Demographic Structure Of Population Research Articles

Patterns of differentiation in the life history and demography of four recently described species of the Brachionus calyciflorus cryptic species complex

Abstract Brachionus calyciflorus is arguably the most studied freshwater monogonont rotifer. Although it has been recognised as a cryptic species complex for more than a decade, a formal (re‐)description of the four species known so far (B. calyciflorus, Brachionus dorcas, Brachionus elevatus, and Brachionus fernandoi) has only recently been made. Information on the ecology of these species is very scant and fragmented. The aim of this study was to test for ecological divergence between these four species, specifically their life history strategy and population demography. We conducted a life history experiment using 12–16 genotypes per species. For each species, genotypes were extracted from at least three different natural populations. In addition, we performed population‐level culture experiments with the aim to compare population growth rates and demographic structure of experimental populations among species. Finally, we searched the literature for life history studies with molecular data allowing retrospective species identification. We found pronounced differences in life history traits between B. fernandoi and the other three species. B. fernandoi had higher egg and juvenile development times and a lower egg production rate and mictic ratio. We detected no significant life history differences among B. calyciflorus, B. elevatus, and B. dorcas. Population growth rates of B. fernandoi and B. calyciflorus were higher than those of B. elevatus and B. dorcas. Life history divergence resulted in marked differences in the demographic structure of populations. Populations of B. fernandoi contained larger fractions of pre‐reproductive females and lower fractions of adult females with sexual eggs than populations of B. calyciflorus, B. elevatus, and B. dorcas. Mortality was found to be highest in B. elevatus and lowest in B. calyciflorus populations. Our results show that a reverse taxonomy approach is powerful in revealing sources of variation in ecologically relevant traits of cryptic species, such as life history and demographic structure. Explicit consideration of this variation is crucial for future studies of their dynamics in natural communities.

ДИНАМИКА СТОМАТОЛОГИЧЕСКОЙ ЗАБОЛЕВАЕМОСТИ ДЕТСКОГО НАСЕЛЕНИЯ ГОРОДА ЕКАТЕРИНБУРГА

Subject. Epidemiological surveys are important for assessing the compliance of dental programs with the treatment needs of various population groups. 
 Objectives ― we set a goal to compare the dynamics of indicators of epidemiological surveys of dental diseases in the city of Ekaterinburg over the past 15 years. 
 Methods. After analyzing reports and publications on the WHO methodology, a high prevalence and intensity of caries and signs of periodontal damage was noted, they deteriorate with age. The reduction in the incidence of dental diseases that began in 2008 did not persist in 2015. The change in the social and demographic structure of the children's population of Yekaterinburg is accompanied by an increase in rates of dental diseases. Estimating the proportion of people with signs of periodontal diseases in children 12 and 15 years compared with the results of a previously conducted national epidemiological study in 2008, we do not see a decrease in the prevalence rate of periodontal diseases. An assessment of the need for emergency dental care in children of Yekaterinburg of 6, 12 and 15 years according to the WHO criteria showed a high level of need for “preventive or conventional treatment” in all groups of children examined. 
 Conclusions. The high prevalence of dental diseases in the city of Ekaterinburg indicates the need to find preventive measures. The increase in the intensity of caries is especially active in children of school age, which requires development of a comprehensive program of school prevention. The absence of a reduction in the prevalence rate of periodontal lesions in adolescents in all 3 national surveys suggests the need to find new approaches in prevention, including use of Smart Technologies.

