Search results for " Speciation"

The geography of hybrid speciation in plants

2015

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 …

Speciation studies of iron in ancient pots from Sicily (Italy)

2011

Abstract Manufacture technology involves several aspects of pottery making, such as the type and the atmosphere of firing to obtain the finished item. During the firing of clay, at different environment of the oven, different compounds of iron (Fe(II) and Fe(III)) are formed and this is the reason for a different color of the ceramic body. Despite the great interest in this field, no works are devoted to the study the speciation of iron in ancient ceramics. The proposed method, even if considered destructive by archaeologists, allows the speciation of iron, using quantity of sample in the order of milligram. In order to achieve information about their firing conditions, thirty-nine pottery …

Development of a γ-γ-perturbed angular correlation one-detector method (1-PAC) for investigation of physico-chemical properties of matter

2002

Abstract A new method of the perturbed angular γ – γ -correlation (PAC) measurements was developed using one HPGe detector only (1-PAC). For quantifying the perturbation factor, the ratio R γ 1 + γ 2 of the summing peak composed of two cascade γ -rays (the perturbation-affected parameter) to the summing peak composed of one γ -ray and one X-ray (the perturbation non-affected parameter) was used. This method was demonstrated for the radionuclides 111 In and 111m Cd, identifying the chemical status of the radionuclides in aqueous solutions.

BythinellaMoquin-Tandon, 1856 (Gastropoda: Rissooidea: Bythinellidae) in Romania: species richness in a glacial refugium

2009

Mitochondrial cytochrome oxidase I (COI) and ribosomal internal transcribed spacer 1 (ITS-1) sequences were analysed in 12 Romanian Bythinella populations. Phylogenetic relationships were inferred using maximum parsimony, maximum likelihood and Bayesian techniques. For COI, the Kimura two-parameter (K2P) distances and haplotype networks were computed. Two sympatric and four allopatric groups were distinguished. The K2P distances are similar to those for congeneric rissooids, so each of the six groups represents a species. Two are identified as Bythinella molcsanyi H. Wagner, 1941, and Bythinella dacica Grossu, 1946. The other four groups cannot be ascribed to any known Bythinella. The occur…

Metal distribution in road dust samples collected in an urban area close to a petrochemical plant at Gela, Sicily

2006

Eight samples of road dust were collected from three different localities (industrial, urban, peripheral) of the town of Gela (Italy) to characterize their chemical composition and to assess (a) the influence of the petrochemical plant and the urban traffic on the trace element content in different grain-size fractions of street dust and (b) the solid-phase speciation of the analysed metal using sequential extraction. The samples were sieved into six particle size ranges: 500–250, 250–125, 125–63, 63–40, 40–20 and <20 μm and then analysed for 15 trace elements by ICP-MS. Sequential extraction of metals was performed on each subsample. A principal component analysis was also carried out to d…

Pleistocene allopatric differentiation followed by recent range expansion explains the distribution and molecular diversity of two congeneric crustac…

2021

AbstractPleistocene glaciations had a tremendous impact on the biota across the Palaearctic, resulting in strong phylogeographic signals of range contraction and rapid postglacial recolonization of the deglaciated areas. Here, we explore the diversity patterns and history of two sibling species of passively dispersing taxa typical of temporary ponds, fairy shrimps (Anostraca). We combine mitochondrial (COI) and nuclear (ITS2 and 18S) markers to conduct a range-wide phylogeographic study including 56 populations of Branchinecta ferox and Branchinecta orientalis in the Palaearctic. Specifically, we investigate whether their largely overlapping ranges in Europe resulted from allopatric differe…