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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Mate Choice, Genetic Variation, and Population Structure in Hybrid Zones

Culumber, Zachary Wyatt 2011 December 1900 (has links)
Natural hybrid zones provide opportunities to study a range of evolutionary phenomena from speciation to the genetic basis of fitness-related traits. Additionally, investing the structure of hybrid zones can provide valuable insight in the ecology and evolution of species. The present dissertation approaches the investigation of natural hybrid zones between Xiphophorus birchmanni and X. malinche from a population genetics perspective. The goal of the chapters herein are to investigate the genetic structure of these natural hybrid zones overall and the genetic structure of the populations within them in an effort to better understand the factors producing and maintaining spatial genetic patterns among this species pair and their hybrids. Using informative single nucleotide polymorphisms (SNPs) in one mitochondrial and three nuclear intron loci, I show that hybrid zones occur in replicated fashion in multiple stream reaches along a gradient from high to low elevation. Tests of FIS and linkage disequilibrium (LD) revealed significant genetic structure within a small subset of populations. Specifically, parentals and hybrids all three occur in some locations while other locations appear to be hybrid swarms. I then investigated a behavioral mechanism of reproductive isolation - social association, which might affect population structure. In clean water, individuals shoaled significantly more closely with conspecifics. Additionally, genotyping of females and their embryos revealed signatures of non-random mating in structured populations. Taken together, assortative social grouping, which may translate to assortative female mate choice, likely plays a role in maintaining population structure. Finally, I show that fluctuating asymmetry is significantly higher in unstructured than structure populations. This is a further indication that some form of non-random mating occurs in structured populations and has effects on male phenotypes.
2

Testing Taxon Tenacity of Tortoises: evidence for a geographical selection gradient at a secondary contact zone

Edwards, Taylor, Berry, Kristin H., Inman, Richard D., Esque, Todd C., Nussear, Kenneth E., Jones, Cristina A., Culver, Melanie 05 1900 (has links)
UA Open Access Publishing Fund / We examined a secondary contact zone between two species of desert tortoise, Gopherus agassizii and G. morafkai. The taxa were isolated from a common ancestor during the formation of the Colorado River (4–8 mya) and are a classic example of allopatric speciation. However, an anomalous population of G. agassizii comes into secondary contact with G. morafkai east of the Colorado River in the Black Mountains of Arizona and provides an opportunity to examine reinforcement of species’ boundaries under natural conditions. We sampled 234 tortoises representing G. agassizii in California (n = 103), G. morafkai in Arizona (n = 78), and 53 individuals of undetermined assignment in the contact zone including and surrounding the Black Mountains. We genotyped individuals for 25 STR loci and determined maternal lineage using mtDNA sequence data. We performed multilocus genetic clustering analyses and used multiple statistical methods to detect levels of hybridization. We tested hypotheses about habitat use between G. agassizii and G. morafkai in the region where they co-occur using habitat suitability models. Gopherus agassizii and G. morafkai maintain independent taxonomic identities likely due to ecological niche partitioning, and the maintenance of the hybrid zone is best described by a geographical selection gradient model.
3

MAZACORNET: Mobility Aware Zone based Ant Colony Optimization Routing for VANET

Rana, Himani 18 December 2012 (has links)
Vehicular Ad hoc Networks (VANET) exhibit highly dynamic behavior with high mobility and random network topologies. The performance of Transmission Control Protocols in such wireless ad hoc networks is plagued by a number of problems: frequent link failures, scalability, multi-hop data transmission and data loss. To address these VANET routing issues, I have used the ideas from swarm intelligence. The Ant Colony Optimization (ACO), which is a branch of swarm intelligence, is the main source of my inspiration. I have designed an ant-based routing algorithm which addresses routing issues prevalent in VANETs: adaptivity, robustness and scalability. One attractive feature of ACO is that they provide multiple routes from source to destination, resulting in more robust network. In this work, together with ACO, I have used the ideas from zone routing protocols to develop my algorithm: Mobility Aware Zone based Ant Colony Optimization Routing for VANET that exhibits locality and scalability.
4

MAZACORNET: Mobility Aware Zone based Ant Colony Optimization Routing for VANET

Rana, Himani 18 December 2012 (has links)
Vehicular Ad hoc Networks (VANET) exhibit highly dynamic behavior with high mobility and random network topologies. The performance of Transmission Control Protocols in such wireless ad hoc networks is plagued by a number of problems: frequent link failures, scalability, multi-hop data transmission and data loss. To address these VANET routing issues, I have used the ideas from swarm intelligence. The Ant Colony Optimization (ACO), which is a branch of swarm intelligence, is the main source of my inspiration. I have designed an ant-based routing algorithm which addresses routing issues prevalent in VANETs: adaptivity, robustness and scalability. One attractive feature of ACO is that they provide multiple routes from source to destination, resulting in more robust network. In this work, together with ACO, I have used the ideas from zone routing protocols to develop my algorithm: Mobility Aware Zone based Ant Colony Optimization Routing for VANET that exhibits locality and scalability.
5

