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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.
301

Spawning Site Selection and Fry Development of Invasive Lake Trout in Yellowstone Lake, Yellowstone National Park, Wyoming

Simard, Lee 01 January 2017 (has links)
Since their discovery in Yellowstone Lake in 1994, Lake Trout (Salvelinus namaycush) have been the object of an intensive gillnet suppression program due to their predation on native Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri). Managers are also interested in targeting early life stages to augment suppression. A benthic sled was used to sample for Lake Trout eggs at 24 locations, hypothesized to be spawning sites, that encompassed a range of depths, slopes, and substrate composition to determine the location and characteristics of spawning sites in Yellowstone Lake. Lake Trout eggs were collected at seven sites, five of which had not been previously confirmed as spawning sites. Habitat characterization at these sites indicate Lake Trout spawning in Yellowstone Lake is limited to areas with rocky substrate, but is not constrained to areas with interstitial spaces or contour breaks as is seen within the species' native range. Lake Trout fry were captured around Carrington Island, an additional spawning site in Yellowstone Lake, in 2014 and 2015. These fry were significantly larger at each developmental stage, consumed more food beginning at earlier stages, and were captured much later into the summer than fry captured at a spawning site in Lake Champlain. The lack of potential egg and fry predators in Yellowstone Lake could be driving these differences in spawning site selection and fry behavior. This information will allow managers to identify additional spawning locations for suppression and evaluate the impact their efforts might have on the Lake Trout population in Yellowstone Lake.
302

Shrinking the Janzen-Connell Doughnut: Consequences of an Invasive Multiplier (Microstegium vimineum) on the Mid-canopy in a Mixed Pine-Oak Forest

Shaw, Rebekha 04 May 2009 (has links)
Introduction of invasive species can alter seed fate predictions made by the Janzen-Connell Escape Hypothesis (JCEH). The JCEH states that there is a suitable region around a plant that is ideal for seed germination, growth, and recruitment. Seeds dispersed too close to the maternal plant are subject to competition from the maternal individual and perhaps density-dependent predation, whereas seeds dispersed further away may end up in suboptimal habitats. Invasive species may change the amount of these suitable habitats for native plants by creating unsuitable light environments and as a result, may influence the size of the ideal recruitment zone surrounding a parent plant. This study examines the extent to which the invasive grass species, Microstegium vimineum, influences recruitment of the understory tree, Cornus florida. In general, M. vimineum was found to reduce both germination and early seedling success and may have significant consequences for future forest structure.
303

Spatial Patterns of Herbaceous and Woody Recruitment in a Recently Restored Mixed Tidal Regime Freshwater Wetland

Deemy, James B. 03 May 2012 (has links)
Ecological restoration of a converted wetland was characterized within a recently drained impoundment along the James River in Charles City County, Virginia. Colonizing vegetation was assessed over three growing seasons in both tidal and non-tidal environments. Study objectives were to (1) examine geospatial relations of recruitment patterns among colonizing species over three growing seasons, (2) quantify species composition and potential differences between extant species cover and soil seed banks across restored and natural wetland habitats and (3) assess geospatial patterns to develop a GIS model of bald cypress (Taxodium distichum L.) recruitment. The two most common native colonizing species during 2009, 2010 and 2011 growing seasons were narrow-leaf cattail (Typha angustifolia L.) and rice cutgrass (Leersia oryzoides L.). Vegetative communities dominated by these two species covered 72% of the basin in each growing season. Differences were observed between extant species cover in the field and seed bank species across habitats. Two hundred and eighty T. distichum individuals have been located in wetland habitats at the VCU Rice Center. Using a GIS weighted suitability model we identified potential areas within the restored wetland for natural and facilitated bald cypress recruitment. At the VCU Rice Center ~9.7 ha have potential for natural regeneration and ~48.5 ha have potential for facilitated restoration of T. distichum.
304

Nepůvodní živočichové v ČR a jejich význam / Alien Species in the Czech Republic and their Importance

Kotrbová, Tereza January 2013 (has links)
This text is intended for all interested parties from the general public, but primarily a narrow range of educational material for teachers in secondary schools, science schools, etc. The work includes chapters devoted to non-original animals in the world, the issue of non-native animals in the CR and their significance. The research deals with the knowledge of elementary school students related to the topic of non-native species.
305

Determining the pollination mechanism of a problematic invasive species in the Gulf South: Triadica sebifera

Clark, Jennifer Wester 13 May 2016 (has links)
Understanding the ecology of invasive species is vital to curb the homogenizing of ecosystems, yet the pollination mechanisms of the Chinese tallow tree (Triadica sebifera) in its introduced habitat remain ambiguous. This study examines self-pollination, wind pollination, and flower-visiting insects of tallow in a bottomland hardwood forest and Longleaf pine savannah in the U.S. Gulf South. These data suggest that self-pollination and airborne pollination are possible, but likely rare occurrences, although the possibility of apoxisis was not investigated. Seed production in exclusion experiments was significantly less than in open-pollinated flowers, and wind dispersal of tallow pollen dropped to essentially zero 8 meters from the source. Results show that tallow is primarily bee pollinated, with external pollen loads of Apis, Melissodes, and halictids visiting at similar rates, and Xylocopa species visiting less frequently. The researchers believe that to date, this is the first study of the pollination mechanisms of T. sebifera in its introduced range and recommend further study to understand the ecology of this destructive invasive species.
306