Cartographic storytelling: 150 years of Swiss Federal Population Census

Abstract. The Swiss Federal Statistical Office (FSO) was founded in 1850 with the first exhaustive Population Census, which from then on was conducted on a ten-year cycle until 2000, and which was replaced after that by the annual “structural surveys” based on a population sample and the use of data from administrative registers. In 2018, the FSO started a project aiming to emphasize the full value of historical data from these previous Population Censuses records in order to publish some significant historical results and present on that basis some of the major developments that have occurred in Switzerland in the last 150 years. In this context, analog data have been digitized, and with this raw material, stories on important themes concerning the development of modern Switzerland have been written. These stories consist of a narrative approach that focuses on visual communication by mixing cartographic visualizations, charts and historical photographs, which support the written text and significantly contribute to the narrative.Eight stories were drafted under this project, and their choice is based on both the availability of data over time, as well as the importance of these topics for the Swiss population and society – with the activity of official statistics always being a mirror that reflects society’s concerns. The various topics addressed in this project are population dynamics and demographic structure, cultural and religious aspects, the development of building area and the occupation of the territory, the structural development of the economy and finally the changes in the institutional structure of the country. These topics are addressed in their temporal and spatial dimension, and cover a period of more than 150 years.This narrative approach – unique in the context of the FSO’s statistical dissemination – requires important work in the field of data visualization in particular with regard to thematic maps. Indeed, the spatial resolution of the digitized data –the smallest institutional spatial division; the Swiss municipalities – has required the production of new historicized geometries for every single Population Census since 1850. The fusions and dissociations of spatial units that have occurred during the past 150 years have profoundly marked the institutional structure of Switzerland. This dynamic is a challenge in the ongoing work of data management and cartographic production, and the FSO is proud to now have basemaps that precisely describe the state of the geometry for every census. This enables the production of numerous series of thematic maps at municipality level, and provides map readers the opportunity to observe changes in Swisssociety and its structures with unprecedented resolution over a very long time.The dissemination of these stories is ensured through a website created ad hoc for the occasion. The production work is carried out in close collaboration with a web developer, a graphic designer and the FSO’s cartography competence center. The aim is to produce a new, original web publication intended for a broad audience, that is both relevant and attractive, and has a layout optimized to invite the user onto a visual journey in time along the history of the Federal Population Census.With regard to cartographic visualizations, the produced maps have been the subject of a rehabilitated layout for maximum readability and efficiency and a high aesthetic quality. The addition of comments and the focus on specific observations facilitates reading and interpreting maps and supports the narrative. To provide maximum flexibility with respect to the graphics and enable quick loading of visualizations, these are integrated into HTML pages as SVG, which can subsequently be animated in the website. In a concurrent and complementary way, the produced maps are also made available in the Interactive Statistical Atlas of Switzerland (which is the FSO’s main means of thematic maps dissemination). This allows for the interactive exploration of maps, the visualization of animated time series, and data dissemination in the form of downloadable Excel files directly from the application.This attempt at (carto)graphic narration is an opportunity to question narrative approaches in the field of graphic visualization in a very concrete framework of historical data valorization. Since storytelling and its cartographic variants in the form of story maps are an important trend today, this project provides an example and a contribution to this approach. The presentation will focus on presenting the structure and content of the stories, focusing on the cartographic and technical aspects of storytelling, and presenting the different choices and challenges encountered. In addition, editorial and technical strengths and weaknesses will also be discussed. As this project is a work in progress that will take place throughout 2019, this contribution also aims to be submitted to peer review, in order to improve our products in the future.

Population demography of Oldham's leaf turtle (Cyclemys oldhamii) in protected and disturbed habitats in Thailand.

BackgroundFreshwater turtle populations are vulnerable to a range of human activities because of particular life history attributes, and anthropogenic impacts can cause shifts in demographic traits, including survival, density and population structure. Asian freshwater turtles have undergone dramatic population declines in recent decades principally because of collection for food, pet, and traditional medicine markets. Despite this, few studies have been conducted on the population demography of these turtles, thereby limiting our understanding of population trends and the development of conservation actions. Oldham’s leaf turtle (Cyclemys oldhamii) is one of the most commonly traded turtles in Asian markets, but previous published studies have focused solely on systematics.MethodsWe conducted a mark-recapture study of C. oldhamii at three sites in northeastern Thailand—a protected stream, a degraded stream, and human-constructed ponds—and evaluated differences in survival, density, population structure, and sexual dimorphism among sites.ResultsWe captured 77 turtles at the protected stream, 67 at the constructed ponds, and two in the degraded stream. Survival was 12% lower and density was 35% lower in the constructed ponds than in the protected stream. Size class structure was skewed toward smaller individuals at the constructed ponds, and both sites exhibited subadult-skewed age class structure. Sex ratios were not statistically different than 1:1 at either site and did not differ between sites. We did not document sexual dimorphism in either population.DiscussionExplanations for lower survival, lower densities, and skewed size class structure at the constructed ponds include collection for consumption or Buddhist prayer release locally, collection for illegal export from Thailand, predation by domestic dogs associated with humans living nearby, or lower habitat quality. Evidence from our study suggests that collection, either for local use or export, is the most likely explanation for differences in demographic characteristics between the two sites. The information gained from this study may contribute to a status assessment for C. oldhamii and development of conservation actions should they become necessary to protect populations in Thailand.

