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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.
11

Phylogenetic relationships of the "Briza complex" to other members of the subfamily Pooideae (Poaceae) : Based on molecular data from the nuclear regions ITS and GBSSI, and the chloroplast gene matK

Persson, Nannie January 2015 (has links)
No description available.
12

Paraphyly of the Malagasy genus Carphalea (Rubiaceae, Rubioideae, Knoxieae) and its taxonomic implications

Ferm, Julia January 2013 (has links)
No description available.
13

New insights into the deep divergences of Ephedra (Gnetales) using molecular data

Thureborn, Olle January 2014 (has links)
No description available.
14

A new genus of dimeropygid trilobites from the Great Basin of the western USA

Losso, Sarah 01 May 2018 (has links)
Dimeropygidae Hupé, 1953 is a family of highly vaulted and small trilobites from the paleotropics of the uppermost Cambrian through the Ordovician. Specimens are known from Laurentia, Baltica, Avalonia, Siberia, Australia, North China, and South China. Dimeropygids are difficult to recover because of their small size and vaulted, tuberculate, and often spiny exoskeletons. Thus, most of their diversity is known from secondarily silicified material which preserves remarkable amounts of detail on the sclerites. Such faunas, while often rare, are common in the Great Basin of the western USA. Trilobite research has been conducted in the Great Basin has been since the late 1800s. Recent high intensity sampling and collection of larger sample sized from silicified horizons has increased the known diversity of trilobites from Lower Early Ordovician. New collections from the Lower Ordovician are providing crucial new insight into the groups early evolutionary history (e.g., Adrain & Westrop, 2007, McAdams & Adrain, 2009, Adrain et al., 2014a). Skullrockicurus n. gen. is a new genus of dimeropygid trilobites including at least seven new species. Five of the new species are well known enough from silicified material to formally name: S. greeni (Garden City Formation, Idaho and House Formation, Utah), S. plummeri (House Formation, Utah), S. judyi (House Formation, Utah), S. massarellai (House Formation, Utah), and S. brocki (House Formation, Utah). Synapomorphies of the new genus include four pairs of tubercles on the glabella, a posteriorly bowed glabella, long preglabellar field, and semilunate pygidium with a corona of tubercles or spines at the fulcrum.
15

Systematics of the Onychoteuthidae Gray, 1847 (Cephalopoda: Oegopsida)

Bolstad, Kathrin S. Unknown Date (has links)
Squids in the family Onychoteuthidae Gray, 1847 have been reported from every ocean but the Arctic, are taken frequently in deep-sea fisheries by catch, and are ecologically important in the diets of many marine predators including cetaceans, pinnipeds, sharks, and seabirds. However, the diversity and systematic of the family have remained poorly understood. Of the 60+ nominal species, 12–14 have generally been accepted in recent studies. Challenges to clarity include insufficient species descriptions, original descriptions published in eight languages and often based solely on early life stages, non-designation or subsequent loss of type material, and the existence of several unresolved species complexes. In light of the general systematic disarray of the Onychoteuthidae, a global revision of the family follows, based on ~1500 specimens examined from 19 repositories. Type material has been examined wherever possible; for some species, photographs of type specimens, original illustrations, and/or the original descriptions have provided the only information available. It has not been possible to fully disambiguate taxa in some cases (e.g. Gen. nov. 2), given the limited material and information available, but for all species treated in this revision (25 out of 26 species; no material was available for Kondakovia nigmatullini), descriptions and illustrations are provided to a consistent standard that will enable their reidentification. External and internal morphological characters and states are described for sub adult to adult stages of most species, with external characters reported through ontogeny as permitted by available material. Historically important characters are treated (general external morphology, body proportions, tentacle clubs, photophores, gladius, lower beak, radula), augmented by several more recently recognised characters (palatine teeth, detailed morphology of the tentacular hooks in adults, tentacular suckers in paralarvae, chromatophore patterns). The systematic value of both historical and new morphological characters at the generic and species levels are discussed; at all ontogenetic stages, tentacular club and hook morphology are considered the most valuable characters, although body proportions and gladius also prove useful. Partial disambiguation of the Onychoteuthis banksii complex has been possible in the Pacific and Atlantic Oceans, resulting in the resurrection of Onychoteuthis bergii Lichtenstein, 1818 and Onychoteuthis aequimanus Gabb, 1868, the description of two new species, Onychoteuthis lacrima and Onychoteuthis prolata (in press), and the expansion of one species’ recognised distribution (Onychoteuthis compacta) to include the Atlantic Ocean. The genus Moroteuthis Verrill, 1881 is considered a junior synonym of Onykia Lesueur, 1821, in accordance with the findings of several earlier authors. However, morphological differences in the species ‘Moroteuthis’ ingens necessitate the resurrection of the subgenus Moroteuthopsis Pfeffer, 1908b, with all other Onykia species placed into a new subgenus, Onykia (Onykia). Sexual dimorphism is reported in the beaks of Onykia (Moroteuthopsis) ingens (new comb.), and revised sex-specific equations are given for estimating this species’ biomass based on LRL. Morphological and historical genetic data suggest a more distant relationship between Onykia and the species ‘Moroteuthis’ knipovitchi Filippova, 1972 than was suggested by earlier classifications. This species is therefore considered to represent an undescribed genus, herein referred to as Gen. Nov. 1, which cannot be more fully diagnosed and described at present due to limited material. The generic position of ‘Onykia’ rancureli (Okutani, 1981) is also uncertain; it may be allied to Walvisteuthis virilis Nesis & Nikitina, 1986 (family Walvisteuthidae Nesis & Nikitina, 1986), but confirmation is impossible without examining type material of W. virilis. A second new genus, Gen. Nov. 2, is therefore described for ‘Onykia’ rancureli and several morphological variants reported from the Pacific and Atlantic Oceans. Given that the majority of available onychoteuthid material was collected after 1950, resulting in the descriptions of over half of the generally accepted genera and species since 1960, ongoing collection programmes are necessary to further resolve onychoteuthid systematic.
16

