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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

Intraspecific relationships among the stygobitic shrimp Typhlatya mitchelli, by analyzing sequence data from mitochondrial DNA

Webb, Michael Scott 30 September 2004 (has links)
Intraspecific relationships among the anchialine cave shrimp Typhlatya mitchelli were examined by sequencing a total of 1505 bp from portions of three mitochondrial DNA genes. Cytochrome b, cytochrome oxidase I, and 16S rRNA were partially sequenced and analyzed for specimens from six different cenotes (water-filled caves) across the Yucatan Peninsula, Mexico. The conspecific Typhlatya pearsei that is sympatric with T. mitchelli was also sequenced and used as the outgroup. Comparisons among specimens of T. mitchelli yielded low sequence divergence values (0-1.7%), with the majority being less than 0.4%. Phylogenetic tree topologies reconstructed with neighbor-joining, maximum likelihood, and maximum parsimony were in agreement in regards of the resolution of deep branches. Also, there was no obvious geographic differentiation among the majority of T. mitchelli samples, with the exception of specimens from Cenote San Antonio Chiich (Yokdzonot, Yucatan, Mexico) which all clustered into an extremely well supported monophyletic group. The level of differentiation of this group, together with the nearly total absence of differentiation among T. mitchelli from distant cave systems, suggests that this is an Evolutionary Significant Unit (ESU), which may correspond to a new species. This unidentified Typhlatya from Cenote San Antonio Chiich was helpful in establishing a period in which the epigean ancestor colonized the cenotes. Based on pairwise distance data and previously published shrimp molecular clocks (Baldwin et al., 1998), T. mitchelli and the putative new Typhlatya species last shared a common ancestor between 3-5 million years ago (mya), during the mid-Pliocene era, while T. mitchelli and T. pearsei was approximately 7-10 mya (middle to late Miocene). The ancestor to T. mitchelli and the unidentified Typhlatya species abandoned its shallow coastal water existence in the early Pliocene and eventually expanded its range across the peninsula. Approximately 4 mya, Cenote San Antonio Chiich became isolated from the remaining gene pool thereby halting gene flow. As the regional water table fluctuated in response to the rise and fall of Pleistocene sea levels, T. mitchelli actively colonized the peninsula. The discovery of a single, continuous subterranean freshwater system provides for a better understanding of anchialine biogeography within the Yucatan Peninsula.
2

Environmental biosafety of field scale GM triticale (xTriticosecale Wittmack) cultivation for bioindustrial applications

Kavanagh, Vanessa B Unknown Date
No description available.
3

Developmental timing in aquatic embryos : linking intraspecific heterochrony and evolution

Tills, Oliver A. January 2013 (has links)
The main aim of this thesis is to understand the extent to which intraspecific variation in developmental event timing might provide the raw material from which heterochronies may originate. To this end I studied the timing of a suite of both morphological and physiological events in the embryonic development of Radix balthica, a species of aquatic snail known to exhibit event timing variation during the embryonic period (Tills et al. 2010; Rundle et al. 2011) and that sits within an evolutionary clade, in which extensive heterochrony has been documented (Smirthwaite et al. 2007). I found that variation in embryonic developmental event timing within R. balthica is pervasive (Chapters 2 - 5) and distributed primarily at low (inter-individual and egg mass), rather than high (population) biological levels (Chapter 3). This variation also appears to have a genetic basis (Chapter 2) and to be heritable (Chapters 4 and 5). Examination of the development of function in the cardiovascular (CV) system in Chapter 5 also revealed extensive variation, including differences between egg masses in the timing of aspects of this development, and differences between populations in the rates of change in heart rate during different phases of ontogeny. Variation in CV development also had effects on life history, which suggest that altered embryonic development might have implications for Darwinian fitness (Chapter 5). This thesis demonstrates that intraspecific variation in developmental event timing represents a fundamental link between ontogeny and phylogeny and that study of altered timing at the inter-individual level provides the opportunity to address questions concerning its evolvability and implications.
4

Intraspecific relationships among the stygobitic shrimp Typhlatya mitchelli, by analyzing sequence data from mitochondrial DNA

