Search results for "ECOSYSTEMS"

Variability in the mutation rates of RNA viruses

2014

ABSTRACT:  It is well established that RNA viruses show extremely high mutation rates, but less attention has been paid to the fact that their mutation rates also vary strongly, from 10-6 to 10-4 substitutions per nucleotide per cell infection. The causes explaining this variability are still poorly understood, but candidate factors are the viral genome size and polarity, host-specific gene expression patterns, or the intracellular environment. Differences between animal and plant viruses, or between arthropod-borne and directly transmitted viruses have also been postulated. Finally, RNA viruses may be able to regulate the rate at which new mutations spread in the population by modifying f…

Variation in RNA virus mutation rates across host cells.

2014

It is well established that RNA viruses exhibit higher rates of spontaneous mutation than DNA viruses and microorganisms. However, their mutation rates vary amply, from 10−6 to 10−4 substitutions per nucleotide per round of copying (s/n/r) and the causes of this variability remain poorly understood. In addition to differences in intrinsic fidelity or error correction capability, viral mutation rates may be dependent on host factors. Here, we assessed the effect of the cellular environment on the rate of spontaneous mutation of the vesicular stomatitis virus (VSV), which has a broad host range and cell tropism. Luria-Delbrück fluctuation tests and sequencing showed that VSV mutated similarly…

Eresus kollari (Araneae: Eresidae) calls for heathland management

2011

Northwest Europe’s largest heather-dominated sandy habitats are located in the nature reserve Lu¨neburgerHeide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as theladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of thesespecies. The habitat requirements of this endangered spider species were investigated in order to obtain data that will helpstabilize the last remnants of the species’ population in northwest Germany. Several heathland habitats were surveyed bypitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic reg…

Stochastic 0-dimensional Biogeochemical Flux Model: Effect of temperature fluctuations on the dynamics of the biogeochemical properties in a marine e…

2021

Abstract We present a new stochastic model, based on a 0-dimensional version of the well known biogeochemical flux model (BFM), which allows to take into account the temperature random fluctuations present in natural systems and therefore to describe more realistically the dynamics of real marine ecosystems. The study presents a detailed analysis of the effects of randomly varying temperature on the lower trophic levels of the food web and ocean biogeochemical processes. More in detail, the temperature is described as a stochastic process driven by an additive self-correlated Gaussian noise. Varying both correlation time and intensity of the noise source, the predominance of different plank…

A novel method to simulate the 3D chlorophyll distribution in marine oligotrophic waters

2021

Abstract A 3D advection-diffusion-reaction model is proposed to investigate the abundance of phytoplankton in a difficult-to-access ecosystem such as the Gulf of Sirte (southern Mediterranean Sea) characterized by oligotrophic waters. The model exploits experimentally measured environmental variables to reproduce the dynamics of four populations that dominate phytoplankton community in the studied area: Synechococcus, Prochlorococcus HL, Prochlorococcus LL and picoeukaryotes. The theoretical results obtained for phytoplankton abundances are converted into chl-a and Dvchl-a concentrations, and the simulated vertical chlorophyll profiles are compared to the corresponding experimentally acquir…

Toward Unified Control of Networks of Switches and Sensors Through a Network Operating System

2018

Wireless sensor networks (WSNs) are an integral part of an Internet of Things (IoT) ecosystem. In fact, a typical IoT service deployment considers an integrated network of switches and sensors (as well as actuators). In order to manage this heterogeneous network infrastructure, the use of software defined networking (SDN) technologies is anticipated. However, existing SDN-enabling technologies consider only isolated networks and there has been no concrete solution that treats the whole network in a unified way. In this paper, a network operating system is proposed as a way to address the above issue. Starting from the open network operating system, which currently supports only OpenFlow net…

Forest management optimization across spatial scales to reconcile economic and conservation objectives

2019

Conflicts between biodiversity conservation and resource production can be mitigated by multi-objective management planning. Optimizing management for multiple objectives over larger land areas likely entails trading off the practicability of the process against the goodness of the solution. It is therefore worthwhile to resolve how large areas are required as management planning regions to reconcile conflicting objectives as effectively as possible. We aimed to reveal how the extent of forestry planning regions impacts the potential to mitigate a forestry-conservation conflict in Finland, represented as a trade-off between harvest income and deadwood availability. We used forecasted data f…

STOCHASTIC DYNAMICS OF TWO PICOPHYTOPLANKTON POPULATIONS IN A REAL MARINE ECOSYSTEM

2013

A stochastic reaction-diffusion-taxis model is analyzed to get the stationary distribution along water column of two species of picophytoplankton, that is picoeukaryotes and Prochlorococcus. The model is valid for weakly mixed waters, typical of the Mediterranean Sea. External random fluctuations are considered by adding a multiplicative Gaussian noise to the dynamical equation of the nutrient concentration. The statistical tests show that shape and magnitude of the theoretical concentration profile exhibit a good agreement with the experimental findings. Finally, we study the effects of seasonal variations on picophytoplankton groups, including an oscillating term in the auxiliary equation…

TOOLS TO DETECT, IDENTIFY AND MONITOR PHYTOPHTHORA SPECIES IN NATURAL ECOSYSTEM

2007

Stochastic models for phytoplankton dynamics in marine ecosystems

2014

In this thesis, the stochastic advection-reaction-diffusion models are analyzed to obtain the vertical stationary spatial distributions of the main groups of picophytoplankton, which account about for 80% of total chlorophyll on average in Mediterranean Sea. In Chapter 1 we give a short presentation of the experimental and phytoplanktonic data collected during different oceanographic surveys in Mediterranean Sea. In Chapter 2 we introduce the deterministic and stochastic approaches (one-population model) adopted to describe the picoeukaryotes dynamics in Sicily Channel. Moreover, numerical results for the biomass concentration are compared with experimental data by using chi-squared goodnes…