A convenient ready-to-use algorithm for a conditional quantile estimator

Abstract: This paper contains a complete procedure for calculating the value of a conditional quantile estimator. The concept is based on the nonparametric kernel estimator method, which frees the algorithm from the random variables ’ distributions. The procedure was worked out in a ready-to-use form – specific formulas for functions and the parameter used were given. The practical implementation of this method is very simple, and its computational complexity is linear with respect to random sample size as well as the dimension of conditioning variable. Thanks to a clear, near intuitive interpretation it can easily be modified or generalized depending on the individual needs of atypical applications. In particular, conditioning variables can be taken into account, not only continuous (real), but also binary, discrete and categorized, or any of their combinations

The role of food quality in clonal succession in Daphnia: an experimental test

A high genetic variation and recurrent changes in the genetic structure have been found in many pelagic populations. However, evidence that directly links these changes to differences in the ecological performance of particular genotypes is scarce. We hypothesized that within Daphnia, the specialization of clones occurring in a particular season to the food quality specific for that time of the year is responsible for the observed changes in the genetic structure of a population. This hypothesis was tested by comparing the fitness of spring and summer clones of the Daphnia longispina group, given food of biochemical quality relevant to these seasons. We identified significant intraspecific differences between clones of Daphnia that are specific for particular seasons, but there was no evidence that clones are adapted to the food quality available at the respective times of year. Summer clones reproduce at smaller size, and have a lower juvenile specific growth rate as compared to spring clones, irrespective of food quality. Spring clones invest more energy in somatic growth at the cost of reproduction, whereas summer clones invest more energy in reproduction at the cost of somatic growth. On the basis of the observed differences between spring and summer clones in their patterns of energy allocation, we suggest that other factors, most likely predation, are the major forces driving phenotypic and genetic diversity in the investigated Daphnia population of a large lake

Differential Levels of Stress Proteins (HSPs) in Male and Female Daphnia magna in Response to Thermal Stress: A Consequence of Sex-Related Behavioral Differences?

In two independent experiments, we compared: (1) water depth selection (and accompanying temperature selection) by male and female Daphnia magna under different kinds of environmental stress, including the presence of filamentous cyanobacteria, the risk of predation from fish, and the presence of toxic compounds; and (2) sex-dependent production of heat shock proteins (HSP60, 70, and 90) in response to a sudden change in temperature. Male D. magna selected deep water strata, which offer a relatively stable environment, and thereby avoided the threat of predation and the presence of toxic compounds in surface waters. Correlated with this behavior, males reduce their molecular defenses against stress, such as the production of heat shock proteins (HSPs), and do not maintain the physiological machinery that triggers an increase in HSP levels in response to stress. In contrast, female D. magna actively select habitats that offer optimal conditions for growth and production of offspring. Consequently, females are exposed to variable environmental conditions that may be associated with increased stress. To permit survival in these different habitats, D. magna females require molecular mechanisms to protect their cells from rapid changes in stress levels. Thus, they maintain high constitutive levels of the heat shock proteins from HSP 60, 70, and 90 families, and they have the potential to further enhance the production of the majority of these proteins under stress conditions. The results of this study indicate that the separate habitats selected by male and female D. magna result in different patterns of HSP production, leading us to hypothesize that that male and female Daphnia magna adopt different strategies to maximize the fitness of the species

Diel vertical migration in Chaoborus flavicans: Population patterns vs. individual tracks

Sixty Chaoborus flavicans 4th instar larvae were enclosed individually in a 1 m deep laboratory system, designed to mimic the thermal and light conditions of a stratified lake, and their vertical displacements were monitored for over 30 days. Though separated, the larvae exhibited a synchronous behavior either when exposed to a chemical stimulus from fish, or when left undisturbed without any predator cues. Under low predator stress the animals moved asynchronously and an averaged population depth displacements poorly reflected the behaviour of individual larvae. These observations support the concept of diel vertical migration as an evolutionary stable strategy

Trade-offs in diel vertical migration by zooplankton: The costs of predator avoidance

