Effects Of Community Size Research Articles

Community‐based processes behind species richness gradients: contrasting abundance–extinction dynamics and sampling effects in areas of low and high productivity

ABSTRACTAim To consider the role of local colonization and extinction rates in explaining the generation and maintenance of species richness gradients at the regional scale.Location A Mediterranean biome (oak forests, deciduous forests, shrublands, pinewoods, firwoods, alpine heathlands, crops) in Catalonia, Spain.Methods We analysed the relative importance of direct and indirect effects of community size in explaining species richness gradients. Direct sampling effects of community size on species richness are predicted by Hubbell's neutral theory of biodiversity and biogeography. The greater the number of individuals in a locality, the greater the number of species expected by random direct sampling effects. Indirect effects are predicted by the abundance–extinction hypothesis, which states that in more productive sites increased population densities and reduced extinction rates may lead to high species richness. The study system was an altitudinal gradient of forest bird species richness.Results We found significant support for the existence of both direct and indirect effects of community size in species richness. Thus, both the neutral and the abundance–extinction hypotheses were supported for the altitudinal species richness gradient of forest birds in Catalonia. However, these mechanisms seem to drive variation in species richness only in low‐productivity areas; in high‐productivity areas, species richness was uncorrelated with community size and productivity measures.Main conclusions Our results support the existence of a geographical mosaic of community‐based processes behind species richness gradients, with contrasting abundance–extinction dynamics and sampling effects in areas of low and high productivity.

To fission or to fusion: effects of community size on wild chimpanzee (Pan troglodytes verus) social organisation

To balance advantages and disadvantages of group living, some species have fission-fusion social systems in which members of the same group form frequently changing subgroups. This allows flexible responses of group size to external conditions while at the same time retaining group stability. In chimpanzees, subgroup (party) size and composition depend mainly on the presence of receptive females, food availability and the activity of the party. Here we analyse the extent to which fission-fusion parameters are influenced by changes of demographic variables like community size and composition. Data were collected from a habituated West African chimpanzee community (Tai forest, Cote d’Ivoire) over 10 years, during which total community size decreased from 51 to 21, and the number of adult males decreased from 9 to 2. Tai chimpanzees are highly gregarious, as they spend more than 80% of their time with unrelated conspecifics. With decreasing community size, party size, party duration and male-female association increased. Neither activity nor the presence of receptive females or feeding competition could explain the observed changes in grouping patterns. Thus, the decrease in community size led to an increase of party cohesion and also enhanced cohesiveness between the sexes, while general sociality remained unchanged. Therefore, our data support the notion that small communities are more cohesive and have a less flexible fission-fusion system.

Risks of adverse pregnancy outcomes among Inuit and North American Indian women in Quebec, 1985-97.

We used Statistics Canada's linked stillbirth, live birth and infant death files to assess the risks of adverse pregnancy outcomes among Inuit and North American Indian vs. other ethnic women in Quebec, 1985-97 (1 125 462 singleton births). Mother tongue was used to define ethnicity, with the largest French language group as the reference. Main outcome measures are adjusted odds ratios (AOR) for preterm birth, small-for-gestational-age (SGA), stillbirth, neonatal and postneonatal death controlled for maternal age, education, marital status, parity, infant sex, community size, and community-level random effects using multilevel logit models. Inuit women had higher risks of preterm birth (AOR = 1.49, 95% CI [1.25, 1.78]) and immaturity-related infant mortality (AOR = 3.03 [1.36, 6.74]), while Indian women did not. Infants of Inuit (AOR = 0.39 [0.31, 0.49]) and Indian (AOR = 0.27 [0.24, 0.31]) women had substantially lower risks of SGA. Elevated risks of stillbirth were observed among Indian women [AOR = 1.53 (1.09, 2.15)], and of postneonatal death among both Inuit (AOR = 4.45 [2.74, 7.22]) and Indian (AOR = 1.86 [1.28, 2.70]) infants. Both Inuit and Indian infants had much higher risks of sudden infant death syndrome (SIDS) and infection-related mortality. Although the absolute risks of adverse outcomes declined from 1985-87 to 1995-97, the relative disparities between aboriginal and non-aboriginal women changed little over this period. We conclude that Inuit and Indian women have different risk profiles for adverse pregnancy outcomes, and that prevention of preterm birth among Inuit women, and of SIDS and infection-related infant mortality in both aboriginal groups, are important targets for future research and intervention.

