Dissertations / Theses on the topic 'Speciation'
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1
Venditti, Christopher D. "Speciation and molecular evolution." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493810.
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Speciation is fundamental to genetical evolution in being the process that separates reproductively isolated populations of genes into two or more independently replicating communities of genes. The theory of Punctuated Equilibrium and the Red Queen hypothesis are two enduring and controversial macro-evolutionary ideas proposed by palaeontologists from examination of the fossil record through time. One has implications for the nature of genetical evolution at speciation, the other for its timing.
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Branch, Simon. "Arsenic speciation in food." Thesis, University of Plymouth, 1990. http://hdl.handle.net/10026.1/2138.
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A high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) method has been developed for the separation and quantification of ~g kg-1 levels of arsenobetaine, monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA) , arsenite and arsenate. Using this coupling, arsenic species in fruit and vegetables grown on soils containing up to 1.4% w\w arsenic have been surveyed and DMAA, MMAA, arsenite and arsenate identified in the plants. Although extraction efficiencies were poor, typically 10%, total arsenic determinations demonstrated that arsenic uptake by the plants was low, with the highest arsenic level being 60-70 mg kg-1 dry weight in unpeeled potato. Provided the plants are washed thoroughly they pose no dietary risk. Using the same HPLC-ICP-MS coupling non-toxic arsenobetaine was identified as the major arsenic species in cod, dab, haddock, lemon sole, mackerel, plaice and whiting. Levels ranged between 1.0 mg kg-1 dry weight in the mackerel, to 187 mg kg-1 in the plaice. Mackerel also contained DMAA and possibly a lipid bound arsenic species. No degradation of arsenobetaine to more toxic species was observed when an enzymatic digestion procedure, based on the action of trypsin, was applied to fish except in the case of one of the plaice specimens for which DMAA was characterised in the digest at the mg kg-1 level. Ten volunteers participated in a dietary trial in which they were given set conventional meals. The main source of arsenic was fish and the predominant species was arsenobetaine. All of the arsenic, as arsenobetaine, was excreted in the urine within 72 hours of consumption. Urinary levels of MMAA, DMAA and inorganic arsenic were all below 10 µg. For total arsenic determination in the urine nitrogen introduction ICP-MS was used to overcome the polyatomic ion 40Ar 35Cl+. This method gave good agreement between observed and certified values for a range of reference materials.
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Hurford, Simon Ronald. "Speciation and trace metals." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276927.
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Chow, Stephanie S. Wold Barbara J. "Speciation in digital organisms /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-06062005-171257.
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Pennings, Pleuni. "Models of adaptation and speciation." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-66567.
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Montilla, Alfonso. "Sample treatment for arsenic speciation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0010/MQ60154.pdf.
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Jarratt, Jason Aldrin. "Validation of chemical speciation models." Thesis, Manchester Metropolitan University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263802.
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Morrison, Gregory Mark. "Metal speciation in urban runoff." Thesis, Middlesex University, 1985. http://eprints.mdx.ac.uk/6559/.
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A literature review has identified free and weakly complexed dissolved as well as solid surface associated, metal species as those forms most likely to be bio available. To analyse bio available Zn, Cd, Pb and Cu fractions in urban runoff a speciation scheme was devised which provided a relatively rapid technique for separating the dissolved and suspended solid phases of storm water into appropriate fractions. A new method, termed Dialysis with Receiving Resins, which responds to bio available metal species by incorporating a specially developed cysteine resin, within a dialysis membrane, has been devised and tested, A small scale gullypot study allowed the identification of six major processes which affect metal mobilisation and transport. The relevance of these processes is discussed with reference to gullypot outflow loadings of the different metal fractions. Acid rain mobilisation was found to greatly increase the levels of bio available free and weakly complexed metal fractions. Mass balance studies showed that Zn, Cd and Cu have a residence time in the road surface/gullypot system of little more than one storm event whereas Pb tends to be more persistent due to its predominant association with the solid phase. The speciation scheme was also applied to the analysis of metal fractions in storm water outfall samples collected from urban catchments in Sweden and the U.K. Significant concentrations and loadings of metals were found for both catchments with, on average, bio available metal forms representing 68% of the Zn, 76% of the Cd, 66% of the Pb and 32% of the Cu. Individual metal species were found to load at different rates onto metal chemographs and can be explained in terms of controlling parameters, as well as the influence of mobilisation and transport processes. Cadmium and Cu concentrations in storm water were regularly found to exceed Water Quality Standards and also to accumulate to significant levels in the Dialysis with Receiving Resins method. These metals may therefore represent a direct threat to receiving water quality.
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Dean, Laura L. "Speciation in three-spined stickleback." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52951/.
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Speciation, the division of one species into two, has provided evolutionary biologists with a rich ensemble of questions, conundrums and revelations for over a century, and yet our understanding of many of the factors affecting this complex, multidimensional process remains limited. In this thesis, I aimed to further our understanding of speciation using divergent populations of three-spined stickleback (Gasterosteus aculeatus) on the island of North Uist, Scottish Western Isles. Firstly, I explored the degree of morphological and genetic separation between three stickleback ecotypes, showing that both strongly reproductively isolated, and admixed populations exist in close proximity. I then attempted to identify the ecological and genetic origins of strongly isolated species-pairs, testing two competing explanations for their existence. I showed that a recent 'double-invasion' is unlikely, but found stark differences in the long-term genetic history between ecotypes, indicating that the evolution of species-pairs may be related to secondary contact between anciently diverged mitochondrial lineages. I then conducted mate choice trials to assess mating preferences between ecotypes, and to test for reinforcement in species-pairs. Consistent with the idea that speciation in this case is not driven purely by ecological factors, I found no evidence that reinforcement drives assortative mating in species-pairs. Rather, it appears that extant mating preferences have developed as a by-product of other adaptations. Finally, I took a brief interlude to document and investigate an exciting chance finding, internally developed embryos retained within the ovaries of a normally oviparous species, before concluding by summing up my findings, their relevance for scientific progress, and avenues opened up for further research.
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Yodle, Chan. "Iodine speciation in marine aerosol." Thesis, University of East Anglia, 2015. https://ueaeprints.uea.ac.uk/56772/.
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Iodine chemistry in the marine aerosol plays important roles in the marine boundary layer such as ozone destruction and new aerosol particle formation. Iodine has a complex chemistry in the gas and aerosol phases and to date, what controls iodine speciation, the interactions and roles of individual iodine species are not well understood. This research aims to identify key controls on iodine speciation in marine aerosol. Effects of filter types on iodine and extraction methods were tested to provide optimum conditions for extraction of iodine species. Coupling of ion chromatography and inductively coupled plasma – mass spectrometry (IC-ICP-MS) for the measurement of iodine speciation was developed to provide a reliable analytical method. These optimised methods were used to determine iodine speciation in samples collected during cruises in the Atlantic Ocean (AMT21) and the Pacific Ocean (TransBrom and SHIVA). Major ions were also determined in these samples by ion chromatography (IC) with the results providing insight into the chemical characteristics aerosol samples. A high variability of the total soluble iodine (TSI) was observed between AMT21 (12–82, median 30 pmol m-3) and TransBrom (1.6–27, median 6.9 pmol m-3) and SHIVA (5.9–15, median 8.4 pmol m-3). The proportions of iodide (I-), iodate (IO3-) and soluble organic iodine (SOI) on the three cruises also showed a high variability: AMT21: I- 5.2–39%, median 14%; IO3- 36–99%, median 66%; and SOI 13–47%, median 28%, TransBrom: I- 8.8–64%, median 46%; IO3- 1.8–65%, median 6.2%; and SOI 5.9–50%, median 39%, SHIVA: I- 22–79%, median 42%; IO3- 17–66%, median 39%; and SOI non-determinable value–41%, median 14%. Three main types of aerosol with distinctive iodine speciation were identified: polluted aerosol, clean seasalt and mineral dust. pH seems to play an important role in regulating iodine speciation. The formation of HOI and the reduction of iodate are driven by acidic conditions in polluted aerosol. In clean less acidic seasalt aerosol, a high iodine enrichment was observed (565–1675, median 725), especially in the fine mode aerosol. For mineral dust, uptake of HIO3 on calcium carbonate surfaces seems to dominate.
