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1
Holmes, Jennifer K. « A Phylogentic Analysis of PLATZ Transcription Factors in Plants ». University of Toledo / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=toledo149339721432989.
Texte intégral
2
CICCOLELLA, SIMONE. « Practical algorithms for Computational Phylogenetics ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/364980.
Texte intégralRésumé :
In questo manoscritto vengono discussi le principali sfide computazionali
nel campo della inferenza di filogenesi tumorale a vengono proposte
diverse soluzione per i tre principali problemi di
(i) ricostruzione dell'evoluzioni di un campione tumorale,
(ii) clustering di dati SCS per una piu' pulita e veloce inferenza
e (iii) il confronto di diverse filogenesi.
Inoltre viene discusso come combinare le diverse soluzioni
in una singola pipeline per una piu' rapida analisi.In this manuscript we described the main computational challenges of the cancer phylogenetic field and we proposed different solutions for the three main problems of (i) the progression reconstruction of a tumor sample, (ii) the clustering of SCS data to allow for a cleaner and faster inference and (iii) the evaluation of different phylogenies. Furthermore we combined them into a usable pipeline to allow for a faster analysis.
3
Kang, Qiwen. « UNSUPERVISED LEARNING IN PHYLOGENOMIC ANALYSIS OVER THE SPACE OF PHYLOGENETIC TREES ». UKnowledge, 2019. https://uknowledge.uky.edu/statistics_etds/39.
Texte intégralRésumé :
A phylogenetic tree is a tree to represent an evolutionary history between species or other entities. Phylogenomics is a new field intersecting phylogenetics and genomics and it is well-known that we need statistical learning methods to handle and analyze a large amount of data which can be generated relatively cheaply with new technologies. Based on the existing Markov models, we introduce a new method, CURatio, to identify outliers in a given gene data set. This method, intrinsically an unsupervised method, can find outliers from thousands or even more genes. This ability to analyze large amounts of genes (even with missing information) makes it unique in many parametric methods. At the same time, the exploration of statistical analysis in high-dimensional space of phylogenetic trees has never stopped, many tree metrics are proposed to statistical methodology. Tropical metric is one of them. We implement a MCMC sampling method to estimate the principal components in a tree space with the tropical metric for achieving dimension reduction and visualizing the result in a 2-D tropical triangle.
4
Jirásková, Kristýna. « Metody rekonstrukce fylogenetických superstromů ». Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219518.
Texte intégralRésumé :
The phylogenetic reconstruction has noted great development in recent decades. The development of computers and device for sequencing biopolymers have been an enormous amount od phylogenetic data from different sources and different types. The scientists are trying to reconstruct a comlet tree of life from these data. The phylogenetic supertree are theoretically this option because a supertree alow a combination of all information gathered so far – in contras to the phylogenetic trees. This thesis present the method of reconstruction supertrees using average konsensus method.
5
Kosíř, Kamil. « Metody rekonstrukce fylogenetických superstromů ». Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220860.
Texte intégralRésumé :
The Phylogenetic reconstruction has seen great development in the last 30 years. Computers have become more powerful and more generally accessible, and computer algorithms more sophisticated. It comes the effort of scientists to reconstruct the entire tree of life from a large amount of phylogenetic data. Just for this purpose are formed phylogenetic supertrees that allow the combination of all information gathered so far. The aim of this work is to find a method to construct supertree that will give correct results.
6
Faller, Beáta. « Combinatorial and probabilistic methods in biodiversity theory ». Thesis, University of Canterbury. Mathematics and Statistics, 2010. http://hdl.handle.net/10092/3985.
Texte intégralRésumé :
Phylogenetic diversity (PD) is a measure of species biodiversity quantified by how
much of an evolutionary tree is spanned by a subset of species. In this thesis, we study
optimization problems that aim to find species sets with maximum PD in different scenarios,
and examine random extinction models under various assumptions to predict the
PD of species that will still be present in the future.
Optimizing PD with Dependencies is a combinatorial optimization problem in
which species form an ecological network. Here, we are interested in selecting species
sets of a given size that are ecologically viable and that maximize PD. The NP-hardness
of this problem is proved and it is established which special cases of the problem are
computationally easy and which are computationally hard. It is also shown that it is
NP-complete to decide whether the feasible solution obtained by the greedy algorithm is
optimal. We formulate the optimization problem as an integer linear program and find
exact solutions to the largest food web currently in the empirical literature. In addition,
we give a generalization of PD that can be used for example when we do not know the
true evolutionary history. Based on this measure, an optimization problem is formulated.
We discuss the complexity and the approximability properties of this problem.
In the generalized field of bullets model (g-FOB), species are assumed to become
extinct with possibly different probabilities, and extinction events are independent. We
show that under this model the distribution of future phylogenetic diversity converges to
a normal distribution as the number of species grows. When extinction probabilities are
influenced by some binary character on the tree, the state-based field of bullets model
(s-FOB) represents a more realistic picture. We compare the expected loss of PD under
this model to that under the associated g-FOB model and find that the former is always
greater than or equal to the latter. It is natural to further generalize the s-FOB model to
allow more than one binary character to affect the extinction probabilities. The expected
future PD obtained for the resulting trait-dependent field of bullets model (t-FOB) is
compared to that for the associated g-FOB model and our previous result is generalized.
7
Powell, Robyn Faye. « Systematics, diversification and ecology of the Conophytum-clade (Ruschieae ; Aizoaceae) ». University of the Western Cape, 2016. http://hdl.handle.net/11394/5453.