Connectivity of mule deer (Odocoileus hemionus) populations in a highly fragmented urban landscape

Urbanization is a substantial force shaping the genetic and demographic structure of natural populations. Urban development and major highways can limit animal movements, and thus gene flow, even in highly mobile species. Characterizing varying species responses to human activity and fragmentation is important for maintaining genetic continuity in wild animals and for preserving biodiversity. As one of the only common and wide-ranging large wild herbivores in much of urban North America, deer play an important ecological role in urban ecosystems, yet the genetic impacts of development on deer are not well known. We assessed genetic connectivity for mule deer to understand their genetic response to habitat fragmentation, due to development and highway barriers, in an increasingly urbanized landscape. Using non-invasive sampling across a broad region of southern California, we investigated genetic structure among several natural areas that were separated by major highways and applied least-cost path modelling to determine if landscape context and highway attributes influence genetic distance for mule deer. We observed significant yet variable differentiation between subregions. We show that genetic structure corresponds with highway boundaries in certain habitat patches, and that particular landscape configurations more greatly limit gene flow between patches. As a large and highly mobile species generally considered to be well adapted to human activity, mule deer nonetheless showed genetic impacts of intensive urbanization. Because of this potential vulnerability, mule deer and other ungulates may require further consideration for effective habitat management and maintenance of landscape connectivity in human-dominated landscapes.

Demographic situation in the regions of Ukraine as a prerequisite of labor potential formation and development

The formation of labor potential is a crucial prerequisite for the socio-economic stability of the country, and its effective use is the basis of productivity of the national economy. In the context of Ukraine's integration into the world economic space, an important task is to study the internal and external factors that influence the country’s labor potential formation. The factors of external influence include: the level of socio-economic development of the region, country; level of demographic development of the region, country; state of the national and regional labor market and conditions of labor price formation; the legal framework governing social and labor relations; social and entrepreneurial investment. The magnitude of the labor potential of the country and the region depends more on the demographic situation (total population, its structure, life expectancy, birth rate and death rate). Demographic factors mainly influence the quantitative component of labor potential. The article deals with the issues of population dynamics in the regions of Ukraine, as well as birth rate, death rate, middle age, population reproduction. The regions of Ukraine are grouped according to the age structure of the population, and the regions with the prevalence of the share of pensioners over adolescents, the regions with the prevalence of the share of the population younger than the working age, and also the regions with the highest proportion of the working population respectively. In addition to natural population growth / decline, the population's demographic potential is affected by mechanical movement of the population, that is, features of migration processes of the population. According to the indicators of migration growth / reduction, the corresponding groups of regions of Ukraine are highlighted. At the present stage there are significant changes in the population demographic structure, which in turn caused a significant deterioration in the quantitative and qualitative status of the country's labor potential. Population reductions, high death rates and low birth rates, and a negative migration balance, indicate that the demographic situation needs a lot of attention from the state. It is extremely necessary to respond and implement appropriate measures, if not to increase the quantitative parameters of labor potential, at least to preserve the existing status. The main levers of regulation of labor potential include: increase in income and standard of living; increase in life expectancy; increase in natality; return of compatriots working abroad, etc.

