Population Movement Patterns Research Articles

An automatic system for in vitro cell migration studies

This paper describes a system for in vitro cell migration analysis. Adult neural stem/progenitor cells are studied using time-lapse bright-field microscopy and thereafter stained immunohistochemically to find and distinguish undifferentiated glial progenitor cells and cells having differentiated into type-1 or type-2 astrocytes. The cells are automatically segmented and tracked through the time-lapse sequence. An extension to the Chan-Vese Level Set segmentation algorithm, including two new terms for specialized growing and pruning, made it possible to resolve clustered cells, and reduced the tracking error by 65%. We used a custom-built manual correction module to form a ground truth used as a reference for tracked cells that could be identified from the fluorescence staining. On average, the tracks were correct 95% of the time, using our new segmentation. The tracking, or association of segmented cells, was performed using a 2-state Hidden Markov Model describing the random behaviour of the cells. By re-estimating the motion model to conform with the segmented data we managed to reduce the number of tracking parameters to essentially only one. Upon characterization of the cell migration by the HMM state occupation function, it was found that glial progenitor cells were moving randomly 2/3 of the time, while the type-2 astrocytes showed a directed movement 2/3 of the time. This finding indicates possibilities for cell-type specific identification and cell sorting of live cells based on specific movement patterns in individual cell populations, which would have valuable applications in neurobiological research.

The design and use of an agent‐based model to simulate the 1918 influenza epidemic at Norway House, Manitoba

Agent-based modeling provides a new approach to the study of virgin soil epidemics like the 1918 flu. In this bottom-up simulation approach, a landscape can be created and populated with a heterogeneous group of agents who move and interact in ways that more closely resemble human behavior than is usually seen in other modeling techniques. In this project, an agent-based model was constructed to simulate the spread of the 1918 influenza pandemic through the Norway House community in Manitoba, Canada. Archival, ethnographic, epidemiological, and biological information were used to aid in designing the structure of the model and to estimate values for model parameters. During the epidemic, Norway House was a Hudson's Bay Company post and a Swampy Cree-Métis settlement with an economy based on hunting, fishing, and the fur trade. The community followed a traditional, seasonal travel pattern of summer aggregation and winter dispersal. The model was used to examine how seasonal community structures and associated population movement patterns may have influenced disease transmission and epidemic spread. Simulations of the model clearly demonstrate that human behavior can significantly influence epidemic outcomes.

A mobility model for classical swine fever in feral pig populations

We present a simulation model which explicitly captures the movement of wild animals over the landscape and the effect which herd mobility has on the temporal and spatial course of an epidemic. Using the example of classical swine fever in feral pig populations in the tropical savannas, we demonstrate that seasonal factors influencing population density and movement patterns are an important factor in the transmission of the disease. Pig population density is much greater at the start of the dry season than at the start of the wet season, with an epidemic most likely to occur if initiated at the start of the dry season. Spatial heterogeneity due to scarcity of water in the dry season causes herds to congregate around water sources. This concentration of herds, and the consequential isolation of sub-populations, reduces overall disease transmission compared with a model where the population is more evenly distributed over the landscape. The presence of adult male pig herds, which travel over greater distances than family herds, is shown to increase the overall scale of an outbreak in the dry season by connecting together otherwise isolated family herds. Eradication strategies are more likely to be successful in the dry season if they target long-range adult male herds. Our simulation method is generic and is equally applicable to other diseases where the host species is mobile.

Population assessment and movement patterns of lake sturgeon (Acipenser fulvescens) in the Manistee River, Michigan, USA

Summary Lake sturgeon (Acipenser fulvescens) population characteristics and migration patterns were evaluated in the Manistee River system, Michigan. Sturgeon (n = 102) were captured using gillnets, tagged and released in the system between 2001 and 2005. Biological data (weight, length, age, sex and spawning status) were collected to calculate length–weight relationships and relative condition factor (Kn), determine age structure, and estimate the annual spawning population size. Sturgeon were also implanted with radio and sonic transmitters, and migration patterns of 22 sturgeon were determined. The weight–length equation for sturgeon in the Manistee River system was log10 W = 3.17log10TL−5.52 and did not differ by sex. Kn equaled 0.72 and did not differ by sex or spawning status. Ages ranged from age 5 to age 54. Sexually mature male and female sturgeon were captured over the course of the study, and the size of the spawning population ranged from 21 to 66 spawners. Sturgeon migration movements up and down the Manistee River varied with date, water temperature, and discharge. The sturgeon appeared to use two different spawning sites in the Manistee River. The Manistee River system supports a remnant lake sturgeon population; the presence of a wide range of age classes and availability of a limited number of suitable spawning sites suggest continued recruitment to the population.

