This paper discusses and illustrates various approaches for the longitudinal analysis of personal networks (multilevel analysis, regression analysis, and SIENA). We combined the different types of analyses in a study of the changing personal networks of immigrants. Data were obtained from 25 Argentineans in Spain, who were interviewed twice in a two-year interval. Qualitative interviews were used to estimate the amount of measurement error and to isolate important predictors. Quantitative analyses showed that the persistence of ties was explained by tie strength, network density, and alters' country of origin and residence. Furthermore, transitivity appeared to be an important tendency, both for acquiring new contacts and for the relationships among alters. At the network level, immigrants' networks were remarkably stable in composition and structure despite the high turnover. Clustered graphs have been used to illustrate the results. The results are discussed in light of adaptation to the host society.

In addition to all the usual ethical problems that can arise with any kind of inquiry, network analyses, by their very nature, introduce special ethical problems that should be recognized. This paper delineates some of these problems, distinguishing between problems that arise in purely academic studies and those that arise in managerial practice settings. In addition, the paper raises the long-term question of whether the use of network analysis for making managerial decisions will make collecting valid network data impossible in the future, seriously harming the academic field of social network research. The paper concludes with a short set of principles intended to form the basis for a set of guidelines designed to safeguard participants in social network studies and protect the long term viability of the network research enterprise.

This article presents an analysis of personal network visualization based on systematic evaluations of alter pairs compared to freestyle drawings respondents made of their personal network. In most cases, personal network visualization provided important details that are different from respondents' perceptions. Several case studies are discussed that highlight the additional data provided when using personal network visualization.

This article investigates whether personal networks influenced ethnic self-identifications of migrants in Spain. During the years 2004-6, data were collected about personal networks of migrants in Spain (N = 294) through a questionnaire and a structured interview. The networks were classified into five network profiles on the basis of both variables about structure (e.g. density, betweenness and number of cohesive subgroups) and composition (e.g. country of origin and percentage of family members). Profiles were related to the different ways in which migrants identified themselves. Personal networks in which network members, mostly family and people from the country of origin, formed one dense cluster were associated with ethnic exclusive self-identifications, whereas more heterogeneous personal networks tended to exhibit more plural definitions of belonging. The results show that both individual and network characteristics contribute to an understanding of ethnic self-identification.

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ABSTRACT. Medicinal plants provide indigenous and peasant communities worldwide with means to meet their healthcare needs. Homegardens often act as medicine cabinets, providing easily accessible medicinal plants for household needs. Social structure and social exchanges have been proposed as factors influencing the species diversity that people maintain in their homegardens. Here, we assess the association between the exchange of medicinal knowledge and plant material and medicinal plant richness in homegardens. Using Tsimane' Amazonian homegardens as a case study, we explore whether social organization shapes exchanges of medicinal plant knowledge and medicinal plant material. We also use network centrality measures to evaluate people's location and performance in medicinal plant knowledge and plant material exchange networks. Our results suggest that social organization, specifically kinship and gender relations, influences medicinal plant exchange patterns significantly. Homegardens total and medicinal plant species richness are related to gardeners' centrality in the networks, whereby people with greater centrality maintain greater plant richness. Thus, together with agroecological conditions, social relations among gardeners and the culturally specific social structure seem to be important determinants of plant richness in homegardens. Understanding which factors pattern general species diversity in tropical homegardens, and medicinal plant diversity in particular, can help policy makers, health providers, and local communities to understand better how to promote and preserve medicinal plants in situ. Biocultural approaches that are also gender sensitive offer a culturally appropriate means to reduce the global and local loss of both biological and cultural diversity.

We propose a method to visually summarize collections of networks on which a clustering of the vertices is given. Our method allows for efficient comparison of individual networks, as well as for visualizing the average composition and structure of a set of networks. As a concrete application we analyze a set of several hundred personal networks of migrants. On the individual level the network images provide visual hints for assessing the mode of acculturation of the respondent. On the population level they show how cultural integration varies with specific characteristics of the migrants such as country of origin, years of residence, or skin color.

ABSTRACT. Interest in landraces conservation has grown in the last decades with research on the topic focusing on in situ conservation of agrobiodiversity in the tropics. Researchers agree that home gardens play a key role in the maintenance of in situ agrobiodiversity, but few studies have analyzed how farmers actually maintain agrobiodiversity in home gardens and what mechanisms they use to avoid genetic erosion. We evaluate the functioning of a network of seed exchange and explore its contribution to agrobiodiversity conservation. We focus on the exchange of seeds and seedlings among 55 home garden keepers who grow a total of 62 home gardens in Vall Fosca (Catalan Pyrenees). Fieldwork included visits to gardens and surveys to register the frequency and management of local landraces. We also asked about the farmers' network of seed exchange. We identified 20 local landraces belonging to 17 species. People who were mentioned more often in the network of seed exchange (highest indegree) and who had a higher level of intermediation among other people in their personal network (highest egobetweenness) conserved more local landraces and had more local landrace knowledge than people who were less central in the network. Our findings suggest that local landrace conservation is strongly associated with individual position in the network of seed exchange.