Asian water monitors (Varanus salvator) remain common in Peninsular Malaysia, despite intense harvesting

Context Each year, between 50000 and 120000 Asian water monitors (Varanus salvator, to >2 m total length) are harvested from the wild in Peninsular Malaysia for their skins. Under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), international trade is allowable only if it is sustainable. Aims To assess the sustainability of Malaysia’s harvest of water monitors by quantifying the abundance and demography of V. salvator in the wild, and to develop cost-effective methods for estimating the parameters needed to evaluate sustainability. Methods We conducted trapping surveys to determine the abundance, population demography and density of V. salvator in four habitat types in five states in Peninsular Malaysia in 2010, 2011, 2012 and 2018. Key results Of 1025 lizards captured, only 63% (mostly females) were within the preferred body-size range exploited for commercial trade. Densities were high (37–372 lizards km–2 based on estimated population sizes; 1–35 lizards km–2 based on number of animals captured). Anthropogenic habitats (e.g. oil palm plantations) contained denser populations of monitors than did natural habitats where no hunting occurs, but mean body sizes were smaller. Conclusions Despite intensive harvesting for many decades, V. salvator remains abundant and widespread. Harvesting alters the demographic structure of lizard populations, but harvests of V. salvator in Malaysia are likely to be sustainable because a significant proportion of the population is not exploited. Implications Ongoing monitoring is required to continually reassess harvest sustainability. For this purpose, relatively simple population approaches, such as line-trapping transects to elucidate relative abundances, can provide important data on the makeup of hunted populations of water monitors more cost-effectively than can mark–recapture studies for assessments of sustainable use of these economically important lizards.

The importance of fire in the success of a 15 hectare subtropical heathland translocation

Fire is a key factor in the maintenance of many ecosystems; however, little is known on how it affects the success of translocated fire-dependent plant species and communities. Further, translocation success is currently limited, creating uncertainty around the effectiveness of translocations in mitigating the negative impacts of urbanisation on biodiversity. Translocation evaluations may improve future outcomes by providing vital information: therefore, the aim of the present study was to investigate the long-term success of a large-scale subtropical heathland translocation as well as the impacts of a fire management regime eight years after it was completed. Original performance criteria and monitoring data combined with new site surveys were utilised to assess the ongoing success of the translocation. Specifically, the structure and composition of the heath vegetation and the population size and demographic structure of five specific threatened plant species were assessed. Results showed that translocation still met the performance criteria requirements and so can continue to be classed as a success. Fire played a key role in enabling the vegetation to meet the performance criteria by promoting regeneration of target species and maintaining community composition. This was likely supported by the immediate availability of seed through the preservation of the seedbank. Long-term success in translocated fire-dependent plant species and communities will depend largely on the application of appropriate fire regimes.

Changing landscape of public health and medical education curriculum.

The landscape of public health in many sub-Saharan African countries has been changing rapidly over the past few decades. Marked changes have been seen in the demographic structure of populations, economics, lifestyle changes, social upheavals (war and migration) and these have impacted disease patterns.

An emerging viral pathogen truncates population age structure in a European amphibian and may reduce population viability.

Infectious diseases can alter the demography of their host populations, reducing their viability even in the absence of mass mortality. Amphibians are the most threatened group of vertebrates globally, and emerging infectious diseases play a large role in their continued population declines. Viruses belonging to the genus Ranavirus are responsible for one of the deadliest and most widespread of these diseases. To date, no work has used individual level data to investigate how ranaviruses affect population demographic structure. We used skeletochronology and morphology to evaluate the impact of ranaviruses on the age structure of populations of the European common frog (Rana temporaria) in the UK. We compared ecologically similar populations that differed most notably in their historical presence or absence of ranavirosis (the acute syndrome caused by ranavirus infection). Our results suggest that ranavirosis may truncate the age structure of R. temporaria populations. One potential explanation for such a shift might be increased adult mortality and subsequent shifts in the life history of younger age classes that increase reproductive output earlier in life. Additionally, we constructed population projection models which indicated that such increased adult mortality could heighten the vulnerability of frog populations to stochastic environmental challenges.