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Hawkes, Jeffrey Alistair. "Iron speciation in hydrothermal plumes." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/359134/.
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Irwin, Darren E. "Ring speciation in Asian warblers /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9984301.
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Sulaiman, Azli Bin. "New approaches to elemental speciation." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/25760.
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Elemental speciation has been one of the principal growth areas in analytical atomic spectrometry. This reflects the recognition that in the environmental and biological sciences, the transport, pool dynamics and toxicology of the elements are dependent on their chemical speciation. Significant progress has been made in elemental speciation by the direct coupling of separation techniques, notably the various forms of chromatography, to powerful elemental detectors such as ICP-MS. However, the strength of such hyphenated techniques, that they provide almost unambiguous identification of elemental associations, is often achieved at the expense of losing information about the ligands that are responsible for the speciation. The challenge must be to bring the two approaches to bear simultaneously so that quantitative and qualitative information on both the inorganic and organic components can be obtained simultaneously. Capillary electrophoresis (CE) has developed into one of the most powerful separation techniques offering rapid separations with high resolution. However, these advantages are offset by low sensitivity which is a consequence of the very small (nl) samples that the technique can handle. These problems can be overcome by using high sensitivity detectors and hence the interest in coupling CE to .ICP-MS. Coupling of CE to ICP-MS (CE-ICP-MS) has, therefore, the potential to provide rapid and quantitative elemental speciation information that is complementary to that provided by other techniques. This thesis describes an interface for coupling CE to ICP-MS and its applications to some common metal species. A particular interest in this work has been to investigate the potential of CE for studying metal complexes with humic and fulvic acids. A technique that offers potential for determining both free element and complexed forms, without prior separation IS electrospray/ion spray ionisation-mass spectrometry. Preliminary work is presented that investigates the applications of electrospray/ion spray ionisation-mass spectrometry to some common metal-ligand systems.
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Hinojosa, Galisteo Joan Carles 1993. "Exploring the butterfly speciation continuum : A study on butterfly speciation in the transition to genomic techniques." Doctoral thesis, Universitat Pompeu Fabra, 2021. http://hdl.handle.net/10803/672348.
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Butterflies are among the best studied animals, but despite the research efforts carried out during
centuries, our knowledge on their diversity and on the mechanisms generating it is still incomplete.
In order to understand how butterflies diversify, the speciation continuum of six study cases was
examined using morphometrics and several genetic techniques (from sequencing specific markers
to genomics). The analysis of phenotypic and genetic variation combined with gene flow evidence
allowed to identify the states of the speciation continuum, i.e. to study the relationships between
populations. This approach was used as a framework (1) to make grounded taxonomic hypotheses
and (2) to extract clues about the mechanisms that drive speciation. As a result, we described and
proposed several cases of overlooked and oversplit taxa. We documented the existence of three
types of mechanisms producing diversification in butterflies: drift, selection and hybridisation.
Selection acted through adaptation to biotic environmental factors, which caused reproductive
character displacement, host plant shift and allochrony mediated by adaptation to host plant
flowering period. Additionally, the genetic techniques employed were evaluated and their
advantages and limitations discussedLes papallones són un dels animals més ben estudiats però, malgrat els esforços dedicats a la seva recerca, el coneixement que tenim sobre la seva diversitat i sobre els mecanismes que la generen és encara incomplet. Per tal d'entendre com les papallones diversifiquen, s'ha examinat el continu de l'especiació en sis casos mitjançant l'ús de la morfometria i de diverses tècniques genètiques (des de la seqüenciació de marcadors específics fins a la genòmica). L'anàlisi de la variació fenotípica i genètica combinada amb evidències sobre el flux genètic ha permès identificar els estats del continu de l'especiació, i.e. l'estudi de les relacions entre poblacions. Aquesta aproximació s'ha usat com a marc (1) per fer hipòtesis taxonòmiques fonamentades i (2) per extreure pistes sobre els mecanismes que dirigeixen l'especiació. Com a resultat, hem descrit i proposat diversos casos de tàxons que havien passat desapercebuts o que s'havien dividit excessivament. Documentem l'existència de tres tipus de mecanismes productors de diversitat en papallones: deriva, selecció i hibridació. La selecció actuà mitjançant l'adaptació a factors ambientals biòtics, que causaren desplaçament de caràcters reproductius, canvi de planta nutrícia i a\ll ocronia produïda per l'adaptació al període de floració de la planta nutrícia. Addicionalment, les tècniques genètiques emprades són avaluades i els seus avantatges i inconvenients discutits.
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Hlinka, Vojtech. "Genetic speciation of archaeological fish bones /." St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17168.pdf.
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Smith, D. Scott. "Metal speciation determined using multiresponse fluorescence." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0030/NQ66237.pdf.
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Matni, Gisèle. "Speciation of selenium in food supplements." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40393.
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Selective isolation protocols of selenium (Se) species integrated to Se specific atomic absorption spectroscopy (AAS) detection were developed and optimized for Se speciation in food supplements, including selenized yeasts. By ultrafiltration, 69.18% of Se in the extract was found as a low molecular weight soluble form, the remaining 30.82% was bound to high molecular weight components. After a cation-exchange chromatography of the ultrafiltrate, 3.77% of the Se in the extract was found in the aqueous washings of the column indicating the presence of free inorganic anions of Se; the 65.41% of Se retained on the column corresponded to the free organic Se cations. The limit of detection for the HPLC-THG-AAS system was 1.85 ng of Se. Se was shown to be widely distributed over all the proteins with one sharp peak corresponding to the free forms of Se. Four major peaks were found at MW $>$ 250 000 Da (15.97% of Se recovered), between 102 330 and 117 490 Da (7.06%), between 48 977 and 53 703 Da (12.71%) and close to the dye migration band (17.25%).Selective isolation and HPLC-AAS protocols were also developed and optimized for the determination of free organic forms e.g. selenomethionine (SeMet), selenocystine (SeCystine) and inorganic forms of selenium in aqueous solutions, and in complex matrices such as nutritional supplements and mixtures of free amino acids. The selenoamino acid in alkaline solution was first derivatized with 1-fluoro-2,4-dinitrobenzene. After removal of excess of reagent by partitioning with diethyl ether, the N-dinitrophenyl (DNP)-derivatized selenoamino acid was acidified and extracted with diethyl ether. Inorganic Se(IV) was extracted from the acidic aqueous phases by complexation with 1,2-phenylenediamine, forming a piazselenol. Se derivatives were determined selectively by HPLC-THG-AAS. A selective chromatographic mechanism based on $ pi$-electron interactions was optimized using a silica stationary phase derivatized with p-nitrophenyl moieties. Co-injections of DNP-SeMet, DNP-SeCystine and piazselenol save retention times of 3.7, 4.0 and 4.9 min, respectively, using a methanolic mobile phase containing 1.5% triethylamine and 0.013M acetic acid. Primary analytical validation parameters including stability, linearity and limits of detection were obtained using purified DNP-SeMet, DNP-SeCystine and piazselenol standards which were characterized by $ sp1$H-, $ sp{13}$C- and $ sp{77}$Se-NMR analysis and/or fast atom bombardment MS techniques. The calibration graphs for sequential dilutions of these Se standards were linear and the limits of detection from the resultant calibration graphs were 17 ng, 0.21 ng and 18.53 ng of Se, respectively. The purified DNP-SeMet and DNP-SeCystine were found to be photosensitive. The recovery of SeMet, SeCystine and inorganic Se from the stock solutions and/or nutritional supplements was virtually quantitative. In the presence of a 500-fold excess of other amino acids, the recovery of SeMet and SeCystine (96.1 $ pm$ 3.9% and 98.08 $ pm$ 4.2%, respec
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Dundar, Mustafa Sahin. "Speciation studies on dietary trace elements." Thesis, University of Hull, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337335.