Vektory, šíření a genetická variabilita patogenu račího moru v oblastech, kam byl zavlečen / The crayfish plague pathogen Aphanomyces astaci in its introduced ranges: vectors, introduction pathways, genetic variation and host-pathogen interactions

Mrugała, Agata January 2016 (has links)
- ABSTRACT - The crayfish plague pathogen, Aphanomyces astaci, is responsible for substantial declines and local extinctions of native European crayfish populations. As a consequence, the pathogen is now listed among 100 world's worst invasive alien species. The spread of A. astaci is greatly facilitated by its natural hosts, North American crayfish, that thanks to a long co-evolutionary history with the crayfish plague pathogen evolved efficient defence mechanisms. In contrast, European, Australian and Asian crayfish species are highly susceptible to this disease agent. However, progress of A. astaci infection in native European crayfish was observed to differ between distinct pathogen strains, indicating variability in their virulence. Indeed, we demonstrated a relationship between patterns in crayfish immune response and A. astaci virulence in an experimental infection involving the European noble crayfish and three differently virulent crayfish plague strains. The European continent is currently inhabited by at least eight North American crayfish species. The carrier status was confirmed in six of them, including also Orconectes cf. virilis occurring in the Netherlands and the UK. In this country, we detected Aphanomyces astaci presence in some populations of the non-indigenous crayfish species as well...
307

Blomsterlupinens utbredning och täthet vid asfaltsvägar och grusvägar. : Påverkar vägtypen artens växtsätt? / The distribution and density of Garden lupine along asphalt and gravel roads. : Does the road type affect the species’ way of growing?

Karlsson, Emma January 2019 (has links)
Blomsterlupin (Lupinus polyphyllus) är en välkänd invasiv växt i Sverige som frekvent växer i vägkanter. På grund av dess egenskaper, som konkurrensförmåga och kvävefixering, kan den ha negativa effekter på biodiversiteten vid vägkanter, vilket är habitat som utgör en tillflykt för många inhemska ängsväxter. Trots skötsel av vägkanter är blomsterlupin vanlig längs vägar av olika storlekar. Detta arbete undersöker om det finns skillnader i artens fördelning, täthet och storlek mellan asfaltsvägar och grusvägar. Eftersom asfaltsvägarnas vägkanter sannolikt utsätts för en mer intensiv skötsel, var mina hypoteser att grusvägar hade fler plantor per m2 inom populationerna och att en högre andel av deras vägkanter täcktes av lupin jämfört med asfaltsvägar. Femton lämpliga sträckor av vardera vägtyp var slumpmässigt utvalda och deras lupinpopulationer mättes. Mätningarna inkluderade populationsarea, antal plantor, plantstorlekar, det minsta avståndet mellan plantor och väg, samt vägkantsbredd. Efter analysen av datan med hjälp av Chi2-test och t-tester hittades enbart ett fåtal signifikanta skillnader mellan vägtyper. Det fanns en tendens att blomsterlupin förekommer längs fler asfaltssträckor jämfört med grusvägar men grusvägar hade en högre täthet inom populationer, täckning av kanterna, större populationer och större genomsnittlig plantstorlek. En signifikant skillnad var att plantor växte längre från vägen längs asfaltsvägar jämfört med grusvägar, vilket kan indikera att plantor som undkommer röjningen kan bevara populationerna längs asfaltsvägar. / Garden lupine (Lupinus polyphyllus) is a well-known invasive plant in Sweden that frequently inhabits road verges. Because of its traits, such as competitive ability and nitrogen-fixation, it may have negative effects on biodiversity of road verges, which are habitats that represent a refuge for many native meadow plant species. Despite management of roadsides, Garden lupine is common along roads of different sizes. The present work investigates if there are differences in the species’ distribution, density and size among asphalt roads and gravel roads. As the asphalt roads’ road verges most likely experience a more intense management, my hypotheses were that gravel roads had more plants per m2 within the populations and a higher proportion of their verges were covered by lupine compared to asphalt roads. Fifteen suitable sections of each road type were randomly chosen and their lupine populations were measured. The measurements included population area, number of lupine plants, the plant sizes, the minimum distance of plants to the road and road verge width. After analyzing the data using Chi2-test and t-tests only a few significant differences between road types were found. There was a tendency of Garden lupine to occur in more sections of asphalt roads compared to gravel roads but gravel roads had a higher density within populations, coverage of the verges, larger populations and larger average plant size. One significant difference was that plants grew further away from the road along asphalt than on gravel roads, which could indicate that plants that escape management through clipping may sustain the populations along asphalt roads.
308

