An individual-based model for competingDrosophila populations

An individual-based model forDrosophila is formulated, based on competition amongst larvae consuming the same batch of food. The predictions of the model are supported by data for single speciesDrosophila populations reared in the laboratory. The model is used to build a simple discrete model for the dynamics ofDrosophila populations that are kept over a number of generations. The dynamics of a single species is shown to give either a stable equilibrium or fluctuations which can be periodic or chaotic. When the dynamics of a species in the absence of the other is periodic or chaotic, we found coexistence or two alternative states, on neither of which the species can coexist.     

The estimation of the fitness function from two samples taken from a population

Summary The fitness of animals subjected to natural selection can be defined as the probability of surviving selection for a given interval of time, or some convenient multiple of this probability. If the fitness of animals is related to some quantitative variableX (such as size) then this relationship is expressed mathematically in the fitness functionw(x) and this function can be estimated by comparing the distribution ofX in samples taken before and after selection. In this note five methods for estimating the fitness function on the basis of samples from a large population are discussed. They are compared on three previously published sets of data and as a result estimation according to weighted multiple regression is recommended.     

Measuring Social Cohesion: An Experiment using the Canadian National Survey of Giving,Volunteering, and Participating

Social cohesion is a concept difficult to define and to measure. As there can be many definitions, so there can be many measurements. The main problem, either in defining or measuring the concept, is its multilevel and multidimensional nature. At one extreme, country is the most commonly used level to view social cohesion but measurement at this level is of little use for any interventions. At the other extreme, community is the most useful level but it is a social construct for which data are difficult to get, given the administrative boundaries used in social surveys. As an initial attempt to measure social cohesion at a subcountry level, this study focuses on census metropolitan areas for which data on several dimensions of social cohesion are available. We use the information gathered by the National Survey on Giving, Volunteering and Participating (NSGVP) on three dimensions of social cohesion: political (voting and volunteering), economic (occupation, income, labour force participation) and social (social interactions, informal volunteering). Using statistical techniques including factor analysis and standardization, we create an overall index of social cohesion for each CMA. We point out use of this measure for further analysis of social dynamics.     

The life-expectancy of industrial civilization: The decline to global equilibrium

A new paradigm is needed for industrial civilization, because neither the traditional theory of exponential industrial growth nor the more recent steady-state hypothesis can satisfactorily explain historical data. As a basis for the paradigm, the long sweep of human history is divided into three phases: (1)pre-industrial, (2)industrial, and (3)de-industrial. This essay focuses on the second, or industrial, phase. The paradigm is embodied in four theories. The first theory states that industrial civilization can be graphed over time by energy-use per person in the shape of asingle pulse waveform. The second theory is derived from a well-established principle of human ecology. It defines a set ofnecessary conditions for the advance, stagnation and decline of industrial civilization in terms of world total energy-use and world total population. Next, the subject ofgoverning is analyzed in terms of ten requirements for system control. The third theory is derived from this analysis. It relates thesize, orcomplexity, of a society over time to the average energy-use per person in that society. Historical population and energy-use data and other considerations are used as the basis for the fourth theory. This, a predictive theory, states that thelife-expectancy of industrial civilization is less than 100 years.     

Seasonal host alternation by the andromeda lace bug,Stephanitis takeyai (Heteroptera: Tingidae) between its two main host-plant species

I studied the seasonal occurrence of the andromeda lace bug,Stephanitis takeyai, on its two main host-plant species. In a secondary forest in Kyoto, this bug altered its hosts seasonally, i.e., from an evergreen shrub,Pieris japonica, in winter to a deciduous shrub,Lyonia elliptica, in summer. In contrast, in Nara park where fewL. elliptica were available, the bug exploited onlyP. japonica. Thus, seasonal host alternation by this bug is not obligate. A comparison of adult longevity and fecundity on the two host-plant species demonstrated the higher quality ofL. elliptica as a food resource. Corresponding to this difference in host quality, there was a dramatic difference in the seasonal population growth in the two study sites. In Nara, the population size at the beginning of the 2nd generation was almost the same as in the overwintered generation, whereas in Kyoto the population size in the 2nd generation was approximately one hundred times as large as in the overwintered generation. Thus seasonal host alternation is adaptive for the bug. In a previous study, I reported that overwintering as eggs in living leaves of their hosts is likely to be common among all the related species of this bug. Thus, this trait can be considered to be a phylogenetic constraint to the group. I speculate that host alternation by this bug has been derived because it is more adaptive from autoecy on an evergreen plant, similar to the pattern currently found in Nara, and that this bug can not only exploit deciduous host due to a phylogenetic constraint.     

