Airport and city-centre temperatures in the evaluation of the association between heat and mortality

A variety of ambient exposure indicators have been used to evaluate the impact of high temperature on mortality and in the identification of susceptible population sub-groups, but no study has evaluated how airport and city centre temperatures differ in their association with mortality during summer. This study considers the differences in temperatures measured at the airport and in the city centre of three Italian cities (Milan, Rome and Turin) and investigates the impact of these measures on daily mortality. The case-crossover design was applied to evaluate the association between daily mean apparent temperature (MAT) and daily total mortality. The analysis was conducted for the entire population and for subgroups defined by demographic characteristics, socioeconomic status and chronic comorbidity (based on hospitalisation during the preceding 2 years). The percentage risk of dying, with 95% confidence intervals (95% CI), on a day with MAT at the 95th percentile with respect to the 25th percentile of the June-September daily distribution was estimated. Airport and city-centre temperature distributions, which vary among cities and between stations, have a heterogeneous impact on mortality. Milan was the city with the greatest differences in mean MAT between airport and city stations, and the overall risk of dying was greater when airport MAT (+47% increase, 95%CI 38-57) was considered in comparison to city MAT (+37% increase, 95%CI 30-45). In Rome and Turin, the results were very similar for both apparent temperature measures. In all cities, the elderly, women and subjects with previous psychiatric conditions, depression, heart and circulation disorders and cerebrovascular disease were at higher risk of dying during hot days, and the degree of effect modification was similar using airport or city-centre MAT. Studies on the impact of meteorological variables on mortality, or other health indicators, need to account for the possible differences between airport and city centre meteorological variables in order to give more accurate estimates of health effects.     

The genetic impact of aztec imperialism: Ancient mitochondrial DNA evidence from Xaltocan,Mexico

In AD 1428, the city‐states of Tenochtitlan, Texcoco, and Tlacopan formed the Triple Alliance, laying the foundations of the Aztec empire. Although it is well documented that the Aztecs annexed numerous polities in the Basin of Mexico over the following years, the demographic consequences of this expansion remain unclear. At the city‐state capital of Xaltocan, 16th century documents suggest that the site's conquest and subsequent incorporation into the Aztec empire led to a replacement of the original Otomí population, whereas archaeological evidence suggests that some of the original population may have remained at the town under Aztec rule. To help address questions about Xaltocan's demographic history during this period, we analyzed ancient DNA from 25 individuals recovered from three houses rebuilt over time and occupied between AD 1240 and 1521. These individuals were divided into two temporal groups that predate and postdate the site's conquest. We determined the mitochondrial DNA haplogroup of each individual and identified haplotypes based on 372 base pair sequences of first hypervariable region. Our results indicate that the residents of these houses before and after the Aztec conquest have distinct haplotypes that are not closely related, and the mitochondrial compositions of the temporal groups are statistically different. Altogether, these results suggest that the matrilines present in the households were replaced following the Aztec conquest. This study therefore indicates that the Aztec expansion may have been associated with significant demographic and genetic changes within Xaltocan. Am J Phys Anthropol 2012. © 2012 Wiley Periodicals, Inc.     

Poverty in the Midst of Plenty: Unmet Needs and Distribution of Health Care Resources in South Korea

Background

The unmet needs for health care have been used as an alternative measurement to monitor equity in health services. We sought to examine contextual influences on unmet needs for health care whereas precedent studies have been focused on individual characteristics on them.

Methods and Findings

The current study conducted multilevel logistic regression analysis to assess the effects of individual- and contextual-level predictors in meeting individual health care needs in South Korea. We sampled 7,200 individuals over the age of 19 in the Fourth Korea National Health and Nutrition Examination Survey in 2009. Included in the regression model were individual predictors such as demographic variables, socio-economic status, and self-rated health; the density of beds and physicians in public and private sectors within different regions were used as contextual-level predictors. This study showed the inverse association between unmet needs and regional resources in private sectors after controlling for the effects of individual-level predictors.

Conclusion

Our findings suggest that increasing regional resources in private sectors might produce inefficiency in the health care system and inequity in access to health services, particularly where the competition in private health care sectors was highly stimulated under the fee-for-service reimbursement scheme. Policies for the reallocation of health care resources and for reduction of individual health care costs are needed in Korea.     