A systematic study of select species complexes of Eleocharis subgenus Limnochloa (Cyperaceae)

Rosen, David Jonathan 15 May 2009 (has links)
A systematic study of two complexes of closely related species within Eleocharis subg. Limnochloa was conducted to better define poorly understood species and to lay the foundation for a worldwide revision of this group. Research utilized scanning electron microscopy (SEM), study of more than 2300 herbarium specimens and types from 35 herbaria, multivariate analysis, and field studies in the southeast United States and Mexico. Examination of achene gross- and micromorphology using SEM indicated a relationship among the species of the Eleocharis mutata complex (comprising E. mutata, E. spiralis, and E. cellulosa), their distinctness from the E. acutangula complex (comprising E. acutangula s.l. and E. obtusetrigona) and support the placement of all taxa studied within subg. Limnochloa. All species examined shared micromorphological characters typical of subg. Limnochloa. A systematic study of the worldwide morphological variation of E. mutata suggests it is represented by a single taxon throughout its distribution and is native to the New World and probably introduced in tropical Africa. The taxonomic relationship of Eleocharis mutata and E. spiralis was explored using discriminant analysis, PCA and phyto-geography, supporting the recognition of the two taxa as distinct at the rank of species. A systematic study of E. cellulosa suggests it is represented by a single taxon throughout its distribution, with an apparent Caribbean genotype distinguished by the presence of perianth bristles with retrorse spinules. A systematic study of the worldwide variation of E. acutangula s.l. resulted in its segregation into two infraspecific taxa, E. acutangula subsp. acutangula and E. acutangula subsp. breviseta, and two new South American species, E. neotropica and E. steinbachii. Nomenclatural history and lectotypification of certain taxa studied are discussed, and two basyionyms and two synonyms of accepted taxa are lectotypified. A taxonomic treatment is provided that includes a key, detailed descriptions and complete synonymy of each species, line drawings prepared from select specimens examined, and notes on habitat and distribution. Future research goals and needs are discussed.
17

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.
18

A systematic study of select species complexes of Eleocharis subgenus Limnochloa (Cyperaceae)

Rosen, David Jonathan 15 May 2009 (has links)
A systematic study of two complexes of closely related species within Eleocharis subg. Limnochloa was conducted to better define poorly understood species and to lay the foundation for a worldwide revision of this group. Research utilized scanning electron microscopy (SEM), study of more than 2300 herbarium specimens and types from 35 herbaria, multivariate analysis, and field studies in the southeast United States and Mexico. Examination of achene gross- and micromorphology using SEM indicated a relationship among the species of the Eleocharis mutata complex (comprising E. mutata, E. spiralis, and E. cellulosa), their distinctness from the E. acutangula complex (comprising E. acutangula s.l. and E. obtusetrigona) and support the placement of all taxa studied within subg. Limnochloa. All species examined shared micromorphological characters typical of subg. Limnochloa. A systematic study of the worldwide morphological variation of E. mutata suggests it is represented by a single taxon throughout its distribution and is native to the New World and probably introduced in tropical Africa. The taxonomic relationship of Eleocharis mutata and E. spiralis was explored using discriminant analysis, PCA and phyto-geography, supporting the recognition of the two taxa as distinct at the rank of species. A systematic study of E. cellulosa suggests it is represented by a single taxon throughout its distribution, with an apparent Caribbean genotype distinguished by the presence of perianth bristles with retrorse spinules. A systematic study of the worldwide variation of E. acutangula s.l. resulted in its segregation into two infraspecific taxa, E. acutangula subsp. acutangula and E. acutangula subsp. breviseta, and two new South American species, E. neotropica and E. steinbachii. Nomenclatural history and lectotypification of certain taxa studied are discussed, and two basyionyms and two synonyms of accepted taxa are lectotypified. A taxonomic treatment is provided that includes a key, detailed descriptions and complete synonymy of each species, line drawings prepared from select specimens examined, and notes on habitat and distribution. Future research goals and needs are discussed.
19

