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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

Molecular phylogenetics and taxonomic issues in dragonfly systematics (Insecta: Odonata)

Hovmöller, Rasmus January 2006 (has links)
Dragonflies (Odonata) are one of the ancestral groups of extant insects. They represent one of the three most basal branches in the phylogeny of winged insects. The other two groups are the Ephemeroptera, mayflies, and Neoptera, the latter which covers the remaining winged insects. The first paper is about the phylogenetic position of Odonata in relation to the other basal insect clades using 18S and 28S rDNA sequences. It was demonstrated that there are under certain parameters a strong statistical support for a sister-group relationship between Odonata and Neoptera forming the group Palaeoptera. The second paper is about the phylogeny of the Holarctic dragonfly Leucorrhinia. Dragonfly larvae are frequently equipped with spines on the abdomen, with great variation in spinyness between species. From an analysis of sequences of ITS and 5.8S rDNA it was found that spines have been lost at least twice in Leucorrhinia, in the European L. rubicunda and again in a clade of North American species. The third paper is on the subfamily Ischnurinae (Odonata: Coenagrionidae), a group dominated by the two larger genera Ischnura and Enallagma along with several mono- or oligotypic genera. From the presented molecular study, using mitochondrial 16S rDNA and COII sequences, it is demonstrated that Ischnurinae, and Ischnura are monophyletic. Enallagma is not monophyletic, and the genus name Enallagma should be restricted to the E. cyathigerum clade. he fourth paper is a catalog of the genus Coenagrion, with full information on synonymy, type material and bibliographical data. The fifth paper is an appeal to the International Commission on Zoological Nomenclature to suppress the genus group name Agrion. The letter of appeal elucidates the priority of Agrion, and demonstrates why it has fallen out of use. A case if made for why Agrion should be placed on the list of unavailable names, and Calopteryx given full validity.
2

Molecular phylogenetics and taxonomic issues in dragonfly systematics (Insecta: Odonata)

Hovmöller, Rasmus January 2006 (has links)
<p>Dragonflies (Odonata) are one of the ancestral groups of extant insects. They represent one of the three most basal branches in the phylogeny of winged insects. The other two groups are the Ephemeroptera, mayflies, and Neoptera, the latter which covers the remaining winged insects. The first paper is about the phylogenetic position of Odonata in relation to the other basal insect clades using 18S and 28S rDNA sequences. It was demonstrated that there are under certain parameters a strong statistical support for a sister-group relationship between Odonata and Neoptera forming the group Palaeoptera. The second paper is about the phylogeny of the Holarctic dragonfly <i>Leucorrhinia</i>. Dragonfly larvae are frequently equipped with spines on the abdomen, with great variation in spinyness between species. From an analysis of sequences of ITS and 5.8S rDNA it was found that spines have been lost at least twice in <i>Leucorrhinia,</i> in the European<i> L. rubicunda</i> and again in a clade of North American species. The third paper is on the subfamily Ischnurinae (Odonata: Coenagrionidae), a group dominated by the two larger genera Ischnura and Enallagma along with several mono- or oligotypic genera. From the presented molecular study, using mitochondrial 16S rDNA and COII sequences, it is demonstrated that Ischnurinae, and Ischnura are monophyletic. Enallagma is not monophyletic, and the genus name Enallagma should be restricted to the <i>E. cyathigerum </i>clade. he fourth paper is a catalog of the genus Coenagrion, with full information on synonymy, type material and bibliographical data. The fifth paper is an appeal to the International Commission on Zoological Nomenclature to suppress the genus group name Agrion. The letter of appeal elucidates the priority of Agrion, and demonstrates why it has fallen out of use. A case if made for why Agrion should be placed on the list of unavailable names, and Calopteryx given full validity.</p>
3

A revision of the Nearctic Species of Platycheirus Lepeletier and Serville (Diptera: Syrphidae)

Young, Andrew D. 09 May 2012 (has links)
The Nearctic members of the genus Platycheirus Lepeletier and Serville are revised. Five species, Platycheirus alpigenus Nielsen and Barkalov, Platycheirus brunnifrons Nielsen, Platycheirus clausseni Nielsen, Platycheirus speighti Doczkal, Stuke, and Goeldlin, and Platycheirus splendidus Rotheray, are newly recorded for the Nearctic Region, while three species, Platycheirus sp. trichopus, Platycheirus sp. “hyperboreus dark form” and Platycheirus n. sp. “perpallidus1” are new manuscript names. Females of 42 species are described for the first time. The genus Pyrophaena Schiner is resurrected. The genus Tuberculanostoma Fluke is synonymized with Platycheirus. An illustrated key to all 73 males and 52 females of Platycheirus and the males and females of the 3 species of Pyrophaena occurring in the Nearctic region is provided. Morphological and combined morphological/molecular COI phylogenetic analyses of the Platycheirus albimanus group are presented, as well as a molecular analysis of all available Platycheirus COI sequences. The species groups within Platycheirus are redefined based on these analyses. / NSERC-CANPOLIN
4