Genetic patterns and conservation of the Scarlet Macaw (<Emphasis Type="Italic">Ara macao</Emphasis>) in Costa Rica

Once widely distributed throughout the lowland forests of Costa Rica, scarlet macaws (Ara macao) have been reduced to two major, geographically separated, populations along the Pacific slope. Past demographic declines raise conservation concerns regarding the detrimental effects of population fragmentation. This investigation aimed to evaluate the current status of scarlet macaws along the Pacific slope by examining levels of genetic variation and patterns of genetic structure within and among remnant populations. Statistical analyses using multilocus genotypes revealed strong differentiation between Central and South Pacific populations, suggesting local geographic barriers have historically restricted gene flow between these localities. High genetic diversity suggests neither population suffers from genetic erosion, likely resulting from relatively large population sizes and high dispersal capacity and longevity. However, evidence of disequilibrium within the Central Pacific population infers anthropogenic threats have disrupted natural population dynamics. These results advocate on focusing available resources on habitat restoration and nest protection, as a means to assist in reestablishing demographic stability and maintain the genetic health of wild scarlet macaws in Costa Rica.     

Differential mortality in Turkana agriculturalists and pastoralists

Nomadic pastoral populations appear to have much lower rates of growth than the otherwise very high growth rates now characteristic of populations in developing nations. Because dramatic declines in infant mortality have been a primary contributor to increased population growth rates in these countries, it has been assumed that nomadic pastoral populations are still characterized by high levels of mortality in the first few years of life. Few studies, however, have been undertaken to estimate demographic parameters for nomadic pastoral populations, and even fewer of a comparative nature have been undertaken to document the impact of subsistence strategy on demographic processes. This study compares indirect childhood mortality estimates for Turkana nomadic pastoralists with childhood mortality in a settled agricultural group within the same population and finds that pastoralists have substantially higher levels of mortality. Based on the childhood mortality estimates, model life tables are selected for pastoral and agricultural groups from which values for mean life expectancy and infant mortality are estimated and compared. Recent improvements in primary health care for the settled agricultural group are ruled out as being an important cause of their lower mortality levels, and some aspects of life-style associated with subsistence strategy are discussed as likely determinants of the mortality differences.     

Population persistence in a landscape context: the case of endangered arctic fox populations in Fennoscandia

Anthropogenic fragmentation of habitat and populations is recognized as one of the most important factors influencing loss of biodiversity. Since it is difficult to quantify demographic parameters in small populations, we need alternative methods to elucidate important factors affecting the viability of local populations. The Fennoscandian arctic fox inhabits a naturally fragmented alpine tundra environment, but historic anthropogenic impacts have further fragmented its distribution. After almost 80 yr of protection, the population remains critically endangered. Both intrinsic factors (related to the isolation and size of sub‐populations) and extrinsic factors (related to environmental conditions influencing patch quality and interspecific competition) have been proposed as explanations for the lack of population growth. To distinguish between these hypotheses, we conducted a spatially explicit analysis that compares areas where the species has persisted with areas where it has become locally extinct. We used characteristics of the fragments of alpine tundra habitat and individual arctic fox breeding dens (including both currently active dens and historically active dens) within the fragments to evaluate the importance of habitat characteristics and connectivity in explaining variation in persistence within a fragment. The number of reproductive events in a fragment was related to the size of the fragment, but not more than expected following a 1:1 relationship, suggesting little effect of fragment size on the relative number of reproductions. The likelihood of a den being used for breeding was positively associated with factors minimising interspecific competition as well as increasing within‐fragment connectivity. These results support the idea that the failure of Fennoscandian arctic fox to recover is caused by demographic factors that can be related to fine‐scale Allee or Allee‐like effects, as well as environmental influences related to increased competition and exclusion by red foxes.     

Interpretable machine learning for high-dimensional trajectories of aging health

We have built a computational model for individual aging trajectories of health and survival, which contains physical, functional, and biological variables, and is conditioned on demographic, lifestyle, and medical background information. We combine techniques of modern machine learning with an interpretable interaction network, where health variables are coupled by explicit pair-wise interactions within a stochastic dynamical system. Our dynamic joint interpretable network (DJIN) model is scalable to large longitudinal data sets, is predictive of individual high-dimensional health trajectories and survival from baseline health states, and infers an interpretable network of directed interactions between the health variables. The network identifies plausible physiological connections between health variables as well as clusters of strongly connected health variables. We use English Longitudinal Study of Aging (ELSA) data to train our model and show that it performs better than multiple dedicated linear models for health outcomes and survival. We compare our model with flexible lower-dimensional latent-space models to explore the dimensionality required to accurately model aging health outcomes. Our DJIN model can be used to generate synthetic individuals that age realistically, to impute missing data, and to simulate future aging outcomes given arbitrary initial health states.     