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Rosser, N. S. "Speciation and biogeography of heliconiine butterflies." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1386054/.
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In this thesis I investigate the speciation and biogeography of neotropical heliconiine butterflies (Lepidoptera: Nymphalidae: Heliconiina). In Chapter 2, I present a large database of locality records for heliconiine species and subspecies, and use these data to test evolutionary and biogeographic hypotheses for their diversification. I find evidence that geographical gradients in species richness are driven at least in part by variation in speciation and/or extinction rates, rather than via evolutionary age or niche conservatism alone. The eastern Andes are characterised by high species richness and short phylogenetic branch lengths, suggesting that new species frequently arise there. Conversely, the Amazon basin is notable for high intra-specific phenotypic diversity. In Chapter 3, I use the geographic data to estimate the frequency of sympatric speciation in heliconiines. I find that the patterns of range overlap observed in heliconiines are consistent with sympatric speciation. However, parapatric speciation followed by a tendency for daughter species to expand rapidly into one another’s ranges presents a plausible alternative explanation. I also present evidence that shifts in mimetic wing colour patterns and host plants are associated with speciation in heliconiines, suggesting that ecological adaptation may be important in triggering speciation events. In Chapter 4, I test the prediction that hybrid zones between Andean and Amazonian races of Heliconius should be moving towards the Andes. I find the position of the hybrid zones to be unchanged from 1986 – 2011, and located on a band of peak rainfall at the edge of the Andes. This suggests that rainfall peaks act as "sinks" for dispersal in butterflies and stabilise the hybrid zones on this low fitness region. The results oppose the Pleistocene Refugium theory, which predicts that centres of ranges, rather than contact zones at the edges, should be centred on current rainfall peaks.
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McKenzie, Andy. "Stochastic speciation models for evolutionary trees." Thesis, University of Canterbury. Mathematics and Statistics, 2000. http://hdl.handle.net/10092/5597.
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Phylogenetic trees are widely used in biology to represent evolutionary relationships between species. As the details of the evolutionary process are mostly unknown, modelling work on the shapes of these trees has had to incorporate a random component. Two null models introduced for this purpose are the uniform model and the Yule model. A third model, the comb model, is useful for giving bounds on theoretical results. We investigate some mathematical properties of these three models.
Let the distance between two nodes be the number of edges separating them. We find exact formulae for the mean distance of a randomly chosen leaf from the root, and for the mean distance between two randomly chosen leaves of a rooted tree. In addition, for the Yule model we find the probability distribution for the distance of randomly chosen leaf from the root.
A cherry is a pair of leaves which are adjacent to a common node. By realising the process of cherry formation by extended Polya urn models we show that the number of cherries is asymptotically normal. This allows us to develop simple statistical tests for the Yule and uniform null hypotheses for the growth of rooted trees. A triplet is a cherry and a pendant edge that are adjacent to a common node. We also show that the asymptotic distribution of triplets is normal for the Yule model, and put forward a conjecture for the distribution under the uniform model.
The construction of an evolutionary tree is generally a two stage process: an unrooted tree is constructed, then it is rooted. We investigate a method for rooting a tree based on the shape of the tree and the Yule model for the growth of rooted trees. We show that even for trees with large number of leaves the approximate location of the root can be located with high probability.
Let S be a set of two rooted binary trees for which the leaf sets L1, L2 form a partition of the set {l, 2, ... ,n}. We derive a recursion for the number of trees on n leaves that are compatible with the set S. We extend this recursion for a set S of three trees, but show that the numbers of terms required in the recursion grows at least exponentially with the number of trees in the set S.
Let S be a set of rooted binary trees. A tree which is a sub-tree of each of the trees in the set is called an agreement sub-tree, and such a tree with the maximum number of possible leaves is called a maximum agreement sub-tree (MAST). We derive an upper bound for the probability that two randomly generated trees have a MAST with number of leaves greater than or equal to a given value s. We find the form the upper bound takes when the trees are generated according to the uniform and Yule models.
The entropy of a probability distribution is equal to the mean information, where the information of an event E is - log P (E). We derive exact and asymptotic formulae for the entropy of the comb, uniform and Yule probability distributions. We show that the comb, uniform, and Yule models satisfy a property called group elimination. A special case of the property of group elimination is sampling consistency.
We show that for any probability distribution on trees that satisfies sampling consistency there is an upper bound on the probability of the fully symmetric tree shapes.
We introduce a modification of the Yule model in which the speciation rate is a function of the time since the last speciation event of a lineage. Using analytical methods we investigate the probability (conditional and unconditional) of the symmetric tree on four leaves under this modified model. If the speciation rate is constant then the probability of the symmetric tree is the same as in the Yule model. Making the speciation rate zero for a period after a speciation event, then constant afterwards, is found to make the symmetric tree more probable. If the speciation rate is constant for some period after a speciation event, then subsequently zero, the symmetric tree is found to be less probable.
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Simpson, Stuart L. "Speciation of aluminium in environmental systems." Thesis, University of Canterbury. Chemistry, 1996. http://hdl.handle.net/10092/6704.
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This thesis is directed towards the development of a speciation protocol for Al in natural waters and soil solutions. Factors that might influence the accuracy of the speciation results are investigated.
The equilibrium reactions between aluminium(III) and (i) pyrocatechol violet (PCV) and (ii) 4-nitrocatechol have been studied by potentiometric titration in aqueous solution, I=0.10 M K(CI), 25.0 dc. The adsorption behaviour of pyrocatechol violet on the surface of the aluminium-oxide hydroxide boehmite [α- AlO(OH)] has been investigated. In this work, the experimental data for surface complexation were evaluated on the basis of the electrostatic constant capacitance model. The acidity constants of the surface hydroxy groups at the boehmite-solution interface were evaluated as a prerequisite to studying the ligand adsorption behaviour. This work and the equilibrium reactions between aluminium(III) and pyrocatechol violet (PCV) were performed at Umea University, Sweden.
A comparison of the chromophores chrome azurol S (CAS), eriochrome cyanine R (ECR) and pyrocatechol violet (PC V) for the determination of Al was made. These studies were performed using computer modelling calculations. The pH and mass action effects were calculated for the representative 'interferents' citrate, oxalate, salicylate and fluoride. The effects of complexation kinetics on the use of PCV for the determination of 'labile' Al in the competitive systems: 'PCV- Al ³+-citrate 1 and 'PCV-Al³+-oxalate' was investigated. These studies also validated the 'H+ -Al ³+ -pyrocatechol violet' equilibrium data for typical analytical conditions.