Effects of climate and demography on reproductive phenology of a harvested marine fish population

Shifts in phenology are a well-documented ecological response to changes in climate, which may or may not be adaptive for a species depending on the climate sensitivity of other ecosystem processes. Furthermore, phenology may be affected by factors in addition to climate, which may accentuate or dampen climate-driven phenological responses. In this study, we investigate how climate and population demographic structure jointly affect spawning phenology of a fish species of major commercial importance: walleye pollock (Gadus chalcogrammus). We use 32years of data from ichthyoplankton surveys to reconstruct timing of pollock reproduction in the Gulf of Alaska and find that the mean date of spawning has varied by over 3weeks throughout the last >3 decades. Climate clearly drives variation in spawn timing, with warmer temperatures leading to an earlier and more protracted spawning period, consistent with expectations of advanced spring phenology under warming. However, the effects of temperature were nonlinear, such that additional warming above a threshold value had no additional effect on phenology. Population demographics were equally as important as temperature: An older and more age-diverse spawning stock tended to spawn earlier and over a longer duration than a younger stock. Our models suggest that demographic shifts associated with sustainable harvest rates could shift the mean spawning date 7days later and shorten the spawning season by 9days relative to an unfished population, independent of thermal conditions. Projections under climate change suggest that spawn timing will become more stable for walleye pollock in the future, but it is unknown what the consequences of this stabilization will be for the synchrony of first-feeding larvae with production of zooplankton prey in spring. With ongoing warming in the world's oceans, knowledge of the mechanisms underlying reproductive phenology can improve our ability to monitor and manage species under changing climate conditions.

Ancestry informative alleles captured with reduced representation library sequencing in Theobroma cacao.

As the source of chocolate, cacao has become one of the most important crops in the world. The identification of molecular markers to understand the demographic history, genetic diversity and population structure plays a pivotal role in cacao breeding programs. Here, we report the use of a modified genotyping-by-sequencing (GBS) approach for large-scale single nucleotide polymorphism (SNP) discovery and allele ancestry mapping. We identified 12,357 bi-allelic SNPs after filtering, of which, 7,009 variants were ancestry informative. The GBS approach proved to be rapid, cost-effective, and highly informative for ancestry assignment in this species.

Male Body Size Predicts Reproductive Success But Not Within-Clutch Paternity Patterns in Gopher Tortoises (Gopherus polyphemus).

In many vertebrates, body size is an important driver of variation in male reproductive success. Larger, more fit individuals are more likely to dominate mating opportunities, skewing siring success and resulting in lower effective population sizes and genetic diversity. The mating system of the gopher tortoise (Gopherus polyphemus) has been characterized as both female-defense and scramble-competition polygyny. Mating systems are typically not fixed and can be influenced by factors such as population density, demographic structure, and environmental conditions; however, most populations will have a predominant strategy that results from local conditions. We assessed how male body size influences patterns of paternity and reproductive success in a natural population of gopher tortoises in Florida, United States. Using microsatellites, we assigned parentage of 220 hatchlings from 31 nests collected during 2 reproductive seasons. Larger males were significantly more likely to sire offspring and sired more offspring than smaller males; however, the likelihood of a clutch being multiply sired was unrelated to male body size. We also found evidence of mate fidelity across years. Although paternity patterns in this high-density population are more consistent with defense polygyny, female monopoly by males was incomplete, with both large and small males contributing to multiply sired clutches. Additional behavioral data are needed to clarify the role of female mate selection in paternity outcomes. The context-dependence of mating systems underscores the need to compare parentage patterns across populations and to recognize the potential for more than 1 strategy to be employed within a single population.

Is population genetic structure of vascular plants shaped more by ecological or geographic factors? A study case on the Mediterranean endemic Centaurea filiformis (Asteraceae).

All known populations of the Sardinian endemic Centaurea filiformis Viv. (Asteraceae) were studied in order to understand the impact of both geographic and ecological factors on the genetic structuring of this species. Fourteen populations and 234 individuals were sampled. The demographic structure of the populations and the reproductive ecology were estimated in 28 plots. Population genetic analyses were based on SSR markers. Genetic structure was investigated by spatial Bayesian methods. Average densities of 0.51 individuals m-2 were detected, with a prevalence of adults. Ten species of pollinators were identified; C.filiformis ability to self-pollinate and myrmecochory were demonstrated experimentally. The populations displayed an average heterozygosity value of He =0.576 and high genetic differentiation (overall FST =0.218). Bayesian analysis suggests that five is the most probable number of gene pools of origin. A strong correlation between geographic distances and genetic distances among populations was highlighted. The demographic population structure of C.filiformis is dominated by adults, suggesting that it is a stable-regressive or senile species, investing more in local persistence than colonisation ability. Despite the scattered distribution, the populations studied do not present evidence of genetic erosion. The analysis of genetic differentiation reveals very high differentiation levels among populations, thus indicating that effective barriers exist against gene flow. A general conclusion is that population distribution results in a clear genetic structure for the populations studied, and that geography and not ecology is shaping the present distribution of this species.