Characteristics of Neutral and Deleterious Protein-Coding Variation among Individuals and Populations

Whole-genome and exome data sets continue to be produced at a frenetic pace, resulting in massively large catalogs of human genomic variation. However, a clear picture of the characteristics and patterns of neutral and deleterious variation within and between populations has yet to emerge, given that recent large-scale sequencing studies have often emphasized different aspects of the data and sometimes appear to have conflicting conclusions. Here, we comprehensively studied characteristics of protein-coding variation in high-coverage exome sequence data from 6,515 European American (EA) and African American (AA) individuals. We developed an unbiased approach to identify putatively deleterious variants and investigated patterns of neutral and deleterious single-nucleotide variants and alleles between individuals and populations. We show that there are substantial differences in the composition of genotypes between EA and AA populations and that small but statistically significant differences exist in the average number of deleterious alleles carried by EA and AA individuals. Furthermore, we performed extensive simulations to delineate the temporal dynamics of deleterious alleles for a broad range of demographic models and use these data to inform the interpretation of empirical patterns of deleterious variation. Finally, we illustrate that the effects of demographic perturbations, such as bottlenecks and expansions, often manifest in opposing patterns of neutral and deleterious variation depending on whether the focus is on populations or individuals. Our results clarify seemingly disparate empirical characteristics of protein-coding variation and provide substantial insights into how natural selection and demographic history have patterned neutral and deleterious variation within and between populations.     

Can time-averaged flow boundary conditions be used to meet the clinical timeline for Fontan surgical planning?

Cardiovascular simulations have great potential as a clinical tool for planning and evaluating patient-specific treatment strategies for those suffering from congenital heart diseases, specifically Fontan patients. However, several bottlenecks have delayed wider deployment of the simulations for clinical use; the main obstacle is simulation cost. Currently, time-averaged clinical flow measurements are utilized as numerical boundary conditions (BCs) in order to reduce the computational power and time needed to offer surgical planning within a clinical time frame. Nevertheless, pulsatile blood flow is observed in vivo, and its significant impact on numerical simulations has been demonstrated. Therefore, it is imperative to carry out a comprehensive study analyzing the sensitivity of using time-averaged BCs. In this study, sensitivity is evaluated based on the discrepancies between hemodynamic metrics calculated using time-averaged and pulsatile BCs; smaller discrepancies indicate less sensitivity.The current study incorporates a comparison between 3D patient-specific CFD simulations using both the time-averaged and pulsatile BCs for 101 Fontan patients. The sensitivity analysis involves two clinically important hemodynamic metrics: hepatic flow distribution (HFD) and indexed power loss (iPL). Paired demographic group comparisons revealed that HFD sensitivity is significantly different between single and bilateral superior vena cava cohorts but no other demographic discrepancies were observed for HFD or iPL. Multivariate regression analyses show that the best predictors for sensitivity involve flow pulsatilities, time-averaged flow rates, and geometric characteristics of the Fontan connection. These predictors provide patient-specific guidelines to determine the effectiveness of analyzing patient-specific surgical options with time-averaged BCs within a clinical time frame.     

Impact of management and habitat on demographic traits of Primula vulgaris in an agricultural landscape

Question: Is demographic performance of Primula vulgaris correlated with habitat characteristics of the small landscape elements in which it occurs? Can we use this species as an indicator for species‐rich semi‐natural habitats? Location: Flanders, Belgium. Methods: To capture differences in demographic traits and habitat characteristics, both within and between populations, a two‐level survey was carried out. Population size and structure of 89 P. vulgaris populations in different types of small landscape elements was recorded in 1999. At plot level, densities of different life stages were determined and these were related to edaphic conditions and vegetation structure and composition. Results: Three different population types were distinguished: (1) dynamic populations, characterized by seedling and juvenile proportions, (2) normal populations with relatively more adults, but with considerable numbers of seedlings and juveniles and (3) senescent populations, mainly consisting of adults. Senescent populations were significantly smaller than populations with a dynamic demographic structure. At plot level, comparison of demographic characteristics between different management regimes revealed that recruitment rates and total plant density of P. vulgaris were highest in plots that received a regime that included mowing and clearing of ditch banks whereas densities were lower along forest edges. For these plots, it was shown that nutrient levels were higher. Densities of adults as well as juvenile and seedling densities were negatively correlated with vegetation height. Conclusions: Local disturbance and heterogeneity may mask the relationship between unfavourable conditions and demographic characteristics at population level, but it is clear that in small populations recruitment needs to be lifted to guarantee its persistence. Performance of P. vulgaris in small landscape elements can be a first indication of plant species diversity in small landscape elements.     