Texte intégralRésumé :
Philosophiae Doctor - PhDThe Ruschieae is the most diverse and speciose tribe within the large subfamily Ruschioideae (Aizoaceae), with approximately 71 genera and a distribution centred in the arid parts of the Greater Cape Floristic Region (GCFR) of South Africa. Recent phylogenetic analyses provided the first insights into generic relationships within the tribe, with a number of novel generic relationships discovered. The tribal phylogeny recovered 12 large clades, of which the Conophytum-clade was one the most morphologically diverse based on leaf and capsule characters. The Conophytum-clade is an early-diverging lineage of the Ruschieae and includes the following 10 genera: Cheiridopsis N.E.Br., Conophytum N.E.Br., Enarganthe N.E.Br., Ihlenfeldtia H.E.K.Hartmann, Jensenobotrya A.G.J.Herre, Namaquanthus L.Bolus, Octopoma N.E.Br., Odontophorus N.E.Br., Ruschianthus L.Bolus and Schlechteranthus Schwantes. The present study presents an expanded phylogenetic analysis of the Conophytum-clade, with the sampling of the majority of species in the genera and a representative sampling (56% of species) of the speciose genus Conophytum. Phylogenetic data for up to nine plastid gene regions (atpB–rbcL, matK, psbJ–petA, rpl16, rps16, trnD– trnT, trnL–F, trnQᶷᶷᶢ–rps16, trnS–trnG) were produced for each of the sampled species. The produced plastid data was analyses using maximum parsimony, maximum likelihood and Bayesian inference. The combined plastid phylogenetic analyses were used in combination with morphological, anatomical and palynological data to assess generic and subgeneric circumscriptions within the clade. Upon assessment of generic circumscriptions in the Conophytum-clade, the number of recognised genera in the clade decreased from ten to seven. Arenifera A.G.J.Herre, which had not been sampled in any phylogeny of the Ruschieae, and Octopoma were recovered as polyphyletic, with species placed in the Conophytum-clade, while the type species was placed in the xeromorphic clade of the tribal phylogeny. The species of Arenifera and Octopoma placed in the Conophytum-clade were subsequently included in Schlechteranthus upon assessment of generic circumscriptions between the taxa. Two morphological groupings were recognised within Schlechteranthus, one including the species of Schlechteranthus and the other including species previously recognised as Arenifera and Octopoma. These two morphological groupings were treated as subgenera, with the erection of the new subgenus Microphyllus R.F.Powell. A detailed taxonomic revision of subgenus Microphyllus is presented with a key to species, descriptions of the species (including a new species: S. parvus R.F.Powell & Klak), known geographical distributions and illustrations of the species. In addition to the changes mentioned above, the expanded sampling and phylogenetic analyses of the Conophytum-clade recovered Ihlenfeldtia and Odontophorus embedded in Cheiridopsis. The species of Ihlenfeldtia were recovered with species of heiridopsis subgenus Aequifoliae H.E.K.Hartmann, while the species of Odontophorus were recovered as polyphyletic within the Cheiridopsis subgenus Odontophoroides H.E.K.Hartmann clade. Cheiridopsis was subsequently expanded to include the species of Ihlenfeldtia and Odontophorus, with these species accommodated in the subgenera of Cheiridopsis. The phylogenetic placement and relationship of these species was supported by the shared capsule morphology. The expanded sampling of the clade did not resolve the phylogenetic relationship of the monotypic genera Enarganthe, Jensenobotrya, Namaquanthus and Ruschianthus, with these genera unresolved in the Conophytum-clade. These genera however, exhibit a unique combination of morphological characters, such as a glabrous leaf epidermis and variation in pollen exine and colpi structure, in contrast to the other genera of the clade. The assessment of the generic circumscription of these genera, based on the molecular, morphological, anatomical and palynological data suggested that the generic statuses of these monotypic genera should be maintained. The expanded phylogenetic sampling of the morphologically diverse and speciose genus Conophytum recovered the genus as monophyletic. This monophyly was supported by the unique floral type in Conophytum, with the fused petaloid staminodes forming a tube. None of the sectional classifications were recovered as monophyletic but the phylogenetic analyses did recover a few clades which more or less corresponded to the current sectional classification of the genus. A number of clades were also recovered which included species from a range of different sections. Diverse leaf and floral traits were shown to have evolved numerous times across the genus. This was particularly interesting with regards to the selected floral traits, as the phylogeny indicated a number of switches in floral morphologies across the genus. The floral diversity was assessed in complex species communities of Conophytum across the GCFR, where up to 11 species of Conophytum are found occurring sympatrically, and floral traits were shown to be different across the species within the communities. Pollination competition and adaptation were suggested as possible drivers of floral diversity in the genus, with differences in phenology, anthesis and floral morphology within the species complex communities. The unique floral type of Conophytum has enabled the species to develop a diverse range of specialised flowers, with a variety of structures, scents and colours, resulting in the diverse floral morphologies found across the genus. The complex Conophytum species communities included both closely as well as distantly related species, suggesting the soft papery capsules of Conophytum are wind dispersed. This adaptation to long distance seed dispersal resulted in a significantly higher phylogenetic diversity in Conophytum when compared to its sister genus, Cheiridopsis. A population genetics study of Conophytum also suggested that the capsules may be wind dispersed, with an indication of genetic connectivity between the geographically isolated populations of C. marginatum Lavis across the Bushmanland Inselberg Region. Although the capsules are dispersed by wind, the seeds are released from the hygrochastic capsules by runoff during rainfall events. The relationship between seed dispersal and runoff is evident from the genetic structure of populations of C. maughanii N.E.Br. and C. ratum S.A.Hammer that occur on the tops and the surrounding bases of the inselbergs, as the drainage pattern was found to directly influence population structure in these species. In addition, the AFLP analyses provided insight into the conservation of the flagship species C. ratum. The summit populations of this species were shown to sustain the populations at the base of the Gamsberg. This finding is especially important, as the distribution of the species is restricted to the Gamsberg inselberg, where mining has already commenced as of this year.
National Research Foundation (NRF)
8
Spindler, Frederik. « The basal Sphenacodontia – systematic revision and evolutionary implications ». Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2015. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-171748.
Texte intégralRésumé :
The presented study comprises a complete morphological and phylotaxonomic revision of basal Sphenacodontia, designated as the paraphyletic ‘haptodontines’. Ianthodon from the Kasimovian is known from newly identified elements, including most of the skull and particular postcrania. This species is determined as the best model for the initial morphology of the Sphenacomorpha (Edaphosauridae and Sphenacodontia). Remarkably older sphenacodontian remains from the Moscovian indicate a derived, though fragmentarily known form, possibly basal Sphenacodontoidea. The genus Haptodus is conclusively revised, including the revalidation of the type species H. baylei from the Artinskian. Haptodus grandis is renamed as Hypselohaptodus, gen. nov. “Haptodus” garnettensis is not monophyletic with Haptodus, moreover the material assigned to it yielded a greater diversity. Thus, its renaming includes Eohaptodus garnettensis, gen. nov., Tenuacaptor reiszi, gen. et spec. nov., and Kenomagnathus scotti, gen. et spec. nov. Along with Ianthodon and the basal edaphosaurid Ianthasaurus, these taxa from a single assemblage are differentiated by dentition and skull proportions, providing a case study of annidation. Since Ianthodon can be excluded from Sphenacomorpha, the larger, stem-based taxon Haptodontiformes is introduced. More derived ‘haptodontines’ apparently form another radiation, named as Pantherapsida. This new taxon includes Cutleria, Tetraceratops, Hypselohaptodus, the Palaeohatteriidae (Pantelosaurus and Palaeohatteria), and the Sphenacodontoidea. The ‘pelycosaur’-therapsid transition is affirmed as a long-term development. An integrative evolutionary hypothesis of basal sphenacodontians is provided, within which the ghost lineage of Early Permian therapsids can be explained by biome shift.