A preliminary survey was made of the electrochemical properties of a series of Al ³+-ligand systems using cyclic voltammetry. This was to identify redox-active ligands which may be used as electrochemical probes for Al. Flow injection analysis (FIA) methods for the determination of Al which exploit the indirect electrochemical detection of AI using the ligands pyrocatechol violet and tetrahydroxy-l,4-quinone were investigated.
The development of an Al ³+ speciation procedure is described. It is based on a 2-s reaction with oxine-derivatised Fractogel positioned in a 22 μL column reactor in an FIA manifold. A1³+ (pre )concentrated on the column from a 650 J.LL sample was selectively eluted (via the rapid quantitative conversion of resin-bound Al ³+ to the Al (OH)4- ion) with 150-250 μL of 0.02 mol L-1 NaOH and detected spectrophotometric ally as the Al -CAS (chrome azurol S) complex at pH 5.0.
The resultant FIA method was tested for (i) the selective separation of reactive Al from Fe, (ii) the sequestering of Al from its citrate, oxalate, malonate and fluoride complexes and (iii) retention of Al -hydroxy polymers [e.g. Al13(OH)327+] by the adsorbent. The method was applied to humic waters and soil solutions and the results for 'free' Al ³+ were compared with those obtained by the previously published 7-s CAS method. The method's detection limit and linear working range were evaluated. The potential for further development of this Al speciation technique is discussed.
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Hilscher, Rainer. "Agent based models of competitive speciation." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413887.
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Findlow, James Andrew. "Chemical speciation of aluminium in milk." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329705.
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Bull, Vanessa Jane. "Genealogy and speciation in Heliconius butterflies." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408421.
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Achterberg, Eric Pieter. "Trace metal speciation in natural waters." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359194.
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Hayward, John. "Models of speciation by sexual selection." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364220.
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Aborode, Fatai Adigun. "Selenium and arsenic speciation in plants." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201647.
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Selenium and arsenic are important metalloids in the food chain from nutritional and toxicological point of view. These two metalloids are potentially enriched through geogenic processes and anthropogenic activities and they could sometimes co-exist in nature and become available to plants thereby entering the food chain. While selenium is known as an essential element to humans, it could also be toxic. Arsenic on the other hand is a potentially toxic element posing serious health risks to livestock and humans. They have been found to neutralise each other’s effects in animals but their interactions in plants are not well understood. Speciation analysis, which is a set of activities leading to identification and quantification of different forms or species of elements present in an entity, is required for a holistic understanding of the mechanisms and interactions involved in the plants’ metabolism of contaminants and essential elements. Many techniques are currently being used for speciation of selenium and arsenic in plants and they sometimes give contradictory outcomes. The hyphenation of HPLC with MS and synchrotron techniques are the two most commonly used state of the art techniques for speciation of these metalloids. This research therefore sought to access, explore and/ or develop analytical methods appropriate for the speciation of selenium and arsenic in plants. Many selenium and arsenic species have been identified and reported in the literature using well established procedures. The presence of elemental selenium in plants has also been widely reported in plants but to our knowledge this presence has never been experimentally proven and fully quantified. Because this species is non toxic, its proven occurrence in plants will represent a potential detoxification mechanism. Therefore in this study, a method was specifically developed for identification and quantification of elemental selenium. In order to investigate the occurrence of elemental selenium in plants, the newly developed method was applied using Thunbergia alata as a model plant. Arsenic is known to activate the synthesis of PC using glutathione and the complexation of the activating arsenic ions with the synthesised PCs is a well established detoxification mechanism for arsenic. However, very little is known about the role of glutathione and PCs in selenium detoxification. In order to be able to gain better insight into the interaction between selenium and arsenic in plants, the role of glutathione and PCs in selenium metabolism was investigated using Arabidopsis thaliana as a model plant. Sensitivity tests and speciation analysis were carried out on Arabidopsis thaliana WT and the mutants’ one of which is deficient in GSH synthesis and the other deficient in PC synthesis using selenite and arsenate as toxicants. The study revealed that selenium induces the synthesis of glutathione but rather use it as reductant and precursor for transformation and incorporation into peptides and neither GSH nor PCs play any role in selenium detoxification. It was also observed that when selenium and arsenic co-exist there could be competition for PCs between the ions of the metalloids with potentials for increasing arsenic toxicity. Human exposure to inorganic arsenic, a group 1 carcinogen, through Oryza sativa (rice), the staple food for about half the population of the world, has raised serious concerns. Most worrisome are the findings that rice grown in arsenic contaminated areas is characterised by reduced essential amino acids and micronutrients including selenium. A study was therefore conducted to to investigate and understand the interactions between selenium and arsenic in rice. The study confirmed that arsenic could limit the amount of selenium that is taken and translocated to the grains. Selenium was also found to reduce the toxicity of arsenic and most importantly, the study showed that at an appropriate selenium concentration, arsenic uptake and translocation can be reduced.
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Lum, Tsz Shan. "Elemental imaging and speciation for bioanalysis." HKBU Institutional Repository, 2016. https://repository.hkbu.edu.hk/etd_oa/328.
Full textAbstract:
Elemental detection is an emerging area in bioanalysis. Thanks to the rapid advancement in instrumentation such as inductively coupled plasma-mass spectrometry (ICP-MS), low detection limit and quick analysis can be achieved. Besides, ICP-MS also suffers less matrix effect as compared to molecular mass spectrometry, so a precise and accurate detection of toxic or essential elements can be provided. Different types of sample introduction or separation systems such as laser ablation (LA) and liquid chromatograph (LC) are excellent hyphenation options for the elemental detection apart from the total analysis of standalone ICP-MS analysis. Spatial analysis and speciation of the two mentioned techniques provide additional merits to the elemental detection in bioanalysis.;LA-ICP-MS makes use of a laser to ablate the solid sample, and the generated sample aerosol is then transferred to ICP-MS for detection. It can be used for bioimaging. There are examples of LA mapping of biological tissues to reveal the spatial distribution of metal, to study the neurodegenerated disease in brain or the accumulation in metallodrug in tumor mass. In order to incorporate the imaging tool in drug development, in the first part of this thesis, LA-ICP-MS bioimaging of liver and kidney was performed to compare the differential spatial distribution of two structurally different platinum-based anti-cancer drug candidates. It was expected that this approach can assist the chemical modification in drug development.;To put this idea a step further, the spatial analysis tool was tested for its potential in therapeutic drug monitoring. Hair profiling in whiskers of mice treated with vanadium anti-diabetic complex or gadolinium-based contrasting agents at different dosage levels were conducted. Results shown that different deposition behaviors and accumulation/elimination profile can be observed, demonstrating a great potential in routine clinical application.;On the other hand, LC-ICP-MS offers the possibility for speciation study. Several accessories for organic solvent introduction in ICP-MS make the coupling of reverse phase chromatography using high percentage of organic solvent in the mobile phase more convenient. To demonstrate the advantage of this configuration, a speciation of bromine-containing drug in mice urine and plasma was included in the last part of this project for metabolite profiling study.;In Short, this work presents several useful hyphenated techniques of ICP-MS in bioanalysis, proving the tremendous potential of elemental detection in drug development (assisting molecular modification in drug design and metabolite profiling) and therapeutic drug monitoring (hair profiling)
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Derbyshire, Michelle. "Speciation of chromium in environmental matrices." Thesis, Sheffield Hallam University, 2001. http://shura.shu.ac.uk/19556/.
