Patterns Of Spatial Segregation Research Articles

Measuring the Spatial Pattern of Residential Segregation

This paper discusses a new measure of residential segregation by race that incorporates spatial proximity among neighbourhoods into the calculation of the index. The basis for the measure is the Gini index of segregation. Unlike other similar measures discussed in recent years, this measure satisfies the 'principle of transfers', is flexible enough to quantify a range of pre-specified spatial patterns of segregation and is easy to compute using spatial statistics software packages. The properties of the index are illustrated using several simple simulations and a case study of non-White-White segregation in Atlanta, Georgia. The application of the index in Atlanta suggests that spatial proximity among adjacent neighbourhoods has a large impact on overall levels of racial segregation.

Escaping poverty neighbourhoods in the Netherlands

While patterns of spatial segregation and concentration of ethnic minority groups in European cities have been well documented, more dynamic data on migration have been rare until now. In particular, little is known about the potential for different kinds of households to escape from poverty areas. Escaping these areas can be important in order to escape unwanted housing and living conditions. The analyses in this paper show that in the Netherlands the chance to escape such poverty neighbourhoods partly depends on ethnic descent: some immigrant groups are less able to escape than are Dutch households.

Speciation along environmental gradients.

Traditional discussions of speciation are based on geographical patterns of species ranges. In allopatric speciation, long-term geographical isolation generates reproductively isolated and spatially segregated descendant species. In the absence of geographical barriers, diversification is hindered by gene flow. Yet a growing body of phylogenetic and experimental data suggests that closely related species often occur in sympatry or have adjacent ranges in regions over which environmental changes are gradual and do not prevent gene flow. Theory has identified a variety of evolutionary processes that can result in speciation under sympatric conditions, with some recent advances concentrating on the phenomenon of evolutionary branching. Here we establish a link between geographical patterns and ecological processes of speciation by studying evolutionary branching in spatially structured populations. We show that along an environmental gradient, evolutionary branching can occur much more easily than in non-spatial models. This facilitation is most pronounced for gradients of intermediate slope. Moreover, spatial evolutionary branching readily generates patterns of spatial segregation and abutment between the emerging species. Our results highlight the importance of local processes of adaptive divergence for geographical patterns of speciation, and caution against pitfalls of inferring past speciation processes from present biogeographical patterns.

Sexual Segregation in White-Tailed Deer: Density-Dependent Changes in Use of Space, Habitat Selection, and Dietary Niche

Abstract Sexual segregation, defined as the exclusive use of different areas by males and females at specified spatial and temporal scales, is common among polygynous ruminants and in cervids in particular. Underlying mechanisms for such segregation are not understood fully, and reports have included female cervids segregating into habitats of both poorer and better quality than those used by males. Furthermore, two competing hypotheses of sexual segregation (body-size hypothesis, reproductive-strategy hypothesis) predict different responses to changes in population density; an increase in degree of sexual segregation with increasing density in the former and a decrease in segregation in the latter. We examined patterns of sexual segregation among white-tailed deer (Odocoileus virginianus) on the Welder Wildlife Refuge in south Texas at moderate (39 deer/km2) and high (77 deer/km2) population densities during 1974–1977. At moderate density, females with young made greater use of chaparral-mixed grass habitat with dense cover than did males, where preferred herbaceous forage was less abundant, presumably for reasons of predator avoidance. At high density, which was a result of predator control, sexual segregation among male and females decreased during all seasons (P < 0.05). Males that otherwise used more open habitats increased their use of the chaparral-mixed grass as levels of intraspecific competition increased. As spatial segregation between males and females decreased at the high population density, diets of both sexes shifted toward more graminoids and browse, and shifts were more pronounced among males. The result was decreased dietary overlap between sexes when measured by principal-component analysis. Measures of fat reserves suggested that although both females and males were in poorer condition at high density, females were affected to a greater extent than were males. This outcome suggested that females were not driving patterns of spatial segregation by being better able to compete with males for closely-cropped forages. Rather, predator avoidance by females with young related to the reproductive-strategy hypothesis best explained patterns we observed, and competition between sexes was rejected as a cause of sexual segregation.