9
Hernandez, Rosales Maribel. « The Orthology Road ». Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-127823.
Texte intégralRésumé :
The evolution of biological species depends on changes in genes. Among these changes are the gradual accumulation of DNA mutations, insertions and deletions, duplication of genes, movements of genes within and between chromosomes, gene losses and gene transfer. As two populations of the same species evolve independently, they will eventually become reproductively isolated and become two distinct species. The evolutionary history of a set of related species through the repeated occurrence of this speciation process can be represented as a tree-like structure, called a phylogenetic tree or a species tree. Since duplicated genes in a single species also independently accumulate point mutations, insertions and deletions, they drift apart in composition in the same way as genes in two related species. The divergence of all the genes descended from a single gene in an ancestral species can also be represented as a tree, a gene tree that takes into account both speciation and duplication events.
In order to reconstruct the evolutionary history from the study of extant species, we use sets of similar genes, with relatively high degree of DNA similarity and usually with some functional resemblance, that appear to have been derived from a common ancestor. The degree of similarity among different instances of the “same gene” in different species can be used to explore their evolutionary history via the reconstruction of gene family histories, namely gene trees.
Orthology refers specifically to the relationship between two genes that arose by a speciation event, recent or remote, rather than duplication. Comparing orthologous genes is essential to the correct reconstruction of species trees, so that detecting and identifying orthologous genes is an important problem, and a longstanding challenge, in comparative and evolutionary genomics as well as phylogenetics.
A variety of orthology detection methods have been devised in recent years. Although many of these methods are dependent on generating gene and/or species trees, it has been shown that orthology can be estimated at acceptable levels of accuracy without having to infer gene trees and/or reconciling gene trees with species trees. Therefore, there is good reason to look at the connection of trees and orthology from a different angle: How much information about the gene tree, the species tree, and their reconciliation is already contained in the orthology relation among genes? Intriguingly, a solution to the first part of this question has already been given by Boecker and Dress [Boecker and Dress, 1998] in a different context. In particular, they completely characterized certain maps which they called symbolic ultrametrics. Semple and Steel [Semple and Steel, 2003] then presented an algorithm that can be used to reconstruct a phylogenetic tree from any given symbolic ultrametric. In this thesis we investigate a new characterization of orthology relations, based on symbolic ultramterics for recovering the gene tree.
According to Fitch’s definition [Fitch, 2000], two genes are (co-)orthologous if their last common ancestor in the gene tree represents a speciation event. On the other hand, when their last common ancestor is a duplication event, the genes are paralogs. The orthology relation on a set of genes is therefore determined by the gene tree and an “event labeling” that identifies each interior vertex of that tree as either a duplication or a speciation event. In the context of analyzing orthology data, the problem of reconciling event-labeled gene trees with a species tree appears as a variant of the reconciliation problem where genes trees have no labels in their internal vertices. When reconciling a gene tree with a species tree, it can be assumed that the species tree is correct or, in the case of a unknown species tree, it can be inferred. Therefore it is crucial to know for a given gene tree whether there even exists a species tree. In this thesis we characterize event-labelled gene trees for which a species tree exists and species trees to which event-labelled gene trees can be mapped. Reconciliation methods are not always the best options for detecting orthology. A fundamental problem is that, aside from multicellular eukaryotes, evolution does not seem to have conformed to the descent-with-modification model that gives rise to tree-like phylogenies. Examples include many cases of prokaryotes and viruses whose evolution involved horizontal gene transfer. To treat the problem of distinguishing orthology and paralogy within a more general framework, graph-based methods have been proposed to detect and differentiate among evolutionary relationships of genes in those organisms. In this work we introduce a measure of orthology that can be used to test graph-based methods and reconciliation methods that detect orthology. Using these results a new algorithm BOTTOM-UP to determine whether a map from the set of vertices of a tree to a set of events is a symbolic ultrametric or not is devised. Additioanlly, a simulation environment designed to generate large gene families with complex duplication histories on which reconstruction algorithms can be tested and software tools can be benchmarked is presented.
10
Guillory, Wilson. « Comprehensive phylogenomic reconstruction of Ameerega (Anura : Dendrobatidae) and introduction of a new method for phylogenetic niche modeling ». OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2654.
Texte intégralRésumé :
To understand present patterns of biodiversity, knowledge of a lineage’s past – both evolutionary and geographic – is required. Here I present the first comprehensive phylogenomic study of an Amazonian poison frog genus, Ameerega, as well as the introduction of a new method for characterizing ancestral distributions via phylogenetic niche modeling, which I use to investigate Ameerega’s biogeographic past. I sequenced thousands of ultraconserved elements from over 100 tissue samples, representing almost every described Ameerega species, as well as undescribed cryptic diversity. My phylogenetic inference diverged strongly from those of previous studies. I also introduce a new phylogenetic niche modeling method, which accounts for issues of bias in other methods by incorporating knowledge of evolutionary relationships into niche models. Given modern-day and paleoclimatic data, species occurrence data, and a time-calibrated phylogeny, my method constructs niche models for each extant taxon, uses ancestral character estimation to reconstruct ancestral niche models, and projects these models into paleoclimate data to provide a historical estimate of the geographic range of a lineage. I demonstrate my method on the Ameerega bassleri group. I also use simulations to show that my method can reliably reconstruct the niche of a known ancestor in both geographic and environmental space.
11
Wanke, Stefan, Mendoza Carolina Granados, Julia Naumann, Marie-Stéphanie Samain, Paul Goetghebeur et Smet Yannick De. « A genome-scale mining strategy for recovering novel rapidly-evolving nuclear single-copy genes for addressing shallow-scale phylogenetics in Hydrangea ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-192196.
