of-n comparison is not used by individual ants, although individual sequential comparisons are not ruled out. However, by using a simple threshold rule, decision-making groups are able to effectively compare options, without relying on any form of direct comparison of alternatives by individuals. This parsimonious mechanism could promote collective rationality in group decision-making.  相似文献   

8.
This study of undocumented immigrant Nepalese workers in Japan analyses their ethnic history, demographics, migration strategies and work experiences. The majority belong to ethnic groups which the British designated 'martial races', whose tradition of foreign service as 'Gurkha' soldiers in the British and Indian Armies produced a culture of emigration and a remittance economy in rural Nepal. As a result, the present generation has been socialized to be familiar with international migration as an economic option, and has access to networks for its accomplishment. Japan's industrial structure and relative affluence have generated chronic shortages of workers to fill jobs shunned by Japanese in manufacturing and construction industries. This has elevated wages to levels which attract economically distressed foreign migrants such as those from Nepal. Despite the isolation and discrimination which they suffer, these Nepalese find the financial rewards to be sufficient to outweigh the hardships.  相似文献   

9.
By ‘working with the willing’, the National Industrial Symbiosis Programme (NISP) has successfully facilitated industrial symbiosis throughout the United Kingdom and, in the process, delivered significant economic and environmental benefits for both Programme members and the country as a whole. One of the keys to NISP's success is that, unlike failed attempts to plan and construct eco‐industrial systems from scratch, the Programme works largely with existing companies who have already settled in, developed, and successfully operate within a given locale. This article argues that existing and mature industrial systems provide the best prospects for identifying opportunities for, and ultimately facilitating, industrial symbiosis. Due to levels of diversification and operational fundamental niches that, in the fullness of time, develop within all industrial systems, industrially mature areas are deemed to be industrial symbiosis ‘conducive environments’. Building on the conservation biology concept of a habitat suitability index, the article presents a methodology for comparing a potential site for eco‐industrial development to a known baseline industrial ‘habitat’ already identified as being highly conducive to industrial symbiosis. The suitability index methodology is further developed and applied to a multi‐criteria evaluation geographic information system to produce a ‘habitat’ suitability map that allows practitioners to quickly identify potential industrial symbiosis hotspots (the methodology is illustrated for England). The article concludes by providing options for the development of symbiosis suitability indices and how they can be used to support the facilitation of industrial symbiosis and regional resource efficiency.  相似文献   

10.
The Nepalese Gurkhas have often been regarded as brave warriors in the scheme of British military recruitment since the 1800s. Today, their descendants have settled in various parts of South East and South Asia. How can one conceive of a Gurkha diaspora, and what are the Gurkhas and their families’ experiences of belonging in relation to varied migratory routes? This paper locates Gurkhas as migrants by deliberating upon the connection between military service and migration paths. I employ the lens of methodological transnationalism to elucidate how the Gurkha diaspora is both constructed and experienced. Diasporic consciousness and formation undergo modification alongside subsequent cycles of migration for different members of a diaspora. The article thus evaluates the transnational lives of migrants, and how these are connected to re-territorialized dimensions of identity and belonging.  相似文献   

11.
A universal law of the characteristic return time near thresholds   总被引:1,自引:0,他引:1  
C. Wissel 《Oecologia》1984,65(1):101-107
Summary Dramatic changes at thresholds in multiple stable ecosystems may be irreversible if caused by man. The characteristic return time to an equilibrium increases when a threshold is approached. A universal law for this increase is found, which may be used to forecast the position of a threshold by extrapolation of empirical data. Harvesting experiments on populations are proposed that can be used to verify the method. Preliminary harvesting experiments on rotifer populations display a good agreement with the theory.  相似文献   

12.
Conditional strategies are the most common form of discrete phenotypic plasticity. In a conditional strategy, the phenotype expressed by an organism is determined by the difference between an environmental cue and a threshold, both of which may vary among individuals. The environmental threshold model (ETM) has been proposed as a mean to understand the evolution of conditional strategies, but has been surprisingly seldom applied to empirical studies. A hindrance for the application of the ETM is that often, the proximate cue triggering the phenotypic expression and the individual threshold are not measurable, and can only be assessed using a related observable cue. We describe a new statistical model that can be applied in this common situation. The Latent ETM (LETM) allows for a measurement error in the phenotypic expression of the individual environmental cue and a purely genetically determined threshold. We show that coupling our model with quantitative genetic methods allows an evolutionary approach including an estimation of the heritability of conditional strategies. We evaluate the performance of the LETM with a simulation study and illustrate its utility by applying it to empirical data on the size-dependent smolting process for stream-dwelling Atlantic salmon juveniles.  相似文献   

