Analysis of spatial association between two species based on the interspecies mean crowding

Summary and Conclusion The measurement of spatial association between two species is considered on the basis of interspecies mean crowding. Two indices of overlapping, γ andC _p, are derived as geometric and weighted arithmetic means of the same component ratios related to inter-and intraspecies mean crowdings. Both indices behave in a similar way, ranging from 1 when the distributions of two species are completely overlapped to 0 when they are completely exclusive with each other. The former is essentially identical with indices proposed byKuno (1968) andPianka (1973), and the latter is a modified form ofMorisita's (1959)C _σ index. Indices to measure the degree of spatial correlation between species, Ω andR _μ, are then derived for both kinds of overlapping indices, which vary from 1 in complete overlapping, through 0 in independent occurrence, to −1 in complete exclusion. Various kinds of interspecies association are analyzed using these indices and an extended form of the regression graph which provides a convenient way of indicating the spatial interrelation between two species as well as distribution patterns of respective species. The method presented in this paper may also be applicable to compare temporal distribution patterns between species, similarity between communities, etc. For such a wider application which includes continuous as well as discrete distributions, the interpretation of intra-and interspecies mean crowdings is not necessarily appropriate, and hence the concept of mean concentration with the symbols and for intraspecies relation and and for interspecies relation is suggested. This study was supported by Science Research Fund (No. 148041) from the Ministry of Education.     

Population momentum: A wider definition

Summary

Keyfitz has derived an elegant formula for estimating the ultimate size of an initially stable, growing population that abruptly reduces its fertility to replacement level. Reduction of fertility is achieved by the rather unrealistic device of dividing the original age schedule nffertility rates by the net reproduction rate. Only the inertia of the age distribution is thus accounted for, but not that of the fertility schedule. The key idea of an abrupt imposition of a fixed regimen capable in the long run of generating zero population growth may be retained, but the regimen made more realistic. By elaborating the population setting, such disparate ZPG regimens as reduction of marital fertility by contraception, delayed and/or less universal marriage, raised mortality risks, or permanent net out-migration may be formulated. Convergence of the populaton to stationarity becomes a two-phase process: a primary adjustment period of changing fertility rates followed by a period of age adjustment.

The present paper treats what happens when a fixed ZPG sterilization regimen, defined by a minimum age of sterilization γ and constant continuous risk φ of sterilization among unsterilized wives aged γ to β, is imposed abruptly (or else progressively over an interval T) upon an initially stable, growing population. Additional sources of residual growth are: (1) the nine-month lag in sterilization effect owing to pregnancy: (2) the more youthful pattern of child-bearing under sterilization: (3) the extra adjustment period (of length β-γ-0.75) of changing fertility rates; and (4) any delays in exposing elements of the population to the sterilization regimen.

Two questions are pursued. First, how important are the additional sources of residual growth? Secondly, how do their relative sizes vary as a function of the characteristics of the initial population?     

An Anthropology of ‘The Good Life’ in the Bolivian Plateau

This paper addresses my understanding of well-being as harmonious relations in the city of El Alto, Bolivia. My approach shows the complexity of issues emerging when dealing with social relations. First of all, I analyse a specific case study showing the moral obligation involved among household members. Then I attempt to provide an insight into other aspects of social life to realise that the same degree of moral duty can be found when people participate in religious festivities or social protests. Collaboration, unity and co-operation often coexist with conflicts and moral obligation. The paper argues that this picture of complex coexistence is rather different from the substantive freedom described by Sen (Development as freedom. Oxford University Press, 1999) in his capability approach. By taking Sen’s theoretical framework as a point of departure for this investigation, it aims to emphasise the value of ethnography and other qualitative methods to the study of well-being. In the field of well-being, social interaction may greatly affect people’s capabilities to choose the lives they have reason to value, obliging them to follow certain models based on shared values and preferences. The paper contributes to debates on this specific issue, trying to shed light on the picture emerging when engaging with ethnographic research.

Population momentum: A wider definition

Summary Keyfitz has derived an elegant formula for estimating the ultimate size of an initially stable, growing population that abruptly reduces its fertility to replacement level. Reduction of fertility is achieved by the rather unrealistic device of dividing the original age schedule nffertility rates by the net reproduction rate. Only the inertia of the age distribution is thus accounted for, but not that of the fertility schedule. The key idea of an abrupt imposition of a fixed regimen capable in the long run of generating zero population growth may be retained, but the regimen made more realistic. By elaborating the population setting, such disparate ZPG regimens as reduction of marital fertility by contraception, delayed and/or less universal marriage, raised mortality risks, or permanent net out-migration may be formulated. Convergence of the populaton to stationarity becomes a two-phase process: a primary adjustment period of changing fertility rates followed by a period of age adjustment. The present paper treats what happens when a fixed ZPG sterilization regimen, defined by a minimum age of sterilization γ and constant continuous risk φ of sterilization among unsterilized wives aged γ to β, is imposed abruptly (or else progressively over an interval T) upon an initially stable, growing population. Additional sources of residual growth are: (1) the nine-month lag in sterilization effect owing to pregnancy: (2) the more youthful pattern of child-bearing under sterilization: (3) the extra adjustment period (of length β-γ-0.75) of changing fertility rates; and (4) any delays in exposing elements of the population to the sterilization regimen. Two questions are pursued. First, how important are the additional sources of residual growth? Secondly, how do their relative sizes vary as a function of the characteristics of the initial population?     