Texte intégralRésumé :
Background
Identifying orthologous molecular markers that potentially resolve relationships at and below species level has been a major challenge in molecular phylogenetics over the past decade. Non-coding regions of nuclear low- or single-copy markers are a vast and promising source of data providing information for shallow-scale phylogenetics. Taking advantage of public transcriptome data from the One Thousand Plant Project (1KP), we developed a genome-scale mining strategy for recovering potentially orthologous single-copy markers to address low-scale phylogenetics. Our marker design targeted the amplification of intron-rich nuclear single-copy regions from genomic DNA. As a case study we used Hydrangea section Cornidia, one of the most recently diverged lineages within Hydrangeaceae (Cornales), for comparing the performance of three of these nuclear markers to other "fast" evolving plastid markers.
Results
Our data mining and filtering process retrieved 73 putative nuclear single-copy genes which are potentially useful for resolving phylogenetic relationships at a range of divergence depths within Cornales. The three assessed nuclear markers showed considerably more phylogenetic signal for shallow evolutionary depths than conventional plastid markers. Phylogenetic signal in plastid markers increased less markedly towards deeper evolutionary divergences. Potential phylogenetic noise introduced by nuclear markers was lower than their respective phylogenetic signal across all evolutionary depths. In contrast, plastid markers showed higher probabilities for introducing phylogenetic noise than signal at the deepest evolutionary divergences within the tribe Hydrangeeae (Hydrangeaceae).
Conclusions
While nuclear single-copy markers are highly informative for shallow evolutionary depths without introducing phylogenetic noise, plastid markers might be more appropriate for resolving deeper-level divergences such as the backbone relationships of the Hydrangeaceae family and deeper, at which non-coding parts of nuclear markers could potentially introduce noise due to elevated rates of evolution. The herein developed and demonstrated transcriptome based mining strategy has a great potential for the design of novel and highly informative nuclear markers for a range of plant groups and evolutionary scales.
12
Wanke, Stefan, Mendoza Carolina Granados, Julia Naumann, Marie-Stéphanie Samain, Paul Goetghebeur et Smet Yannick De. « A genome-scale mining strategy for recovering novel rapidly-evolving nuclear single-copy genes for addressing shallow-scale phylogenetics in Hydrangea ». BMC Evolutionary Biology, 2001. https://tud.qucosa.de/id/qucosa%3A29147.
Texte intégralRésumé :
Background
Identifying orthologous molecular markers that potentially resolve relationships at and below species level has been a major challenge in molecular phylogenetics over the past decade. Non-coding regions of nuclear low- or single-copy markers are a vast and promising source of data providing information for shallow-scale phylogenetics. Taking advantage of public transcriptome data from the One Thousand Plant Project (1KP), we developed a genome-scale mining strategy for recovering potentially orthologous single-copy markers to address low-scale phylogenetics. Our marker design targeted the amplification of intron-rich nuclear single-copy regions from genomic DNA. As a case study we used Hydrangea section Cornidia, one of the most recently diverged lineages within Hydrangeaceae (Cornales), for comparing the performance of three of these nuclear markers to other 'fast' evolving plastid markers.
Results
Our data mining and filtering process retrieved 73 putative nuclear single-copy genes which are potentially useful for resolving phylogenetic relationships at a range of divergence depths within Cornales. The three assessed nuclear markers showed considerably more phylogenetic signal for shallow evolutionary depths than conventional plastid markers. Phylogenetic signal in plastid markers increased less markedly towards deeper evolutionary divergences. Potential phylogenetic noise introduced by nuclear markers was lower than their respective phylogenetic signal across all evolutionary depths. In contrast, plastid markers showed higher probabilities for introducing phylogenetic noise than signal at the deepest evolutionary divergences within the tribe Hydrangeeae (Hydrangeaceae).
Conclusions
While nuclear single-copy markers are highly informative for shallow evolutionary depths without introducing phylogenetic noise, plastid markers might be more appropriate for resolving deeper-level divergences such as the backbone relationships of the Hydrangeaceae family and deeper, at which non-coding parts of nuclear markers could potentially introduce noise due to elevated rates of evolution. The herein developed and demonstrated transcriptome based mining strategy has a great potential for the design of novel and highly informative nuclear markers for a range of plant groups and evolutionary scales.
13
Bauer, Jennifer E. « A Phylogenetic and Paleobiogeographic Analysis of the Ordovician Brachiopod Eochonetes ». Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1397486053.
Texte intégral
14
Gonzalez, Vanessa Liz. « Evolution of Bivalvia : Multi-level phylogenetic and phylogenomic reconstructions within Bivalvia (Mollusca) with emphasis on resolving familial relationships within Archiheterodonta (Bivalvia : Heterodonta) ». Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11172.
Texte intégralRésumé :
With an estimated 8,000-20,000 species, bivalves represent the second largest living class of molluscs (Bieler et al. 2013). Revived interest in molluscan phylogeny has resulted in a torrent of molecular sequence data from phylogenetic, mitogenomic, and phylogenomic studies. Despite recent progress, basal relationships of the class Bivalvia remain contentious, owing to conflicting hypotheses often between morphology and molecules.
15
Mecham, Jesse L. « Jumpstarting phylogenetic searches / ». Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1403.pdf.
Texte intégral
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McHugh, Sean W. « Phylogenetic Niche Modeling ». Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104893.