Genomová analýza hybridní zóny myší domácích / Whole-genome analysis of the house mouse hybrid zone

Janoušek, Václav January 2016 (has links)
Hybrid zones provide a valuable opportunity to study the process of speciation in real time. Untested combinations of genes from diverging populations come to the contact here causing a breakdown of genetic interactions and giving rise to reproductive isolation. Two house mouse subspecies (Mus musculus musculus/Mus musculus domesticus) form a narrow zone of secondary contact across Central Europe which is thought to be maintained by a balance between selection against unfit hybrids and dispersion of individuals. During my PhD study my collaborators and I used an array of ~ 1400 SNP markers to study patterns of introgression on a genome-wide scale across two/three house mouse hybrid zone transects. Our aim was to identify the genomic regions putatively harboring genes which are involved in the reproductive isolation between the two subspecies, characterize their distribution in mouse genome and assess genomic features associated with them. We were able to confirm on a genome-wide scale the importance of the X chromosome in the evolution of reproductive isolation. This chromosome exhibited introgression corresponding to strong negative epistasis and the patterns were consistent between transects pointing out to a common basis of reproductive isolation playing a role in two transects. Contrary to the...
6

The relation between buildings and public spaces in the context of sustainable compact cities : Understanding the impacts on human behavior- cases of Ørestad and Hammarby Sjöstad / Förhållandet mellan byggnader och offentliga platser i de hållbara kompakta städerna : Förstå effekterna på mänskligt beteende - fall av Ørestad och Hammarby Sjöstad

Baron Zenari, Leonardo January 2019 (has links)
This master thesis discusses the relation between the buildings and public space in the context of the compact cities, and how it interferes on human behavior related to walking experience and pleasurability. In order to illustrate how the human scale is portrayed in different scenarios, two case studies - Ørestad District, Copenhagen and Hammarby Sjöstad, Stockholm - have been selected to be studied in different scales, shifting from the block structure to the use of the building groundfloor. This enables me to identify the similarities in the process of composition of each compact city and, in case of contrasting comparisons, have a more critical discussion and understand the negative impacts on the user experience.
7

Hlasové projevy dvou druhů slavíků v jejich hybridní zóně / Vocalization of two nightingale species in their hybrid zone

Vokurková, Jana January 2011 (has links)
6 ABSTRACT Bird song is a sexually selected trait that is crucial for mate choice and for maintenance of pre-mating reproductive barriers. Secondary contact of closely related and partially reproductively isolated song bird species may result in changes in their songs; these can either diverge and strengthen the reproductive barrier between the two species, or converge and contribute to mixing of their gene pools. The Thrush Nightingale (Luscinia luscinia) and its congener Common Nightingale (L. megarhynchos) may serve as model species suitable for studying these phenomena. In their secondary contact zone, an interspecific hybridization has been documented, as well as convergence of songs of Thrush Nightingales caused by copying of heterospecific songs. Such copying may be a result of erroneous learning of species- specific songs or by genetic introgression. We tested these hypotheses by simultaneous analyses of DNA and song recordings of both species from allopatry (Czech Republic and northeastern Poland) and sympatry (central Poland). Comparisons between our recordings and a catalogue of songs recorded in a Common Nightingale population from allopatry (Germany) confirmed that most of Thrush Nightingale males from the sympatric region were 'mixed singers' that use Common Nightingale phrases in their...
8

Postglacial Population History of the Common Shrew (Sorex araneus) in Fennoscandia : Molekylära studier av återkolonisation, könsbundet genflöde och kromosomrasbildning. / Den vanliga näbbmusens (Sorex araneus) postglaciala populationshistoria i Fennoskandien : Molekylära studier av återkolonisation, könsbundet genflöde och kromosomrasbildning.