13.
Studies of population structure often focus on the effects of population size and migration rates on genetic variation. Few studies, however, have investigated the relationship between these two factors. The purpose of this paper is to determine the extent to which migration (and gene flow) is density-dependent (that is, affected by population size) for populations in historical Massachusetts. Data from 4,859 marriage records were analyzed from four populations in north-central Massachusetts during the time period 1741 to 1849. These data were placed into 29 samples defined in terms of population and time cohort. Within each cohort the overall exogamy rate was computed along with three estimates of gene flow based on marital migration: local migration (k), long-distance migration (m), and effective migration rate (me). Three samples show unusually low rates that reflect the history of settlement. Regression analyses were used with the remaining samples, and they show nonlinear density-dependent migration that is unrelated to temporal trends. Migration is highest in samples with small population sizes (less than 800) and large population sizes (greater than 1,600). Migration is lowest in medium-sized populations. Two processes are suggested to explain this curvilinear relationship of migration and population size. In small populations, the lack of suitable potential mates and/or availability of settled land leads to an increase in migration into the population. As population size increases, this migration decreases. After populations reach a certain size, migration increases again, most likely reflecting the economic pull of larger populations. These patterns could act to enhance, or counter, genetic drift, depending on the direction of density dependence.  相似文献   

14.
The Aromuns represent a small and almost unknown people that live scattered over the Balkan Peninsula. Due to their language, that is very similar to classical Latin, they are in a special position. The Aromuns settled only in more recent times. Until now they lived as shepherds, as caravan guides and merchants and lead a semi-nomadic life. We are currently carrying out studies to determine the genetic structure of this population. To facilitate the interpretation of these data, we are also trying to obtain other important parameters that pertain to migration processes and the genealogical structure of this populations. The data arise from three areas in Albania, the Republic of Macedonia and Romania. The inbreeding coefficient and the proportion of repeated pairs of surnames was calculated through the use of genealogies and the isonymy method. The difference between these three populations are due primarily to confounding by selection of mates and family composition.  相似文献   

15.
The Boyden chamber assay provides a convenient method of assessing cell migration and measuring cell motility coefficients at the population level. Previous models of this assay completely ignore cell sedimentation in the suspension, assuming that all cells have already settled on the filter surface before commencing migration within the filter. However, ignoring cell sedimentation could lead to poor data interpretation because the time required for cells to settle through the suspension is close to the incubation period of only a few hours. This study models the Boyden chamber assay by incorporating the cell settling process to account for the cells remaining in the upper well when other cells migrate in the filter. The simulations in this study elucidate the experiments in the literature that test the haptotactic and chemotactic responses of rabbit chondrocytes to type II collagen. This study determines the cell population random motility, as well as the haptotaxis and chemotaxis coefficients, by fitting the experimental data. Results show that the chemotactic motility coefficient is 100 times greater than the haptotactic coefficient, and the equilibrium collagen-receptor dissociation constant is about 10-fold the haptotactic counterpart. Diffusion causes the soluble collagen gradients in the chemotactic case to decline over time, while the coated collagen gradients in the haptotactic assay are likely to remain fixed. As a result, the chemotactic case exhibits a lower number of migrated cells than the haptotactic assay. This study also demonstrates the influences of the dimensionless parameters that control cell behavior in the Boyden assay, providing a reference for future experiment designs.  相似文献   

16.
Archived blood fractions (plasma, settled red cells, white cells) have proved to be a rich and valuable source of DNA for human genetic studies. Large numbers of such samples were collected between 1960 and the present for protein and blood group studies, many of which are languishing in freezers or have already been discarded. More are discarded each year because the usefulness of these samples is not widely understood. Data from DNA derived from 10-35-year-old blood samples have been used to address the peopling of the New World and of the Pacific. Mitochondrial DNA haplotypes from studies using this source DNA support a single wave of migration into the New World (or a single source population for the New World), and that Mongolia was the likely source of the founding population. Data from Melanesia have shown that Polynesians are recent immigrants into the Pacific and did not arise from Melanesia.  相似文献   

