Preference and performance linkage in aPhyllocolpa sawfly on the willow,Salix miyabeana, on Hokkaido

A leaf-folding sawfly in the genusPhyllocolpa (Hymenoptera: Tenthredinidae) attackingSalix miyabeana (Salicaceae) was studied near Sapporo, Hokkaido, along the Ishikari River in 1993. Host plant individuals were young trees 4–7 years old which were growing rapidly, producing some long shoots with large leaves. On a gradient of shoot length classes from 0–5 cm long to over 80 cm long, shoots were much more abundant in the shorter shoot length classes. However, attacks by ovipositing females increased as shoot length increase from 0 attacks on the shortest shoots to 5.17 attacks per shoot on the longest shoots. The frequency of attack per leaf increased from 0 to 0.13 over the same range of shoot lengths. This pattern of attack resulted in a high frequency of larval establishment in feeding sites, between 0.96 and 1.00, in all attacked shoot length categories. However, probability of survival to a late instar larva increased with shoot length and corresponded to the attack pattern, indicating a preference-performance linkage between female ovipositional decisions and larval survival. The patterns found for thisPhyllocolpa species are similar for galling sawflies in North America and Europe, especially in the genusEuura, members of which make stem, bud and leaf midrib galls. Extending the pattern to aPhyllocolpa species broadens identification of pattern and ultimately the generality of the emerging theory on populations of galling sawflies.     

Seasonal change of nest survival and related aspects in an aggregation ofLasioglossum duplex (Dalla torre), a eusocial halictine bee (Hymenoptera: Halictidae)

Summary Nest survival in an aggregation of a eusocial halictine bee,Lasioglossum duplex, was censused through an annual cycle. Out of 2,500 nests marked at the beginning of solitary phase in the spring, only 25.5% attained eusocial phase. But 60.5% of 636 nests attaining eusocial phase successfully produced sexual offspring. This shows that solitary phase is the most vulnerable period in the annual cycle. A very low productivity in eusocial phase in the census year was clarified from examination of 99 nests in the autumn. The number of prospective foundresses surviving to the next year was estimated upon the number of brood cells in examined nests and of old females surviving these nests. Deviation between this estimate and the number of nests made in the next spring was 8.8%, confirming a drop of population size to less than one third in the next year. Some nests solitarily made in the summer by dispersed females were examined. Productivity in such nests was extremely low, hence these nests should contribute virtually nothing to the next generation. Possible factors affecting the low productivity in eusocial phase were enumerated though none of these were supported by concrete evidence. Some considerations were given on the relation between obtained results and colony life cycle in eusocial insects, particularly in halictine bees. Bionomics of the eusocial halictine bee,Lasioglossum duplex. VI.     

“人均预期寿命提高1岁”的实证研究

温家宝总理在政府工作报告中首次提出十二五时期"人均预期寿命提高1岁"的目标。本文在生命表数据基础上,通过计算平均预期寿命贡献率并进行相关分析与回归分析后得出:我国目前平均预期寿命虽然已高于绝大多数发展中国家,但其绝对增速正逐渐放慢。而降低60～90岁年龄段老年人口死亡率、提高居民消费水平、缩小家庭规模、迁移有条件的离退休老人到低海拔地区养老是实现人均预期寿命提高1岁目标的有效路径。     

A host shift from wild blue cohosh to cultivated potato by the phytophagous ladybird beetle, Epilachna yasutomii (Coleoptera, Coccinellidae)

Life history traits of the phytophagous ladybird beetle Epilachna yasutomii were compared between a nonpest population feeding on wild blue cohosh and a pest population feeding on cultivated solanaceous crops, mainly potato. Newly emerged adults of the nonpest population entered diapause early in midsummer when blue cohosh withered, while adults of the pest population were found in tomato and eggplant fields until late autumn. The pest population had larger females, a higher population growth rate, a shorter larval developmental period, and reduced longevity of overwintered females, compared with the nonpest population. ANOVA indicated that all these life history traits were influenced by the food plant, and that the number of eggs laid per female and the longevity of overwintered females were also affected by the population type. These findings suggest that the life history pattern of E. yasutomii changed to high fecundity with a short life span from low fecundity with a long life span as a result of the host shift from wild blue cohosh to cultivated solanaceous crops. Received: May 22, 1998 / Accepted: January 13, 1999     

Theoretical consideration of effect of fishing mortality on growth and reproduction of fish populations

Summary An increase in fish mortality due to fishing can theoretically change the growth and reproduction of fish populations from the viewpoint of adaptation. We address the issue of how an iteroparous fish should convert surplus energy into somatic growth and reproduction at each age under given conditions of mortality. A model of life history, which maximizes the net reproductive rate using the discrete maximum principle, is improved employing a new relationship between body weight and surplus energy which we have recently proposed. The model is applied to the North Sea plaicePleuronectes platessa, for which it has been reported that the average length of young fish had increased whereas that of old ones had decreased for some decades. Although the model cannot directly explain the former phenomenon, the two phenomena can be interpreted as a change in the optimal life history due mainly to an increase in mortality.     