Tubificids with trifid chaetae: morphology and phylogeny of Heterodrilus (Clitellata, Annelida)

Sjölin, Erica January 2007 (has links)
Heterodrilus is a marine group of small (3-25 mm) clitellates that occur interstitially in sandy sediments from the intertidal zone down to about 150 m depths. The taxon includes 42 valid species and has been recorded from localities in the Mediterranean Sea, the North-west Atlantic Ocean (including the Caribbean), the Galapagos Islands, and the Indo-Pacific Region. A majority of the species of Heterodrilus are characterized by having trifid anterior chaetae (i.e., chaetae with three teeth at the distal end). A few species have bifid chaetae, but these are regarded as having lost the third tooth secondarily. Within the taxon, species are distinguished by morphological characters in the internal organization of the male and female genitalia, but also by characters in the form and number of chaetae. In this thesis, two new taxa are introduced, Heterodrilus tripartitus and H. ursulae, both from the Mediterranean Sea. The ultrastructure of the cuticle in four species (H. paucifascis, H. pentcheffi, H. flexuosus, H. minisetosus) is studied and it is shown that there is interspecific variation in the morphology of the cuticle. One of the studied species, H. paucifascis, shows intraspecific variation, which is associated with sample locality. The systematic position of Heterodrilus within Tubificidae is studied with molecular markers, and the results support that Heterodrilus (earlier classified as a member of Rhyacodrilinae) is positioned within Phallodrilinae. Furthermore, the phylogenetic relationships within Heterodrilus are estimated based on molecular characters from mitochondrial COI, the 16S rRNA gene, and the nuclear 18S rRNA gene, and the result indicate that the two major clades in our tree corresponds to different geographical distributions. This thesis also includes a checklist, as well as a key, to the species of Heterodrilus.
5

Aspects of carnivoran evolution in Africa

Dehghani, Reihaneh January 2008 (has links)
This thesis concerns the evolution of African small carnivorans, with emphasis on East African Viverridae and Herpestidae (Carnivora, Mammalia). Viverridae and Herpestidae are two Old World feliform (belonging to the cat branch) carnivoran families with a confusing, and sometimes even misleading, taxonomic and systematic history, in addition to a scarce fossil record. A new genus and species from Fort Ternan, western Kenya, dated to ca 14 Mya (million years ago), was described and tentatively assigned to the Viverridae. The excellent preservation of this material has the potential to shed much light on the evolution of feliform carnivorans from Africa. The fossil record of Carnivora from Laetoli, a Pliocene hominid-bearing site in northern Tanzania, was also described and placed in an evolutionary context. The age of the fossil fauna from Laetoli ranges from 4.3 Mya to 2.5 Mya. The fossil material from this site is remarkable for two reasons: it is extensive in both number of taxa represented and amount of fossil material, especially of small carnivorans, and it is fossilized and preserved under aeolian conditions. In addition to these paleontological studies, two studies concerning extant Viverridae and Herpestidae were conducted. First, the phylogeography of the white-tailed mongoose, Ichneumia albicauda, (Herpestidae), was examined, with the tentative conclusion that its origin is southern African. Second, the ecomorphology and biogeography of African and Eurasian Viverridae and Herpestidae was analysed in order to investigate if these features can be used to help assess their evolutionary history in the absence of fossils. The pattern that emerges in this study is that the species of Viverridae and Herpestidae do not generally overlap in ecomorphology where they overlap geographically, which indicates considerable competitive interactions between the families in both Africa and Eurasia.
6

Tubificids with trifid chaetae: morphology and phylogeny of <i>Heterodrilus</i> (Clitellata, Annelida)