A Teaching Framework for Cross-cultural Health Care—Application in Family Practice

Significant demographic changes in patient populations have contributed to an increasing awareness of the impact of cultural diversity on the provision of health care. For this reason methods are being developed to improve the cultural sensitivity of persons responsible for giving health care to patients whose health beliefs may be at variance with biomedical models.Building on methods of elicitation suggested in the literature, we have developed a set of guidelines within a framework called the LEARN model. Health care providers who have been exposed to this educational framework and have incorporated this model into the normal structure of the therapeutic encounter have been able to improve communication, heighten awareness of cultural issues in medical care and obtain better patient acceptance of treatment plans.The emphasis of this teaching model is not on the dissemination of particular cultural information, though this too is helpful. The primary focus is rather on a suggested process for improved communication, which we see as the fundamental need in cross-cultural patient-physician interactions.     

中国东海海岸带地区生态系统健康评估及其尺度依赖性

维持生态系统健康是实现社会经济可持续发展的关键性工作之一。本文基于邻域变异度和人为干扰修正后的活力-组织-弹性-服务模型,从5 km至地级市设置8个评估尺度单元,定量化的评估了我国东海海岸地区（包括上海、嘉兴、宁波、温州、台州、宁德、福州、莆田、泉州、厦门和漳州共11个城市）1990—2015年的生态系统健康状况,并分析了其时序变化特征和空间分异规律,探究了生态系统健康的尺度依赖性效应,得到以下结论：1）研究时段内,研究区生态系统健康水平以2000年为节点先下降后上升,但整体呈下降趋势。自2000年起生态系统健康值分布更加离散,呈现健康的生态系统更加健康,劣化的生态系统不断劣化的分化趋势。2）生态系统健康在空间分布上具有较高的异质性特征。沿海地区、宁波以北地区的生态系统健康值较低;远离海洋部分的山地丘陵的生态系统健康值较高。小尺度下上海市中心生态健康最差,地级市尺度下嘉兴市生态健康状况最差。3）生态系统健康评估工作具有一定的空间尺度依赖性。大尺度生态系统健康评估结果趋于平均化,可用于刻画变化趋势的空间分布格局。小尺度评估结果能够更好的解释生态系统健康程度的聚类分异细节。因而,在生态系统健康评估中不存在最佳的研究尺度,多尺度的设置有助于全面解析生态系统健康的时空分异特征。     

Demographic and Lifestyle Characteristics,but Not Apolipoprotein E Genotype,Are Associated with Intelligence among Young Chinese College Students

Background

Intelligence is an important human feature that strongly affects many life outcomes, including health, life-span, income, educational and occupational attainments. People at all ages differ in their intelligence but the origins of these differences are much debated. A variety of environmental and genetic factors have been reported to be associated with individual intelligence, yet their nature and contribution to intelligence differences have been controversial.

Objective

To investigate the contribution of apolipoprotein E (APOE) genotype, which is associated with the risk for Alzheimer’s disease, as well as demographic and lifestyle characteristics, to the variation in intelligence.

Methods

A total of 607 Chinese college students aged 18 to 25 years old were included in this prospective observational study. The Chinese revision of Wechsler Adult Intelligence Scale (the fourth edition, short version) was used to determine the intelligence level of participants. Demographic and lifestyle characteristics data were obtained from self-administered questionnaires.

Results

No significant association was found between APOE polymorphic alleles and different intelligence quotient (IQ) measures. Interestingly, a portion of demographic and lifestyle characteristics, including age, smoking and sleep quality were significantly associated with different IQ measures.

Conclusions

Our findings indicate that demographic features and lifestyle characteristics, but not APOE genotype, are associated with intelligence measures among young Chinese college students. Thus, although APOE ε4 allele is a strong genetic risk factor for Alzheimer’s disease, it does not seem to impact intelligence at young ages.     