Comment: Fertility, mobility, and changing household dynamics in South Africa

Much has changed since the transition to democracy in South Africa more than a decade ago. Racial barriers are breaking down, a small but emerging black middle class has sprung up, and South Africa has become a major migration destination for people from all over Africa. But equally true, as evidenced by the papers in this section, is the persisting legacy of the apartheid era. Patterns of disease, population movement, household structure, and fertility continue to be shaped by severe inequalities in the distribution of wealth and resources. While such factors were well-known features of apartheid-era South Africa, it is perhaps less well known that postapartheid South Africa remains one of the world’s most unequal societies. The country’s severe HIV epidemic is superimposed on this reality. The three papers in this section address the epidemic – and how it impacts on and is impacted by fertility, migration, and household coping strategies. Rural areas in South Africa continue to demonstrate remarkable fluidity, and many places like Agincourt have experienced rapid change in the last decade. Household fluidity, fuelled by migration and HIV mortality, has become even more pronounced with increasing numbers of women entering the migrant labour market. These rapidly changing conditions underscore the central strength in the data brought together in this issue: a health and demographic surveillance system that has been in place since 1992 and has generated quality data on approximately 70,000 people in a rural, former ‘‘homeland’’ area in the northeast of South Africa. All of the papers in this section offer longitudinal analyses of these data, shedding light on the changing dynamics of fertility and rural livelihoods during this critical period of South Africa’s political and social transition. Garenne and colleagues show the consistent decline in fertility over the last 25 years, when the fertility rate decreased from 6.0 in 1979 to 2.3 in 2004, and the net reproduction rate declined to 1. This decline is faster than expected and represents perhaps the first time that fertility below replacement level has been measured in rural Africa. Garenne estimates that HIV is responsible for about 20% of the fall [1]. Concurrent with the measured decline in fertility, Madhavan & Schatz examined household structure and composition in 1992, 1997, and 2003. Their findings – that average household size decreased, that the proportion of female-headed households increased, and that the proportion of households with at least one maternal orphan doubled – point again to the impact of the HIV epidemic [2]. High mortality due to AIDS is already restructuring family coping strategies, decisions on whether or not to migrate and countless other variables that have yet to be examined. Collinson’s paper addresses the complexity of defining ‘‘urbanization’’ in a dynamic environment characterized (at least in part) by the maintenance of family ties to rural areas and the associated largescale circular migration so prevalent throughout southern Africa [3]. He rightly makes the point that, if we define urbanization as simply a massive, permanent movement to town, we end up missing much about the complexity, frequency, and indeed impact of such movement. His comparison between

Can whisker spot patterns be used to identify individual polar bears?

AbstractStudies of population dynamics, movement patterns and animal behavior usually require identification of individuals. We evaluated the reliability of using whisker spot patterns to noninvasively identify individual polar bears Ursus maritimus. We obtained the locations of polar bear whisker spots from photographs taken in western Hudson Bay, tested the independence of spot locations, estimated the complexity of each spot pattern in terms of information and determined whether each whisker spot pattern was reliable from its information content. Of the 50 whisker spot patterns analyzed, 98% contained enough information to be reliable, and this result varied little among observers. Photographs taken <50 m from polar bears were most useful. Our results suggest that individual identification of polar bears in the field based on whisker spot pattern variations is reliable. Researchers studying polar bear behavior or estimating population parameters can benefit from this method if proximity to the bears is feasible.

Fish population size and movement patterns in a small intermittently open South African estuary

The population size and movement patterns of small fish (>50 mm SL) in a small intermittently open estuary (Grant's Valley estuary: 33°40′12.1″S, 26°42′12.6″E) situated on the south-east Cape coast of South Africa were examined during the closed phase over the period May and August 2004. The estuary was subdivided into four discrete areas and the fish within each area sampled using a 30 m seine net (15 mm mesh). Fish captured were marked by fin clipping according to the area of capture. Fish population size was estimated by using three methods: the Schnabel estimator, the Hilborn estimator, and a derived estimator. A total of 12 species was captured and marked during the study. The total number of fish in the estuary was estimated at ca. 12 000 individuals (11 219–13 311). Marine-breeding species ( Rhabdosargus holubi, Monodactylus falciformis, and two mullet species) numerically dominated the ichthyofauna, possibly as a result of their effective use of overtopping events, when seawater washes over the sandbar, to enter the estuary during the closed mouth phase. The two mullet species, Myxus capensis and Liza richardsonii, and the Cape stumpnose, R. holubi moved extensively throughout the estuary, while the remaining species exhibited restricted movement patterns possibly due to the preference for refuge and foraging areas associated with reed beds. The observed movement patterns of individual fish species appeared to be associated with both foraging behaviour and habitat selection.

