Changes in the adult sex ratio of six duck species breeding populations over two decades

Despite all efforts,long-term changes in the adult sex ratios of breeding duck populations are still unclear;this uncertainty is especially true for male-bias populations,which are often under the scrutiny of researchers lacking convenient results for the active protection of endangered species.Species with male-bias populations are usually strongly affected by a decline in population size that leads to a higher extinction risk.In this study,we examined our long-term data of the abundance of breeding populations in six duck species(Mallard Anas platyrhynchos,Gadwall Mareca strepera,Red-crested Pochard Netta rufina,Common Pochard Aythya ferina,Tufted Duck Aythya fuligula,and Common Goldeneye Bucephala clangula)from fishponds in South Bohemia,Czechia,between 2004 and 2022.This evidence was used to assess long-term changes in the adult sex ratio in these breeding populations and investigate the possible effects of the NAO index(North Atlantic Oscillation index)on them,indicating climate conditions in winter.We determined a long-term decrease of the proportion of females in the breeding season in two of the six examined species:Common Pochard and Red-crested Pochard,which is driven by the long-term increase in the number of males in contrast to the decreasing or stable number of females likely caused by different migration behaviours between females and males.In the case of Common Pochard,in breeding populations,we estimated 60-65%of males in the early 2000s rising to 75-80%in the early 2020s.However,we establish no significant effects linked to climate conditions of the previous winter in these species as a crucial cause of the changes of the proportion of females in the breeding population.

The population structure and sex ratios of Bursaphelenchus xylophilus under a-pinene stress

Pine wood nematode(PWN), Bursaphelenchus xylophilus, is a serious pathogen of pines throughout the world. Previous work indicated that different concentrations of a-pinene could affect nematode reproduction,however the mechanism of that influence is not clear. In order to examine the reproductive strategies of PWN in response to the stress of the volatile material a-pinene, we investigated different aspects of population changes of B.xylophilus under two concentrations of a-pinene. The results show that a high concentration(214.5 mg ml-1)promoted population growth while a low concentration(56.33 mg ml-1) decreased the population. Population structure was analyzed and it was found that a high concentration of a-pinene decreased the percentage of adults but increased the percentages of larvae and eggs.Furthermore, from the results of an evaluation of sex ratios(female/male), it was determined that a high concentration could elevate sex ratios but a low concentration decreased ratios sharply. These results suggest that the PWN could regulate its population by changing sex ratios under stress of a-pinene. This study has provided a theoretical basis for the prevention and control of pine wilt disease caused by the pine wood nematode.

Comparative Analysis of Variations in Human Sex Ratios of Live Births Among African Populations and at Global Levels

Definition： The final net live birth delivery from the mother＇s womb, with distinct male and female genetic traits, forms a ratioof male live births per 100 female live births, termed as Sex Ratio at Birth （SRB）. Study areas and source of data： The studyareas are Africa and major worldwide continents and countries. The basic data are compiled from the National Populationand Housing Censuses, Demographic Sample Surveys, Demographic and Health Surveys, and Vital Registration Systems.Analytical approaches： The factors influencing the variations in SRB are identified by reviewing various documents, analysisof variance （ANOVA） techniques, and statistical measures of central tendency and dispersion. Results： The ratios areconsistently higher for advanced countries than the developing countries, with highest for China and India. The ANOVAresults show slight differences among the S0 African countries but show differences among the African regional states,whereas the standard deviation of the SRB among the advanced countries, including some Asian and Latin Americancountries shows non-significant variations. In conclusion, the mean SRB for African populations is 103 as against 106 forother countries.

GROWTH, REPRODUCTION & POPULATION STRUCTURE OF THE FRESHWATER CRAB SINOPOTAMON YANG TSEKIENSE BOTT, 1967, FROM ZHEJIANG, CHINA

Monthly investigatiom were made on the population of Chinese freshwater crab, Sinopotamon yangteskiense Bott, 1967 from April, 1984 to Match, 1985. The data on 4413 specimens show that the growth was affected mainly by temperature. During the April to November growth period, the crabs’ major development occured from June through October. One year was required for a fine white oocyte to develop into a mature egg. The reproduction period was June-October. Females bearing eggs were taken from June-August, and crabs with young were found from July-October. The females reproduced once a year but could for more than one year. The number of eggs carried by a female varied greatly according to the size of the crab, ranging from 30 to 100 eggs. New-bom crabs become mature after 1-2 yeats. The sex ratio was approximately 1:1 in the overall population. However, the larger crabs are predominantly male. The age distribution of S. yangtsekinese was estimated from size frequency histograms. There were more adult