Texte intégralRésumé :
Projecting environmental niche models through time is a common goal when studying species response to climatic change. Species distribution models (SDMs) are commonly used to estimate a species' niche from observed patterns of occurrence and environmental predictors. However, a species niche is also shaped by non-environmental factors--including biotic interactions and dispersal barrier—truncating SDM estimates. Though truncated SDMs may accurately predict present-day species niche, projections through time are often biased by environmental condition change. Modeling niche in a phylogenetic framework leverages a clade's shared evolutionary history to pull species estimates closer towards phylogenetic conserved values and farther away from species specific biases. We propose a new Bayesian model of phylogenetic niche implemented in R. Under our model, species SDM parameters are transformed into biologically interpretable continuous parameters of environmental niche optimum, breadth, and tolerance evolving under multivariate Brownian motion random walk. Through simulation analyses, we demonstrated model accuracy and precision that improved as phylogeny size increased. We also demonstrated our model on a clade of eastern United States Plethodontid salamanders by accurately estimating species niche, even when no occurrence data is present. Our model demonstrates a novel framework where niche changes can be studied forwards and backwards through time to understand ancestral ranges, patterns of environmental specialization, and niche in data deficient species.Master of Science
As many species face increasing pressure in a changing climate, it is crucial to understand the set of environmental conditions that shape species' ranges--known as the environmental niche--to guide conservation and land management practices. Species distribution models (SDMs) are common tools that are used to model species' environmental niche. These models treat a species' probability of occurrence as a function of environmental conditions. SDM niche estimates can predict a species' range given climate data, paleoclimate, or projections of future climate change to estimate species range shifts from the past to the future. However, SDM estimates are often biased by non-environmental factors shaping a species' range including competitive divergence or dispersal barriers. Biased SDM estimates can result in range predictions that get worse as we extrapolate beyond the observed climatic conditions. One way to overcome these biases is by leveraging the shared evolutionary history amongst related species to "fill in the gaps". Species that are more closely phylogenetically related often have more similar or "conserved" environmental niches. By estimating environmental niche over all species in a clade jointly, we can leverage niche conservatism to produce more biologically realistic estimates of niche. However, currently a methodological gap exists between SDMs estimates and macroevolutionary models, prohibiting them from being estimated jointly. We propose a novel model of evolutionary niche called PhyNE (Phylogenetic Niche Evolution), where biologically realistic environmental niches are fit across a set of species with occurrence data, while simultaneously fitting and leveraging a model of evolution across a portion of the tree of life. We evaluated model accuracy, bias, and precision through simulation analyses. Accuracy and precision increased with larger phylogeny size and effectively estimated model parameters. We then applied PhyNE to Plethodontid salamanders from Eastern North America. This ecologically-important and diverse group of lungless salamanders require cold and wet conditions and have distributions that are strongly affected by climatic conditions. Species within the family vary greatly in distribution, with some species being wide ranging generalists, while others are hyper-endemics that inhabit specific mountains in the Southern Appalachians with restricted thermal and hydric conditions. We fit PhyNE to occurrence data for these species and their associated average annual precipitation and temperature data. We identified no correlations between species environmental preference and specialization. Pattern of preference and specialization varied among Plethodontid species groups, with more aquatic species possessing a broader environmental niche, likely due to the aquatic microclimate facilitating occurrence in a wider range of conditions. We demonstrated the effectiveness of PhyNE's evolutionarily-informed estimates of environmental niche, even when species' occurrence data is limited or even absent. PhyNE establishes a proof-of-concept framework for a new class of approaches for studying niche evolution, including improved methods for estimating niche for data-deficient species, historical reconstructions, future predictions under climate change, and evaluation of niche evolutionary processes across the tree of life. Our approach establishes a framework for leveraging the rapidly growing availability of biodiversity data and molecular phylogenies to make robust eco-evolutionary predictions and assessments of species' niche and distributions in a rapidly changing world.
17
Mecham, Jesse Lewis. « Jumpstarting Phylogenetic Searches ». BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/483.
Texte intégralRésumé :
Phylogenetic analysis is a central tool in studies of comparative genomics. When a new region of DNA is isolated and sequenced, researchers are often forced to throw away months of computation on an existing phylogeny of homologous sequences in order to incorporate this new sequence. The previously constructed trees are often discarded, and the researcher begins the search again from scratch. The jumpstarting algorithm uses trees from the prior search as a starting point for a new phylogenetic search. This technique drastically decreases search time for large data sets. This kind of analysis is necessary as researchers analyze tree of life size data sets.
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Krig, Kåre. « Methods for phylogenetic analysis ». Thesis, Linköping University, Department of Mathematics, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-56814.
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In phylogenetic analysis one study the relationship between different species. By comparing DNA from two different species it is possible to get a numerical value representing the difference between the species. For a set of species, all pair-wise comparisons result in a dissimilarity matrix d.
In this thesis I present a few methods for constructing a phylogenetic tree from d. The common denominator for these methods is that they do not generate a tree, but instead give a connected graph. The resulting graph will be a tree, in areas where the data perfectly matches a tree. When d does not perfectly match a tree, the resulting graph will instead show the different possible topologies, and how strong support they have from the data.
Finally I have tested the methods both on real measured data and constructed test cases.
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Pardi, Fabio. « Algorithms on phylogenetic trees ». Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611685.
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Wang, Min-Hui. « Classification using phylogenetic trees / ». The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488190595939375.
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Sundberg, Kenneth A. « Partition Based Phylogenetic Search ». BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2583.
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Evolutionary relationships are key to modern understanding of biological systems. Phylogenetic search is the means by which these relationships are inferred. Phylogenetic search is NP-Hard. As such it is necessary to employ heuristic methods. This work proposes new methods based on viewing the relationships between species as sets of partitions. These methods produce more parsimonious phylogenies than current methods.
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Hansen, Michael. « Algebra and Phylogenetic Trees ». Scholarship @ Claremont, 2007. https://scholarship.claremont.edu/hmc_theses/194.
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One of the restrictions used in all of the works done on phylogenetic invariants for group based models has been that the group be abelian. In my thesis, I aim to generalize the method of invariants for group-based models of DNA sequence evolution to include nonabelian groups. By using a nonabelian group to act one the nucleotides, one could capture the structure of the symmetric model for DNA sequence evolution. If successful, this line of research would unify the two separated strands of active research in the area today: Allman and Rhodes’s invariants for the symmetric model and Strumfels and Sullivant’s toric ideals of phylogenetic invariants. Furthermore, I want to look at the statistical properties of polynomial invariants to get a better understanding of how they behave when used with real, “noisy” data.
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Broe, Michael Brian. « Phylogenetics of the Monotropoideae (Ericaceae) with Special Focus on the Genus Hypopitys Hill, together with a Novel Approach to Phylogenetic Inference Using Lattice Theory ». The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417442819.
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Arvestad, Isaac, et Henrik Lagebrand. « Implementing Bayesian phylogenetic tree inference with Sequential Monte Carlo and the Phylogenetic Likelihood Library ». Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-229429.
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We investigate the usability of the Phylogenetic Likelihood Library (PLL) in Bayesian phylogenetic tree inference using Sequential Monte Carlo (SMC) algorithms. This is done by implementing two different versions of the same algorithm with two different approaches of the use of PLL. The implementation using the main PLL API encountered performance issues that the lower level implementation did not. We conclude that it is possible to use PLL in SMC methods but it is unclear if the main API is suitable.Vi undersöker om programspråksbiblioteket Phylogenetic Likelihood Library (PLL) kan användas för bayesiansk inferens av phylogenetiska träd med en sekventiell Monte Carlo-metod (SMC). Genom att implementera algoritmen med två olika delar av PLL:s programmeringsgränssnitt visar vi att det går att använda PLL för att implementera SMC-algoritmen men att det är oklart om det huvudsakliga programmeringsgränssnittet är lämpligt.