Warning coloration in sawflyAthalia rosae larva and concealing coloration in butterflyPieris rapae larva feeding on similar plants evolved through individual selection

Summary Green larvae of the butterflyPieris rapae and black larvae of the sawflyAthalia rosae feed on green leaves of the same cruciferous plants. To demonstrate thatP. rapae has concealing coloration and thatA. rosae has warning coloration, the larvae of the two species were supplied to naive chicksGallus gallus on white, green or black backgrounds.P. rapae larvae were palatable and their green body color acted as a concealing coloration. On the other hand,A. rosae larvae were unpalatable and their black body color acted as a warning coloration. There is a general consensus that warning coloration is an altruistic character which needs victims, and thus can evolve through kin selection or green beard selection. However, blackA. rosae larvae were seldom injured by chicks' attack, in particular, on the green background. Therefore, the warning coloration ofA. rosae larvae can be a selfish character and hence can evolve through individual selection as well as concealing coloration ofP. rapae.     

Differences in Life Expectancy and Disability Free Life Expectancy in Italy. A Challenge to Health Systems

Background Measures of health expectancy such as Disability Free Life Expectancy are used to evaluate and compare regional/national health statuses. These indicators are useful for understanding changes in the health status and defining health policies and decisions on the provision of services because provide useful information on possible areas needing interventions and burden of care to health systems. Methods Two databases have been used for the analysis: the Italian Health Interview Survey and the European Community Household Panel. The data were analyzed by gender and geographic area. DFLE was calculated by the Sullivan method. Results In 2005 in Italy women have a longer life expectancy than men: 84 and 78 years, respectively. But if we consider life without disability in Italy the male disadvantage reduces: men live 85% of their years without disability, women only 75%. Geographic differences do exist because Disability Free Life Expectancy is longer in Northern and in Central regions; shorter in the South. At a European level similar data can be found: on average women live longer but they have a longer time of life with disability. Conclusion In Italy women live longer but have a worse quality of health than men; in the South there is a worse quality of health. Similar findings can be identified at a European level. The Italian situation with the highest percentage of DFLE at 65 out of the total LE at 65 and one of the longest LE witnesses ageing is not necessarily associated to a worsening of health.     

Precarious employment among South Korean women: Insights from a comparison to France

Family responsibilities for women are often associated with precarious employment. This relation varies depending on whether women can reconcile family life and work or not. Based on the Korean Labor and Income Panel Study from 1998 to 2008 and on the French part of the European Community Household Panel between 1998 and 2001, a multiple correspondence analysis shows that precariousness in employment is correlated with family life and levels of education. The better conditions of work-family balance in France enable young mothers to combine family life with stable employment of good quality, which is not the case for South Korean women. The comparison of the two countries highlights the necessary reforms in favor of women’s better being.     

The Swedish Tant: A Marker of Female Aging

This article presents and analyzes findings from interviews with women aged 45–65; popular magazines targeting women in this age category, and popular books and blogs on a Swedish age-sensitive concept, tant. The term can be used in many different senses, ranging from polite to derogatory, connoting “aunt,” or “granny,” but also “little old lady” and “biddy”; the term tantig translating to “frumpish.” The article discusses different representations of tant, how she is used as a symbol of invisibility and no longer being seen as a sexual being, but outdated. The concept is used as a warning, indicating an unwanted way to grow old, when addressing middle-aged and older women. As of recently, tant has come to be celebrated by young women, praised for moral courage, for thrift and being represented as free from the male gaze, no longer aiming to please or fretting about appearances. The article sheds light on the different uses of the concept, where who is categorizing whom is of utmost importance. The tant is used as a symbol for doing age either by derogation or by celebration.     

Can Regional Variations in Demographic Structure Explain Regional Differences in Car Use? A Case Study in Austria

Due to its manifold impact on the environment private car use represents an important dimension of environmental behavior in industrialized countries. Obviously, private car use is related to demographic characteristics of households such as the life-cycle stage and the living arrangement the household lives in. In addition systematic regional differences of private car use have to be taken into account. In this paper a causal model is derived, which aims to explain regional differences in car ownership and car use by regional demographic differences and region-specific control factors such as the car technology and institutional factors. Using aggregate data from a household survey in Austria and data from Austrian official statistics causal effect coefficients are then estimated. By applying path analysis the estimated effects of regional demographic characteristics on region-specific car ownership and car use can be decomposed into direct and indirect effects, with the latter effects being mediated by the control factors. Except for the average age of household heads and population density no significant direct demographic effects on regional patterns of car ownership and car use can be found. Car ownership and car use are best predicted by using the considered control factors as predictor variables. Nevertheless, many of the presumed indirect effects turn out to be of importance since demographic factors are closely linked to measures of regional institutional settings like per capita income, ownership of house/apartment and net commuting index.     