Settling-site selection and survival of two scale insects,Ceroplastes rubens andC. ceriferus, on citrus trees

Summary We studied settling-site selection and the resulting survival of two sessile scale insects,Ceroplastes rubens andC. ceriferus, in the citrus tree,Citrus unshiu, in central Japan. C. rubens preferred 0-year-old twigs most as a settling-site; the density of nymphs settling on 0-year-old twigs was significantly higher than those on ≥1-year-old twigs, and few nymphs settled on ≥3-year-old twigs. The mean survival rates from settling until reproduction in the next year were significantly higher on more preferred twigs than on less preferred ones. InC. ceriferus, nymphs significantly preferred 1- and 2-year-old twigs to 0- and ≥3-year-old ones, and the mean survival rates on the more preferred 1- and 2-year-old twigs were significantly higher than those on less preferred ≥3-year-old twigs. However, the survival rate on less preferred 0-year-old twigs was slightly higher than those on 1- and 2-year-old ones. Thus, in both species of scale, it was the preferred twigs which were more profitable sites for survival after settling, except for less preferred 0-year-old twigs forC. ceriferus. In both scale species, most mortality was due to growth cessation, which is believed to be related to the twig quality as a food source. Predators and parasitoids were minor mortality factors. Both species showed constant survival rates until the density of settled nymphs exceeded double the “upper-limit” density, whereupon they decreased drastically. Nymphs ofC. rubens settling on twigs of high scale density showed a spacing-out distribution, those ofC. ceriferus did not. InC. rubens, an increase in preference for originally less profitable twigs at the later stage of the settling season was observed, but not inC. ceriferus. Accordingly, individuals ofC. rubens showed a stronger tendency to avoid conspecifics than didC. ceriferus. Although nymphs of the two scales clearly preferred more profitable sites, their settling-site selection did not agree with the predictions from the ideal free distribution theory (Fretwell and Lucas, 1970). The discrepancies were (1) frequent settling on less profitable sites at the early stage of the settling season, (2) insufficient utilization of the most profitable twigs, and (3) virtually 100% mortality on overcrowded twigs under conditions where unoccupied profitable twigs still remained. These discrepancies are thought due to the limited dispersal time of nymphs. Contribution to the ecological studies of scale insects 2.     

An index of spatial distribution

Summary The index , which takes the value of −1 for a perfectly regular distribution, +1 for a highly aggregated distribution and 0 for the distribution implied by the theoretical varianceσ ², is proposed and a significance table provided.     

How three rocky shore snails coexist on a limited food resource

Summary Competition theory poses a major problem when several species coexist on what appears to be one resource. ThreeThais species living on the Pacific Northwest Coast provide an example: at many sites, all three depend primarily on one barnacle species. Growth rates of three species were measured for 3 years and these provide an indirect means to assess how these snails use their common food resource. Major temporal differences were observed:T. lamellosa grew 0–1 mm/mo during the spring and 2–3 mm/mo during the summer, whileT. emarginata andT. canaliculata grew 2–3 mm/mo during the spring and 0–1 mm/mo during the summer. However, all species are opportunists when food is available, and seasonal and interspecific differences disappeared when all three species were kept well fed together in the laboratory. Therefore, temporal differences arise from spatial segregation rather than from intrinsic differences in activity, and must arise because barnacle abundance patterns differe consistently from one area of the shore to another. Species-specific activity patterns lead each species to a food intake that is independent of the food supply on the shore as a whole and is also independent of food intake by the other two species. Where two snail species depend upon a single food species, their use of the food supply appears to make it function as two different resources. This resource use is possible because prey quality is markedly dependent on shore level.     

The Compensating Income Variation of Social Capital

There is a small but growing literature on the determinants of social capital. Most of these studies use a measure of trust to define social capital empirically. In this paper we use three different measures of social capital: the size of the individual’s social network, the extent of their social safety net and membership of unions or associations. A second contribution to the literature is that we analyze what social capital contributes to our well-being. Based on this, we calculate the compensating income variation of social capital. We find differences in social capital when we differentiate according to individual characteristics such as education, age, place of residence, household composition and health. Household income generally has a statistically significant effect. We find a significant effect of social capital on␣life␣satisfaction. Consequently, the compensating income variation of social capital is substantial. Thanks to Tijl Woortman for his research assistance.     