EXPERIENCE IN USING QUALITATIVE PROBLEMS IN TEACHING THE COURSE OF DEMOGRAPHY FOR BACHELOR ECONOMISTS

One of the tasks that the teacher must deal with when preparing the Demography course for bachelor students who do not specialize in demography is to interest students with the subject by demonstrating the application of the indicators and trends they study. Another important task is to check the learning outcomes both during the semester and during the exam. Qualitative problems can be used to simultaneously solve both problems. Unlike traditional calculation tasks that require the knowledge of formulas of indicators, qualitative tasks are designed to help students see the links between demographic processes and population structures, better understand the nature of demographic indicators, pay attention to the possible socio-economic consequences of demographic processes in dynamics. In discussing a text problem, it is important to draw the attention of students to the need to build logical chains of reasoning, rather than simply listing the reasons or factors required by the statement. Such exercises teach students to critically comprehend the information they receive from journalism and when reading scientific publications, employ the knowledge they received in the course of Demography to solve applied problems.

Navigating the Interface Between Landscape Genetics and Landscape Genomics.

As next-generation sequencing data become increasingly available for non-model organisms, a shift has occurred in the focus of studies of the geographic distribution of genetic variation. Whereas landscape genetics studies primarily focus on testing the effects of landscape variables on gene flow and genetic population structure, landscape genomics studies focus on detecting candidate genes under selection that indicate possible local adaptation. Navigating the transition between landscape genomics and landscape genetics can be challenging. The number of molecular markers analyzed has shifted from what used to be a few dozen loci to thousands of loci and even full genomes. Although genome scale data can be separated into sets of neutral loci for analyses of gene flow and population structure and putative loci under selection for inference of local adaptation, there are inherent differences in the questions that are addressed in the two study frameworks. We discuss these differences and their implications for study design, marker choice and downstream analysis methods. Similar to the rapid proliferation of analysis methods in the early development of landscape genetics, new analytical methods for detection of selection in landscape genomics studies are burgeoning. We focus on genome scan methods for detection of selection, and in particular, outlier differentiation methods and genetic-environment association tests because they are the most widely used. Use of genome scan methods requires an understanding of the potential mismatches between the biology of a species and assumptions inherent in analytical methods used, which can lead to high false positive rates of detected loci under selection. Key to choosing appropriate genome scan methods is an understanding of the underlying demographic structure of study populations, and such data can be obtained using neutral loci from the generated genome-wide data or prior knowledge of a species' phylogeographic history. To this end, we summarize recent simulation studies that test the power and accuracy of genome scan methods under a variety of demographic scenarios and sampling designs. We conclude with a discussion of additional considerations for future method development, and a summary of methods that show promise for landscape genomics studies but are not yet widely used.

Status of <i>Astragalus cornutus</i> Pall. populations in the Samara Region

This paper examines features of the demographic structure of natural populations of a rare representative of the steppe flora Astragalus cornutus Pall. (Fabaceae). The rarity of the species makes it necessary to include it in the Red Books of the Russian Federation and some steppe regions. In the Samara Region, species populations require additional protection in connection with the peculiarities of biology and ecology, a significant anthropogenic load on communities, and a reduction in the number of habitats. We studied the features of the structure of populations in the Samara Trans-Volga Region. A total of 84 cenopopulations were surveyed, tendencies of population change, features of demographic and spatial structure were revealed. The structure of populations is affected by the ecological and phytocenotic conditions of the environment and anthropogenic factors. The replacement and recovery of individuals in A. cornutus populations is slow. The ontogenetic structure of populations has a fluctuation dynamics. Assessment of the studied geographical populations by L.A. Zhivotovsky efficiency criterion (2001) showed that they are all mature. Specific cenopopulations of A. cornutus are aging (5%) and old (8%). The average density of individuals is about 3 individuals/m. The average effective density is 2,4 individuals/m, the largest - 4,1, the smallest - 1,3. The condition of all studied populations (even in a satisfactory state) on the territory of the Samara Region causes alarm. Populations of the species in the region need additional protection measures.