Segregation in Vienna: Impacts of Market Barriers and Rent Regulations

Market barriers may have an enormous influence on the spatial segregation patterns of immigrant groups. This is specifically the case in Vienna, Austria, where accessibility rules with respect to different segments of the housing stock can be seen as one of the most important factors in explaining the residential patterns of Turks and Yugoslavs. Describing and explaining the patterns of these groups is the central issue in this paper. Conclusions are drawn with a reference to recent economic and social trends and the ongoing deregulation of the housing market.

Building up walls: the new pattern of spatial segregation in São Paulo

Building up walls: the new pattern of spatial segregation in São Paulo

Sex determination in Miocene catarrhine primates

Canines of fossil hominoids and primitive catarrhines from several early, middle, and late Miocene sites were analyzed according to the shape indices described in Kelley (1995) and compared to those of males and females of extant great apes. In bivariate plots of the fossil canines utilizing the indices, 90% of the upper canines and 85% of the lower canines fell within or just outside the exclusively male or exclusively female territories delimited by the extant great apes. The remainder fell in the male-female overlap zones. Sex assignments based on these distributions were nearly 100% concordant with classifications according to canine height, suggesting a high degree of accuracy. There were various taxon-specific shifts in bivariate space among fossil genera, reflecting subtle differences in canine shape between taxa within the overall pattern of similarity to extant great apes as a whole. In many cases these shifts are matched by particular extant-ape species and subspecies, while other fossil taxa have no exact analogue for canine shape among the extant great apes. However, the pattern of spatial segregation of canines identified as either male or female at each of the sites largely mirrors that of males and females within the extant-ape sample, indicating that Miocene catarrhines shared with extant great apes a common pattern of shape differences between male and female canines, regardless of taxon-specific morphologies. These observations demonstrate that the canines of fossil catarrhines can be sexed with a high degree of confidence based solely on intrinsic features of shape. This will permit more reliable characterizations of morphological sexual dimorphism among fossil species. It is also argued that canine shape is a more reliable indicator of sex in fossil taxa than are canine/molar size ratios.

Foraging patterns of Water Pipits (Anthus spinoletta) with nestlings

Foraging patterns of pairs of Water Pipits (Anthus spinoletta) nesting in alpine habitat in Wyoming were examined for sex-specific differences in division of space, how foraging behavior changes with nestling age, and how foraging behavior is modified to reduce the risk of nest detection by predators. Parental investment (measured by number of deliveries to nestlings, fecal sac removal, and time spent incubating and brooding) was not useful in predicting patterns of sexual niche partitioning of foraging space. There were no consistent patterns as to which sex foraged farthest from the nest. Distribution of the orientation of trip departures from nests, however, was significantly different between pair members in all cases. The mechanism(s) maintaining this pattern of spatial segregation is not known, but it may be the result of female dominance during the breeding season. Delivery rate of food to nestlings was positively correlated to nestling age. There was a concurrent positive correlation between delivery rate and percentage of foraging trips less than 50 m from the nest. Adult pipits flew significantly longer distances from nests when departing with fecal sacs. This is probably an adaptation to reduce the probability of nest detection by predators, and represents a trade-off between energy-efficient foraging and reproductive success.

Modeling the segregation of the urban population

The paper is concerned with the effects of spatial externalities on urban development. With the Herbert-Stevens model of the housing market as the point of departure, equilibrium conditions are formulated. Similar to those of stationary points in quadratic programming, these conditions allow the adaptation of the corresponding algorithms. The nonconvexities caused by the externalities lead to multiple equilibria which may be associated with different city sizes and spatial configurations. The model can be used for the simulation of different empirically observed spatial segregation patterns such as sectors, concentric rings, and multiple nuclei.