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Published methods for single and sequential extraction, separation and determination of chromium(III) and (VI) in sewage sludge, soil and dried plant material were critically evaluated. The results obtained illustrate the difficulties of speciation analysis in such complex matrices. A method based on single extraction with 0.43 mol L[-1] acetic acid followed by on-line ion chromatography with chemiluminescence detection was found to be simple, sensitive, free of interferences, and more importantly the integrity of the chromium species was maintained. Instrumental parameters affecting the sensitivity of the chemiluminscence signals were optimised using a multivariate optimisation approach. A linear calibration was obtained from 0.01 to 50 mug L[-1]. Limits of detection were found to be 0.002 mug L[-1] for both Cr(III) and Cr(VI). Limits of determination were found to be 0.02 mug L[-1] for both Cr(III) and Cr(VI). The precision, determined using a 10 mug L[-1] solution of Cr(III) and Cr(VI) was 10.6 +/- 0.52mug L[-1] (4.9%) for Cr(III) and 10.1 +/- 0.50 mug L[-1] (4.9%) for Cr(VI) (n=6). Validation of the method was carried out using two water reference materials certified for total chromium content; LGC CRM 6010 49 mug L[-1] +/- 4 mug L[-1] and NIST SRM 1643d 18.53 mug L[-1] +/- 0.20 mug L[-1]. Results obtained showed good agreement with the certified values; 49.21 mug L[-1] +/- 1.81 mug L[-1] and 19.03 mug L[-1] +/- 1.50 mug L[-1] respectively. The developed method was used to study the distribution of Cr(III) and Cr(VI) species in soils. The species extraction procedure was validated using a certified reference material (CRM): BCR CRM 483. The changes in the distribution of both species in soil that had been through similar pre-treatment steps as in the production of reference materials were studied. This investigation showed that contamination or chemical oxidation could alter the chromium species present within a natural sample during production steps such as milling, homogenisation and sieving. As a result the metal speciation in the product is different from that in the starting material. In order to limit the effect of oxidation jet rather than ball milling is recommended.
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Shaw, Philip Neil. "Studies on cobalt speciation in groundwaters." Thesis, Loughborough University, 1990. https://dspace.lboro.ac.uk/2134/32076.
Full textAbstract:
The use of Sephadex G-10 gel chromatography with a groundwater mobile-phase to separate bound and free cobalt in concentrated groundwater samples has proven to be a relatively non-invasive technique for the investigation of groundwater chemistry. Trace amounts of cobalt as would be expected to be released from a radioactive waste repository do exhibit association with groundwater species from a test site near the Drigg low-level nuclear waste site in Cumbria.
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Kim, Dae Ji. "Tritium speciation in nuclear decommissioning materials." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72145/.
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Tritium is a by-product of civil nuclear reactors, military nuclear applications, fusion programmes and radiopharmaceutical production. It commonly occurs, though not exclusively, as tritiated water (HTO) or organically-bound tritium (OBT) in the environment but may exist as other forms in nuclear-related construction and fabrication materials. During the lifetime of nuclear sites (especially those involving heavy water) tritium becomes variably incorporated into the fabric of the buildings. When nuclear decommissioning works and environmental assessments are undertaken it is necessary to accurately evaluate tritium activities in a wide range of materials prior to any waste sentencing. Of the various materials comprising UK radioactive wastes, concrete and metal account for approximately 20% of the total weight of low level waste (LLW) and 12% and 35% of the total weight of intermediate level waste (ILW). Proper sampling and storage of samples are significant factors in achieving accurate tritium activities. The degree of loss of 3H and cross-contamination can be significantly reduced by storing samples in an air/water tight container in a freezer (-18°C). The potential for tritium contamination is dependent on the 3H form. Most 3H loss originates from tritiated water which is easily exchanged with atmospheric hydrogen in the form of water vapour at room temperature. However, the loss of more strongly bound 3H, produced in-situ in materials by neutron activation, is not significant even at room temperature. Such tritium is tightly retained in materials and does not readily exchange with water or diffuse. In nuclear reactor environments tritium may be produced via several neutron-induced reactions, 2H(n,g)3H, 6Li(n,a)3H, 10B(n,2a)3H and ternary fission (fission yield <0.01%). It may also exist as tritiated water (HTO) that is able to migrate readily and can adsorb onto various construction materials such as structural concrete. In such locations it exists as a weakly-bound form that can be lost at ambient temperatures. Bioshield concretes present a special case and systematic analysis of a sequence of sub-samples taken from a bioshield core (from UKAEA Winfrith) has identified a strongly-bound form of 3H in addition to the weakly bound form. The strongly bound 3H in concrete is held more strongly in mineral lattices and requires a temperature of >850°C to achieve quantitative recovery. This more strongly retained tritium originates from neutron capture of trace lithium (6Li and potentially 10B) distributed throughout minerals in the concrete. The highest proportion of strongly bound 3H was observed in the core sections closest to the core. Weakly bound tritium is associated with water loss from hydrated mineral components. Tritium is retained in metals by absorption by free water, hydrated surface oxidation layer, H ingress into bulk metal and also as lattice-bound tritium produced via in-situ neutron activation. Away from the possible influence of neutrons, the main 3H contamination to metals arises from absorption and diffusion via atmospheric exposure to the HTO. Here contamination is mainly confined to the metal surface layer. The tritium penetration rate into metal surfaces is controlled by the metal type and its surface condition. Where metals are exposed to a significant neutron flux and contain 6Li, 7Li and 10B then in situ 3H production will occur which may propagate beyond the surface layer. In such cases tritium may exist in two forms namely a weakly bound HTO form and a non-HTO strongly bound form. The HTO form is readily lost at moderate temperatures (~120°C) whereas the non-HTO requires up to 850°C for complete extraction.
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Tabatchnick, Melissa Danielle. "Mercury Speciation in Temperate Tree Foliage." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1284516685.
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Papadopulos, Alexander Savas Thomas. "Plant speciation on Lord Howe Island." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7069.
Full textAbstract:
Lord Howe Island (LHI) is an ideal location for researching the speciation process. The diversity of unique species, its isolation and minute size offer a rare opportunity to investigate the contribution that speciation has made to the entire flora of an ecosystem. On LHI, speciation in sympatry has been documented previously in Howea palms and this project sought to investigate whether this divergence was an exceptional occurrence or if the process is more general. A phylogenetic approach was used to acquire the first estimates of the frequency of sympatric speciation and speciation with gene flow in a community of island plants. The results indicate that speciation with gene flow may be relatively common on LHI. Biogeographic patterns show that Australia is a major source of species for LHI and that, for a given region, the number of immigrants that can establish and speciate is dependent on dispersal limitation and niche conservatism. Speciation events in two genera (Metrosideros and Coprosma) were examined in greater detail to determine whether ecological divergent selection may have promoted the evolution of reproductive isolation. In both cases, evidence is presented demonstrating that natural selection, habitat isolation and competitive exclusion may have played vital roles in these speciation events. Closer examination of speciation in Coprosma revealed that six species have evolved following a single colonisation of LHI, the first documented evidence for a sympatric radiation in plants. Four of these species have evolved via speciation with gene flow and two species are derived from hybrid speciation events; supporting theories that speciation with gene flow and hybrid speciation may be integral to the onset of an adaptive radiation. Together with speciation in Howea, these new cases show that ecologically driven speciation with gene flow is an important source of biodiversity on LHI and potentially in other botanical communities.