Stabilization of the population of a parasite on fruit by the population of a cleptoparasite

Summary When there exist two species such that one is a parasite on fruit and the other exploits the parasitized fruits, they must compete for a limited resource with each other. The relation betweenDacus cucurbitae andAtherigona orientalis is an example of such a situation. We raise a question whether the population of a parasite on fruit can be stabilized by the existence of the cleptoparasite of the parasite on fruit. The changes in their population densities are represented as a differential equation with time delayed parameters, which is deduced from the context of life histories of the two species. An index representing degree of overlapping of generations (g) is defined as an average oviposition period devided by the average preoviposition period, and the value is assumed to be the same in the two species. The stability of the system is classified by three parameters: the reproductive rate of the parasite on fruits (R), the survival probability of it through competition against the cleptoparasite (p), and the generation overlapping index (g). For small values ofg, e.g. less than some 0.5, the stability is determined mainly by a product ofRp: the values larger than 1 result in no equilibrium and infinite increase of both species, the values near 0 lead to large amplitude oscillations, and the intermediate values make stable equilibria or regular small oscillations. Asg takes the larger values, the stability region in the space (p, R) occupies the larger area. The model presented here is well adjusted to the fluctuating pattern of the population ofD. cucurbitae on Okinawa Is., and would also be applied to analysis of both hyperparasitisms and inquilin. This study was supported partly by Science Research Fund (No. 574092) from the Ministry of Education, Japan.     

A note on the estimation of selective values from recaptures of marked animals when selection pressures remain constant over time

Summary An equation is given for the estimation of selective values from data obtained by mark-recapture experiments, assuming that selective pressures remain constant while the experiments are carried out. The equation does not have an explicit solution but can readily be solved using a trial-and-error method. The use of the equation is illustrated on some data reported byKettlewell et al. (1969) from an experiment involvingtypica andedda morphs of the mothAmathes glareosa. It is found that theedda morph apparently had a selective advantage of about 12% per day compared to thetypica morph and that this is significantly different from zero. Using another methodKettlewell concluded that the selective advantage of theedda morph was only 7% and that this was not statistically significant.     

The learning abilities of the white cabbage butterfly,Pieris rapae, foraging for flowers

This study examines the role of learning and memory in the butterflyPieris rapae crucivora Boisduval during foraging for flowers. In an outdoor cage with 6 flower species,P. rapae showed various visiting patterns: some visited only one species, while others visited several species in a day. The foraging process for flowers ofErigeron annuus (L.) Pers. could be divided into two successive steps: (1) landing on the nectaring caputs, and (2) finding the source of nectar in the caput. Butterflies learned to proceed through the two steps more efficiently with successive attempts: they gradually decreased landings on nectarless caputs and probings on the nectarless petals of ligulate flowers respectively. As a result, handling time per unit caputs became shorter, and apparent rewards per unit time, i.e. the efficiency of collecting nectar, increased. In addition, once learned,P. rapae could remember a rewarding flower color for 3 days, which was not interfered with by learning another flower color. This indicates thatP. rapae keeps memory for a period longer than 3 days, and that they can remember at least two flower species as suitable flower resources. Furthermore, data indicated that they sometimes can apply the foraging skills obtained on other flower species to a novel one. These abilities could enable butterflies to easily switch flower species, or to enhance labile preference. It has been known thatP. rapae also shows flower constancy, which may be due to memory constraints. Therefore, they may appropriately use two foraging tactics: visit consistency and labile preference, to get enough nectar according to their circumstances.     

Persistence of a fig wasp population and evolution of dioecy in figs: a simulation study

The relationship between fig trees and their pollinator wasps is a well-known example of species-specific obligate mutualism. In this article we present a stochastic model of this mutualistic system, referring to data on a dioecious fig (Ficus schwarzii) in Borneo, and examine the conditions for the persistence of a wasp population for a given period. (1) When the average duration of the flowering interval of fig trees is short, even a small fig population can sustain a wasp population successfully. A population whose average period of flowering cycle is half that of another population can sustain a wasp population with a number of trees less than half of the other population. (2) The wasp survival rate (WSR) is higher when (a) the variation of the interval periods of fig flowering is smaller, (b) the fig population size is larger, and (c) figs can prolong their receptivity to wait for a wasp if no wasps are available. (3) WSR is predictable from the average proportion of the fig's receptive phases, in which wasps are available, to their total receptive phases. (4) The persistence period of a wasp population increases exponentially with the number of fig trees. Based on these results we propose a new hypothesis, as a possible scenario, on the evolution of dioecy from monoecy in Ficus. Received: November 13, 1998 / Accepted: July 14, 1999     

Estimation of life expectancy — cohort life table

Life tables are traditionally built with linear assumptions for the survival curve. Here, considering that survivors can remain at the end of the observation period, the author shows that non linear modeling is more appropriate. With data on cervix uteri cancer, e0 ≈ 12.5 years with standard error ≈ 2.8 years with infinite time horizon, but e0 ≈ 6.0 years with standard error ≈ 0.1 year in interval with finite time horizon [0, 12 years]. The average hazard function is introduced to estimate the life expectancy, and the actuarial estimate of the hazard function is showed to under‐estimate the true hazard values under the exponential distribution. Finally, a sensitivity analysis of the probabilities of death on the estimation of life expectancy completes the study.     