Social science methods for twins data: integrating causality, endowments, and heritability

Twins have been extensively used in economics, sociology, and behavioral genetics to investigate the role of genetic endowments on a broad range of social, demographic, and economic outcomes. However, the focus in these literatures has been distinct.: The economic literature has been primarily concerned with the need to control for unobserved endowments--including as an important subset, genetic endowments--in analyses that attempt to establish the impact of one variable, often schooling, on a variety of economic, demographic, and health outcomes. Behavioral genetic analyses have mostly been concerned with decomposing the variation in the outcomes of interest into genetic, shared environmental, and non-shared environmental components, with recent multivariate analyses investigating the contributions of genes and the environment to the correlation and causation between variables. Despite the fact that twins studies and the recognition of the role of endowments are central to both of these literatures, they have mostly evolved independently. In this paper we develop formally the relationship between the economic and behavioral genetic approaches to the analyses of twins, and we develop an integrative approach that combines the identification of causal effects, which dominates the economic literature, with the decomposition of variances and covariances into genetic and environmental factors that are the primary goal of behavioral genetic approaches. We apply this integrative ACE-beta approach to an illustrative investigation of the impact of schooling on several demographic outcomes such as fertility and nuptiality and health.     

Seroprevalence and Potential Risk Factors for Helicobacter pylori Infection in Brazilian Children

Background: Helicobacter pylori infection has been proved to be of great relevance to public health in unindustrialized countries, especially in low socioeconomic groups. Poor hygiene, deficient sanitation, and crowded conditions have been reported as risk factors for this infection. In this work, we investigated whether social and demographic characteristics were associated with anti‐H. pylori IgG antibodies in 1104 children aged 4–11 years old from Salvador, a large city located in northeastern Brazil. Methods: Standardized questionnaires were used to obtain social, demographic, and environmental data for the studied population in two periods of time (from 1997 to 2003 and in 2005). Anti‐H. pylori IgG antibodies were assessed by indirect enzyme‐linked immunosorbent assay in 2005. Results: Anti‐H. pylori IgG antibody was present in 28.7% of the children. Among the studied variables, the following were positively associated with the presence of anti‐H. pylori antibodies in multivariable analyses: age above 8 years old (OR = 1.72, 95% CI = 1.23–2.40), a larger sibling number (OR = 1.66, 95% CI = 1.26–2.18), nursery attendance (OR = 1.49, 95% CI = 1.04–2.12), location of the house at an unpaved street (OR = 2.03, 95% CI = 1.44–2.87) and absence of a flush toilet (OR = 1.32, 95% CI = 1.00–1.74). Conclusion: Our data show that H. pylori infection in children from a major Brazilian city is associated with variables indicative of a crowded environment and deficient sanitation/habitation conditions, leading to the conclusion that improvements in hygiene and social conditions may protect children against this infection.     

Regional Disparities in Mortality after Ischemic Heart Disease in a Brazilian State from 2006 to 2010

Background

High technology in the field of interventional cardiology applied in tertiary hospitals has brought enormous benefits in the treatment of ischemic heart disease (IHD). However, IHD mortality rates remain high. We analyzed the relationship between IHD mortality rate and the socioeconomic, demographic, and geographic conditions in 399 cities in Parana state, Brazil, from 2006 to 2010.

Methods and Results

Data were obtained from the Mortality Information System and the Brazilian Institute of Geography and Statistics and evaluated through Exploratory Spatial Data Analysis. GeoDa™ was used to analyze 29.351 deaths across 399 cities. We found a positive spatial autocorrelation regarding IHD mortality (I = 0.5913, p = 0.001). There was a significant positive association between each of three socioeconomic and demographic indicators and IHD mortality rate: Population Elderly Index (I = 0.3436), Illiteracy Rate (I = 0.1873) and City Development Index (I = 0.0900). In addition, two indicators presented significant negative association with IHD mortality rate: Adjusted Population Size (I = −0.1216) and Gross Domestic Product (I = −0.0864). We also found a positive association between IHD mortality rates and the geographic distances between patients’ city of residence and their corresponding regional referral centers in interventional cardiology (I = 0.3368). Cities located within Regional Health Units with Reference Interventional Cardiology Center presented a significantly lower average specific mortality rate by IHD. The high mortality rate by IHD within the Regional Health Units was not restricted to socioeconomic and demographic variables, but dependent on the distance between each city and their reference interventional cardiology center.

Conclusions

We conclude that geographic factors play a significant role in IHD mortality within cities. These findings have important policy implications regarding the geographic distribution of cardiac health care networks in Latin America and in other emerging countries.     