On Nonstable and Stable Population Momentum

This article decomposes total population momentum into two constituent and multiplicative parts: “nonstable” momentum and “stable” momentum. Nonstable momentum depends on deviations between a population’s current age distribution and its implied stable age distribution. Stable momentum is a function of deviations between a population’s implied stable and stationary age distributions. In general, the factorization of total momentum into the product of nonstable and stable momentum is a very good approximation. The factorization is exact, however, when the current age distribution is stable or when observed fertility is already at replacement. We provide numerical illustrations by calculating nonstable, stable, and total momentum for 176 countries, the world, and its major regions. In short, the article brings together disparate strands of the population momentum literature and shows how the various kinds of momentum fit together into a single unifying framework.     

Is population growth a deterrent to development in the South Pacific?

Some have argued that population growth deters development, while others claim that population growth either aids development or has no significant effect on development. In a sample of South Pacific nations, population growth and size were found to be unrelated to economic development, defined as GDP per capita. However, when indices of quality of life or social development such as mortality, health services and education were used, population growth and size were found to be negatively related to these indices. If these “quality of life” indices are valued by nations, an argument may exist for policy support for family planning.     

Studies on the spatial distribution pattern of larvae of the mosquito,Anopheles sinensis, in rice fields

Summary The spatial distribution patterns of the population ofAnopheles sinensis larvae were studied in the rice field area in the suburb of Urawa city in Japan, during the summer seasons in 1973 and 1974. The distribution pattern of the larval population within the field, analysed by the m−m regression method, indicated that the basic component of larval distribution was not a group of individuals but a single individual and such components were distributed contagiously over the field. This basic pattern did not change significantly according to developmental stage, census date or field. Therefore, we could describe the distribution pattern of the population in a rice field by the single linear regression, x=0.021+1.339x(r²−0.912). Also, the relation for the whole population in the field area including the five fields could be shown by the linear regression, x=0.049+1.749x(r²−0.959). The value of α remained to be nearly equal to zero, but the value of β became larger than the value for the single-field relation. Such a change in distribution pattern seemed to reflect the greater heterogeneity in conditions among the fields than within individual field. Using the information on the distribution patterns mentioned above, some considerations were given on the sampling plans for mosquito larvae, including samplesize determination and application of sequential methods to estimate population size as well as to classify population level.     

Population policy: Authoritarianism versus cooperation

The people whose interests are most adversely affected by frequent bearing and rearing of children are young women. Social changes that expand the decisional power of young women (such as expansion of female literacy, or enhancement of female employment opportunity) can, thus, be major forces in the direction of reducing fertility rates. This “cooperative” route seems to act more securely – and often much faster – than the use of “coercion” in reducing family size and birth rates. This essay examines the comparative evidence from India and China on this subject as well as the interregional contrasts within India. JEL classification: J11, J13, O15 Received August 20, 1996/Accepted November 14, 1996     

Modeling female fertility using inflated count data models

For modeling complete female fertility we propose a zero-and-two-inflated count data model, which accounts for a relative excess of both zero and two children. As the underlying distribution of counts we use the standard Poisson distribution and the more general Gamma count distribution. We compare our proposed model with standard count data models by using data on complete fertilities for a sample of Swedish women. The preferred specification for Swedish fertility data is the zero-and-two inflated Gamma count data model. The estimated “extra” probabilities of zero and two children, when modelled as individual specific probabilities, vary substantially across individuals, with mean of 0.05 and 0.16, respectively. These extra probabilities show that women who formed a family later in life have a higher probability of being childless, and women of our youngest cohort have a higher probability of forming a two-child family. Received: 7 January 1999/Accepted: 19 May 1999     

Where are the Children? Children’s Role in Measuring and Monitoring Their Well-Being

This paper starting point is the dynamic changes and shifts in the field of measuring and monitoring children’s well being. In the paper we focus on one specific change – the “new” role of children in measuring and monitoring their own well being – a role of active participants rather then of subjects for research. We then turn to present based on a sequence of arguments and findings what role children should carry in measuring and monitoring their well being. Followed by a presentation of five possible roles for children involvement in such studies and in regard to the specific roles existing knowledge from various studies and suggested directions for future research are presented. The danger of children’s involvement is such studies are then discussed followed by a presentation of what do children think on this all issue. Finally we conclude that the potential involved in children’s involvement is much greater then the hazards.     