Diel vertical migration (DVM) of zooplankton is a behavioral antipredator defense that is shaped by the trade-off between higher predation risk in surface waters and reduced growth in deeper waters. We conducted two laboratory experiments to quantify the costs connected with DVM. In the first experiment, Daphnia magna were kept individually in thermally stratified flow-through tubes and exposed to seven different concentrations of fish-exuded kairomones. Above a threshold concentration, the strength of migration increased with increases in the concentration of fish exudates. Enhancement of migration resulted in a lower mean ambient temperature experienced by the animals and marked decreases in individual growth and reproduction rates. In order to separate costs due to low hypolimnetic temperatures in a stratified system from costs due to reduced food concentrations in deeper waters, we conducted an experiment with a 2 x 2 factorial design (fish presence vs. absence and high vs. low food conditions). Differences in mean ambient temperature between Daphnia that performed DVM and nonmigrating animals were found to have a much stronger impact on life history parameters than food effects. A reevaluation of field data on DVM in Daphnia further supports the view that vertical temperature gradients are more important than food gradients

A Convenient Ready-to-Use Algorithm for a Conditional Quantile Estimator

This paper contains a complete procedure for calculating the value of a conditional quantile estimator. The concept is based on the nonparametric kernel estimator method, which frees the algorithm from the random variables’ distributions. The procedure was worked out in a ready-to-use form – specific formulas for functions and the parameter used were given. The practical implementation of this method is very simple, and its computational complexity is linear with respect to random sample size as well as the dimension of conditioning variable. Thanks to a clear, near intuitive interpretation it can easily be modified or generalized depending on the individual needs of atypical applications. In particular, conditioning variables can be taken into account, not only continuous (real), but also binary, discrete and categorized, or any of their combinations

Integrated Approach to Information Analysis for Planning the Transport of Sensitive Cargo

This article presents the methodology of information analysis, required for planning safe road transport of sensitive cargoes. Based on the literature studies we found that the traditional approaches applied to analyze traffic information are insufficient to ensure safe transport of sensitive loads as they fail to take into account several threatening factors. In addition, the need was noted to develop the procedures that may allow to choose a transport route considering appearance of so-called high-risk zones within road infrastructure, analyze the interdependence of such zones with errors made during the design or operation of road infrastructure and investigate the impact of road traffic on the frequency of road accidents involving Heavy Goods Vehicle. Therefore, article aims to present an integrated approach to traffic information analysis. Thus a multiple stage data ordering procedures were proposed, based on grouping information on accident rates and inclusion of audit results of selected route sections. Considering that transport infrastructure plays an important role in transport safety, the proposed methodology includes the analysis of errors in infrastructure and a merger in the sections the detected risk zones within the road infrastructure in any location. Application of this methodology can improve the planning of road transport of sensitive cargoes. Its verification was carried out on the example of a selected route running through Poland. During the audit of the route, it was found that a number of incorrect design solutions were applied on its separate sections, which may lead to high values of the severity factor for potential collisions and indicator of possible post-accidental losses. As a result of the research, the areas of the route were identified, where high-risk zones are located that threaten the safety of road traffic of vehicles, including those carrying sensitive loads. Research results may be of interest for those, who are involved in planning and organization of sensitive cargo transport, both in domestic and in international relations

Daphnia fed algal food grown at elevated temperature have reduced fitness

Lake water temperature is negatively correlated with fatty acids content and P:C ratio in green algae. Hence, elevated temperature may indirectly reduce the fitness of Daphnia due to induced decrease in algal food quality. The aim of this study was to test the hypotheses that quality of algal food decreases with increasing temperature of its culture and that large-bodied Daphnia are more vulnerable to the temperature-related deterioration of algal food quality than small-bodied ones. Laboratory life-table experiments were performed at 20 degrees C with large-bodied D. pulicaria and small-bodied D. cucullata fed with the green alga Scenedesmus obliquus, that had been grown at temperatures of 16, 24 or 32 degrees C. The somatic growth rates of both species decreased significantly with increasing algal culture temperature and this effect was more pronounced in D. pulicaria than in D. cucullata. In the former species, age at first reproduction significantly increased and clutch size significantly decreased with increasing temperature of algae growth, while no significant changes in these two parameters were observed in the latter species. The proportion of egg-bearing females decreased with increasing algal culture temperature in both species. The results of this study support the notion that the quality of algal food decreases with increasing water temperature and also suggest that small-bodied Daphnia species might be less vulnerable to temperature-related decreases in algal food quality than large-bodied ones