Variation in population dynamics and movement patterns between two geographically isolated populations of the dusky hopping mouse (Notomys fuscus)

The ecology of the dusky hopping mouse (Notomys fuscus) was studied at Pelican Waterhole in south-west Queensland and Montecollina Bore in north-east South Australia over an eight-year period. Population parameters of N. fuscus differed markedly between the two study sites. Whilst the population at Montecollina Bore exhibited large fluctuations in size, captures at Pelican Waterhole were lower but more consistent. Recaptures between sessions at Montecollina Bore peaked at 60% but no individuals were recaptured at Pelican Waterhole. No evidence of seasonal breeding was recorded at either site. Male N. fuscus captured at Montecollina Bore were significantly heavier (average 31.4 g) than Pelican Waterhole animals (average 26.6 g). Over a 1–4-night period, the maximum linear distance moved by radio-collared individuals was 1.5 km (average 481 m) at Pelican Waterhole and 400 m (average 199 m) at Montecollina Bore. Differences in population dynamics between the two sites are ascribed to food availability and habitat quality. Whilst Pelican Waterhole may constitute a more stable, less degraded environment, Montecollina Bore appears to be defined by periods of either very high or very low resource availability depending on rainfall. The abundance of dingoes and low cat and fox activity may contribute to the persistence of N. fuscus at the two study sites.

Population sizes, site fidelity and residence patterns of Australian snubfin and Indo-Pacific humpback dolphins: Implications for conservation

Very little is known about the ecology of snubfin Orcaella heinsohni and Indo-Pacific humpback dolphins Sousa chinensis in Australian waters. We used photo-identification data collected between 1999 and 2002 in Cleveland Bay, northeast Queensland, to estimate abundance, site fidelity and residence patterns of these species in order to make recommendations for their effective conservation and management. Our abundance estimates indicate that less than a hundred individuals of each species inhabit this coastal area. Even with relatively unbiased and precise abundance estimates population trends will be extremely difficult to detect in less than three years unless changes in population size are very high (>20% p.a.). Though both species are not permanent residents in Cleveland Bay, they both used the area regularly from year to year following a model of emigration and reimmigration. Individuals of both species spend periods of days to a month or more in coastal waters of Cleveland Bay before leaving, and periods of over a month outside the study area before entering the bay again. Because of their small population sizes and movement patterns, snubfin and humpback dolphins are particularly vulnerable to local extinction. Our results illustrate that: (1) detection of population trends should not be a necessary criterion for enacting conservation measures of both species in this region, and (2) efforts to maintain viable populations of both species in Cleveland Bay must include management strategies that integrate anthropogenic activities in surrounding areas.

Microsatellites reveal a lack of structure in Australian populations of the diamondback moth, Plutella xylostella (L.)

The diamondback moth, Plutella xylostella, is renowned for developing resistance to insecticides and causing significant economic damage to Brassica vegetable crops throughout the world. Yet despite its economic importance, little is known about the population structure and movement patterns of this pest both at local and regional scales. In Australia, the movement patterns and insecticide resistance status of P. xylostella infesting canola, vegetables, forage brassicas and weeds have fundamental implications for the management of this pest. Here we use six polymorphic microsatellite loci to investigate population structure and gene flow in Australian populations of P. xylostella. Samples of P. xylostella from New Zealand, Malaysia, Indonesia and Kenya were also scored at these loci. We found no evidence of population structure within Australia, with most populations having low inbreeding coefficients and in Hardy-Weinberg equilibrium. In addition, a sample from the North Island of New Zealand was indistinguishable from the Australian samples. However, large genetic differences were found between the Australia/New Zealand samples and samples from Kenya, Malaysia and Indonesia. There was no relationship between genetic distance and geographic distance among Australian and New Zealand samples. Two of the loci were found to have null alleles, the frequency of which was increased in the populations outside the Australia/New Zealand region. We discuss these results with reference to insecticide resistance management strategies for P. xylostella in Australia.