Population statistics] as of October 1, 1994

As of October 1, 1994, Thailand's population was comprised of 29,413,000 males and 29,448,000 females, 18,588,000 of whom resided in urban areas. 11,501,000 lived in the North, 20,007,000 to the Northeast, 7,310,000 in the South, 12,732,000 in central Thailand excluding Bangkok, and 7,311,000 in the Bangkok metropolis. 16,952,000 were under 15 years old, 19,682,000 aged 6-21, 37,612,000 aged 15-59, 35,793,000 aged 20 and over, and 4,297,000 aged 60 and over. There were 15,195,000 women aged 15-44. The crude birth rate was 17.6/1000, crude death rate 5.8/1000, natural growth rate 1.2%, and infant mortality rate 34.13 per 1000 live births. Male and female life expectancies at birth were respectively 67.7 and 72.4 years, while male and female life expectancies at 60 were 18.8 and 22.0. Rates of total fertility per woman and contraceptive prevalence were respectively 1.95 and 75.0%. The population is projected to total 71,637,000 in the year 2012.     

Seasonal life cycle and autogeny in the mosquitoAedes togoi in northern Kyushu, Japan, with experimental analysis of the effects of temperature, photoperiod and food on life-history traits

We studied seasonal changes in the larval population structure, adult size, and autogeny (egg production without a bloodmeal) of the mosquitoAedes togoi on the seacoast of northern Kyushu, Japan. The effects of temperature, photoperiod and food conditions on larval development, adult size and autogeny were studied in the laboratory.Aedes togoi overwintered in both the egg and larval stages and was multivoltine. Adult size was greater in spring and autumn and smaller in summer. Autogeny occurred in spring and autumn but not in summer. Autogenous females were larger than anautogenous females, and larger autogenous females produced more eggs. Laboratory experiments showed that autogeny was promoted under low temperature and short-day conditions which corresponded with spring/autumn conditions in the field. Experimental food limitation in the larval stage greatly reduced adult size and autogenous egg production. In the field, large inter-pool variations in adult size and autogeny rate probably resulted from variations in nutrient and crowding conditions. Seasonal autogeny ofAedes togoi was discussed in terms of life-history strategy under fluctuating environmental conditions where relative advantages of autogenous and anautogenous reproduction alternate seasonally.     

One-host one-parasitoid system: Population dynamics of a zygaenid mothPryeria sinica Moore in an undisturbed habitat

Summary The population dynamics ofPryeria sinica was investigated in an undisturbed area in 1976–1979. We analyzed the process stabilizing the local population by the life table approach for immature stages and the mark-recapture method for the adult stage. Females usually layed about 130 eggs in an egg-mass. The shape of the survivorship curve was convex and was characterized by a relatively low mortality in the egg and larval stages and by a relatively high mortality in the prepupal and pupal stages. The low mortality in the early stage seemed to be not only due to the peculiar life cycle of this species (larvae develop in early spring when natural enemies are not active) but due to their protective nest-webs, larval warning coloration and repellent smell. The high mortality after cocooning was caused by severe parasitization byAgrothereutes minousubae. The number of adult in the population varied by 2.10-fold, which was less than that of other gregarious moths. The life table data and field observations suggest that adult female dispersal would have acted as a stabilizing factor, andA. minousubae as a conditioning factor on the dynamics of the moth population.     

The Legacy of the Great Recession in Italy: A Wider Geographical,Gender, and Generational Gap in Working Life Expectancy

Under the pressure of population aging the Italian pension system has undergone reforms to increase labor force participation and retirement age, and, thus, the length of working life. However, how the duration of working life has developed in recent years is not well understood. This paper is the first to analyze trends in working life expectancy in Italy. We use data from a nationally representative longitudinal sample of 880,000 individuals from 2003 to 2013 and estimate working life expectancy by gender, occupational category, and region of residence using a Markov chain approach. We document large and increasing heterogeneity in the length of working life. From 2003–2004 to 2012–2013, working life expectancy for men declined from 35.2 to 27.2 years and for women from 34.7 to 23.7 years, increasing the gender gap to 3.5 years. Both young and old were hit, as roughly half of the decline was attributable to ages below 40, half above 40. Working life expectancy declined for all occupational groups, but those in manual occupations lost most, 8.5 years (men) and 10.5 years (women). The North–South economic gradient widened such that men living in the North were expected to work 8 years longer than women living in the South. The fraction of working life of total life expectancy at age 15 declined to record lows at 40% for men and 34% for women in 2012–2013. Policies aiming at increasing total population working life expectancy need to take into consideration the socio-demographic disparities highlighted by our results.