A Theory of Ratio Selection—Lattice Model for Obligate Mutualism

Mutualisms are cooperative interactions between members of different species. We focus on obligate mutualism, where each species cannot survive without the other. From a theoretical aspect, obligate mutualism is similar to the relationship between male and female. Empirical data indicate a sex-ratio selection: male and female have a specific ratio in their population sizes. In the present paper, we apply lattice model to obligate mutualism between two species, and present a theory of “ratio selection” which is a generalization of sex-ratio selection. Computer simulations are carried out by two methods: local and global interactions. In the former, interactions occur between neighbouring cells, while in the latter they occur between any pair of cells. Simulations in both interactions show the so-called Allee effect: both species can survive, when both densities are large in some extent. However, we find a large difference between local and global simulations. In the case of local interaction, restriction for survival is found to be extremely severe compared to global interaction. Both species require a proper ratio for their sustainability. This result leads to the theory of ratio selection: when interaction occurs locally, the ratio of both species is uniquely determined. We discuss that the ratio selection explains not only the evolution of endosymbionts from free-living ancestors but also the evolution from endosymbionts to organelles.

Mating and reproductive characteristics of the pathogenic nematode Bursaphelenchus xylophilus

Pine wood nematode(B ursaphelenchus xylophilus),one of the most destructive invasive species,has caused extremely serious economic,ecological and social losses in many countries throughout the world.Since the high reproductive rate of B.xylophilus PWN is the main cause of rapid death of its pine hosts(Pinus spp.),understanding the reproductive and population biology and the ecology of this nmatode are of great importance.This study mainly focused on analyzing the mating process and population structure under different combinations of sex ratios for mating.Reproductive efficiency of B.xylophilus peaked when the sex ratio(female to male)was 3.4:1.Phases of the mating process for the different sex-ratio combinations indicated that B.xylophilus had evolved alternative reproductive strategies to cope with complex copulating conditions to obtain a suitable population structure for further propagation.This research provides fundamental information on the mechanism that is responsible for the rapid population growth of B.xylophilus.

Adults have more male-biased sex ratios than first-winter juveniles in wintering duck populations

Background:The long-term monitoring of demographic changes in waterbird populations remains limited,but such information can be valuable for conservationists and waterbird managers.Biased sex ratios can indicate differences in survival rates between sexes.In particular,differences in the sex ratios of fledged juveniles and adults can provide insight into the development of male bias among populations.Methods:In this study,we used data from individual birds captured over a 57-year period to assess the extent,and temporal variability in male bias in nine populations of ducks wintering in the United Kingdom:Gadwall(Mareca strepera),Northern Mallard(Anas platyrhynchos),Northern Pintail(Anas acuta),Common Pochard(Aythya ferina),Common Shelduck(Tadorna tadorna),Northern Shoveler(Spatula clypeata),Eurasian Teal(Anas crecca),Tufted Duck(Aythya fuligula),and Eurasian Wigeon(Mareca penelope).Results:Overall,eight of these populations were significantly male-biased and adults were more male-biased than first-winter juveniles for all nine populations.The increased male bias among adults is consistent with the hypothesis that factors such as higher mortality of reproductive-age females during the breeding season is a major cause of male bias in duck populations.However,such predation cannot explain the male bias detected in first-winter juveniles in four of the populations.The temporal trends in male bias differed between adults and first-winter juveniles in Northern Mallard,Northern Pintail,Common Pochard,Common Shelduck,Eurasian Teal,Tufted Duck,and Eurasian Wigeon.Over the study period we found increased male bias among adult Northern Mallard,Northern Pintail,Common Pochard,Common Shelduck,and Tufted Duck as well as both adult and first-winter juvenile Northern Shoveler.Conclusions:We provide evidence that among wintering duck populations,sex ratios are typically male-biased,with adults exhibiting stronger male-biased sex ratios than first-winter juveniles.Improved monitoring of sex ratios of wintering waterbirds would help to increase our understanding of changes in waterbird demography,population structure,and observed population trends;our study shows that birds caught during ringing projects can be a valuable source of such data.

On Sex Ratios at Birth and in Childhood

The 1982 and 1990 census data showed the sex ratio of Tibet's population increased from 97.76 to 100.16.But it was still low as compared with the natianal average of 106.6.The sex ratio at birth of Tibet s population also rose fram 99.42 in 1982 to 100.31 in 1990.However,they are lower than the corre sponding national figures.