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Fleissner, Roland. « Sequence alignment and phylogenetic inference ». Berlin : Logos Verlag, 2004. http://diss.ub.uni-duesseldorf.de/ebib/diss/file?dissid=769.
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Rehmsmeier, Marc. « Database searching with phylogenetic trees ». [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963977423.
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Deepak, Akshay. « SearchTree mining robust phylogenetic trees / ». [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1476290.
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Haber, Matthew Horace. « The centrality of phylogenetic thinking / ». For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Schmidt, Heiko A. « Phylogenetic trees from large datasets ». [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968534945.
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Fleissner, Roland. « Sequence alignment and phylogenetic inference ». [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971844704.
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Gottschling, Marc. « Phylogenetic analysis of selected Boraginales ». [S.l. : s.n.], 2003. http://www.diss.fu-berlin.de/2003/30/index.html.
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Högnabba, Filip. « Phylogenetic studies of cyanobacterial lichens / ». Helsinki : Yliopistopaino, 2007. http://ethesis.helsinki.fi.
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Roos, Marinus Cornelis. « Phylogenetic systematics of the Drynarioideae / ». Amsterdam [u.a.] : North-Holland, 1985. http://www.gbv.de/dms/bs/toc/013141155.pdf.
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Jetté, Migüel. « Reconstructing functions on phylogenetic trees ». Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99187.
Texte intégralRésumé :
This thesis introduces three new tools for studying the evolution of different organisms given the evolutionary, or phylogenetic, tree that relates them. First, we show how posterior state probabilities can be used for exploring phylogenetic uncertainty, through posterior entropy of ancestral states. Second, we derive an explicit formula for the expected number of substitutions on a branch in a phylogeny, given the pattern at the leaves. Algorithms were implemented, as part of the ATV software, to calculate these values. They are used, in conjunction with SplitsTree4, to assess variation in rates over sites and lineages, and to predict model violations. Third, we show how techniques for spline interpolation and function approximation can be applied to estimate functions defined on a tree. We also present an example of the usage of interpolations on phylogenetic trees, by analyzing continuous traits on a phylogenetic tree through fossil data sets.
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Ryder, Robin Jeremy. « Phylogenetic models of language diversification ». Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543009.
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Stolzer, Maureen. « Phylogenetic Inference for Multidomain Proteins ». Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/47.
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In this thesis, I present a model of multidomain evolution with associated algorithms and software for phylogenetic analysis of multidomain families, as well as applications of this novel methodology to case-studies and the human genome.
Phylogenetic analysis is of central importance to understanding the origins and evolution of life on earth. In biomedical research, molecular phylogenetics has proved an essential tool for practical applications. Current molecular phylogenetic methods are not equipped, however, to model many of the unique characteristics of multidomain families. Genes that encode this large and important class of proteins are characterized by a mosaic of sequence fragments that encode structural or functional modules, called domains. Multidomain families evolve via domain shuffling, a process that includes insertion, internal duplication, and deletion of domains. This versatile evolutionary mechanism played a transformative role in major evolutionary transitions, including the emergence of multicellular animals and the vertebrate immune system.
Multidomain families are ill-suited to current methods for phylogeny reconstruction due to their mosaic composition. Different regions of the same protein may have different evolutionary histories. Moreover, a protein may contain domains that also occur in otherwise unrelated proteins. These attributes pose substantial obstacles for phylogenetic methods that require a multiple sequence alignment as input. In addition, current methods do not incorporate a model of domain shuffling and hence, cannot infer the events that occurred in the history of the family. I address this problem by treating a multidomain family as a set of co-evolving domains, each with its own history. If the family is evolving by vertical descent from a conserved set of ancestral domains, then all constituent domains will have the same phylogenetic history. Disagreement between domain tree topologies is evidence that the family evolved through processes other than speciation and gene duplication. My algorithms exploit this information to reconstruct the history of domain shuffling in the family, as well as the timing of these events and the ancestral domain composition. I have implemented these algorithms in software that outputs the most parsimonious history of events for each domain family. The software also reconstructs a composite family history, including duplications, insertions and losses of all constituent domains and ancestral domain composition.
My approach is capable of more detailed and accurate reconstructions than the widely used domain architecture model, which ignores sequence variation between domain instances. In contrast, my approach is based on an explicit model of events and captures sequence variation between domain instances. I demonstrate the utility of this method through case studies of notch-related proteins, protein tyrosine kinases, and membrane-associated guanylate kinases. I further present a largescale analysis of domain shuffling processes through comparison of all pairs of domain families that co-occur in a protein in the human genome. These analyses suggest that (1) a remarkably greater amount of domain shuffling may have occurred than previously thought and (2) that it is not uncommon for the same domain architecture to arise more than once through independent events. This stands in contrast to earlier reports that convergent evolution of domain architecture is rare and suggests that incorporating sequence variation in evolutionary analyses of multidomain families is a crucial requirement for accurate inference.
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Welbourn, Warren Calvin. « Phylogenetic studies of trombidioid mites / ». The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487262825074137.
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Kashiwada, Akemi. « Constructing Phylogenetic Trees from Subsplits ». Scholarship @ Claremont, 2005. https://scholarship.claremont.edu/hmc_theses/171.
Texte intégralRésumé :
Phylogenetic trees represent theoretical evolutionary relationships among various species. Mathematically they can be described as weighted binary trees and the leaves represent the taxa being compared. One major problem in mathematical biology is the reconstruction of these trees. We already know that trees on the leaf set X can be uniquely constructed from splits, which are bipartitions of X. The question I explore in this thesis is whether reconstruction of a tree is possible from subsplits, or partial split information. The major result of this work is a constructive algorithm which allows us to determine whether a given set of subsplits will realize a tree and, if so, what the tree looks like.
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Riester, Markus. « Genealogy Reconstruction ». Doctoral thesis, Universitätsbibliothek Leipzig, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-38656.
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Genealogy reconstruction is widely used in biology when relationships among entities are studied. Phylogenies, or evolutionary trees, show the differences between species. They are of profound importance because they help to obtain better understandings of evolutionary processes. Pedigrees, or family trees, on the other hand visualize the relatedness between individuals in a population. The reconstruction of pedigrees and the inference of parentage in general is now a cornerstone in molecular ecology. Applications include the direct infer- ence of gene flow, estimation of the effective population size and parameters describing the population’s mating behaviour such as rates of inbreeding.