     

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.     

Interannual fluctuations in recruitment and growth of the sardine,Sardinops melanostictus, in the sea of Japan and adjacent waters

Recruitment and growth of the sardineSardinops melanostictus fluctuated markedly in the Sea of Japan and adjacent waters between 1978 and 1993. Stock size was calculated using Virtual Population Analysis and average body length in each age class was determined by the number of annual rings on the scales. There is an inverse correlation between average water temperature at a depth of 50 m in the coastal area of the mainland of Japan in winter (January to March) and recruitmentR defined as the number of individuals at 1 year old. There is also an inverse correlation between spawning stock sizeE and reproductive success in (R/E). A multiple regression model using spawning stock size and water temperature in winter as independent variables can explain 73% of variance in reproductive success. It suggests that both density-dependent and density-independent factors perform important roles determining reproductive success. There is an inverse correlation between body length and stock size and this suggests that there is a density-dependent effect on the growth of the sardine.     

Population statistics] as of July 1, 2000

This Mahidol Population Gazette presents Thailand's population and demographic estimates as of July 1, 2000, using the standard techniques of demographic analysis. The paper provides estimates of Thailand's total population, population by sex, population in urban and rural areas, population by region, and by age group. In addition, figures of crude birth and death are listed per 1000 population, natural growth rate, and infant mortality rate per 1000 live births, male and females' life expectancy at birth and at age 60, total fertility rate, contraceptive prevalence rate. The number of the aged population in 2020 is also presented. Presented in a bar graph is a population pyramid for Thailand in the year 2000, illustrating male and females' age and year of birth.     

The population dynamics of the large pine aphid,Cinara pinea (Mordv.)

Summary The large pine aphid,Cinara pinea lives exclusively onPinus species, where it feeds on the foliated shoots of the current and previous year. The paper describes the development of a computer model designed to simulate the aphid’s population dynamics on saplings in the controlled environment of the laboratory, i.e. in the absence of natural enemies. The model was able to account for about 80% of the variation in aphid numbers within and between trees over a three month period. Sensitivity analysis revealed that the number of pine aphids is limited primarily by nymphal emigration, the operation of which is sensitive both to density and to plant quality as reflected in aphid growth rates. Of secondary importance are changes in reproduction acting through increased reproductive delay, again a result of altered growth rates and adult size. Development, too, has an important secondary influence. Contrary to expectation and conventional belief, however, alate production proved to be of negligible importance, either in limiting or regulating population numbers. Alatae are produced in too few numbers and for too short a period to significantly alter the pattern of population change.     

预期寿命增长、年龄结构改变与我国国民储蓄率

人口年龄结构趋于老龄化和人均预期寿命逐步增长是目前我国人口发展的两个典型特征,而年龄阶段不同,个人的收入、消费与储蓄行为也不同。基于生命周期理论,在选定相关分析指标的基础上,文章使用我国省际平衡面板数据,实证分析了我国人口预期寿命增长和年龄结构改变对国民储蓄率的影响。分析结论表明,人口预期寿命增长提高了我国国民储蓄率;不考虑时间效应时,幼年人口负担比提高会减少国民储蓄率,而老年人口负担比提高会增加国民储蓄率;在考虑时间效应时,幼年人口负担比提高会增加国民储蓄率,而老年人口负担比提高会减少国民储蓄率。对此,文章给出了合理的解释。通过使用多种估计方法,我们发现所得到的结论是基本稳健的。     

Population dynamics of the whitebacked planthopper,Sogatella furcifera (Hemiptera: Delphacidae) with special reference to the relationship between its population growth and the growth stage of rice plants

A population census was conducted to describe the effects of the growth stage of rice on the population dynamics ofS. furcifera, in particular, on immigration, seasonal abundance, population growth rate, and wing-form expression. The number of immigrants was highest on rice plants 17 to 30 days after transplanting (DAT), which suggested that immigrants prefer to settle or remain more on rice plants at the tillering stage (approximately 20–30 DAT). Population growth rate from immigration to the 1st generation decreased with an increase in rice plant age. In contrast, population growth rate from the 1st to 2nd generation was not influenced by rice plant age and was negatively density-dependent. The percentage of macropters (flyers) was positively related to the growth stage of rice when rice was in the vegetative or early part of the reproductive stage, and reached 100% at about 10 days before heading (booting stage). Threafter, most adult females molted into macropters regardless of population density. The roles of host plant age and crowding effect on the population dynamics ofS. furcifera are discussed.     

