Population structure in the Connecticut Valley. I. Marital migration

This study reports on an analysis of marital migration among 12 communities in the Connecticut River Valley of Massachusetts during the years 1790-1849. Genetic inferences are drawn, and the requisite assumptions considered. The effect of geographic distance on genetic kinship is predicted using Malécot's isolation-by-distance model. The resulting estimates are discussed in terms of geographic and historical factors. The configuration of communities as predicted by kinship values approximates closely their actual geographic locations. Estimated genetic heterogeneity was low for the historical Connecticut Valley population, and community isolation breaks down rapidly over time. The region thus assumes its place among a number of sedentary, agricultural populations for which the isolation-by-distance model provides an adequate representation. A regression analysis which includes variables in addition to distance indicates that historical and economic factors contribute some additional explanatory power to the distribution of mating frequencies.     

Population structure in the Connecticut Valley: II. A comparison of multidimensional scaling solutions of migration matrices and isonymy

In a previous paper (Swedlund et al., 1984) we have described the population structure of the historical Connecticut River Valley of Massachusetts in terms of matrimonial migration matrices. Using procedures described by Morton (1973), Harpending and Jenkins (1974), Jorde (1980), and others the exchanges between subdivisions which make up the matrices are made column stochastic and analyzed to predict genetic kinship. Subsequently the kinship estimates within and between subdivisions can be interpreted as genetic covariance and compared to the actual geographic distances between the respective subdivisions using a principal components analysis. In the present paper we extend these results by applying nonmetric multidimensional scaling to the migration matrices, and to isonymy matrices based on the same communities. We demonstrate that the multidimensional scaling configurations of marital migration represent the actual geographic relationships between the communities quite effectively for this particular case study from historical Massachusetts. Moreover, we argue that while these migration data may provide good estimates of social and genetic exchange between the subdivisions, surname analysis may also be informative of processes not revealed in the migration matrices alone.     

Density-dependent migration and human population structure in historical Massachusetts

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.     

Policies,Political-Economy,and Swidden in Southeast Asia

For centuries swidden was an important farming practice found across the girth of Southeast Asia. Today, however, these systems are changing and sometimes disappearing at a pace never before experienced. In order to explain the demise or transitioning of swidden we need to understand the rapid and massive changes that have and are occurring in the political and economic environment in which these farmers operate. Swidden farming has always been characterized by change, but since the onset of modern independent nation states, governments and markets in Southeast Asia have transformed the terms of swiddeners’ everyday lives to a degree that is significantly different from that ever experienced before. In this paper we identified six factors that have contributed to the demise or transformation of swidden systems, and support these arguments with examples from China (Xishuangbanna), Laos, Thailand, Malaysia, and Indonesia. These trends include classifying swiddeners as ethnic minorities within nation-states, dividing the landscape into forest and permanent agriculture, expansion of forest departments and the rise of conservation, resettlement, privatization and commoditization of land and land-based production, and expansion of market infrastructure and the promotion of industrial agriculture. In addition we note a growing trend toward a transition from rural to urban livelihoods and expanding urban-labor markets.

Climate change vulnerability of forest biodiversity: climate and competition tracking of demographic rates

Forest responses to climate change will depend on demographic impacts in the context of competition. Current models used to predict species responses, termed climate envelope models (CEMs), are controversial, because (i) calibration and prediction are based on correlations in space (CIS) between species abundance and climate, rather than responses to climate change over time (COT), and (ii) they omit competition. To determine the relative importance of COT, CIS, and competition for light, we applied a longitudinal analysis of 27 000 individual trees over 6–18 years subjected to experimental and natural variation in risk factors. Sensitivities and climate and resource tracking identify which species are vulnerable to these risk factors and in what ways. Results show that responses to COT differ from those predicted based on CIS. The most important impact is the effect of spring temperature on fecundity, rather than any input variable on growth or survival. Of secondary importance is growing season moisture. Species in the genera Pinus, Ulmus, Magnolia, and Fagus are particularly vulnerable to climate variation. However, the effect of competition on growth and mortality risk exceeds the effects of climate variation in space or time for most species. Because sensitivities to COT and competition are larger than CIS, current models miss the most important effects. By directly comparing sensitivity to climate in time and space, together with competition, the approach identifies which species are sensitive to climate change and why, including the heretofore overlooked impact on fecundity.     

Researching and teaching in the field of ethnic and racial studies: a view from continental Europe

In the first part of the article, I make a few general comments inspired by the reading of Banton's article. I claim that the field of ethnic and racial studies is often dominated by an "Anglo-Americentric" vision that leads to a negation of the variety of approaches to ethnic and racial studies throughout the world. I claim that a process of "decentration" is necessary in order to foster the diversity in our field. In the second part of the article, I make specific comments inspired by my experience as researcher and teacher in a fragmented society such as Belgium. One conclusion is that our teaching has to be contextualized in order to avoid misunderstandings and the reproduction of inadequate conceptions and confusions about ethnic and racial issues among our students.     