Demographic changes in Chinook salmon across the Northeast Pacific Ocean

AbstractThe demographic structure of populations is affected by life history strategies and how these interact with natural and anthropogenic factors such as exploitation, climate change, and biotic interactions. Previous work suggests that the mean size and age of some North American populations of Chinook salmon (Oncorhynchus tshawytscha, Salmonidae) are declining. These trends are of concern because Chinook salmon are highly valued commercially for their exceptional size and because the loss of the largest and oldest individuals may lead to reduced population productivity. Using long‐term data from wild and hatchery populations, we quantified changes in the demographic structure of Chinook salmon populations over the past four decades across the Northeast Pacific Ocean, from California through western Alaska. Our results show that wild and hatchery fish are becoming smaller and younger throughout most of the Pacific coast. Proportions of older age classes have decreased over time in most regions. Simultaneously, the length‐at‐age of older fish has declined while the length‐at‐age of younger fish has typically increased. However, negative size trends of older ages were weak or non‐existent at the southern end of the range. While it remains to be explored whether these trends are caused by changes in climate, fishing practices or species interactions such as predation, our qualitative review of the potential causes of demographic change suggests that selective removal of large fish has likely contributed to the apparent widespread declines in average body sizes.

Direct and Indirect Effects of Resource P-Limitation Differentially Impact Population Growth, Life History and Body Elemental Composition of a Zooplankton Consumer.

One of the central tenets of ecological stoichiometry is that consumer growth rate is strongly determined by food phosphorus (P) content. In planktonic organisms population growth rates of zooplankton have repeatedly been shown to be reduced when fed with P-limited algal food sources. However, P-limitation may also affect other quality-related aspects of algae, such as biochemical composition or palatability. We studied the population growth, detailed life history and body elemental composition of the herbivorous rotifer, Brachionus calyciflorus, in response to three different food quality treatments: algae cultured in high phosphorus conditions (average algal molar C:P ≈ 112, ‘HP’), algae cultured in low P conditions (molar C:P ≈ 631, ‘LP’) and low-P cultured algae spiked with P just before feeding (molar C:P ≈ 113, ‘LP+P’). LP+P algae thus combined high P content with a history of growth under P-limited conditions. Total P content and the C:P ratio of rotifers in the LP+P treatment equaled those of rotifers in the HP treatment. Rotifer population growth rates were higher in HP than in LP and intermediate in the LP+P treatment. Similarly, many life history traits observed for animals in the LP+P treatment, such as somatic growth rate, age at maturity, and egg production rate were also intermediate to those observed in the LP and HP treatments. However, there were important deviations from this pattern: size at first reproduction and egg mortality in the LP+P treatment equaled the HP treatment, whereas size and development time of the first eggs equaled those of the LP treatment. Our results indicate that elemental limitation cannot fully explain reduced performance of consumers fed with P-limited algae and strongly suggest that indirect, non-stoichiometric effects of P-limitation, e.g., via changes in biochemical composition or morphology of the algae also play a major role. Furthermore, our study highlights that such indirect effects have a differential impact on major fitness components and may as such also determine the population dynamics and demographic structure of consumer populations.

Identifying regional poverty types in Slovakia

Even today the poverty is an important negative social phenomenon with evident spatial dimension. Areas with high poverty concentration constitute poverty regions with plenty of common but also different or specific characteristics. Research into the specific poverty features in regions lags behind that of the common characteristics and character of poverty. The aim is to show one of ways to carry out typification of poverty regions (on example of Slovakia). A universal conceptual and methodological frame applicable to any country is presented. Regional poverty types were sorted out by application of the hierarchical agglomerative methods of cluster analysis (Ward’s method) with nine indicators capturing the generally applicable dimensions, which determine poverty and profile of poverty regions. Results confirmed the presumption that the different economic, social, demographic, cultural and other different conditions and population structure in regions may determine the character of poverty. Obtained knowledge points not only to the particular population groups, which require attention but also to the regional poverty types that should be identified for the efficient fight against poverty in these regions.