Why Faster,Higher, Stronger isn’t Necessarily Better—The Relations of Paralympian and Women’s Soccer Teams’ Performance to National Well-being

The present study considers how the athletic performance of minority groups relates to national subjective well-being (SWB) and life expectancy. Based on the argument that sports represent a microcosm of society and the reliable finding that national inequality is associated with reduced SWB, we hypothesized that greater opportunities for typically disadvantaged groups within sports should be positively related to national indicators of well-being. Study 1 compared the relation of success in the Paralympics versus the Olympics to national subjective well-being and life expectancy. The results supported our hypothesis. In Study 2 we conceptually replicated these results using the standings of national men’s and women’s soccer teams. Overall, it appears that the opportunities to compete in sports that nations afford to members of disadvantaged groups reflect on the health and well-being of the entire society.

Women’s employment, religion and multiculturalism: Socio-demographic emphasis

Giving the central focus to ‘religious affiliation’ which ‘was once at the forefront of demographic research (McQuillan 2004: 25), this paper examines the association between religion and women’s market employment. Generally speaking, gender characteristics such as high fertility and low employment levels for Muslim women in both intracountry and worldwide comparisons have been asserted in an extensive literature. The context, method and comparison groups of this study provide the opportunity to examine the longstanding debate as to whether religionper se or other determinants explain such gender characteristics in Islamic settings. It is, however, acknowledged that the present study faces limitations mainly associated with the selectivity of migrants. Using logistic regression and the multicultural context of Australia containing a substantially diverse ethnic composition of Muslims, this paper highlights Muslim/non-Muslim employment differentials. The paper also analyses the employment level of Muslim women across the regions of origin representing various contexts in order to provide empirical evidence to examine the above debate.     

Are Father’s or Mother’s Socioeconomic Characteristics More Important Influences on Student Performance? Recent International Evidence

Since the early 1970s the importance of mothers’ socioeconomic characteristics on their children’s educational and occupational attainment has been acknowledged. However, it is not clear if fathers’ characteristics have a stronger influence because men usually have stronger attachments to the labour market, or alternatively mothers’ characteristics are more important because of their greater role in children’s socialization. This study addresses this question by comparing the influence of father’s and mother’s education and occupation on student performance in literacy and numeracy using data from 30 countries. The impact of mother’s education is usually greater or comparable to that of father’s education. In contrast, substantially stronger effects for mother’s occupational status compared to father’s were rare. In most countries the impact of mother’s socioeconomic characteristics (education plus occupation) on student performance is comparable to that for father’s. Of the four indicators of socioeconomic background, father’s occupational status and mother’s educational attainment tend to have stronger effects, although many countries do not conform to this pattern. There are indications that the relative importance of mother’s characteristics have increased over time.

Gender discrimination and efficiency in marriage: the bargaining family under scrutiny

We consider a repeated family bargaining model that links the topics of employment and households. A key aspect of the model is that marital bargaining power is determined endogenously. We show that: (1) the efficiency of household decisions is sometimes inversely related to the prevailing degree of gender discrimination in labor markets; (2) women who are discriminated against have difficulty enforcing cooperative household outcomes because they may be extremely limited to credibly punish opportunistic behavior by their male partners; (3) the likelihood that sharing rules such as “equal sharing” are maintained throughout a marriage relationship is highest when men and women face equal opportunities in labor markets. Responsible editor: Deborah Cobb-Clark     

Child support and non-resident fathers’ contact with their children

The paper presents a model of a non-resident father’s child support and contact with his child, which combines the public good treatment of “child quality” with “trade” in father–child contact time in a setting of non-cooperative interaction. It predicts that father’s income and mother’s non-labour income should have exactly the same effect on the frequency of father–child contact if he chooses to make lump sum payments to the mother. If he does not or there is a binding child support payment order, they have effects opposite in direction. A higher binding support order reduces father–child contact but may well raise “child quality”.

A comparison of species diversity estimators

Although having been much criticized, diversity indices are still widely used in animal and plant ecology to evaluate, survey, and conserve ecosystems. It is possible to quantify biodiversity by using estimators for which statistical characteristics and performance are, as yet, poorly defined. In the present study, four of the most frequently used diversity indices were compared: the Shannon index, the Simpson index, the Camargo eveness index, and the Pielou regularity index. Comparisons were performed by simulating the Zipf–Mandelbrot parametric model and estimating three statistics of these indices, i.e., the relative bias, the coefficient of variation, and the relative root-mean-squared error. Analysis of variance was used to determine which of the factors contributed most to the observed variation in the four diversity estimators: abundance distribution model or sample size. The results have revealed that the Camargo eveness index tends to demonstrate a high bias and a large relative root-mean-squared error whereas the Simpson index is least biased and the Shannon index shows a smaller relative root-mean-squared error, regardless of the abundance distribution model used and even when sample size is small. Shannon and Pielou estimators are sensitive to changes in species abundance pattern and present a nonnegligible bias for small sample sizes (<1000 individuals). Received: May 8, 1998 / Accepted: May 6, 1999