Search results for "Population dynamic."

Environmental Metal Pollution Considered as Noise: Effects on the Spatial Distribution of Benthic Foraminifera in two Coastal Marine Areas of Sicily …

2008

We analyze the spatial distributions of two groups of benthic foraminifera (Adelosina spp. + Quinqueloculina spp. and Elphidium spp.), along Sicilian coast, and their correlation with six different heavy metals, responsible for the pollution. Samples were collected inside the Gulf of Palermo, which has a high level of pollution due to heavy metals, and along the coast of Lampedusa island (Sicily Channel, Southern Mediterranean), which is characterized by unpolluted sea waters. Because of the environmental pollution we find: (i) an anticorrelated spatial behaviour between the two groups of benthic foraminifera analyzed; (ii) an anticorrelated (correlated) spatial behaviour between the first …

Parasites as fish population tags and pseudoreplication problems: the case of striped red mullet Mullus surmuletus in the Spanish Mediterranean

2007

AbstractStudies of parasites as fish population tags often apply a single round of sampling to identify potential stocks or predict harvest localities. However, the lack of replication generates pseudoreplication, implicitly assuming that infection levels are more similar between samples from the same locality than between samples from different localities. We evaluated this assumption in the case of the striped red mullet Mullus surmuletus in three localities of the Spanish Mediterranean separated by c. 300 km. Samples of 25 fish of similar size were collected in each locality in the summer and autumn of two consecutive years. Prevalence and abundance of three long-lived parasite taxa diff…

Microcrustacean and Rotiferan Communities of Two Close Mediterranean Mountain Ponds, Lagunas de Bezas and Rubiales (Spain)

2010

ABSTRACT We compared two freshwater mountain ponds during an annual cycle by focusing on Rotifera and Crustacea. These ponds, Laguna de Bezas and Laguna de Rubiales, are located only 4.5 kilometers apart and share a similar altitude (ca. 1200 m.a.s.1) on the Iberian Mountain range, in Teruel (Spain). Bezas is near-permanent and dries out only in severe droughts; Rubiales is temporary, drying out periodically. They also show important differences in other limnological traits. Bezas has transparent water, harbors a fish population, and has a dense macrophyte cover, whereas Rubiales has elevated turbidity and neither fish nor macrophytes during most of the hydroperiod. These differences are pr…

Hydrodynamism and its influence on the reproductive condition of the edible sea urchin Paracentrotus lividus

2013

Despite the large body of work published in the last two decades on the reproduction of the sea urchin Paracentrotus lividus, the reproductive aspects linked to hydrodynamic conditions and their influence on gonad production remain poorly understood. The present paper aims to evaluate the effect of hydrodynamism on the reproductive cycle of P. lividus. Variability in the gonadosomatic index (GSI) of P. lividus was estimated seasonally from 2007 to 2008 at two shallow sub-littoral flat basaltic areas at Ustica Island (Western Mediterranean). GSI was higher in the sites characterized by low hydrodynamism than in those with high hydrodynamism. Results also suggest a possible role for hydrodyna…

Impact on the water column biogeochemistry of a Mediterranean mussel and fish farm

2002

We investigated and compared the impact of organic loads due to the biodeposition of mussel and fish farms on the water column of a coastal area of the Tyrrhenian Sea (Western Mediterranean). Physico-chemical data (including oxygen, nutrients, DOC and particulate organic matter), microbial variables (picoplankton and picophytoplankton density and biomass) and phytoplankton biomass (as chlorophyll-a) were determined on a monthly basis from March 1997 to February 1998. The results of this study indicate that both fish farm and mussel culture did not alter significantly dissolved inorganic phosphorus and chlorophyll-a values, while inorganic nitrogen concentrations were higher in mussel farm a…

SCAR-based real time PCR to identify a biocontrol strain (T1) of Trichoderma atroviride and study its population dynamics in soils.

2006

Strains of Trichoderma spp. are known for their antagonistic properties against plant pathogens, some are already on the market, others are under development. In order to launch a strain on the market its perfect identification at the species and strain levels is needed. The aim of this study is to (i) design a SCAR marker for specific identification of strain T1 of Trichoderma atroviride and (ii) monitor population dynamics of this strain in soil by real time PCR. A primer pair targeting a 141-bp fragment enabled specific detection of this strain without cross detection of autochthonous populations of Trichoderma in several field soils. In two soils, population dynamics assessed by real ti…

Population history in social spiders repeated: colony structure and lineage evolution inStegodyphus mimosarum(Eresidae)

2009

Social cooperative spiders from diverse taxonomic families share life-history and demographic traits, including highly inbred colony structure. The combination of traits suggests constrained pathways for social evolution in spiders. The genus Stegodyphus has three independently evolved social species, which can be used as replicate samples to analyse population constraints in evolutionary time. We tested colony structure and population history of the social S. mimosarum from South and East Africa using mitochondrial DNA variation, and we compared the results to published data for the independently evolved social congener S. dumicola. S. mimosarum had many and diverse haplotypes (5-7% sequen…

An analysis based on trawl-survey data of the state of the ‘Italian’ stock of Mullus barbatus in the Sicilian Channel, including management advice

1993

Abstract Data on the relative abundance of age groups obtained by statistically designed routine trawl surveys in approximately half of the Sicilian Channel were processed with commonly available microcomputer fish population dynamics packages. The species considered was Mullus barbatus , a unit stock of which had been previously identified in the study area. Analytical and management outcomes were also assessed in relative terms. Conditions and limits on both the analyses and the outcomes are discussed with reference to the particular case study.

Biological interactions in the boreal ecosystem under climate change : are the vole and predator cycles disappearing?

2014

Moment equations in a system of three interacting species subject to colored noise

2009

We study the effects of the colored noise on a Lotka-Volterra system of three interacting species, namely two preys and one predator, in a two-dimensional domain. The three species are affected by an external multiplicative time correlated noise, which accounts for environment fluctuations. Moreover, the interaction parameter between the two preys is a dichotomous stochastic process, which determines two dynamical regimes corresponding to different biological conditions. First, we study the noise effects on the three species dynamics in a single site. Afterwards, by a mean field approach we obtain, in Gaussian approximation, the moment equations for the species densities. Within this formal…