Deciphering the relative weights of demographic transition and vaccination in the decrease of measles incidence in Italy

In Italy, during the course of the past century to the present-day, measles incidence underwent a remarkable decreasing trend that started well before the introduction of the national immunization programme. In this work, we aim at examining to what extent both the demographic transition, characterized by declining mortality and fertility rates over time, and the vaccination programme are responsible for the observed epidemiological pattern. Making use of a non-stationary, age-structured disease transmission model, we show that in the pre-vaccination era, from 1901 to 1982, the decline in birth rates has resulted in a drastic decrease in the effective transmission rate, which in turn has determined a declining trend of measles incidence (from 25.2 to 10.3 infections per 1000 individuals). However, since 1983, vaccination appears to have become the major contributing factor in the decrease of measles incidence, which otherwise would have remained stable as a consequence of the nearly constant birth rates. This led to a remarkable decrease in the effective transmission rate, to a level well below the critical threshold for disease persistence. These findings call for the adoption of epidemiological models, which deviate the age structure from stationary equilibrium solutions, to better understand the biology of infectious diseases and evaluate immunization programmes.     

Contrasting demographic history and phylogeographical patterns in two Indo-Pacific gastropods

Marine species with ranges that span the Indo-Australian Archipelago (IAA) exhibit a range of phylogeographical patterns, most of which are interpreted in the context of vicariance between Indian and Pacific Ocean populations during Pliocene and Pleistocene low sea-level stands. However, patterns often vary among ecologically similar taxa, sometimes even within genera. This study compares phylogeographical patterns in two species of highly dispersive neritid gastropod, Nerita albicilla and Nerita plicata, with nearly sympatric ranges that span the Indo-Pacific. Mitochondrial COI sequences from >1000 individuals from 97 sites reveal similar phylogenies in both species (two divergent clades differing by 3.2% and 2.3%, for N. albicilla and N. plicata, respectively). However, despite ecological similarity and congeneric status, the two species exhibit phylogeographical discordance. N. albicilla has maintained reciprocal monophyly of Indian and Pacific Ocean populations, while N. plicata is panmictic between oceans, but displays a genetic cline in the Central Pacific. Although this difference might be explained by qualitatively different demographic histories, parameter estimates from three coalescent models indicate that both species have high levels of gene flow between demes (2Nem>75), and share a common history of population expansion that is likely associated with cyclical flooding of continental shelves and island lagoons following low sea-level stands. Results indicate that ecologically similar, codistributed species may respond very differently to shared environmental processes, suggesting that relatively minor differences in traits such as pelagic larval duration or microhabitat association may profoundly impact phylogeographical structure.     

The process of ethnogenesis among Haitian and Israeli immigrants in the United States

This article examines the process of ethnic identity formation among two different groups of recent immigrants to the United States: secular kibbutz‐born Israelis and middle‐class Haitians. While the two groups are different in a number of ways, they share an ambivalence with the identities that American society would assign to them ‐ as Jews and blacks respectively. By contrasting these two case studies we identify the role of the ‘proximal host’, the category to which the immigrants would be assigned following immigration. The determination of the ultimate definition of the ethnic identities of these immigrants is a result of the interaction of the conception of identity the immigrants bring with them from their countries of origin, the definitions and reactions of the proximal host group, and the overall ordering and definitions of American society. The ambivalence of both groups of immigrants towards their post‐immigration identities is a result of both macro‐forces determining the definition of categories and micro‐forces of individual choice. In conclusion we show that because of the primacy of race in American society, Israelis are likely to face many more options in the determination of their identities, than are Haitians, although they both face a similar structural dilemma.     

Electrophoretic salivary genetic variation and patterns of dispersion in a Brazilian population

A total of 434 White and 148 Black persons from the southern Brazilian city of Porto Alegre were studied in relation to the Pr, Db, Pa, Ps and amylase electrophoretic salivary systems. Concomitantly, individual migration, parent-offspring and marital distances were recorded for these individuals, their spouses and ancestors. As far as these dispersion measures are concerned, White/Black and intergeneration differences were generally higher in the present study than in earlier ones, although the averages found this time were consistently lower than those observed before. The correlations between these measures indicated a higher degree of independence between generations than was previously inferred. In the genetic studies, 21 comparisons between the Porto Alegre distributions and those found in North American, European and African surveys yelded 7 significant differences. In general the allele frequencies in Porto Alegre show intermediate values between those found elsewhere among Blacks and Whites, suggesting admixture in these two racial segments of that city. Using previous estimates of such admixture the gene frequencies of the putative Porto Alegre parental populations were estimated and compared with present European and African results. Relatively large differences were observed for the Db⁺ andAmy ₁ ^E markers only. No significant associations were detected between the salivary phenotypes and the prevalences of caried, extracted and filled teeth.     