Coral Gardens: Paternity and Drug Testing on the Reef

An international team has used molecular genetics and chemical tagging to trace how baby clownfish travel from their mother's nest through the ocean to the anemone they will live on. More than one out of five juveniles came from nests that were only meters away, despite spending over a week drifting in ocean currents. Such surprising fidelity to a small area of the coral reef bodes well for efforts to preserve coral reef diversity with reserves.

Genetics and the History of Latin America

Genetics and the History of Latin America

Current debates on the Mesolithic-Neolithic transition in Britain and Ireland

In this contribution I address a series of recent publications which present revisionist accounts of the beginning of the Neolithic in the British Isles. New evidence suggests that we need to reconsider issues of population movement, diet, mobility and residence patterns. However, I conclude that a return to a model of colonisation by an agricultural population from the continent is premature, and seek to stress the distinct patterns of change that characterised Britain and Ireland respectively.

Population structure and movement patterns within an isolated and endangered population of the moth Dysauxes ancilla L. (Lepidoptera, Ctenuchidae): implication for conservation

Population structure and movement patterns within an isolated and endangered population of the moth Dysauxes ancilla L. (Lepidoptera, Ctenuchidae): implication for conservation

Dividing Societies: The Socio‐Political Spatial Implications of Restructuring in Australia

This paper reviews trends over the last two to three decades in the socio‐economic divisions in Australia, focusing on their spatial dimensions. It provides empirical evidence that our society is dividing on multiple dimensions – including shifts in industry and occupational structure, income distribution, the incidence of poverty. And it demonstrates that the differentiations across space in socio‐economic phenomena also have complex multiple dimensions, which are explained inadequately by a ‘city/bush’ dichotomy popularly espoused by politicians and reported in the media. Processes of globalisation, economic restructuring and employment shifts, and changing patterns of population movement are combining to create stark differentials between places both within the major cities as well as in regional Australia. As demonstrated by the recent One Nation phenomenon, voter backlash is strong, and it too has specific spatial characteristics.

Migration and Livelihoods in the Era of AIDS: a West African Focus with Emphasis on Ghana

The spread of any infectious disease can be accelerated in a situation of large-scale migration, especially in the face of inadequate facilities to contain the disease. This observation has already been made in Eastern, Central and Southern Africa. The spread of tuberculosis from South Africa to the towns and villages of the neighbouring countries in the fifties and sixties by mine workers who migrated to the South African mines is well documented (Packard 1989). More recently, from the late 70’s to the early 80’s, this pattern of disease spread has occurred again in Eastern and Central Africa with AIDS, fuelled by what Baldo and Cabral (1990) have termed Low Intensity Wars (LIW). Free movement of people, including prostitutes, to where business is profitable, has also been blamed as partly responsible for the high AIDS incidence in the exBritish colonies such as Uganda, Zambia and Tanzania (Konotey-Ahulu 1989). Despite this historical evidence, very little has been done by way of the study of the relationship between migration and AIDS in West Africa until recently (see Painter 1992). Migration and AIDS in West Africa The development of AIDS as a social problem in West Africa occurred several years later than in Eastern and Central Africa, around the mid-eighties. At present the governments in the sub-region have recognized it as a health threat. However, massive mobility of people, which is a common feature in the sub-region, has been observed to have historical pre-eminence over Eastern and Central Africa (Parkin, 1975). Two principal patterns of population movement have been established over the years. The first is the North-South movement within coastal countries of Cote d’Ivoire, Ghana, Togo, Benin and Nigeria, and the second is the movement over longer distance between the hinterland Sahelian countries in the north (Mali, Burkina Faso, Niger and Chad) and the coastal countries to the south. The main feature of the migratory movements in West Africa is that they were male dominated. The migrants were more likely to be young unmarried males and if married, they were more likely to leave their wives behind. Women’s participation in the movement is increasingly becoming important in recent times but as yet their movement seems to be towards a few places in the sub-region (Anarfi 1990). Another feature is its periodic, seasonal nature. This massive, region-wide mobility is strongly linked to the effects of seasonality on the ability of rural dwellers in West Africa to earn the real income that their families need to survive and get ahead (Painter 1992: 3). A situation of seasonally limited opportunities and a scarcity, over a period of 7 to 8 months, related to the rainfall pattern of the Sahelian countries, prevails. Seasonal migration has therefore become a form of strategy to survive harsh conditions imposed by nature. According to Painter (1992) each year, from September through December, hundreds of thousands of men leave their homes in the Sahelian countries in the north and travel to countries along the coast. These men may remain in the coastal countries from four to eight months looking for money, before they return home. It is estimated that from 6 to 16 per cent of the total population of Niger, for example, may be affected each year by seasonal migration. Other studies have observed that men from the Sahelian countries participate in these yearly migrations from 10 to 15 years during their individual lifetimes (Painter 1992). Participating in the migration process has become more or less a way of life for rural households in Sahelian West Africa.