Phylogeny and biogeography of the mayfly family Leptohyphidae (Insecta: Ephemeroptera) with a taxonomic revision of selected genera

Baumgardner, David Eugene 10 October 2008 (has links)
A cladistic analysis of the world genera of the mayfly family Leptohyphidae is presented. Analyses of a matrix of 58 ingroup and 9 outgroup species and 119 morphological characters strongly supports the monophyly of Leptohyphidae and its sister-group relationship with Coryphoridae. Larval and adult taxonomic keys are provided to the 11 recognized extant genera. A synonymical listing, differential diagnosis, list of proposed synapomorphies, diagnostic illustrations, and notes on distribution and included species are given for each genus. The following new synonyms of genus Tricorythodes are proposed: Ableptemetes n. syn., Cabecar n. syn., Epiphrades n. syn., Homoleptohyphes n. syn., Macunahyphes n. syn., Tricoryhyphes n. syn. The former genus Asioplax is newly regarded as a subgenus of Tricorythodes. A species-level revision of North and Central American Leptohyphes is presented. A key to the 15 Leptohyphes species known as larvae is provided. In addition, detailed descriptions, diagnosis, and geographic distributions are given for all species of Leptohyphes known from North and Central America. Biogeographic analysis suggests that the family Leptohyphidae originated in South America, and that its North American species are the descendants of one or more ancestral species that crossed northward over the Panamanian land bridge. The results of this research clearly show that the mayfly family Leptohyphidae is a strongly supported monophyletic clade supported by five unique synapomorphies. Currently recognized genera are also strongly supported; however, little support was found for subfamilies. The sister family is clearly Coryphoridae, which is supported by three unique synapomorphies. Biogeographic analysis indicates that Leptohyphidae originated in South American, with at least five independent invasions from South America to North and Central America during the evolution of Leptohyphidae.
20

A systematic study on the genus Machilus of Taiwan (Lauraceae)

Lu, Sheng-you 28 August 2008 (has links)
Abstract The genus Machilus comprises about 100 species. They are distributing over the tropics and the subtropical zone, mainly in Easten Asia. Eight species and one variety are native plants of Taiwan, including M.konishiiHayata, M. kusanoi Hayata, M. mushaensis Lu, M. obovatifolia (Hayata) Kaneh. et. Sasaki, M. obovatifolia var. taiwuensis Lu & Chen, M. philippinensis Merr., M. pseudolongifolia Hayata., M. thunbergii Siebold & Zucc. and M. zuhoensis Hayata. Machilus japonica Siebold & Zucc. is regarded to be native in Japan, Ryukyu and Korea, but not native to Taiwan. Due to the morphological similarities among several taxa, species identification was a difficult task in the past. Although many scholars have worked on this topic, there are still many unresolved issues left, especially the relationships among M. japonica, M. pseudolongifolia, M. kusanoi, M. zuihonensis and M. mushaensis. This study aims to study Taiwan Machilus taxonomy with an emphasis on a detailed morphological study. In addition, essential oils, DNA sequences and isozymes were also studied. The results are list as follows: 1. Morphological taxonomy: Machilus japonica, M. pseudolongifolia., M. kusanoi, M. zuihonensis and M. mushaensis can be firmily classified into 5 taxa by morphologic characters. 2. Essential oils of leaves: The data of essential oils ca differentiate the closely related species, M. japonica, M. pseudolongifolia, M. kusanoi, M. zuihnensis and M. mushaensis from one another. The data also indicated that M. konishii is better placed in the genus Machilus than in the genus Nothophoebe. 3. DNA sequences: The sequences of the AG1 introns data clearly indicate that M. japonica is distinct from M. pseudolongifolia and M. kusanoi. 4. Isozymes: The data of isozyme analyses can distinctly distinguish the closely related species, M. japonica, M. pseudolongifolia and M. kusanoi. The data also can separate the closely related species, M. zuihonensis and M. mushaensis from each other. With the above data, the author believes that there is no naturally distributed M. japonica in Taiwan and the name M. pseudolongifolia should be used. Machilus pseudolongifolia, M. kusanoi, M. zuihoensis and M. mushaensis are all endemic to Taiwan and are morphologically diistinct. However, the DNA sequences of tested marker genes analyzed indicated that genetically they are not well differentiated. The differences among the DNA sequences of these species were not significant could be due to the possibly relatively short divergent time. Totally, eight indigenous species and one variety of the genus Machilus of Taiwan are recognized. For each species, a morphological description and classification treatment are provided; also included are geographical distribution, ecology, citation of exsiccatae, illustrations and images of type specimens etc.

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