Sjölin, Erica January 2007 (has links)
<p><i>Heterodrilus</i> is a marine group of small (3-25 mm) clitellates that occur interstitially in sandy sediments from the intertidal zone down to about 150 m depths. The taxon includes 42 valid species and has been recorded from localities in the Mediterranean Sea, the North-west Atlantic Ocean (including the Caribbean), the Galapagos Islands, and the Indo-Pacific Region. A majority of the species of <i>Heterodrilus</i> are characterized by having trifid anterior chaetae (i.e., chaetae with three teeth at the distal end). A few species have bifid chaetae, but these are regarded as having lost the third tooth secondarily. Within the taxon, species are distinguished by morphological characters in the internal organization of the male and female genitalia, but also by characters in the form and number of chaetae. In this thesis, two new taxa are introduced, <i>Heterodrilus tripartitus </i>and <i>H. ursulae</i>, both from the Mediterranean Sea. The ultrastructure of the cuticle in four species (<i>H. paucifascis, H. pentcheffi, H</i>. <i>flexuosus, H. minisetosus</i>) is studied and it is shown that there is interspecific variation in the morphology of the cuticle. One of the studied species, <i>H. paucifascis</i>, shows intraspecific variation, which is associated with sample locality. The systematic position of <i>Heterodrilus</i> within Tubificidae is studied with molecular markers, and the results support that <i>Heterodrilus </i>(earlier classified as a member of Rhyacodrilinae) is positioned within Phallodrilinae. Furthermore, the phylogenetic relationships within <i>Heterodrilus</i> are estimated based on molecular characters from mitochondrial COI, the 16S rRNA gene, and the nuclear 18S rRNA gene, and the result indicate that the two major clades in our tree corresponds to different geographical distributions. This thesis also includes a checklist, as well as a key, to the species of <i>Heterodrilus</i>.</p>
7

Aspects of carnivoran evolution in Africa

Dehghani, Reihaneh January 2008 (has links)
<p>This thesis concerns the evolution of African small carnivorans, with emphasis on East African Viverridae and Herpestidae (Carnivora, Mammalia). Viverridae and Herpestidae are two Old World feliform (belonging to the cat branch) carnivoran families with a confusing, and sometimes even misleading, taxonomic and systematic history, in addition to a scarce fossil record. </p><p>A new genus and species from Fort Ternan, western Kenya, dated to ca 14 Mya (million years ago), was described and tentatively assigned to the Viverridae. The excellent preservation of this material has the potential to shed much light on the evolution of feliform carnivorans from Africa. The fossil record of Carnivora from Laetoli, a Pliocene hominid-bearing site in northern Tanzania, was also described and placed in an evolutionary context. The age of the fossil fauna from Laetoli ranges from 4.3 Mya to 2.5 Mya. The fossil material from this site is remarkable for two reasons: it is extensive in both number of taxa represented and amount of fossil material, especially of small carnivorans, and it is fossilized and preserved under aeolian conditions. In addition to these paleontological studies, two studies concerning extant Viverridae and Herpestidae were conducted. First, the phylogeography of the white-tailed mongoose, <i>Ichneumia albicauda</i>, (Herpestidae), was examined, with the tentative conclusion that its origin is southern African. Second, the ecomorphology and biogeography of African and Eurasian Viverridae and Herpestidae was analysed in order to investigate if these features can be used to help assess their evolutionary history in the absence of fossils. The pattern that emerges in this study is that the species of Viverridae and Herpestidae do not generally overlap in ecomorphology where they overlap geographically, which indicates considerable competitive interactions between the families in both Africa and Eurasia.</p>
8

Patterns and Processes of Evolution in Sundaland

den Tex, Robert-Jan January 2011 (has links)
Biodiversity in the tropics is disproportionately high compared to other habitats, and also under disproportionate threat from human impact. It is necessary to understand how this diversity evolved and how it is partitioned across space in order to preserve it. In this thesis I construct phylogenies of tropical forest dependent vertebrates from Southeast Asia and the islands of the Sunda shelf, a region referred to as Sundaland. I focus on the tree squirrels (genus Sundasciurus) and Asian barbets (Aves: Family Megalaimidae), two taxa with similar ecological characteristics. I use these phylogenies to test hypotheses that have been put forward to explain high levels of tropical diversity including the Pleistocene pump and museum hypotheses. I also use phylogenies to elucidate phylogeographic patterns within the region. I find no evidence for an increase in speciation in the Pleistocene, but I do find within species structure that dates to this period. Common phylogeographic patterns were identified between many forest dependent vertebrates that suggest that populations on the island of Sumatra are generally more closely related to Malay Peninsula populations than to populations on Borneo. From a methodological viewpoint we propose careful usage of universal primers in ancient DNA studies because of our finding of increased risk of amplifying pseudogenes of the mtDNA.
9