Andersson, Anna-Carin January 2004 (has links)
The common shrew, Sorex araneus, has one of the most variable karyotypes among mammals, displaying numerous chromosomes races throughout its distribution, which can be categorized into different karyotypic groups. The objective of this thesis was to examine the postglacial population history of Fennoscandian common shrews using autosomal microsatellites, mitochondrial DNA (mtDNA) and a Y chromosome specific microsatellite (L8Y). Autosomal microsatellites and mtDNA revealed weak genetic structure over a hybrid zone between the karyotypically divergent Northern and Western karyotypic groups. However, the genetic structure displayed by the Y chromosome microsatellite was orders of magnitude higher. Hence, considerable chromosomal differences between the groups do not prevent female gene flow, while male gene flow is reduced (cf. Haldane's rule). Further, the results suggest that the Haldane effect may be caused by the chromosomal differences between the karyotypic groups. No mtDNA differentiation was observed either between chromosome races or between the Northern and Western karyotypic groups in Fennoscandia. The combined pattern of karyotypic and mtDNA variation of Fennoscandian common shrews, suggest bi-directional postglacial recolonisation from a single refugium in Europe. The variation of the Y-linked microsatellite supported this conclusion. In contrast, significant mtDNA structure, discordant with the karyotypic variation, revealed that common shrews in southern Finland belong to a different lineage than remaining Fennoscandian regions, implying postglacial recolonisation from a different source. MtDNA variation of the chromosome races in Sweden supports the hypothesis that three races of the Western karyotypic group have been formed through whole arm reciprocal translocations (WARTs), as suggested by their mutual karyotypic variation. The variation of the molecular markers supports the theory of rapid karyotypic evolution in the common shrew.
9

Postglacial Population History of the Common Shrew (<i>Sorex araneus</i>) in Fennoscandia : Molekylära studier av återkolonisation, könsbundet genflöde och kromosomrasbildning. / Den vanliga näbbmusens (<i>Sorex araneus</i>) postglaciala populationshistoria i Fennoskandien : Molekylära studier av återkolonisation, könsbundet genflöde och kromosomrasbildning.

Andersson, Anna-Carin January 2004 (has links)
<p>The common shrew, <i>Sorex araneus</i>, has one of the most variable karyotypes among mammals, displaying numerous chromosomes races throughout its distribution, which can be categorized into different karyotypic groups. The objective of this thesis was to examine the postglacial population history of Fennoscandian common shrews using autosomal microsatellites, mitochondrial DNA (mtDNA) and a Y chromosome specific microsatellite (L8Y).</p><p>Autosomal microsatellites and mtDNA revealed weak genetic structure over a hybrid zone between the karyotypically divergent Northern and Western karyotypic groups. However, the genetic structure displayed by the Y chromosome microsatellite was orders of magnitude higher. Hence, considerable chromosomal differences between the groups do not prevent female gene flow, while male gene flow is reduced (cf. Haldane's rule). Further, the results suggest that the Haldane effect may be caused by the chromosomal differences between the karyotypic groups.</p><p>No mtDNA differentiation was observed either between chromosome races or between the Northern and Western karyotypic groups in Fennoscandia. The combined pattern of karyotypic and mtDNA variation of Fennoscandian common shrews, suggest bi-directional postglacial recolonisation from a single refugium in Europe. The variation of the Y-linked microsatellite supported this conclusion. In contrast, significant mtDNA structure, discordant with the karyotypic variation, revealed that common shrews in southern Finland belong to a different lineage than remaining Fennoscandian regions, implying postglacial recolonisation from a different source.</p><p>MtDNA variation of the chromosome races in Sweden supports the hypothesis that three races of the Western karyotypic group have been formed through whole arm reciprocal translocations (WARTs), as suggested by their mutual karyotypic variation. The variation of the molecular markers supports the theory of rapid karyotypic evolution in the common shrew.</p>
10

Morfologie spermií v sekundární kontaktní zóně slavíka obecného a slavíka tmavého / Sperm morphology in the secondary contact zone of Common Nightingale and Thrush Nightingale

Opletalová, Kamila January 2017 (has links)
The male gametes (sperms) are under strong sexual selection and are therefore very diverse in their morphology and often differ even amongst closely related species. Sperms are thus assumed to play very important role in reproductive isolation between species, due to their fast evolution in morphology. In my master thesis, I have studied the possible role of sperm morphology divergence in reproductive isolation in two sister species of passerine birds, the common nightingale (Luscinia megarhynchos) and the thrush nightingale (L. luscinia). The areas of these species overlap in secondary contact zone running across central and Eastern Europe, where they occasionally hybridize. I have compared sperm morphology of males of both species originating in allopatric and sympatric localities as well as interspecies hybrids. The results showed significant differences in total sperm length which is approximately 20 % longer in the common nightingale. That is caused by great interspecies divergence in midpiece (containing mitochondria) length. Interspecific hybrids showed sperms with intermediate length but despite expectations completely morphologically normal. This outcome corresponds with observed fertility in F1 hybrid males. What I consider to be an essential finding is a significant divergence in head...

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