Webb, Michael Scott 30 September 2004 (has links)
Intraspecific relationships among the anchialine cave shrimp Typhlatya mitchelli were examined by sequencing a total of 1505 bp from portions of three mitochondrial DNA genes. Cytochrome b, cytochrome oxidase I, and 16S rRNA were partially sequenced and analyzed for specimens from six different cenotes (water-filled caves) across the Yucatan Peninsula, Mexico. The conspecific Typhlatya pearsei that is sympatric with T. mitchelli was also sequenced and used as the outgroup. Comparisons among specimens of T. mitchelli yielded low sequence divergence values (0-1.7%), with the majority being less than 0.4%. Phylogenetic tree topologies reconstructed with neighbor-joining, maximum likelihood, and maximum parsimony were in agreement in regards of the resolution of deep branches. Also, there was no obvious geographic differentiation among the majority of T. mitchelli samples, with the exception of specimens from Cenote San Antonio Chiich (Yokdzonot, Yucatan, Mexico) which all clustered into an extremely well supported monophyletic group. The level of differentiation of this group, together with the nearly total absence of differentiation among T. mitchelli from distant cave systems, suggests that this is an Evolutionary Significant Unit (ESU), which may correspond to a new species. This unidentified Typhlatya from Cenote San Antonio Chiich was helpful in establishing a period in which the epigean ancestor colonized the cenotes. Based on pairwise distance data and previously published shrimp molecular clocks (Baldwin et al., 1998), T. mitchelli and the putative new Typhlatya species last shared a common ancestor between 3-5 million years ago (mya), during the mid-Pliocene era, while T. mitchelli and T. pearsei was approximately 7-10 mya (middle to late Miocene). The ancestor to T. mitchelli and the unidentified Typhlatya species abandoned its shallow coastal water existence in the early Pliocene and eventually expanded its range across the peninsula. Approximately 4 mya, Cenote San Antonio Chiich became isolated from the remaining gene pool thereby halting gene flow. As the regional water table fluctuated in response to the rise and fall of Pleistocene sea levels, T. mitchelli actively colonized the peninsula. The discovery of a single, continuous subterranean freshwater system provides for a better understanding of anchialine biogeography within the Yucatan Peninsula.
5

Pathogenicity and taxonomy of fungi associated with the mountain pine beetle in British Columbia

Plattner, Alex 05 1900 (has links)
The mountain pine beetle is associated with a diverse array of fungi. Grosmannia clavigera is the most pathogenic of these fungi. A comparison was made between two methods that have been used to assess fungal pathogenicity. Results were similar for older trees inoculated with G. clavigera using either the alternating flap technique or cork borer method. Using the cork borer method, younger lodgepole pine trees were inoculated with five different isolates of G. clavigera. After a 48 week incubation period, isolates ATCC 18086, B5 and H55 had induced stronger pathogenic indicators compared to isolates KW 1407 and B20. After a 7 week incubation period, only isolate ATCC 18086 had induced stronger pathogenic indicators. Usually, this isolate grew faster at lower temperatures and in a low oxygen environment. Isolate KW 1407 consistently produced milder pathogenic indicators during both incubation periods. Among the non-pathogenic fungal associates of the mountain pine beetle, Ceratocystiopsis minuta may be considered the most important because it is the type species for the genus Ceratocystiopsis. The history of this genus is complicated because no physical specimen exists for C. minuta. The phylogeny of the genus Ceratocystiopsis was evaluated. Many isolates of C. minuta were assessed as potential epitypes. Several isolates of C. minuta from previous work were shown to be misidentified. C. minuta isolate CBS 116796 is recommended for future genetic work within the genus Ceratocystiopsis. For morphological work, using measurements from the literature is recommended since CBS 116796 did not produce fruiting bodies.
6

Pathogenicity and taxonomy of fungi associated with the mountain pine beetle in British Columbia

Plattner, Alex 05 1900 (has links)
The mountain pine beetle is associated with a diverse array of fungi. Grosmannia clavigera is the most pathogenic of these fungi. A comparison was made between two methods that have been used to assess fungal pathogenicity. Results were similar for older trees inoculated with G. clavigera using either the alternating flap technique or cork borer method. Using the cork borer method, younger lodgepole pine trees were inoculated with five different isolates of G. clavigera. After a 48 week incubation period, isolates ATCC 18086, B5 and H55 had induced stronger pathogenic indicators compared to isolates KW 1407 and B20. After a 7 week incubation period, only isolate ATCC 18086 had induced stronger pathogenic indicators. Usually, this isolate grew faster at lower temperatures and in a low oxygen environment. Isolate KW 1407 consistently produced milder pathogenic indicators during both incubation periods. Among the non-pathogenic fungal associates of the mountain pine beetle, Ceratocystiopsis minuta may be considered the most important because it is the type species for the genus Ceratocystiopsis. The history of this genus is complicated because no physical specimen exists for C. minuta. The phylogeny of the genus Ceratocystiopsis was evaluated. Many isolates of C. minuta were assessed as potential epitypes. Several isolates of C. minuta from previous work were shown to be misidentified. C. minuta isolate CBS 116796 is recommended for future genetic work within the genus Ceratocystiopsis. For morphological work, using measurements from the literature is recommended since CBS 116796 did not produce fruiting bodies.
7

Lineage isolation maintained by natural selection despite ongoing gene flow in Japanese wild radish / 遺伝子流動存在下で自然選択によって維持されている日本のハマダイコンの系統隔離

Han, Qingxiang 23 March 2017 (has links)
Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第20459号 / 人博第809号 / 新制||人||194(附属図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 瀬戸口 浩彰, 教授 加藤 眞, 教授 市岡 孝朗 / 学位規則第4条第1項該当
8