Using GIS to establish a public library consumer health collection

BACKGROUND: Learning the exact demographic characteristics of a neighborhood in which a public library serves, assists the collection development librarian in building an appropriate collection. Gathering that demographic information can be a lengthy process, and then formatting the information for the neighborhood in question becomes arduous.As society ages and the methods for health care evolve, people may take charge of their own health. With this prospectus, public libraries should consider creating a consumer health collection to assist the public in their health care needs. Using neighborhood demographic information can inform the collection development librarians as to the dominant age groups, sex, and races within the neighborhood. With this information, appropriate consumer health materials may be assembled in the public library. METHODS: In order to visualize the demographics of a neighborhood, the computer program ArcView GIS (geographic information systems) was used to create maps for specified areas. The neighborhood data was taken from the U.S. Census Department's annual census and library addresses were accumulated through a free database. After downloading the census block information from http://www.census.gov/geo/www/tiger/ the data was manipulated with ArcView GIS and queried to produce maps displaying the requested neighborhood demographics to view in respect to libraries. RESULTS: ArcView GIS produced maps displaying public libraries and requested demographics. After viewing the maps the collection development librarian can see exactly what populations are served by the library and adjust the library's collection accordingly. CONCLUSIONS: ArcView GIS can be used to produce maps displaying the communities that libraries serve, spot boundaries, be it "man-made or natural," that exist prohibiting customer service, and assist collection development librarians in justifying their purchases for a dedicated consumer health collection or resources in general.     

A Multilevel Regression Model for Geographical Studies in Sets of Non-Adjacent Cities

In recent years, small-area-based ecological regression analyses have been published that study the association between a health outcome and a covariate in several cities. These analyses have usually been performed independently for each city and have therefore yielded unrelated estimates for the cities considered, even though the same process has been studied in all of them. In this study, we propose a joint ecological regression model for multiple cities that accounts for spatial structure both within and between cities and explore the advantages of this model. The proposed model merges both disease mapping and geostatistical ideas. Our proposal is compared with two alternatives, one that models the association for each city as fixed effects and another that treats them as independent and identically distributed random effects. The proposed model allows us to estimate the association (and assess its significance) at locations with no available data. Our proposal is illustrated by an example of the association between unemployment (as a deprivation surrogate) and lung cancer mortality among men in 31 Spanish cities. In this example, the associations found were far more accurate for the proposed model than those from the fixed effects model. Our main conclusion is that ecological regression analyses can be markedly improved by performing joint analyses at several locations that share information among them. This finding should be taken into consideration in the design of future epidemiological studies.     

Associations between Green Space and Health in English Cities: An Ecological,Cross-Sectional Study

Green space has been identified as a modifiable feature of the urban environment and associations with physiological and psychological health have been reported at the local level. This study aims to assess whether these associations between health and green space are transferable to a larger scale, with English cities as the unit of analysis. We used an ecological, cross-sectional study design. We classified satellite-based land cover data to quantify green space coverage for the 50 largest cities in England. We assessed associations between city green space coverage with risk of death from all causes, cardiovascular disease, lung cancer and suicide between 2002 and 2009 using Poisson regression with random effect. After adjustment for age, income deprivation and air pollution, we found that at the city level the risk of death from all causes and a priori selected causes, for men and women, did not significantly differ between the greenest and least green cities. These findings suggest that the local health effects of urban green space observed at the neighbourhood level in some studies do not transfer to the city level. Further work is needed to establish how urban residents interact with local green space, in order to ascertain the most relevant measures of green space.     

The importance of sampling scale in the assessment of intraspecific life-history differences in plains killifish,Fundulus zebrinus,populations (Pisces: Cyprinodontidae)

Synopsis The purpose of this study was to determine the effects of unpredictable environmental fluctuations on the demographic and genetic structure of Fundulus zebrinus populations. Collections of F. zebrinus were taken from three rivers in the Arkansas River basin: the Arkansas, Chikaskia, and Ninnescah. Fish were sampled from three sites on each river on nine collection dates throughout 1984 and 1985. Totals of 2100 fish and 6000 fish were included in electrophoretic and demographic analyses, respectively. The results of the study indicate that within a limited geographic region (i.e. within rivers) spatial differences and temporal changes in both demographic and genetic population characteristics occur frequently and are primarily stochastic. However, on a larger spatial scale (i.e. across rivers), general trends emerge for demographic and especially for genetic population characteristics. These results illustrate the importance of sampling scale for conclusions of life-history evolution in fluctuating environments. In addition, it was found that regulation of Fundulus zebrinus populations includes an important density-independent component. Stochastic demographic differences across space and changes through time and spatially and temporally heterogeneous allele frequencies, are both indicative of density-independent regulation. Variation in population parameters, both demographic and genetic, was observed between populations sampled from each river. These population differences were attributed to differences between the rivers themselves.