Affiliation, community size, and person-positivity effect in return of lost letters.

A study using 1,008 "lost letters" was designed to test the hypotheses that returned responses would be greater in smaller rural communities than from cities, that addresses' affiliation with a group opposed to physical education in schools would reduce the return rate, and that a person-positivity effect would influence return rates. Community Size and Person-Positivity conditions were not significantly associated with different rates of return even though returned letters from the smaller rural communities were more frequent than those from the cities across addressee conditions. Findings seem to suggest no community bias in the willingness of people to help a stranger in need by returning a lost letter. Person-Positivity conditions did not seem to improve the technique. Both addressee' affiliations alone and community size and addressee' affiliations were associated with significantly different rates of return in smaller rural communities, with rates of return greater in the smaller rural communities than in the cities (except for the addressee opposed to physical education in schools).

The effect of university host community size on state growth

This study examines the effect of university host community size on state growth. It is argued that if some positive spillovers from universities are localized, needing a host community for capture, or if universities share agglomeration economies with their host communities, and if these effects are large, one may find a significant effect on state growth. Using pooled data from eight U.S. censuses—primarily state-level and university county-level variables—a significant positive effect of university community size is found on state aggregate personal income growth. Weaker effects are found on state employment growth (positive) and state population growth (negative). This suggests that states and perhaps less developed countries could leverage more economic benefits from siting university programs in larger urban areas. A sensitivity analysis reveals no upper bound to the effect on income but a deceleration of the effects on employment growth and population growth when cities become very large. [ JEL I21]

Utility of co-operating Web proxy caches

In this paper, we study the utility of co-operation among intranet proxy caches. We target our study to a corporate intranet environment having multiple Web proxies that each serve a set of hosts. Experiments with our co-operation methods and architectures with real data suggest that daily hit rate improvements due to co-operation can vary from 0.7–28.9%. We study the effect of community size on co-operation performance, and analyze the other side-effects of co-operation, e.g., the extra intranet traffic and server load. We develop metrics to deduce information relevant to making decisions about the effectiveness of co-operation, and draw intuitions on when it makes sense for the caches to co-operate. Our work demonstrates a feasible set of metrics that proxies should measure to help in their evaluation of caching effectiveness and their configuration.

The impact of professional and personal satisfaction on perceptions of rural and urban: Some analytic evidence

Studies of rural-urban location decisions traditionally used ana priori definition of rural/urban based on population size. A group of 29 physicians (study group) practising in communities of less than 10 000, that were part of a larger sample, perceived their communities as ‘urban’. A matched group of physicians (control group) in the same communities, who perceived the communities as ‘rural’, was selected. The research question raised was: Are there personal and professional factors that could reliably predict the perception of rural and urban? A logistic regression analysis was done using professional and personal satisfaction items as predictors of the two groups. The analysis gives some evidence that, once the effect of community size is removed, the perception of rural urban can be explained by satisfaction with the following: (i) access to specialist expertise, (ii) quality of education for children, (iii) quality of life for children and (iv) quality of housing; satisfaction with size of community was not a significant predictor of rural/urban perception.

Metropolitan Size and Participation in Religio-Ethnic Communities

This study investigated the impact of metropolitan size on participation in Protestant, Catholic, and Jewish subcommunities in the United States. Hypotheses were based on Durkheim's theory of community, the Blau and Schwartz macrostructural theory of group relations, and Fischer's subculture theory. The major hypotheses were: 1) The larger the religio-ethnic subcommunity, the less its members participate formally (e.g., organizational membership); 2) the larger the Jewish or Catholic subcommunity, the more its members will participate informally (e.g., within-group friendship); 3) the smaller the religio-ethnic group, the more its members are affected by community size; and 4) the majority subcommunity will be relatively impervious to the effects of community size. Hypothesis 1, 3, and 4 were supported by data from the 1985-1989 General Social Surveys of the National Opinion Research Center and from the National Jewish Population Survey of 1970-71. Hypothesis 2 could be tested only in the Jewish community and was supported.