Noninvasive genetic assessment of the population trend and sex ratio of the Shennongjia population of Sichuan snub-nosed monkeys(Rhinopithecus roxellana)

Effective population management relies on assessments of population size and sex ratio.However,these estimates are difficult to obtain for elusive and rare species.Recently,noninvasive genetic census methods have been developed as an alternative to tradi-tional capture-mark-recapture methods.In this study,we estimated the size of the Sichuan snub-nosed monkey(Rhinopithecus roxellana) population in the Shennongjia Nature Reserve(SNR) using a noninvasive sampling method based on 16 microsatellite loci.We also used a PCR-based genetic method to sex the sampled individuals and infer the population sex ratio.The population size of R.roxellana in the SNR was estimated to be 1044 individuals(95% CITIRM:613-1409) .The estimated population sex ratio is more female-biased than expected,which we attribute to the sampling biased towards one male units and limited sampling of bachelor male units.Moreover,there is no suggestion that the heavy traffic road through the reserve might block movement of monkeys.The results of this study indicate genetic assessments based on a noninvasive sampling method can provide useful in-formation regarding populations of elusive primates.

Zonal distribution and population biology of Ilyoplax frater (Brachyura:Ocypodoidea:Dotillidae) in a coastal mudflat of Pakistan

Zonal distribution and population biology of llyoplaxfrater were studied in a mangrove mudflat area of Pakistan. The crabs were collected from Korangi creek through transect and quadrat method from low tide level to high tide level. Two transects were delimited in a mangrove area of Korangi creek （24°79′N/67°20′E）. On each transect, three 0.25 m quadrats were sampled at three tidal levels on a monthly basis during low tide periods from March 2001 to February 2002. A total of 1124 crabs were obtained, of which 482 were males and 642 were females. Density of crabs varied between 0 and 90/m^2. The density and size distribution varied and showed significant differences from low to high tide level, and were positively correlated with the percent moisture, percent organic matter and sediment grain size. The carapace width （CW） ranged from 2.5 to 11.5 mm for male and 2.5 to 11.0 mm for female and was not significantly different. The overall sex ratio did not differ significantly from the expected 1：1 throughout the year in small crabs but was significantly different in adult crabs （Z2 = 49.73） with more male crabs, Size frequency distribution showed recruitment of juvenile crabs （〈 4 mm） nearly throughout the year except during June and July. Presence of ovigerous females in all months with seasonal peaks in September, October, December and May indicates seasonal continuous breeding. Weight of egg mass increases with weight of ovigerous females and show positive linear relationship. The estimated mean diameter of egg was 2.83±0.25μm, and the average number of eggs was 3065±902.

Assessment of parental contribution and effective population size from a 3×3 diallel cross of clam Meretrix meretrix

Unbalanced parental contribution and small effective population size （Ne） are common issues during the artificial breeding of marine bivalves. The impact of hatchery-spawning practices on parental contribution, effective population size, the Ne/Nratio, and genetic diversity are largely unknown. To address this, we conducted a parentage analysis on a complete 3×3 diallel cross of clam Meretrix meretrix using eight microsatellite markers. The genetic diversity of the parents was higher than that of their respective offspring in most crosses （8/9）. Sires or dams from the same family contributed unequally to the pool of offspring from a particular cross, and the same parent clam exhibited large variation in parental contribution among different crosses. The variance in male contribution was higher than that of the female contribution in most crosses, suggesting that male contribution was more skewed than for females. The No/N ratio for nine crosses ranged from 0.58 to 0.86. There was no linear relationship between the sex ratio and the Ne/Nratio （P〉0.05）. Moreover, a sex ratio closer to one-to-one does not necessarily mean a larger effective population size. A solution to small effective population size in commercial breeding programs is increasing broodstoek numbers and attempting to maintain a balanced sex ratio.

Changes of sex ratio at birth and son preferences in China:a mixed method study

In 2020,China’s sex ratio at birth(SRB)stood at 111.3,still exhibiting a notable bias.Son preference ranks as the most essential and fundamental reason for the skewed SRB.This study,using a mixed-methods approach,seeks to address what the temporal changes and regional differences in SRB and the gender preferences are in China,whether and why son preference persists,how people practice such preferences and how they relate to the persistently high SRB in the Chinese con-text.Analysis of data from five national sample surveys finds that son preference is waning and daughter preference is gaining momentum,consistent with significant downward trends in SRB.The study also reveals that value shifts and intergenera-tional relations have a strong influence on gender preferences and their translation into reproductive behavior.Additionally,this study highlights the challenges that are hindering the decline in son preference,suggesting that more efforts are needed to empower women and to change social norms.