Fine root growth and demographic responses to nutrient patches in four old-field plant species

Proliferation of roots in a nutrient patch can occur either as a result of an increase in root length (morphological response) or by a change in root birth or death rates (demographic responses). In this study we attempted to distinguish between these two mechanisms of response to nutrient patches and to compare the responses of four old-field plant species (two annuals, two perennials). For all four species combined, there were significant increases in root numbers and root length in fertilized patches. Root proliferation in fertilized patches was largely due to increased birth (=branching) rates of new roots. However, there was also a significant increase in root death rates in the fertilized patches which reduced the magnitude of the increase in net root numbers. Plots for individual species suggested they differed in the magnitude and timing of root proliferation in fertilized patches due to differences in root birth and death rates. However, because of the limited sample size in this study, there was only a marginally significant difference among species in root birth rates, and no difference in death rates. Further studies are currently underway to better quantify species differences in the demographic mechanism, as well as magnitude, of response to nutrient patches and if this would affect the ability to exploit small-scale heterogeneity in soil resources.     

Colonial Constructions and African Initiatives: The History of Ethnicity in Northwestern Ghana

The article discusses the colonial construction of ethnic categories, their linkage with precolonial models of identity and the multiple meanings which ethnicity has assumed for different groups over the past decades, using the example of northwestern Ghana – a region which, in the precolonial period, was neither politically centralized nor knew distinct ‘tribes’. The article analyses how ethnic categories, boundaries and institutions were created and continually redefined by colonial officials, anthropologists, chiefs, labour migrants and educated elites, and how the different ethnic discourses fed into each other. It also draws on some of the older literature on ethnicity in Africa because it can still contribute to our understanding of the making of ethnic identities when framed in a deeply historical approach.     

Identity change in Bashkortostan: Tatars into Bashkirs and back

Students of ethnic identity have recently begun to recognize the role of the state in causing identity shift. Constructivists, in particular, focus on the importance of state institutions and policies in creating new identities and transforming old ones. This article focuses on identity creation and change in Bashkortostan, an ethnic region within the Russian Federation. It shows how, at the beginning of the twentieth century, the Russian/Soviet state created new ethnic identities from pre-existing regional, estate-based and religious identities. It also shows how later changes in state institutions and policies played a crucial role in determining the direction of identity change among a mixed population, straddling the geographical and cultural boundaries between the Tatar and Bashkir ethnic groups. By tracing the impact of the state on one ethnic group over an extended time-period, this article shows that state actions can lead to both instrumental and culturally-based shifts in ethnic identity.     

Obesity among male adolescent migrants in Vienna, Austria

Childhood overweight and obesity--especially among migrant children--are health problems in several European countries. The prevalence rates of overweight and obesity among 936 migrant boys of low socio-economic status from Turkey and former Yugoslavia were compared with those of Austrian boys in Vienna. In the longitudinal study, children were measured at the ages of 6, 10 and 15 years. Weight status was estimated by means of the body mass index and percentile curves were used for weight status classification. The prevalence of overweight and obesity was high among migrant boys as well as Austrian boys at all age groups. Ten-year-old boys from Yugoslavia exhibited the highest percentage of overweight (nearly 38%). The lowest percentage of overweight was among 6-year-old Austrian boys (17.2%). Being overweight or obese at the age of 6 years increased the risk of being overweight at 10 and 15 years significantly (p<0.001). This was true of all groups independent of migrant status. The impact of migrant status on weight status at the ages of 10 and 15 was not significant. Therefore, although migrant boys from former Yugoslavia exhibited the highest rates of overweight and obesity, migrant status is not associated significantly with an increased prevalence of obesity in this sample characterized by a generally low socio-economic status. Prevention should start as early as possible for all children, since overweight tends to persist from childhood into adolescence independent of migrant status.     