A colonial perspective on population migration in Soviet Estonia

Industrialisation facilitates social and economic change and its role in modifying population patterns via the process of urbanisation is well documented. The socially selective nature of population redistribution is widely recognised, but in multi-ethnic states this redistribution of population is also culturally selective and has important ramifications for ethnic relations. This paper suggests that the theory of Internal Colonialism remains a useful theoretical framework for explaining the changes seen in Soviet Estonia. Specifically, it examines the influence of industrialisation on patterns of immigration into Estonia, and their consequent impact on Estonia's ethnic geography. We conclude that industrialisation is an important factor influencing patterns of population movement and distribution and that internal colonialism provides a valuable framework for the analysis of societal change in Soviet Estonia, and in other socialist contexts.

A new survey method for Water Shrews (Neomys fodiens) using baited tubes

INTRODUCTION The Water Shrew, Neomys fodiens, is one of Britain’s least known mammals. Although it has a wide geographical distribution within the British Isles, it has a sporadic and localized occurrence, and remarkably little is known about its habitat requirements. The Water Shrew has never been the subject of a nationwide survey in Britain, and evidence of its occurrence is patchy. Although a number of field studies have elucidated much about its population dynamics, feeding ecology and movement patterns (e.g. Shillito, 1963; Wol ¢k, 1976; Churchfield, 1984a,b; Van Bemmel & Voesenek, 1984; Lardet, 1988; Cantoni, 1993; Castien, 1995), little is known of its habitat preferences, and its current conservation status remains unknown. It is an elusive species which leaves little evidence of its presence. Any field signs remain well hidden amongst the vegetation, so it does not easily lend itself to a wide-scale survey. The usual methods of surveying small terrestrial mammals by live-trapping or hair-tubes (Dickman, 1986) are expensive and/or labour-intensive. In order to encourage surveys of Water Shrews over a large area and a range of habitats an alternative economical method is required. The method devised here was based on the observation that shrews (including Water Shrews) readily investigate novel objects and frequently defaecate on and inside such objects. The appearance, consistency and contents of the scats can provide a guide to the species which has produced them. The remains of aquatic invertebrates (e.g. Asellus aquaticus, Gammarus pulex and Trichoptera larvae) in scats confirms the presence of Water Shrews, as coexisting terrestrial shrews very rarely feed on these prey (Churchfield, 1984a). These prey are easily identified in scats by scanning with the aid of a binocular microscope; the presence of freshwater crustaceans can often be detected with the naked eye.

Trends in International Migration in the Asian and Pacific Region

While recognising the antiquity of population migration in the Asian and Pacific region, this article focuses upon the patterns of migration over the last half‐century. The causes of the migration are divided into four clusters of factors: immigration policies of potential destination countries; developments in the Middle East; the political involvement of external powers; and the economic development of parts of East, Southeast and South Asia itself. The principal consequences of the recent migrations are considered in terms of their economic, social and political impacts. The current issues in Asian migration revolve primarily around questions of sovereignty in a globalising worldand the emergence of transnational communities and illegal migration are identified as being of particular concern to the state in Asia. It is suggested that the economic reversals in parts of East and Southeast Asia had relatively little impact on the overall patterns of population movement in the region and that international migration will persist as one of the principal forces for the transformation of Asian and Pacific societies in the twenty‐first century.

Resiliency as Resistance: Eastern Woodland Munsee Groups on the Early Colonial Frontier

A growing body of data from Contact-period sites throughout the Northeast and Middle-Atlantic regions demonstrates the prevalence of Native-American cultural resiliency in the face of European colonization. This article considers the resiliency of cultural traditions among Munsee groups of northern New Jersey, southeastern New York, and northeastern Pennsylvania during the seventeenth and eighteenth centuries. Patterns of population movement and the contextual association of traditional craft items with European trade goods at contact sites throughout this area are examined and reveal a pattern of active resistance to the incessant demands of colonial expansion and acculturation.