In the first part of this thesis, we construct genealogies of various types of cancer. Histopatho- logical classification of human tumors relies in part on the degree of differentiation of the tumor sample. To date, there is no objective systematic method to categorize tumor subtypes by maturation. We introduce a novel algorithm to rank tumor subtypes according to the dis- similarity of their gene expression from that of stem cells and fully differentiated tissue, and thereby construct a phylogenetic tree of cancer. We validate our methodology with expression data of leukemia and liposarcoma subtypes and then apply it to a broader group of sarcomas and of breast cancer subtypes. This ranking of tumor subtypes resulting from the application of our methodology allows the identification of genes correlated with differentiation and may help to identify novel therapeutic targets. Our algorithm represents the first phylogeny-based tool to analyze the differentiation status of human tumors.
In contrast to asexually reproducing cancer cell populations, pedigrees of sexually reproduc- ing populations cannot be represented by phylogenetic trees. Pedigrees are directed acyclic graphs (DAGs) and therefore resemble more phylogenetic networks where reticulate events are indicated by vertices with two incoming arcs. We present a software package for pedigree reconstruction in natural populations using co-dominant genomic markers such as microsatel- lites and single nucleotide polymorphism (SNPs) in the second part of the thesis. If available, the algorithm makes use of prior information such as known relationships (sub-pedigrees) or the age and sex of individuals. Statistical confidence is estimated by Markov chain Monte Carlo (MCMC) sampling. The accuracy of the algorithm is demonstrated for simulated data as well as an empirical data set with known pedigree. The parentage inference is robust even in the presence of genotyping errors. We further demonstrate the accuracy of the algorithm on simulated clonal populations. We show that the joint estimation of parameters of inter- est such as the rate of self-fertilization or clonality is possible with high accuracy even with marker panels of moderate power. Classical methods can only assign a very limited number of statistically significant parentages in this case and would therefore fail. The method is implemented in a fast and easy to use open source software that scales to large datasets with many thousand individuals.
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Olsson, Sanna. « Evolution of the Neckeraceae (Bryopsida) ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1235997342817-20232.
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The group of pleurocarpous mosses comprises approximately 5000 species, which corresponds to about half of all mosses. The pleurocarpous mosses (i.e. “the Core Pleurocarps”) form a monophylum, which consists typically of perennial mosses with creeping stems and abundant lateral branches. In pleurocarpous mosses the archegonium and thus also sporophyte development is restricted to the apices of short, specialized lateral branches, in contrast to most other mosses, where archegonia and sporophytes develop terminally on the main axis (acrocarpous) or on major branches (cladocarpous). Traditionally, pleurocarpous mosses have been divided into three orders based mainly on their sporophytic characters. Brotherus described the Neckeraceae in 1925 and placed it into the Leucodontales, later the family has alternatively been divided into two or three separate families: the Thamnobryaceae, the Neckeraceae and the Leptodontaceae. These families have been placed even in different orders (Neckeraceae and Leptodontaceae among the leucodontalean mosses and Thamnobryaceae among hypnalean mosses) according to their peristome structure and the grade of peristome reduction. A growing amount of evidence indicates that a grouping based on sporophytic characters is artificial and based on convergent evolution. According to the latest phylogenetic studies of pleurocarpous mosses, based on molecular data, the Neckeraceae belong to the order Hypnales and share a sister group relationship with the Lembophyllaceae. In the most recent comprehensive classification 28 genera were included in the Neckeraceae family. This classification was based on both morphological and molecular data, but done with limited taxon sampling that did not cover all species of the family. Some previous studies based on molecular data have challenged the family concept of the Neckeraceae, indicating the need for a revision of the family. Here the family concept of the Neckeraceae is revisited, the closest relatives of the family are resolved and its position within pleurocarpous mosses is shown. In addition, new insights into the morphological evolution of the family are provided. Previous phylogenetic studies indicated that branch lengths among pleurocarpous mosses are usually extremely short. Therefore we chose to use mainly non-coding DNA sequences from rapidly evolving DNA regions. The phylogenetic reconstructions are based on extensive sequence data from all genomes: plastid trnS-trnF and rpl16, nuclear ITS1 & 2 and mitochondrial nad5. Both parsimony (PAUP and PRAP2) and Bayesian statistics (MrBayes) were employed for phylogenetic reconstructions. In order to use the information provided by length mutations indels were included in the analyses as binary data using a simple indel coding approach. No severe conflicts appeared between the different methods used, but the indel coding affected the support values of the inferred topologies. Therefore, all support values resulting from different methods are shown along the phylogenetic trees. The morphological features are studied and synapomorphies for each clade formed in the phylogenetic analyses are interpreted. A new delimitation of the family makes it necessary to reconsider the relevance of the morphological description and the morphological features characteristic of the family need to be reconsidered. Due to new groupings, some changes in the morphological circumscriptions of the genera are necessary, resulting in two new genera and several new combinations. Chapter 1 gives a broad overview of the relationships of the pleurocarpous mosses and shows the need for changes in the definition of genera, families and the corresponding nomenclature in this group. Chapter 2 is a population genetic study on the genus Thamnobryum. The main aim of this chapter is to test the species concept in Thamnobryum that are endemic to strictly restricted regions showing only minor differences in the morphological features in comparison to some more common species. In Chapter 3 the monophyly of the Neckeraceae is tested. In addition, in this chapter the ancestral character states of some morphological characters within the Neckeraceae are reconstructed. Chapters 4 and 5 resolve the genus composition and the relationships within the family in more detail. The results of this thesis show that the Neckeraceae need re-circumscription; this includes changes in the genus composition. The Lembophyllaceae is confirmed to be the sister group of the Neckeraceae. In addition to the new phylogeny, the potential evolution of several characters as a result of environmental selection pressures is analyzed. From the ancestral state reconstructions made (using BayesTraits) for both the habitat and a selection of morphological characters, character state distributions and habitat shift appear congruent, peristome reduction being a good example. However, some character states do not correlate with the habitat, suggesting very complex evolutionary patterns underlying these morphological characters. Many widely distributed genera that are composed of several species and seem to be morphologically coherent (Echinodium, Homalia, Thamnobryum, partly Neckera), are shown in this thesis to be polyphyletic. They are replaced by smaller, geographically more restricted genera that at least in some cases (e.g. Thamnomalia, Homalia s.str., Neckera s.str.) seem to form morphologically heterogeneous genera. In other words, morphology can be misleading in the family Neckeraceae even at the genus level and convergent evolution in both morphological and sequence level characters are common within the family. Special habitat conditions have been shown to result in similar morphological structures also in several other moss groups. This kind of convergent evolution occurs in aquatic mosses, and seems to have occurred among the neckeraceous species Thamnobryum alopecurum and its allies. However, similar morphological structure in similar aquatic habitats can also be due to true phylogenetic relationships as is the case within the Neckeraceae for Handeliobryum sikkimense and Hydrocryphae wardii, or the members of Touwia. The geographical grouping seems to be more strongly correlated with the phylogenetic grouping than thought before.