Sheep grazing causes shift in sex ratio and cohort structure of Brandt’s vole:Implication of their adaptation to food shortage

Livestock grazing has been demonstrated to affect the population abundance of small rodents in grasslands,but the causative mechanism of grazing on demographic parameters,particularly the age structure and sex ratio,is rarely investigated.In this study,we examined the effects of sheep grazing on the cohort structure and sex ratio of Brandt’s vole(Lasiopodomys brandtii)in Inner Mongolia of China by using large manipulative experimental enclosures during 2010-2013.Our results indicated that sheep grazing significantly decreased the proportion of the spring-born cohort,but increased the proportion of the summer-born cohort.Grazing increased the proportion of males in both spring and summer cohorts.In addition,we found a negative relation between population density and the proportion of the overwinter cohort.Our results suggest that a shift in the cohort structure and the sex ratio may be an important strategy for small rodents to adapt to changes in food resources resulting from livestock grazing.

Effect of Sex Composition of Children on the Gender of Next Birth in the Context of Low Fertility in Rural China

China currently has the world's most skewed national sex ratio at birth.In this paper,we use data from China's 2001 National Family Planning and Reproductive Health Survey and employ hierarchical logistic models to study how macro factors(mainly fertility policy and economic indicators,as represented by per capita GDP of the village units sampled in this research)and micro factors(mainly fertility intention and sex composition of children)affect the gender of the next birth.We find that the effect of fertility policies is intertwined with the sex composition of children already born.For those couples who have had a son(or sons),fertility policy exerts no effect;but for those with only daughters,the effect is significant.Furthermore,fertility intention,independent from fertility policy,has a significant effect on the gender of the next birth.

Women’s Political Status and the Sex Ratio at Birth:An Empirical Study Based on 1950-2020 County-Level Data

Women’s emancipation is an important part of the people’s liberation movement led by the Communist Party of China.Improving women’s political status is the basic condition for improving their social welfare rights and interests.Based on the data from county gazetteers covering more than 1,700 counties,the censuses of 1990 and 2000,and other representative surveys,we conducted an empirical study on the long-term effect of women’s political status on the sex ratio at birth.Our research found that the higher the ratio of female Communist Party members in each county in 1950,the more normal was the sex ratio at birth in the following 50 years.The improved political status of women aged 16-20 significantly raised the proportion of girls among surviving children,especially in the era of family planning.This demographic study provides empirical historical evidence for the first time on one aspect of the long-term social impact of the mission of the Chinese people’s liberation.

Can we reestablish a self-sustaining population?A case study on reintroduced Crested Ibis with population viability analysis

Background:One of the most challenging tasks in wildlife conservation and management is clarifying which and how external and intrinsic factors influence wildlife demography and long-term viability.The wild population of the Crested Ibis(Nipponia nippon)has recovered to approximately 4400,and several reintroduction programs have been carried out in China,Japan and Korea.Population viability analysis on this endangered species has been limited to the wild population,showing that the long-term population growth is restricted by the carrying capacity and inbreeding.However,gaps in knowledge of the viability of the reintroduced population and its drivers in the release environment impede the identification of the most effective population-level priorities for aiding in species recovery.Methods:The field monitoring data were collected from a reintroduced Crested Ibis population in Ningshan,China from 2007 to 2018.An individual-based VORTEX model(Version 10.3.5.0)was used to predict the future viability of the reintroduced population by incorporating adaptive patterns of ibis movement in relation to catastrophe frequency,mortality and sex ratio.Results:The reintroduced population in Ningshan County is unlikely to go extinct in the next 50 years.The popula-tion size was estimated to be 367,and the population genetic diversity was estimated to be 0.97.Sensitivity analysis showed that population size and extinction probability were dependent on the carrying capacity and sex ratio.The carrying capacity is the main factor accounting for the population size and genetic diversity,while the sex ratio is the primary factor responsible for the population growth trend.Conclusions:A viable population of the Crested Ibis can be established according to population viability analysis.Based on our results,conservation management should prioritize a balanced sex ratio,high-quality habitat and low mortality.