Seasonality parameters for insect populations

Summary The usefulness of a number of parameters is investigated for describing the seasonal variability in insect populations, especially in relation to sample size. It is found that Seasonal Niche Breadth (B) and its maximal value (BM) are useful only for large samples. For smaller samples one tends to find the same values for these parameters whatever the distribution they are supposed to describe. The “standardized” ratio of these two parameters (B/BM) is completely useless. The Season Length (S. L.), defined as 52 minus the longest series of weeks in which the species was absent, or not observed, was found to be quite useful, especially at smaller sample sizes. For species which occur over a large part of the year and have been observed in large numbers, the ratioMin/Max is found to be quite useful. This is the number of individuals during the four weeks at the low point of the season divided by the number observed during the four weeks in the peak of the season. It is suggested that the seasonal distribution be estimated usingS. L. or, when appropriate,Min/Max in order to estimate the Seasonal Standard Deviation (SSD), which assumes a normal seasonal distribution. With thisSSD the 99 per cent range (Seasonal Range) can be calculated to characterize the seasonal distribution. With this Seasonal Range different species or different areas can profitably be compared in their seasonality characteristics even if there is a large difference in sample size.     

Legacy,Policy, and Circumstance in Fertility Transition

Divergent fertility trends in the course of development are commonly ascribed to differences in state action—that is, to government policy, deliberate or inadvertent. However, fertility outcomes can also, often more persuasively, be traced to differences in cultural and institutional inheritance and in the supply and growth potential of human capital. These are materials that states and societies find themselves endowed with—in brief, their legacy. In reality, legacy and policy are interwoven: policy actions build on some legacy elements and attempt to combat others. And there is a third set of factors influencing fertility outcomes, covering distinctive features of the economic and geopolitical environment and essentially fortuitous events—together termed circumstance. Legacy and circumstance can shrink or shift the policy space, helping to explain past failures in policy achievement. These broad considerations are the basis for a sketch of East Asian/sub‐Saharan African contrasts in fertility transition over the last 50 years. The sketch points to missing avenues of policy action in the African case in seeking to overcome legacy obstacles.     

Television crime series,women police,and fuddy-duddy feminism

This essay argues that Prime Suspect has become a canonical text for feminist television studies and that Helen Mirren's performance of Lynda La Plante's creation has provided an influential template for television, and the broader culture, to imagine what a senior female police officer is like. So Jane Tennison is important not only within the depicted world of the “canteen culture” of the police in Prime Suspect, but also within the broader context of television production where she has demonstrated that crime shows with female leads can be extremely successful. Juxtaposing Prime Suspect with two later “girly” British TV police series, I ask how we might approach the “daughters of Jane Tennison” found in series such as Ghost Squad (2005) and Murder in Suburbia (2004–2006). Are these “postfeminist” shows? I argue that attention to these programmes can productively inform our understanding of what is entailed for women in not being “fuddy-duddy,” and my comments thus engage, in the continuing debate about the utility and periodisation of the notion of “postfeminism.”     

Losses of Expected Lifetime in the United States and Other Developed Countries: Methods and Empirical Analyses

Patterns of diversity in age at death are examined using e ^†, a dispersion measure that equals the average expected lifetime lost at death. We apply two methods for decomposing differences in e ^†. The first method estimates the contributions of average levels of mortality and mortality age structures. The second (and newly developed) method returns components produced by differences between age- and cause-specific mortality rates. The United States is close to England and Wales in mean life expectancy but has higher life expectancy losses and lacks mortality compression. The difference is determined by mortality age structures, whereas the role of mortality levels is minor. This is related to excess mortality at ages under 65 from various causes in the United States. Regression on 17 country-series suggests that e ^† correlates with income inequality across countries but not across time. This result can be attributed to dissimilarity between the age- and cause-of-death structures of temporal mortality reduction and intercountry mortality variation. It also suggests that factors affecting overall mortality decrease differ from those responsible for excess lifetime losses in the United States compared with other countries. The latter can be related to weaknesses of health system and other factors resulting in premature death from heart diseases, amenable causes, accidents and violence.