Search results for "SPECIATION"

The Impact of Humic Substances as Remediation Agents to the Speciation Forms of Metals in Soil

2013

Abstract Humic substances (HS) are the most widespread group of organic substances in natural environment and have high stability. The main terrestrial reserves are found in the form of naturally occurring ore, peat or lignite. The aim of this paper is to study possibilities to use HS as agents for remediation of contaminated with heavy metals soil and impacts of HS of metal speciation forms in it. It has been proved that HS are able to bind to metal ions and change their speciation forms in soils. The ability to form complexes with metal ions depends on the type of soil, type of metal, as well as concentrations of HS in soil. The study was carried out in experimental conditions and analyti…

Spatial and Temporal Patterns in the Evolution of the Flora of the European Alpine System

2003

This paper presents a perspective of how phylogenetic and phylogeographic hypotheses, based on nuclear DNA sequence variation (ITS) or amplified fragment length polymorphisms (AFLPs), can provide insights into the origin and evolution of the European high mountain flora. We focus on a diversity of unrelated herbaceous plant taxa that are broadly co-distributed across the European Alpine System, representing different taxonomic levels, and having either Mediterranean or Asian affinities (i.e., Anthyllis montana, Pritzelago alpina, Globularia vs. Soldanella, and Primula sect. Auricula). Our observations highlight that all taxa investigated began to diversify at the beginning of the Pleistocen…

Unravelling the modus operandi of phytosiderophores during zinc uptake in rice: the importance of geochemical gradients and accurate stability consta…

2020

Abstract Micronutrient deficiencies threaten global food production. Attempts to biofortify crops rely on a clear understanding of micronutrient uptake processes. Zinc deficiency in rice is a serious problem. One of the pathways proposed for the transfer of zinc from soils into rice plants involves deoxymugineic acid (DMA), a phytosiderophore. The idea that phytosiderophores play a wider role in nutrition of Poaceae beyond iron is well established. However, key mechanistic details of the DMA-assisted zinc uptake pathway in rice remain uncertain. In particular, questions surround the form in which zinc from DMA is taken up [i.e. as free aqueous Zn(II) or as Zn(II)–DMA complexes] and the role…

Origin of the natural variation in the storage of dietary carotenoids in freshwater amphipod crustaceans

2020

16 pages; International audience; Carotenoids are diverse lipophilic natural pigments which are stored in variable amounts by animals. Given the multiple biological functions of carotenoids, such variation may have strong implications in evolutionary biology. Crustaceans such as Gammarus amphipods store large amounts of these pigments and inter-population variation occurs. While differences in parasite selective pressure have been proposed to explain this variation, the contribution of other factors such as genetic differences in the gammarid ability to assimilate and/or store pigments, and the environmental availability of carotenoids cannot be dismissed. This study investigates the relati…

The geography of hybrid speciation in plants

2015

A molecular approach to the taxonomy and biogeography of African parrots

2000

Random amplified polymorphic DNA analysis of blood samples from eight African parrot species was performed to study the genetic relationship within the genus Poicephalus and among Poi-cephalus and the two other main African parrot genuses, Agapornis and Psittacus. To this end, DNA from six Poicephalus species, one species, of the Agapornis group and the single Psittacus species was analysed. The amplification pattern was then converted into a binary matrix and scored by the unweighted pair-group method algorithm. The resulting dendrogram showed a neat separation of all the Poicephalus on one side, from Psittacus-Agapornis on the other side. Among the six analysed species of Poicephalus, two…

Bioavailability and assessment of heavy metal pollution in sediment cores off the Mejerda River Delta (Gulf of Tunis): How useful is a multiproxy app…

2016

International audience; Three core samples were taken from zones offshore from the Mejerda River Delta (Tunisia) and analyzed formajor and trace elements to assess their relationships with organic matter, monosulfides and carbonates, aswell as for pollution and bioavailability. Chemical speciation,ΣSEM/AVS, the enrichment factor (EF) and thegeo-accumulation index (I-geo) were used. Iron, cadmium, lead and zinc – the most frequently mined metalsin the Mejerda catchment – were found as contaminants in the offshore areas. Estimations of trace elementaccumulation using the EF and the I-geo index show that lead, and to a lesser extent zinc, are the most pollutingmetals off the Mejerda outlet. Ac…

Chemical speciation of metals from marine sediments : assessment of potential pollution risk while dredging, a case study in southern Sweden

2020

Abstract Contamination associated with metals is a critical concern related to their toxicity, persistence, and bio-accumulation. Trace elements are partitioned into several chemical forms, which some are more labile during fluctuations in the environment. Studying the distribution of metals between the different chemical fractions contributes to assess their bioavailability and to identify their potential risk of contamination to surrounding environments. This study concerns the speciation of metals (Pb, Cr, Ni, Zn and Fe) from sediments coming out from Malmfjarden bay, Sweden. The aim was to assess the potential risk of metal pollution during present and future dredging as well as while u…

Establishing the relative importance of sympatric definitive hosts in the transmission of the sealworm, Pseudoterranova decipiens: a host-community a…

2001

The importance of a given host to a particular parasite can be determined according to three different criteria: host preference, host physiological suitability and host contribution to transmission. Most studies on the sealworm Pseudoterranova decipiens have focussed on the latter factor, but few attempts have been made to develop a quantitative transmission model evaluating the relative importance of each host. The purpose of this study was to propose a flow-chart model to study sealworm transmission within a seal community. The model was applied to hypothetical data of four seal species acting as definitive hosts of P. decipiens sensu stricto in eastern Canada: harp seal Phoca groenlandi…

Disparate movement behavior and feeding ecology in sympatric ecotypes of Atlantic cod

2021

Abstract Coexistence of ecotypes, genetically divergent population units, is a widespread phenomenon, potentially affecting ecosystem functioning and local food web stability. In coastal Skagerrak, Atlantic cod (Gadus morhua) occur as two such coexisting ecotypes. We applied a combination of acoustic telemetry, genotyping, and stable isotope analysis to 72 individuals to investigate movement ecology and food niche of putative local “Fjord” and putative oceanic “North Sea” ecotypes—thus named based on previous molecular studies. Genotyping and individual origin assignment suggested 41 individuals were Fjord and 31 were North Sea ecotypes. Both ecotypes were found throughout the fjord. Seven …