THE OPTIMAL CONTROL OF AGE－DEPENDENT POPULATION DYNAMICS BASED ON PARITY PROGRESSION

ＴＨＥＯＰＴＩＭＡＬＣＯＮＴＲＯＬＯＦＡＧＥ－ＤＥＰＥＮＤＥＮＴＰＯＰＵＬＡＴＩＯＮＤＹＮＡＭＩＣＳＢＡＳＥＤＯＮＰＡＲＩＴＹＰＲＯＧＲＥＳＳＩＯＮ￥ＧＵＯＢａｏｚｈｕ（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃｓ，ＢｅｉｊｉｎｇＩｎ...

Effects of social and climatic factors on birth sex ratio in Macaca mulatta in Mount Taihangshan area

Sex allocation theory predicts the optimal investment to male and female offspring.However,a biased sex ratio requires explanations as to why the deviation occurs.Rhesus macaque(Macaca mulatta)is the most widely distributed nonhuman primate species and the Taihangshan macaque(Macaca mulatta tcheliensis)occupies the northern limit of all rhesus macaque natural populations worldwide.We observed one macaque troop(Wangwu-1[WW-1])inhabiting Taihangshan Macaque National Nature Reserve and recorded all birth events and the sex of newborn macaques from 2004 to 2013.Our aim was to apply the Trivers–Willard hypothesis to this free-ranging rhesus macaque troop,and to understand the relationship between climatic parameters(precipitation and temperature)and birth sex ratio.We found that the total newborn macaques showed a female-biased sex ratio at birth in the WW-1 troop,but there were no significant biased birth sex ratios in all matriarchs and in high-ranking and middle-ranking matrilineal units.However,the low-ranking macaque matrilineal unit was significantly female-biased.Moreover,we found that the annual precipitation of the previous year was positively associated with the birth sex ratio,and there was an interactive effect of troop size and current winter temperature on the birth sex ratio.The underlying mechanisms for the effects of social and climatic factors on birth sex ratio could be complex,and we discuss several plausible explanations.

Parity 3 or More at Haiphong Hospital of Obstetrics and Gynecology in 2016

Background： Although increasing parity increased the risk of pregnancy complications and despite of Vietnam’s family planning policy of two-child, the percent of women having three or more children has tended for five years. Objectives： （1） Find out the prevalence of parity ≥ 3 and their reasons at Haiphong Hospital of Obstetrics and Gynecology in 2016; （2） Describe the methods of labor and its adverse outcomes. Materials and methods： A cross-sectional in 485 women had delivered three or more infants at Haiphong Hospital of Obstetrics and Gynecology from June to August, 2016. Results： The prevalence of parity ≥ 3 is 11.9%, no relation to geopraphy, education and career. The main reasons are unplanned pregnancy and desire to have a baby boy. The sex ratio at birth is 162. The proportion of cesarean delivery is 53.4%, in which is due to an old C-section. Conclusion： serious gender is imbalance among women having three or more baby （162 baby boys per hundred baby girls）.

斑块质量对沙蒿金叶甲种群特征的影响

黑沙蒿(Artemisia ordosica)是我国西北荒漠沙化区主要的防风固沙植物,对控制土壤沙化、保护和改善生态环境、稳定生态平衡具有非常积极的作用。沙蒿金叶甲是黑沙蒿的一种重要食叶类害虫。试验选取位于宁夏灵武白芨滩国家级自然保护区的古窑子(GYZ-A、GYZ-B)、长流水(CLS)及刘家寨(LJZ)4个黑沙蒿植物斑块,于2020年6月—9月期间调查了不同生境中沙蒿金叶甲的种群数量,分析了不同生境斑块中沙蒿金叶甲的形态学特征、性比差异及环境因子对沙蒿金叶甲种群数量、有虫株率的影响。结果显示不同斑块内沙蒿金叶甲成虫种群数量及有虫株率差异显著(P<0.05),种群数量2.28头·株^(-1)—10.43头·株^(-1)、有虫株率56.02%—90.56%。不同斑块内沙蒿金叶甲成虫雌虫数量均多于雄虫(P<0.05),雌雄性比分别为1.38:1、1.05:1、1.2:1、1.23:1。斑块间沙蒿金叶甲体重(0.03 g—0.05 g)、体长(6.89mm—3.76 mm)、体宽(4.09 mm—4.71 mm)均差异显著(P<0.05)。多元逐步回归分析显示沙蒿金叶甲种群数量、有虫株率与植物的丰富度指数(P<0.05)、沙蒿的长势(P<0.01)、土壤全氮(P<0.05)具有显著相关性。沙蒿的盖度、土壤有机质是影响种群结构特征的关键因子。