Urbanism, Migration, and Tolerance: A Reassessment

Previous research has found only modest effects of community size on social psychological characteristics of residents. Focusing on urban experience, Ifind that urbanism's impact on personality may be stronger than previously thought. For respondents whose urban experience is adequately reflected by available community size measures, community size has strong positive effects on tolerance. Migration also promotes tolerance regardless of size of destination community.

The paradoxical effects of Jewish community size on Jewish communal behavior: Intermarriage, synagogue membership and giving to local Jewish Federations

This research note will report on insights gained into Jewish communal behavior by measuring the effects of community size on three aspects of Jewish communal life: rates of 1) intermarriage, 2) synagogue membership, and 3) giving to the Jewish federation. All Jewish communities that have this data available within the past 10 years have been included (See Table 1 for a list of studies included). Size is believed to be an important structural variable affecting communal behavior. This study is an attempt to apply a macrostructural theory of intergroup relations as developed by Blau and Schwartz (1984). Contemporary studies of Jewish intermarriage have shied away from social structure as a possible explanation of current Jewish intermarriage. Mayer (1985), for example, after noting that individual behavior can be affected by population composition and concomitant opportunities for mate selection, discounts this "familiar demographic explanation" of contemporary intermar riage. He notes intermarriage since the 1960s has not only existed in small towns, but also in cities with large Jewish populations, where Jews could more easily find a mate (p. 102). The few studies of Jewish philanthropic behavior have tended to focus on the reasons that individual Jews gave money to Jewish

Involuntary admissions in a Canadian province: the influence of geographic and population factors.

The present study investigated the effects of community size and the availability of admitting facilities on rates of involuntary admissions in a Canadian province with a very small population. The rate was much higher for areas within close proximity of the admitting facility and for communities with populations either less than 500 or greater than 30,000. These findings are discussed in the context of factors such as geographic distribution of population in the province and availability of appropriate psychiatric and social support facilities.

Taking a taxi: Front or back seat? The effects of gender and community size

A study of seat choice, front or back, of solo taxi passengers found that a significantly greater number of men than women sat next to the driver in large urban areas, but that no sex difference in front-seat choice appeared in smaller communities. Very few women taxi drivers were observed. The data were interpreted in terms of sex differences in feelings of security, with solo women feeling more vulnerable than men, particularly in large cities.

The effects of community size on the mix of private and public use of security services

The effects of community size on the mix of private and public use of security services

The theory of public goods: non-nash behaviour

Most treatments of equilibrium public goods provision assume zero conjectural variations in the sense that each individual regards the behaviour of the rest of the community as independent of his own. This paper introduces nonzero conjectural variations into the model. A diagram is introduced which can depict both the individual's and the community's equilibrium in the presence of nonzero conjectural variations. Equilibrium and optimal outcomes are compared, and a specific functional form is used to investigate the effect of community size on the nature of equilibrium. Finally, we discuss the requirement that conjectures should be consistent.

Traditional Religion in Contemporary Society: A Theory of Local-Cosmopolitan Plausibility

Sociological theories of religion typically presuppose a religiously-based nqimative order, and for this reason their appropriateness in a modern, secular society is questionable A localcosmopolitan theory is proposed which attempts to identify an important plausibility structure for traditional, church-type religion today. Analysis of data from a sample of Worth Carolina Episcopalians shows that this theory not only explains multidimensional religiosity patterns, but also provides a parsimonious interpretation for the effects of education and community size. Implications for the changing social basis of church religion in modern society and the process of secularization are discussed.

The Private Enforcement of Law

The Private Enforcement of Law

Conflict in the Community: A Theory of the Effects of Community Size

Two theories of community conflict are examined in this paper with data from elections in 89 cities in the San Francisco Bay area. One theory is developed from the work on group conflict by Georg Simmel and Lewis Coser while the other is a rational choice theory based on assumptions about the costs and risks of conflict in different size cities. Both theories suggest that conflict, while more frequent in larger communities, is likely to become most severe in smaller communities. Both theories are confirmed by the pattern of findings in the analysis, but the rational choice theory proves to have the greater generality, i.e., that it can explain more of the findings in the paper.