Agriculture and Inequality in the Colonial Andes: A Simulation of Production and Consumption Using Administrative Documents

During the sixteenth and seventeenth centuries, indigenous communities in the Viceroyalty of Peru suffered forced resettlement, introduced disease, and onerous colonial tribute levies. These produced an onslaught of petitions for new tribute counts, as their diminished populations were obliged to pay the head taxes set by earlier censuses. The resulting visitas (administrative surveys) provide a wealth of information on the demography and agricultural systems of colonial Andean communities. However, comparatively little quantitative research exists on the distribution of agricultural resources and the nutritional demands of households. We model agricultural production and nutritional demand using household demographic and landholding declarations in the visitas from the Colca Valley of southern highland Peru, combined with ethnographically-derived estimates of agricultural production and nutritional demand. The results indicate that despite surplus agricultural production in the aggregate, there were significant differences in intra- and inter-community land wealth and production sufficiency ratios, leaving about 30% of households with caloric shortfalls. In contrast to regional-scale carrying capacity-type models, this simulation characterizes agricultural inequality within colonial Andean communities, and thus accounts for the hardship evidenced by tributary recount petitions, even in a breadbasket province from which much surplus production was extracted to fill colonial coffers.

Variability and stability in the rank relations of nonhuman primate females: Analysis by computer simulation

This paper summarizes results of simulation analyses aimed at elucidating the way in which two important dimensions of female rank orders—nepotism and age-gradedness—are affected by variation in individual strategies of rank acquisition on the one hand and by variation in population-wide demographic parameters (eg, birth rate, death rate, etc) on the other. Female rank orders in simulated primate groups were characterized by substantial variability on a year-to-year basis in both nepotism and age-gradedness owing to stochastic processes alone. Although, in general, groups characterized by strongly nepotistic rank orders were not also strongly age-graded, quantitative measures of these two rank-order dimensions for individual groups showed little stability over intervals of time exceeding 3 years. Surprisingly, changes in birth and death rates did not strongly affect either nepotism or age-gradedness so long as average group size remained constant. However, in populations characterized by expanding or declining group size, variation in demographic parameters did indeed exert a powerful influence on the structure of female rank orders. Both nepotism and age-gradedness were also strongly affected, and in quite different ways, by changes in the rules of rank acquisition by females. In sum, the present analyses suggest that differences between species in the degree of nepotism and age-gradedness characteristic of their female rank orders does not in and of itself constitute evidence that the females of those species use markedly different strategies of rank acquisition.     

An idea of community and its discontents: towards a more reflexive sense of belonging in multicultural Britain

In many less developed countries economic development is not in conformity with the actual level of consumption. In part this is to be explained by the huge informal sector that is not included in official statistics. However, using Suriname as a case study, it is argued in this article that a significant part of the discrepancies can be explained from private household transfers from The Netherlands. Migration is not a loss in all respects, but sometimes an asset. In contrast the remittances from temporarily migrated workers, the transfers from people constituting a transnational community cannot be taken for granted. This private family aid expresses personal commitments at the primordial level, and is therefore a kind of moral capital. Depending on the size of the migrated community and the moral commitments of their members, these transfers constitute a net surplus from the former metropolis to the periphery.     

Social behaviour in a web-building lynx spider, Tapinillus sp. (Araneae: Oxyopidae)

Social behaviour involving cooperative prey capture and communal feeding is reported for the first time in the spider family Oxyopidae (lynx spiders), in a web-building species of the genus Tapinillus. This social spider inhabits communal webs that may contain several dozen individuals, including adults of both sexes and juveniles of different cohorts. Its colonies occur in clusters and appear to be long-lived, much like those of non-territorial permanently social species such as Anelosimus eximius (Theridiidae) or Agelena consociata (Agelenidae). However, unlike colonies of these other cooperative spiders, the colonies of the social Tapinillus do not have highly female-biased sex ratios. The possible explanations for this difference are discussed.     

Interception and retention of macroscopic bryophyte fragments by branch substrates in a tropical cloud forest: an experimental and demographic approach

Although the significance of canopy plant communities to ecosystem function is well documented, the process by which such communities become established in trees remains poorly known. Colonization of tree surfaces by canopy-dwelling plants often begins with the establishment of bryophytes, so the conditions that affect the dispersal of bryophytes in the forest canopy merit study. We assessed success rates of one mechanism of bryophyte propagation, the aerial dispersal of macroscopic fragments, using an experimental approach. We quantified interception and retention of marked fragments released from a 36 cm×36 cm grid 50 cm above branches of saplings and mature trees of the species Ocotea tonduzii in a montane cloud forest in Costa Rica. Only 1% of bryophyte fragments dropped over sapling crowns in this manner were retained for the 6-month duration of the study, while branches in the forest canopy with intact epiphyte loads and branches that had been stripped of their epiphytes retained 24% and 5%, respectively. Our results suggest that larger-diameter branches and the presence of other epiphytes can both improve the retention of bryophyte fragments on canopy branches. Further work will be needed to address the relative roles of other dispersal mechanisms (spores, gemmae, microscopic bryophyte fragments) and the dynamics of growth and establishment of macroscopic bryophyte fragments following their interception. Received: 1 March 1999 / Accepted: 24 August 1999