Population statistics] as of July 1, 1999

Reported in tabular form are population statistics published by the Institute for Population and Social Research, Mahidol University, in Thailand, as of July 1, 1999. The three objectives of the table were 1) to present the most recent estimates of relevant population numbers and vital rates twice a year, 2) to provide the most accurate demographic estimates possible through the use of standard techniques of demographic analysis, and 3) to disseminate the demographic data to Thailand, and international researchers and planners. The table shows statistics on the following elements: total population; population by sex; population in urban and rural areas; population by region; population by age group; crude birth and death rates; natural growth rate; infant mortality rate; life expectancies at birth and at 60 years and over; total fertility rate; contraceptive prevalence rate; and median age. A new basis for age estimates is also presented.     

Postmetamorphic growth, survival, and age at first reproduction of the salamander,hynobius nebulosus tokyoensis Tago in relation to a consideration on the optimal timing of first reproduction

Summary The postmetamorphic growth and survival of the salamanderHynobius nebulosus tokyoentis Tago were surveyed in the study site located in Habu village of Hinodemachi, a suburb of Tokyo City, during 1975–1981. A laboratory experiment on the growth rate of juveniles was conducted in parallel with the field survey. The result indicated that this salamander grew at the rate of 8,mm in s.v.l. per year during the juvenile stage, but its growth rate decreased markedly as low as 1.8 mm for males and 1.1 mm for females, once it had attained sexual maturity. According to the “capture-recapture” procedure the annual survival rate after metamorphosis was found to be quite high; that is, approximately 0.7. By using the growth rate of juveniles and the difference between the sizes at metamorphosis and sexual maturity, the age at first reproduction was estimated to be 4 year for males and 5 year for females. From the data obtained in this study, the intrinsic rates of increase (r) were calculated for various values of age at first reproduction under different survival schedules, and the relationship between the age at first reproduction and fitness as measured byr was examined. The result indicated that an optimal age maximizing fitness always existed under respective survival schedules, and the observed age at first reproduction of this salamandei was found to coincide well with the predicted optimal age.     

Health-Related Quality of Life Among Abused Women One Year After Leaving a Violent Partner

This is the first follow up study measuring quality of life among abused women who have left their abusive partner. The women (n = 22) answered a questionnaire while staying at women’s shelter and one year later. The aim was to examine long-term effects of intimate partner violence against women on health-related quality of life. Health-related quality of life was measured using the SF-36 Health Survey and the WHOQOL-BREF. The meantime for living in a violent partnership was 11 years, most of the women had children under 10 years living with them, low income and were on sickness absence or disability pension. About half of the women had experienced threats of violence and 6 had experienced violent acts after leaving their partner. SF-36 scores after one year were significantly better in vitality (t-test, P < 0.001), mental health (t-test P < 0.001) and social domains (t-test, P < 0.04). WHOQOL-BREF scores did not change significantly from baseline, showing that the SF-36 showed more responsiveness in this population. Regression analysis showed that serious physical violence reported at baseline predicted significantly less improvement in physical and mental health and role-emotional in the SF-36 and in social relationships and environmental health in the WHOQOL-BREF. High psychological violence at baseline predicted significantly less improvement in mental health in the SF-36 and in social relationships and environmental health in the WHOQOL-BREF.     

An Empirical Analysis of the Effect of Length of Forecast Horizon on Population Forecast Errors

Many studies have found that population forecast errors generally increase with the length of the forecast horizon, but none have examined this relationship in detail. Do errors grow linearly, exponentially, or in some other manner as the forecast horizon becomes longer? Does the error-horizon relationship differ by forecasting technique, launch year, size of place, or rate of growth? Do alternative measures of error make a difference? In this article we address these questions using two simple forecasting techniques and population data from 1900 to 1980 for states in the United States. We find that in most instances there is a linear or nearly linear relationship between forecast accuracy and the length of the forecast horizon, but no consistent relationship between bias and the length of the horizon. We believe that these results provide useful information regarding the nature of population forecast errors.     

The momentum of mortality change

Mortality change is not usually assigned much importance as a source of population growth when future population trends are discussed. Yet it can make a significant contribution to population momentum. In populations that have experienced mortality change, cohort survivorship will continue varying for some time even if period mortality rates become constant. This continuing change in cohort survivorship can create a significant degree of mortality-induced population change, a process we call the ‘momentum of mortality change’. The momentum of mortality change can be estimated by taking the ratio of e ₀ (the period life expectancy at birth) to CAL (the cross-sectional average length of life) for a given year. In industrialized nations, the momentum of mortality change can attenuate the negative effect on population growth of declining fertility or sustained below-replacement fertility. In India, where population momentum has a value of 1.436, the momentum of mortality change is the greatest contributor to its value.