The Dawn of a New Age : Interrelationships of Acoela and Nemertodermatida and the Early Evolution of Bilateria

Wallberg, Andreas January 2009 (has links)
Deciphering the rapid emergence of bilaterian animals around the time of the Cambrian Explosion and reconstructing the interrelationships of animal groups have long been two of the most elusive problems in Zoology. This thesis concerns the phylogenetic interrelationships within and among Acoela and Nemertodermatida, two groups of small worms that are believed to be basal bilaterians and which may provide important clues for understanding the early evolution of animals. In addition to trying to resolve the phylogenetic positions of these groups, major focus is put on inferring how ancestral animals might have looked, given the phylogenetic hypotheses put forward. The data used to infer phylogenies include nuclear ribosomal DNA, the mitochondrial COI gene and microRNAs. Based on phylogenetic analyses of a large number of 18S SSU ribosomal DNA sequences, it is proposed that Cnidaria is the sister taxon to Bilateria. Poor taxon sampling is suggested to be one of the reasons for why earlier assessments of the interrelationships among the most basal animal groups have yielded many conflicting results using the same gene. Analyses of new 18S SSU rDNA and 28S LSU rDNA sequences from six of the nine known species of nemertodermatids corroborate earlier indications that Acoela and Nemertodermatida are not sister taxa, as once thought. Being separate basal bilaterian animal groups, it is suggested that the last common ancestor of all bilaterians shared much of their comparatively simple morphology. Many methods are deployed to assess whether the phylogenetic results are mainly due to long-branch attraction, but no indication of this artifact is detected. The first comprehensive phylogenetic framework of Acoela is reconstructed from the 18S SSU, 28S LSU and COI genes, in combination with morphological data. The ancestral acoel worm is reconstructed using Bayesian methods and morphological observations in extant species. Two indeces, posterior similarity and reconstruction signal, are implemented to assess how similar different species are to the last common ancestor of all acoels and illustrate how clearly different characters or nodes are reconstructed. It is suggested that the ancestral acoel looked much like extant species of Diopisthoporus. The phylogenetic positions of Acoela and Nemertodermatida are assessed using new data on microRNAs in the acoel Hofstenia miamia and the nemertodermatid Meara stichopi. Acoela and Nemertodermatida are again found to be basal bilaterians, in congruence with earlier results. Using the work-flow and indeces developed earlier, it is concluded that the bilaterian ancestral microRNA repertoire can not yet be reconstructed with high confidence. All papers stress the importance of inclusive taxon sampling for making generalized inferences about ancestral features in animals.
10

Species Limits, and Evolutionary History of Glassfrogs

Castroviejo-Fisher, Santiago January 2009 (has links)
Recognizing the mechanisms of speciation and the limits of species is essential to understand the origin of biodiversity and how to conserve it. The general aims of my investigations during my doctoral studies were two-fold: to study evolutionary patterns and processes, and to provide specific and superspecific taxonomic classifications that try to reflect evolutionary history. I have focused my research on anurans in their biodiversity hotspot, the American Tropics. I have used morphological, behavioral (mating calls), and genetic (DNA sequences) characters to study species boundaries between frogs of the genus Pristimantis and the family Centrolenidae (glassfrogs). The results show that the exclusive use of single lines of evidence or the application of arbitrary thresholds impair and bias our ability to recognize new species and limit the possibility to understand evolutionary processes. Only an integrative approach combining every source of evidence provides the necessary feedback to discover all species and test their identity by comparing independent sets of data. This approach further allows identifying those species that probably represent stable comparative units (well supported species hypotheses) and to flag taxa that require further assessment. Phylogenetic reconstructions based on seven nuclear and mitochondrial genes for about 100 species of glassfrogs revealed that previous hypotheses of relationships were mislead by rampant convergent evolution at the phenotypic level. None of the previously suggested classifications fit with the reconstructed evolutionary history. Consequently, we proposed a new classification consistent with this phylogeny. I also studied the tempo and mode of diversification among glassfrogs. Based on sequences from ten genes in 87 species, I estimated species divergence times, age-range correlation between sister species, and reconstructed ancestral areas and dispersal/vicariance events. The results revealed a complex model of diversification where geographical isolation seems to be the dominant scenario for speciation and only clades of altitudinal generalists have been able to spread across the Neotropical rainforests.

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