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Fitzpatrick, Benjamin Minault. "Speciation and barriers to gene flow /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Ebuele, Victor Pghogho. "Phosphorus speciation in soil and plants." Thesis, Bangor University, 2016. https://research.bangor.ac.uk/portal/en/theses/phosphorus-speciation-in-soil-and-plants(c9a2b08e-cca7-48ad-ac49-79b772d17602).html.
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To better understand the dynamics of P in soil and plants, chemical characterization and solution 31P nuclear magnetic resonance spectroscopy (NMR) were applied to a natural vegetation system dominated by bracken (Pteridium aquilinum (L.) Kuhn) and British bluebells (Hyacinthoides non-scripta (L.) Chouard ex Rothm.) and to different types of organically amended agricultural soils. Organic P (Po) was dominant in the natural system while the agricultural soil of the total P more than 80% was inorganic P (Pi) mainly in the form of orthophosphate. A detailed quantitative analysis of the P forms in three fields assigned codes (FWa, FWo and FWp) with contrasting coverage of bracken and bluebell, their original native vegetation was undertaken in 2013. Soils were collected in areas dominated by both plants, from April to September 2013 weeks (W1 – W20) in order to cover the main above-ground lifecycle stages. Chemical characterization of the soils showed differences in total P, total Po and plant available P (Mehlich-3 extraction). The total P content of the soils from the three fields showed a slight non-significant increase after bluebell flowering. Quantitative assessment using 31P NMR showed differences in the nature of P forms in the soil and this was reflected in the nature of the vegetation cover, and extent of plant litter deposition. The most dominant P form found in the NaOH-EDTA soil extracts of FWa and FWo were the organic P forms (68.1 – 84.3 %), (61.3 – 79.1 %) respectively, most especially orthophosphate monoesters (53.1 – 83.8 %), (50.3 – 79.4 %), mainly as myo-inositol hexakisphosphate (myo-IP6) or phytate, while the inorganic P form (32.8 – 58 %) was the most dominant on FWp mainly as orthophosphate (ortho-P) (30.7- 56.8 %). The increased myo-IP6 concentration in the soil was linked to the shedded old bluebell bulb below ground containing up to 40 % myo-IP6. Bluebell seeds, another potential route of P transfer into soil, also contained 60 % myo-IP6 of total P. 31P nuclear magnetic resonance (NMR) spectroscopy was also used in elucidating the speciation and distribution of P species in diverse plant seeds (cumin, fennel, flax, mustard, poppy and sesame seeds). Phosphorus speciation by 31P NMR showed that P was mainly present in organic forms such as phytate and α- and β-glycerophosphate in poppy, sesame, mustard, fennel and cumin seeds. The inorganic P forms detected included orthophosphate and pyrophosphate. In particular, the highest amount of orthophosphate was found in NaOH-EDTA extracts of fennel seeds (41.7 %) and the lowest in mustard seeds (9.3 %) and sesame seeds (6.9 %). For the organic P forms, the highest concentration of phytate was found in mustard xiv seeds (85.2 %) and the lowest in fennel seeds (43.3 %). This result implied that in most seed producing plants P, transferred from the plants vegetative parts to the developing seeds during seed maturation, is converted to phytate (organic P) in addition to being stored as orthophosphate (inorganic P). Phenologically either bracken or bluebells grow actively throughout the year. In a semi-natural ecosystem, competition between bluebell and bracken is highest on bracken crozier emergence, which dense bluebell coverage seem to delay. P speciation was identified as an underpinning driver: For bracken, P was present mainly in form of soluble inorganic orthophosphate (41- 96.1 %), while glycerophosphates were the main Po (2.4 – 58.9 %) detected in rhizome, pinnae or stipe. Contrarily bluebell bulbs contained mostly myo-IP6 (6.7 – 52.3 %) possibly aiding survival at low temperatures, because of bluebell’s active growth starting in early autumn. Within the whole plant, the bulb acts as a source and primary sink of P, mainly as myo-IP6. This might be a survival mechanism against P supply interruption during bluebell’s growth cycle while at the same time making P less available for others. The relatively higher total P content of bluebell bulbs (0.67 – 2.7 g kg-1) compared to bracken rhizomes (0.43 – 1.30 g kg-1) also supports this. Bracken’s competitive advantage relies on its dominance of the extensive rhizome system, for which this study showed its ability to redistribute nutrients. Specifically, there was very little differences in the P species between plant parts; instead orthophosphate was shuttled from rhizome to pinnae and returned. The effect of a variety of organic fertilizers additions (pig or cow slurry, farm yard manures, broiler litter, compost and paper sludge/waste) from 1990 to 2014 on the distribution and accumulation of soil Pi and Po forms in three different soil types Harper Adams (HAU, sandy loam), Terrington (TER, silty clay loam) and Gleadthorpe (GT, loamy sand) was investigated. A sequential fractionation scheme and 31P NMR of NaOH-EDTA soil extracts was used to speciate P. Total P concentration in all soils ranged from 0.76 g kg-1 – 1.49 g kg-1 and was predominantly inorganic P (51.2 – 90.8 %). The differences in pH suggests that P species in HAU and GT (pH 6.5) would likely be bound to Al/Fe oxides and hydroxides. At more alkaline pH for TER (pH 7.9) mainly Ca-P minerals would occur. Phosphorus speciation analysis supported this with orthophosphate (82.9 –95.5 %) as the most dominant P form detected. This high inorganic to organic P ratio in conjunction with a low C/P ratio (< 200) suggested that mineralization of organic P mainly occurred in these soils. Myo-IP6 was the most dominant organic P form (1.6 – 8.9 %) followed by scyllo-IP6 (0.7– 4.6 %). Orthophosphate diesters were detected in only one sample (GT) but in trace amounts (0 – 0.5 %). Polyphosphate and xv phosphonates were not detected in any sample. The similar composition of P species across the various treatments suggests that the additions of different manures to the soil only lead to an increase in inorganic P species mainly ortho-P, likely caused by the rapid mineralization of organic P forms in the manure-treated soils. The result also suggested that the abundance and accumulation (Legacy P) of the various P forms, as determined by sequential extraction, were dependent on the nature of manure treatment, soil type and pH of the soils.
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Hilgenböcker, Kirsten. "Wolbachia's role in classical speciation theory." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2009. http://dx.doi.org/10.18452/16020.