Pathogenicity and taxonomy of fungi associated with the mountain pine beetle in British Columbia

Plattner, Alex 05 1900 (has links)
The mountain pine beetle is associated with a diverse array of fungi. Grosmannia clavigera is the most pathogenic of these fungi. A comparison was made between two methods that have been used to assess fungal pathogenicity. Results were similar for older trees inoculated with G. clavigera using either the alternating flap technique or cork borer method. Using the cork borer method, younger lodgepole pine trees were inoculated with five different isolates of G. clavigera. After a 48 week incubation period, isolates ATCC 18086, B5 and H55 had induced stronger pathogenic indicators compared to isolates KW 1407 and B20. After a 7 week incubation period, only isolate ATCC 18086 had induced stronger pathogenic indicators. Usually, this isolate grew faster at lower temperatures and in a low oxygen environment. Isolate KW 1407 consistently produced milder pathogenic indicators during both incubation periods. Among the non-pathogenic fungal associates of the mountain pine beetle, Ceratocystiopsis minuta may be considered the most important because it is the type species for the genus Ceratocystiopsis. The history of this genus is complicated because no physical specimen exists for C. minuta. The phylogeny of the genus Ceratocystiopsis was evaluated. Many isolates of C. minuta were assessed as potential epitypes. Several isolates of C. minuta from previous work were shown to be misidentified. C. minuta isolate CBS 116796 is recommended for future genetic work within the genus Ceratocystiopsis. For morphological work, using measurements from the literature is recommended since CBS 116796 did not produce fruiting bodies. / Forestry, Faculty of / Graduate
9

Intraspecific variation and ecology of a highly restricted paleoendemic (Witsenia maura) in the south-western Cape

Gwynne-Evans, David 13 February 2017 (has links)
Witsenia is a monospecific genus of the putatively basal group, the woody Iridaceae. This upright iris has extremely long black and yellow flowers ( see fig. 1) that are thought to have been pollinated by an extinct Sunbird. The role of the unusual black floral colouration is investigated as this colour is seldom associated with bird pollination. This plant typically exists in discreet and restricted populations in wet habitats in the South Western Cape (South Africa). The restricted nature of the plant is peculiar as it occurs in either low or high altitudes, yet appears to be extremely sensitive to altitude. Popular belief suggests that Witsenia maura occurs in the Peninsula only, and results from this study show the Peninsula population to be genetically separate from other populations, reflecting a long term separation. Samples from nine populations are sequenced to investigate haplotypic variation within the species, and dispersal of ancestral populations. This thesis investigates the current knowledge of Witsenia, its ecology, history and distribution. An examination of flowers under UV light reveals the first evidence of UV nectar guides in an ornithophilous flower. Conservation issues are also addressed, and it is established that although small and apparently shrinking due to global warming, populations are nonetheless viable if managed properly. A molecular study of the species and examinination of its variation revealed exceptional haplotype diversity. This diversity can best be explained by swamps acting as refugia during interglacial periods.
10

Adaptation of an invasive grass to agriculture: ecological and genomic evidence

Smith, Alyssa Laney 06 June 2017 (has links)
Species vary phenotypically and genetically across their environmental range limits, and this variation can influence ecological processes. Ecologically meaningful intraspecific variation might be particularly important in the context of agricultural weeds and exotic invaders, because intraspecific variation in these species might allow them to rapidly adapt to their unusually dynamic and variable environments. In a greenhouse study, we explored intraspecific variation in the size, rhizome production, and competitive ability of the global invader, Johnsongrass (Sorghum halepense), representing populations from agricultural and non-agricultural habitats across its introduced North American range. We also used these populations to explore the relationship between phenotypic variation and genomic endoreduplication responses to the common stresses herbicides, competition, and clipping. Endoreduplication occurs when plants increase their genome size by increasing their nuclear chromosome number, with some evidence showing correlations with stress response. We found that Johnsongrass plants from agricultural habitats were larger than plants from non-agricultural habitats, but there was no difference between habitats in either rhizome production or competitive ability. Two of the five herbicides we tested, primisulfuron and imazethapyr, had the strongest suppressive effects on Johnsongrass, and also stimulated the greatest rates of endoreduplication. Furthermore, agricultural populations showed higher levels of endoreduplication. We found no overall effect of competition on endoreduplication, although endoreduplication was higher for non-agricultural populations than agricultural populations. When competing with corn, but not with conspecifics, Johnsongrass roots increased endoreduplication by 13%. Clipping induced substantial endoreduplication, but there was no difference between agricultural and non-agricultural populations. Our results suggest that endoreduplication may play a role in some, but not all, stress responses in Johnsongrass. Furthermore, our results indicate that Johnsongrass has adapted in some phenotypic and genomic ways to agricultural habitats in North America. Such adaptation may play a role in this species' success as both an agricultural weed and an exotic invader. / Master of Science in Life Sciences

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