Search results for "Population Dynamic"
showing 10 items of 296 documents
The main trends in the palaeodemography of the 7th-18th century population of Latvia
2006
The study represents palaeodemographic research of osteological material of 3304 individuals from the funds of the Anthropological Laboratory of the Institute of History of the University of Latvia in Riga, dating from the 7 th to the 18 th century AD. Compensated life expectancy at birth is varying between 20.3 and 22.2 years during the research period. Crude mortality has changed between 49.3 and 45 %o. In the early period (7 th - 13 th century) there is a significant male prevalence (2.2 - 1.4); female life expectancy at the age of 20 is on average 6.6 years less than for males. This difference decreases to 5.4 years in the 13 th - 18 th century. According to historical demography, femal…
Exploratory Factor Analysis and Validation Study of the Lifetime Severity Index for Cocaine, Spanish Version (LSI-C-Spanish)
2007
The purpose of the study was to do an exploratory factor analysis and to examine the criterion-related and discriminant validity of the Lifetime Severity Index for Cocaine (LSI-C), Spanish version. A sample of 171 outpatients from 10 drug centers in Spain participated in the study. We conducted the factor analysis with orthogonal rotation and examined correlations between the LSI-C total score and criterion variables as well as the score obtained by a quality of life measure. The factor analysis revealed 2 principal factors that explain 65.8% of the variance. Lower LSI-C scores were associated with taking medication, receiving social help, using cocaine fewer than 30 times during the previo…
Ant Abundance along a Productivity Gradient: Addressing Two Conflicting Hypotheses
2015
The number of individuals within a population or community and their body size can be associated with changes in resource supply. While these relationships may provide a key to better understand the role of abiotic vs. biotic constraints in animal communities, little is known about the way size and abundance of organisms change along resource gradients. Here, we studied this interplay in ants, addressing two hypotheses with opposite predictions regarding variation in population densities along resource gradients- the 'productivity hypothesis' and the 'productivity-based thinning hypothesis'. The hypotheses were tested in two functional groups of ground-dwelling ants that are directly primar…
Climate change and the ecology and evolution of Arctic vertebrates.
2012
25 pages; International audience; Climate change is taking place more rapidly and severely in the Arctic than anywhere on the globe, exposing Arctic vertebrates to a host of impacts. Changes in the cryosphere dominate the physical changes that already affect these animals, but increasing air temperatures, changes in precipitation, and ocean acidification will also affect Arctic ecosystems in the future. Adaptation via natural selection is problematic in such a rapidly changing environment. Adjustment via phenotypic plasticity is therefore likely to dominate Arctic vertebrate responses in the short term, and many such adjustments have already been documented. Changes in phenology and range w…
Ultradeep Sequencing Analysis of Population Dynamics of Virus Escape Mutants in RNAi-Mediated Resistant Plants
2012
Plant artificial micro-RNAs (amiRs) have been engineered to target viral genomes and induce their degradation. However, the exceptional evolutionary plasticity of RNA viruses threatens the durability of the resistance conferred by these amiRs. It has recently been shown that viral populations not experiencing strong selective pressure from an antiviral amiR may already contain enough genetic variability in the target sequence to escape plant resistance in an almost deterministic manner. Furthermore, it has also been shown that viral populations exposed to subinhibitory concentrations of the antiviral amiR speed up this process. In this article, we have characterized the molecular evolutiona…
Microbial Diversity in the Midguts of Field and Lab-Reared Populations of the European Corn Borer Ostrinia nubilalis
2011
Background: Insects are associated with microorganisms that contribute to the digestion and processing of nutrients. The European Corn Borer (ECB) is a moth present world-wide, causing severe economical damage as a pest on corn and other crops. In the present work, we give a detailed view of the complexity of the microorganisms forming the ECB midgut microbiota with the objective of comparing the biodiversity of the midgut-associated microbiota and explore their potential as a source of genes and enzymes with biotechnological applications. Methodological/Principal Findings: A high-throughput sequencing approach has been used to identify bacterial species, genes and metabolic pathways, parti…
Sex in an uncertain world: environmental stochasticity helps restore competitive balance between sexually and asexually reproducing populations
2014
Like many organisms, individuals of the freshwater ostracod species Eucypris virens exhibit either obligate sexual or asexual reproductive modes. Both types of individual routinely co-occur, including in the same temporary freshwater pond (their natural habitat in which they undergo seasonal diapause). Given the well-known two-fold cost of sex, this begs the question of how sexually reproducing individuals are able to coexist with their asexual counterparts in spite of such overwhelming costs. Environmental stochasticity in the form of 'false dawn' inundations (where the first hydration is ephemeral and causes loss of early hatching individuals) may provide an advantage to the sexual subpop…
Mitochondrial DNA Regionalism and Historical Demography in the Extant Populations of Chirocephalus kerkyrensis (Branchiopoda: Anostraca)
2012
BackgroundMediterranean temporary water bodies are important reservoirs of biodiversity and host a unique assemblage of diapausing aquatic invertebrates. These environments are currently vanishing because of increasing human pressure. Chirocephalus kerkyrensis is a fairy shrimp typical of temporary water bodies in Mediterranean plain forests and has undergone a substantial decline in number of populations in recent years due to habitat loss. We assessed patterns of genetic connectivity and phylogeographic history in the seven extant populations of the species from Albania, Corfu Is. (Greece), Southern and Central Italy.Methodology/principal findingsWe analyzed sequence variation at two mito…
Top predators, mesopredators and their prey: interference ecosystems along bioclimatic productivity gradients
2010
1. The Mesopredator Release Hypothesis (MRH) suggests that top predator suppression of mesopredators is a key ecosystem function with cascading impacts on herbivore prey, but it remains to be shown that this top-down cascade impacts the large-scale structure of ecosystems. 2. The Exploitation Ecosystems Hypothesis (EEH) predicts that regional ecosystem structures are determined by top-down exploitation and bottom-up productivity. In contrast to MRH, EEH assumes that interference among predators has a negligible impact on the structure of ecosystems with three trophic levels. 3. We use the recolonization of a top predator in a three-level boreal ecosystem as a natural experiment to test if l…
Optimal Control of the Controlled Lotka-Volterra Equations with Applications - The Permanent Case
2022
In this article motivated by the control of complex microbiota in view to reduce the infection by a pathogenic agent, we introduce the theoretical frame from optimal control to analyze the problem. Two complementary approaches can be applied in the analysis: one is the so-called permanent case, where no digital constraints are concerning the control (taken as a measurable mapping) versus the sampled-data control case taking into account the logistic constraints, e.g. frequency of the medical interventions. The model is the n-dimensional Lotka-Volterra equation controlled using either probiotics or antibiotic agents or transplantation and bactericides. In the permanent case the Maximum princ…