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Wolbachien sind intrazeklluläre Bakterien die zahlreiche Arthropodenarten infizieren. Sie induzieren häufig eine zytoplasmatische Paarungsinkompatibilität die postzygotische Isolation zwischen unterschiedlich infizierten Individuen der gleichen Wirtsart verursacht, weswegen Wolbachien Beachtung als mögliche Katalysatoren von Artbildungsprozessen gefunden haben. Vorherige Arbeiten zur Artbildung untersuchten meist entweder Wolbachia-induzierte oder die klassischen, genetischen postzygotischen Isolationsmechanismen. Normalerweise sollte es aber der Fall sein dass beide Mechanism gleichzeitig auftreten. In dieser Arbeit führen wir Untersuchungen zur Rolle der Wolbachien in der Artbildung fort indem wir die Interaktionen von Wolbachia-induzierten und genetischen Inkompatibilitäten analysieren. Wir werden zeigen dass Wolbachien einen starken Einfluss auf genetisch-basierte Artbildungsprozesse haben. Insbesondere können sich die Mechanism bei gleichzeitigem Auftreten katalysieren. Außerdem werden wir zeigen dass Wolbachia Artbildungsprozesse unter allgemeineren Bedingungen beeinflussen kann als vorherige Studien suggerierten. Da die Rolle der Wolbachien in der Artbildung stark von deren Verbreitung abhängt, werden wir desweiteren eine statistische Metaanalyse von bestehenden Daten zu Infektionsfrequenzen präsentieren. Aufgrund der Methoden der Datenerhebung ist es sehr wahrscheinlich, dass der wirkliche Anteil der infizierten Arten mit 20% deutlich unterschätzt wird. Unsere Analyse bestätigt dies und zeigt dass viel wahrscheinlicher circa zwei Drittel aller Arten infiziert sind. Unsere Resultate der klassischen Artbildungstheorie kombiniert mit denen der statistischen Analyse zu Infektionsfrequenzen von Wolbachia implizieren dass Wolbachien als allgemeine Faktoren in der Evolution von Arthropoden anzusehen sind.Wolbachia are intracellular bacteria that commonly infect arthropod species. Since they often induce a cytoplasmic mating incompatibility (CI) in their hosts that acts as a postzygotic isolating mechanism between differently infected individuals of one species, Wolbachia have received attention as a potential promoter of arthropod speciation processes. Previous studies on speciation focused on either Wolbachia-induced or the classical nuclear-based postzygotic isolating mechanism. However, it should usually be the case that both co-occur. This thesis continues investigations on Wolbachia''s role in speciation by analyzing interactions of Wolbachia-induced CI and nuclear incompatibility (NI) caused by genetic differentiation. We will show that Wolbachia have strong impact on nuclear-based speciation processes. In particular, synergy effects can occur when both isolating mechanisms act simultaneously. Furthermore, we show that Wolbachia can influence speciation processes under more general conditions than previous studies on Wolbachia''s role in speciation suggested. Since the actual role of Wolbachia in arthropod speciation will strongly depend on their abundance, we present a statistical meta-analysis of published data on Wolbachia infection frequencies. Due to the sampling methods applied in studies on Wolbachia infection frequencies, it is likely that current estimates of 20% infected species are underestimates. This is supported by our analysis and we show that more likely about two-thirds of species are infected. Combining both results, this thesis provides strong evidence for Wolbachia being a very general factor in arthropod speciation processes.
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Georgiadis, Myron. "Arsenic Speciation in Soils and Sediments." FIU Digital Commons, 2004. https://digitalcommons.fiu.edu/etd/3579.
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Arsenic speciation in soils and sediments pose a great challenge due to possible conversion and/or re-adsorption. Since arsenic toxicity is dependent on its chemical species, the purpose of this research is to study the extraction process, determine what factors control species change, and develop an extraction method which preserves the arsenic species during extraction for proper quantitation. After investigating the addition of reagents such as hydroxylamine and ethylenediamine-tetraacetic acid (EDTA) without significant improvement, a method was established for the extraction of mobile or mobilizable arsenic species using phosphate and sodium diethyldithiocarbamate (NaDDC) which prevented conversion and re-adsorption. This method was applied on soils and sediments used in the construction of golf courses as well as South Florida native soil of marl type. Using an extrapolation approach, a method was also developed to estimate mobilizable arsenic species to compare and validate the method above giving similar results.
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Peñalba, Joshua Villapa. "Speciation Genomics in Australian Meliphagoid Birds." Phd thesis, Canberra, ACT : The Australian National University, 2017. http://hdl.handle.net/1885/141395.
Full textAbstract:
The speciation process proceeds through a continuum of increasing
genomic divergence and decreasing gene flow between populations.
While sampling across hybrid zones provide insight for an
intermediate stage of speciation, comparative studies of multiple
contact zones between populations at different stages of
speciation would expand our broader understanding of the process
itself. Suture zones provide this ideal framework in a shared
geographic context. For my thesis, I developed and utilized a
suture zone system situated in northeastern Australia. From the
array of contact zones in the region, I focused on species within
the species-rich bird superfamily Meliphagoidea comprising the
honeyeaters, fairywrens, gerygones, and allies. Using a
comparative genomics approach, I tested hypotheses on how genome
divergence and gene flow changes as populations diverge and
proceed through the speciation process.
The first chapter sets the stage for analyzing this new system. I
characterized variation in genetic and morphological divergence
across 27 meliphagoid species through three transition zones that
comprise the system. Among factors that may predict genetic
divergence, I found that taxonomic ranking outperforms
morphological divergence and habitat preference. Establishing
variation in divergence laid out a starting point for comparative
study of gene flow, divergence, and speciation.
The second chapter determines how well current geography predicts
probability of gene flow during population divergence and
speciation. From the initial set of species, I selected eight
that are codistributed in four regions divided by known
biogeographical barriers in northern Australia and Papua New
Guinea. I found that historical connectivity between populations
is a better predictor for likelihood of gene flow compared to
current designations of allopatry or parapatry. Furthermore, this
likelihood of gene flow decreases in a rapid, snowballing manner
with increasing divergence in these populations.
The third chapter characterizes how the geographic extent of gene
flow changes with increasing divergence. From the initial set of
species, I selected those involved in ten contact zones between
parental population pairs in which divergence levels span the
speciation continuum. I found that the cline widths across the
contact zones decrease exponentially with increasing divergence
of the parental populations. Furthermore, this width is
correlated with the geographic range width in the contact zone,
emphasizing the role of geographic range during speciation.
The fourth and final chapter addresses the role of chromosomal
rearrangements in speciation by characterizing inversions across
the avian tree. Using a hybrid approach and a genetic linkage
map, I sequenced and assembled a chromosome-scale reference
genome for the superb fairywren (Malurus cyaneus) which fills a
phylogenetic gap in existing avian genome assemblies. By
comparing this assembly to other existing assemblies, I found
novel fusions in the superb fairywren, confirmed the variation in
inversions between autosomes and the Z chromosome, and revealed
that inversions are much more prevalent in oscines than their
nonpasserine counterparts.
In this thesis, I developed and utilized a new system to take a
comparative approach in speciation genomics. The conclusions
emphasize the role of the context of geography and genome
architecture on the rapid decrease of gene flow and accumulation
of divergence during the speciation process.
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Hatchett, William. "The road toward sympatric speciation in whitefish. : The effects of divergent selection on European whitefish (Coregonus lavaretus) size and behavior, and effects on zooplankton communities." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-110741.