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Porter, Megan L. « Crustacean phylogenetic systematics and opsin evolution ». Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd859.pdf.
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Oldman, James. « Constructing phylogenetic networks based on trinets ». Thesis, University of East Anglia, 2015. https://ueaeprints.uea.ac.uk/59446/.
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The motivation of phylogenetic analysis is to discover the evolutionary relationships between species, with the broader aim of understanding the origins of life. Our understanding of the molecular character- istics of species through DNA sequencing permanently changed the approach to understanding the evolution of species. Indeed, the ad- vancement of technology has played a major role in the fast sequencing of DNA as well as the use of computers in solving biological problems in general. These evolutionary relationships are often visualised and represented using a phylogenetic tree. As a natural generalisation of phylogenetic trees, phylogenetic networks are used in biology to rep- resent evolutionary histories that contain reticulate, or non-treelike events such as recombination, hybridisation and horizontal gene trans- fer. The reconstruction of explicit phylogenetic networks from biolog- ical data is currently an active area of phylogenetics research. Here we consider the problem of constructing such networks from trinets, that is, phylogenetic networks on three leaves. More speci�cally, we present the SeqTrinet and TriLoNet methods, which form a supernet- work based approach to constructing level-1 phylogenetic networks directly from multiple sequence alignments.
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Fischer, Mareike. « Novel Mathematical Aspects of Phylogenetic Estimation ». Thesis, University of Canterbury. Mathematics and Statistics, 2009. http://hdl.handle.net/10092/2331.
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In evolutionary biology, genetic sequences carry with them a trace of the underlying tree that describes their evolution from a common ancestral sequence. Inferring this underlying tree is challenging. We investigate some curious cases in which different methods like Maximum Parsimony, Maximum Likelihood and distance-based methods lead to different trees. Moreover, we state that in some cases, ancestral sequences can be more reliably reconstructed when some of the leaves of the tree are ignored - even if these leaves are close to the root. While all these findings show problems inherent to either the assumed model or the applied method, sometimes an inaccurate tree reconstruction is simply due to insufficient data. This is particularly problematic when a rapid divergence event occurred in the distant past. We analyze an idealized form of this problem and determine a tight lower bound on the growth rate for the sequence length required to resolve the tree (independent of any particular branch length). Finally, we investigate the problem of intermediates in the fossil record. The extent of ‘gaps’ (missing transitional stages) has been used to argue against gradual evolution from a common ancestor. We take an analytical approach and demonstrate why, under certain sampling conditions, we may not expect intermediates to be found.
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Keivany, Yazdan. « Phylogenetic relationships of Gasterosteiformes (Teleostei, Percomorpha) ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ59608.pdf.
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Habib, Farhat Abbas. « Genotype-phenotype correlation using phylogenetic trees ». Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187297400.
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Fuentes, Carvajal Andreina. « Phylogenetic relationships within Coleeae (Bignoniaceae juss.) ». Click here to access thesis, 2007. http://www.georgiasouthern.edu/etd/archive/fall2007/carvajal_a_fuentes/carvajal_andreina_f_200708_MS.pdf.
Texte intégralRésumé :
Thesis (M.S.)--Georgia Southern University, 2007."A thesis submitted to the Graduate Faculty of Georgia Southern University in partial fulfillment of the requirements for the degree Master of Science." In Biology, under the direction of Michelle Zjhra. ETD. Electronic version approved: December 2007. Includes bibliographical references (p. 38-42)
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Ababneh, Faisal. « Models and estimation for phylogenetic trees / ». Connect to full text, 2006. http://hdl.handle.net/2123/927.
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Cho, Anna. « Constructing Phylogenetic Trees Using Maximum Likelihood ». Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/scripps_theses/46.
Texte intégralRésumé :
Maximum likelihood methods are used to estimate the phylogenetic trees for a set of species. The probabilities of DNA base substitutions are modeled by continuous-time Markov chains. We use these probabilities to estimate which DNA bases would produce the data that we observe. The topology of the tree is also determined using base substitution probabilities and conditional likelihoods. Felsenstein [2] introduced this method of finding an estimate for the maximum likelihood phylogenetic tree. We will explore this method in detail in this paper.
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Wu, Qiong. « Phylogenetic Networks : New Constructions and Applications ». Thesis, University of East Anglia, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.514315.
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Fujisawa, Tomochika. « Statistical analyses of genealogical-phylogenetic data ». Thesis, Imperial College London, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556548.
Texte intégralRésumé :
Thanks to the recent advancement of the sequence technologies, generating large volumes of DNA sequence data is now becoming more feasible. Sequencing several samples across many species from a range of clades enables us to connect the two fields of study previously separated due to the lack of data: population genetics and phylogenetics. The former has focused on detailed genetic processes in a few species, while the latter has studied large-scale evolutionary relationships across many species. In this thesis, methods to utilize the new type of data, genealogical-phylogenetic data, are explored to tackle the problems lying between the two fields, including how to delimit species with genetic information and how ecological traits affect species genetic properties. First, a method of species delimitation based on single locus gene tree, called the generalized mixed Yule coalescent method (GMYC method), is evaluated. Its statistical properties are assessed on both simulated and real data, and the method is extended to relax some simplifying assumptions and to give a robust confidence measure. The simulation studies showed that the reliability of the delimitation depends on population parameters and patterns of diversification processes. Assessment of the performance on a dataset of 5196 water beetle mitochondrial DNA sequences sampled from across Europe showed that the method accurately delimited half of the studied species. The accuracy was affected by several factors, notably the presence of pseudogenes and potential undersampling of species range. Then, the water beetle data and the GMYC method are used to test the effects of species ecological traits on genetic properties, focusing on species habitat type. Habitat type had significant effects on genetic variation and substitution rate via effects on range size and latitudinal distribution of species. However, direct effects of habitat type on genetic properties were not observed.