17.
Francisco Pulido 《Oikos》2011,120(12):1776-1783
Partial migration is a common and widespread phenomenon in animal populations. Even though the ecological causes for the evolution and maintenance of partial migration have been widely discussed, the consequences of the genetics underlying differences in migration patterns have been little acknowledged. Here, I revise current ideas on the genetics of partial migration and identify open questions, focussing on migration in birds. The threshold model of migration describing the inheritance and phenotypic expression of migratory behaviour is strongly supported by experimental results. As a consequence of migration being a threshold trait, high levels of genetic variation can be preserved, even under strong directional selection. This is partly due to strong environmental canalization. This cryptic genetic variation may explain rapid de novo evolution of migratory behaviour in resident populations and the high prevalence of partial migration in animal populations. To date the threshold model of migration has been tested only under laboratory conditions. For obtaining a more realistic representation of migratory behaviour in the wild, the simple threshold model needs to be extended by considering that the threshold of migration or the liability may be modified by environmental effects. This environmental threshold model is valid for both facultative and obligate migration movements, and identifies genetic accommodation as an important process underlying evolutionary change in migration status. Future research should aim at identifying the major environmental variables modifying migration propensity and at determining reaction norms of the threshold and liability across variation in these variables.  相似文献   

18.
There are many methods available to predict electron output factors; however, many centres still measure the factors for each irregular electron field. Creating an electron output factor prediction model that approaches measurement accuracy – but uses already available data and is simple to implement – would be advantageous in the clinical setting. This work presents an empirical spline model for output factor prediction that requires only the measured factors for arbitrary insert shapes. Equivalent ellipses of the insert shapes are determined and then parameterised by width and ratio of perimeter to area. This takes into account changes in lateral scatter, bremsstrahlung produced in the insert material, and scatter from the edge of the insert. Agreement between prediction and measurement for the 12 MeV validation data had an uncertainty of 0.4% (1SD). The maximum recorded deviation between measurement and prediction over the range of energies was 1.0%. The validation methodology showed that one may expect an approximate uncertainty of 0.5% (1SD) when as little as eight data points are used. The level of accuracy combined with the ease with which this model can be generated demonstrates its suitability for clinical use. Implementation of this method is freely available for download at https://github.com/SimonBiggs/electronfactors.  相似文献   

19.
Atte Moilanen 《Oikos》2002,96(3):516-530
Parameter estimation is a critical step in the use of any metapopulation model for predictive purposes. Typically metapopulation studies assume that empirical data are of good quality and any errors are so insignificant that they can be ignored. However, three types of errors occur commonly in metapopulation data sets. First, patch areas can be mis-estimated. Second, unknown habitat patches may be located within or around the study area. Third, there may be false zeros in the data set, that is, some patches were observed to be empty while there truly was a population in the patch. This study investigates biases induced into metapopulation model parameter estimates by these three types of errors. It was found that mis-estimated areas influence the scaling of extinction risk with patch area; extinction probabilities for large patches become overestimated. Missing patches cause overestimation of migration distances and colonization ability of the species. False zeros can affect very strongly all model components, the extinction risk in large patches, intrinsic extinction rates in general, migration distances and colonization ability may become all overestimated. Biases in parameter estimates translate into corresponding biases in model predictions, which are serious particularly if metapopulation persistence becomes overestimated. This happens for example when the migration capability of the species is overestimated. Awareness of these biases helps in understanding seemingly anomalous parameter estimation results. There are also implications for field work: it may be reasonable to allocate effort so that serious errors in data are minimized. It is particularly important to avoid observing false zeros for large and/or isolated patches.  相似文献   

20.
Allison K. Shaw  Simon A. Levin 《Oikos》2011,120(12):1871-1879
Migration is used by a number of species as a strategy for dealing with a seasonally variable environment. In many migratory species, only some individuals migrate within a given season (migrants) while the rest remain in the same location (residents), a phenomenon called ‘partial migration’. Most examples of partial migration considered in the literature (both empirically and theoretically) fall into one of two categories: either species where residents and migrants share a breeding ground and winter apart, or species where residents and migrants share an overwintering ground and breed apart. However, a third form of partial migration can occur when non‐migrating individuals actually forgo reproduction, essentially a special form of low‐frequency reproduction. While this type of partial migration is well documented in many taxa, it is not often included in the partial migration literature, and has not been considered theoretically to date. In this paper we present a model for this partial migration scenario and determine under what conditions an individual should skip a breeding opportunity (resulting in partial migration), and under what conditions individuals should breed every chance they get (resulting in complete migration). In a constant environment, we find that partial migration is expected to occur when the mortality cost of migration is high, and when individuals can greatly increase their fecundity by skipping a year before breeding. In a stochastic environment, we find that an individual should skip migration more frequently with increased risk of a bad year (higher probability and severity), with higher mortality cost of migration, and with lower mortality cost of skipping. We discuss these results in the context of empirical data and existing life history theory.  相似文献   

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