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For almost every organism there are large gaps in our knowledge about the processes that leads to speciation. The changes an organism undergoes before divergence has occurred have remained a mystery, as it is difficult to say whether or not a species is going to diverge and when. To investigate this unknown the European whitefish (Coregonus lavaretus) and the northern pike (Esox lucius) were studied, as they produce a repeatable and predictable pattern of speciation in sympatry. To investigate the changes in phenotypes and behaviour in whitefish that precedes divergence, two lake populations were examined, Gräsvattnet and Ringsjön. Gräsvattnet was used as a control, with a population of whitefish but an absence of pike, whereas Ringsjön has a population of whitefish that invaded from Gräsvattnet and a pike population. The presence of pike presumably exerts divergent selection on the whitefish population. Fish and zooplankton were surveyed in both lakes from 1970 to the present day, which allows us to compare how whitefish populations and their resources change in the presence and absence of pike. The results found in Ringsjön show; (1) a change in habitat use, (2) a change in diet from pelagic to benthic, (3) an increase in the relationship between individual body size and diet and (4) a decrease in average size over the course of the study. (1)The presence of pike is believed to have forced the whitefish into the pelagic which could be seen in the result, with an increase in individuals caught in the pelagic. (2) The change in diet is thought to be caused by a resource competition created by individuals being forced to use the pelagic. Although insignificant this led to an overall reduction in zooplankton abundance by almost 40% which could have intensified competition. The resource competition could then have been intensified further by the change in composition of zooplankton relative abundance. (3) The increase in relationship between individual body size and diet is thought to increase due to the resource competition between smaller and larger individuals in the pelagic. Smaller individuals are better competitors than larger individuals for pelagic resource which could have led to the larger individuals switching to a more benthic diet. (4) The decrease in average size is thought to be caused by negative selection for larger individuals. Larger individuals have switched to a more benthic diet, and although the individuals are larger they still face the risk of predation in the littoral zone as they have not outgrown the gape size of the pike. This could have led to the average size reduction that may be the first steps in speciation, and ultimately leading to the divergence of two morphs by sympatric speciation in Ringsjön. In Gräsvattnet over the course of the study there were few and small changes in whitefish size, zooplankton relative abundance in the diet and in the environment. The results in Gräsvattnet could however suggest resource competition for benthic resources. Although resource competition is thought to be an important factor in the speciation of whitefish, without predation pressure no speciation occurs. This result could suggest the importance of predation pressure in the speciation of whitefish.
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Parler, Nichole Erin. "Mercury concentration and speciation in coastal rainwater /." Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/parlern/nicholeparler.html.
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Ozato, Kenjiro. "Mutagenesis, speciation, and genome analysis in medaka." Laboratory of Freshwater Fish Stocks Bioscience Center Nagoya University, 1994. http://hdl.handle.net/2237/13793.
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Hasegawa, Hiroshi. "Seasonal Changes in Arsenic Speciation in Hydrosphere." 京都大学 (Kyoto University), 1997. http://hdl.handle.net/2433/202482.
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Edwards, Danielle L. "Biogeography and speciation of southwestern Australian frogs." University of Western Australia. School of Animal Biology, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0058.
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[Truncated abstract] Southwestern Australia is a global biodiversity hotspot. The region contains a high number of endemic species, ranging from Gondwanan relicts to more recently evolved plant and animal species. Biogeographic models developed primarily for plants suggest a prominent role of Quaternary climatic fluctuations in the rampant speciation of endemic plants. Those models were not based on explicit spatial analysis of genetic structure, did not estimate divergence dates and may be a poor predictor of patterns in endemic vertebrates. Myobatrachid frogs have featured heavily in the limited investigations of the biogeography of the regions fauna. Myobatrachid frogs are diverse in southwestern Australia, and while we know they have speciated in situ, we know little about the temporal and spatial patterning of speciation events. In order to gain insight into the biogeographic history and potential speciation patterns of Myobatrachid frogs in the southwest I conducted a comparative phylogeography of four frog species spanning three life history strategies. I aimed to: 1) assess the biogeographic history of individual species, 2) determine where patterns of regional diversity exist using a comparative framework, 3) determine whether congruent patterns across species enable the development of explicit biogeographic hypotheses for frogs, and 4) compare patterns of diversity in plants with the models I developed for frogs. I conducted fine-scale intraspecific phylogeographies on four species. ... Geocrinia leai: deep divergences, coincident with late Miocene arid onset, divide this species into western and southeast coastal lineages, with a third only found within the Shannon-Gardner River catchments. Phylogeographic history within each lineage has been shaped by climatic fluctuations from the Pliocene through to the present. Arenophryne shows the first evidence of geological activity in speciation of a Shark Bay endemic. Divergence patterns between the High Rainfall and Southeast Coastal Provinces within C. georgiana are consistent with patterns between Litoria moorei and L. cyclorhynchus and plant biogeographic regions. Subdivision between drainage systems along the southern coast (in M. nichollsi, G. leai and the G. rosea species complex) reflect the relative importance of distinct catchments as refuges during arid maxima, similarly the northern Darling Escarpment is identified as a potential refugium (C. georgiana and G. leai). Divergences in Myobatrachid frogs are far older than those inferred for plants with the late Miocene apparently an important time for speciation of southwestern frogs. Speciation of Myobatrachids broadly relates to the onset of aridity in Australia in the late Miocene, with the exception of earlier/contemporaneous geological activity in Arenophryne. The origins of subsequent intraspecific phylogeographic structure are coincident with subsequent climatic fluctuations and correlated landscape evolution. Divergence within frogs in the forest system may be far older than the Pleistocene models developed for plants because of the heavy reliance on wet systems by relictual frog species persisting in the southwestern corner of Australia.
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Wang, Hongjun. "Labile speciation studies using electrospray mass spectrometry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ37657.pdf.
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Adams, Nicholas. "Chemical speciation of silver(I) in freshwater." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0027/NQ50978.pdf.
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Gelting, Johan. "Trace metal speciation in the Baltic sea." Licentiate thesis, Luleå : Luleå tekniska universitet/Tillämpad kemi och geovetenskap/Tillämpad geologi, 2006. http://epubl.ltu.se/1402-1757/2006/74/LTU-LIC-0674-SE.pdf.
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Jianping, Lin. "Iodine speciation in the Yarra River estuary /." Connect to thesis, 1992. http://eprints.unimelb.edu.au/archive/00000216.
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Padmavathiamma, Prabha Kumari. "Phytoremediation and metal speciation in highway soils." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/23479.
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Research was conducted to develop a cost effective and environmentally friendly technology to limit the dispersal of metal contaminants from highway traffic in the soil to the surrounding natural environment. The study comprised preliminary field measurements followed by two pot experiments and a field study. The first study evaluated the phytoextraction/ phytostabilisation potential of five plant species: Brassica napus L (rape), Helianthus annuus L. (sunflower), Lolium perenne L (perennial rye grass), Poa pratensis L (Kentucky blue grass) and Festuca rubra L (creeping red fescue) for metals (Cu, Mn, Pb and Zn), in soils with different metal contamination levels. The promising plant species identified were Lolium perenne, Festuca rubra and Poa pratensis. Total soil and plant metal concentrations, as well as the relative metal partitioning in different soil fractions and in plants were determined to provide an estimate of the mobility and potential bioavailability of metals in the soil. The second study evaluated the effectiveness of soil-plant-amendment interaction in immobilising metals in the soil. The amendments included lime, phosphate and compost individually and in combination, and were applied to the plant species: Lolium, Poa and Festuca. Maximum metal immobilisation was achieved in the soil by the combined application of amendments in conjunction with growth of Festuca for Cu, Poa for Pb and Zn and Lolium for Mn. The results obtained from first and second studies were confirmed by conducting field studies. A completely randomized factorial experiment in split plot design with three plant species (Lolium, Poa, and Festuca) individually and in combination, with and without soil amendments was conducted along Highway 17 soil in southwest British Columbia. The influence of root-soil interactions and seasonal influence on the solubility and bioavailability of metals in the soil with and without soil amendments was also evaluated. The best management practices (BMP) developed from the study have the applicability for phytostabilisation of metal contaminated sites and can be suggested as a risk management activity, reducing long-term associated risks.
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Bryan, Stephen Edward. "Testing models of chemical speciation n freshwaters." Thesis, Lancaster University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249809.
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Lofts, Stephen. "Modelling chemical speciation in the natural environment." Thesis, Lancaster University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421627.
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