Pathogen surveillance (Leptospira spp., Rotavirus, Hepatitis E virus and Norovirus) in a wild golden-headed lion tamarin (Leontopithecus chrysomelas) population from an urban Atlantic Forest park in Niterói, Rio de Janeiro, Brazil / Pesquisa de patógenos (Leptospira spp., Rotavírus, Vírus da hepatite E e Norovírus) em uma população de mico-leão-da-cara-dourada (Leontopithecus chrysomelas) de um parque urbano de Mata Atlântica em Niterói, Rio de Janeiro, Brasil

Molina, Camila Vieira 28 February 2018 (has links)
Most nonhuman primates are distributed throughout tropical countries, most of all in Brazil. However, half of the Brazilian endemic species live in areas where deforestation rates are over 90%. The world currently faces severe biodiversity losses caused by anthropogenic activities such as deforestation, pollution, introduction of exotic species, habitat fragmentation, and climate changes all consequences of the rising of agriculture, livestock and urbanization; a great risk for wild animal species. The golden-headed lion tamarin (GHLT; Leontophitecus chrysomelas) is an endangered species that became invasive in an exotic forested area in Niterói, Rio de Janeiro state, Brazil. The initially few invasive GHLT individuals became hundreds, adapted to living in proximity to humans and domestic animals, frequently found inside houses, digging garbage, crossing streets and in open sewers. These GHLTs were captured as part of a conservation project; some animals were translocated to Bahia state, in southern Brazil, an area within the species original range, whiel the remaining individuals were kept in captivity. Disease ecology in altered environments is still poorly understood; however, these GHLTs likely had contact with many pathogens. Therefore, the present study aimed on surveying this population for possible pathogens: Leptospira spp., Rotavirus A, Norovirus GI and GII, and Hepatitis E virus 3 HEV 3. A total of 939 serum samples from 593 GHLTs were tested for 21 Leptospira serovars, resulting in three positive sera samples from two GHLTs: one for serovar Shermani and one for serovar Hebdomadis. Molecular methods (PCR) were employed on 100 kidney samples from animals that died in captivity due to other reasons: only one sample was positive for a saprophytic Leptospira. Fecal pools from 101 family groups were all negative for RNA RT-PCR (Rotavirus A, Norovirus GI and GII, and HEV 3). Our findings suggest that the epidemiological importance of such pathogens in this GHLT population is either low or non-existent. These results are unexpected and surprising considering the intensely altered environment and biology observed in this GHLT population. These data are important to understand the local disease ecology, as well as to evaluate the efficiency of the translocation project, with the final goal of performing future studies to compare our data with those obtained from the translocated animals. / A maioria dos primatas não humanos está distribuída em países tropicais e o Brasil é mais rico destes, com metade de suas espécies endêmicas em áreas onde mais de 90% do habitat natural já foram devastadas. Realmente, o mundo enfrenta uma perda global de biodiversidade por ações antrópicas. As ações antropogênicas, como o desmatamento, poluição, introdução de espécies exóticas, fragmentação do habitat e mudanças climáticas devido ao aumento da agricultura, pecuária e urbanização representam um grande risco para as espécies de animais selvagens. O Mico-leão-da-cara-dourada (MLCD - Leontophitecus chrysomelas) é uma espécie ameaçada que se tornou invasora em uma área fora de sua distribuição natural, em Niterói, Rio de Janeiro, Brasil. Esses animais se tornaram centenas a partir de poucos indivíduos, se adaptaram vivendo perto de humanos e animais domésticos, frequentemente vistos dentro de casas, remexendo em lixo, atravessando ruas e esgoto à céu aberto. Os MLCDs foram capturados como parte de um projeto de conservação, sendo que parcela dos animais foi translocada para uma área de ocorrência da espécie, no sul da Bahia (Brasil), e parte permaneceu em cativeiro. A ecologia de doenças em ambientes alterados como este não é bem conhecida, mas é factível supor que os MLCD tiveram contato com muitos agentes patogênicos. Desta forma, o presente estudo teve como objetivo pesquisar 4 patógenos (Leptospira spp., Rotavírus A, Norovírus GI e GII e vírus da Hepatite E 3 - VHE 3) nesta população de MLCD de Niterói. Um total de 939 amostras de soro de 593 L. chrysomelas foram testadas para 21 sorovares de Leptospira, resultando em apenas 3 amostras positivas de 2 animais: um para o sorovar Shermani e um para sorovar Hebdomadis. Métodos moleculares (PCR) foram empregados em 100 amostras de rim de animais que vieram a óbito em cativeiro por causas diversas, e apenas uma Leptospira saprófita foi detectada em uma amostra. Para a pesquisa dos RNA vírus (Rotavírus A, Norovirus GI e GII e VHE 3), pool de fezes de 101 grupos familiares foram analisados por RT-PCR, sendo que todas as amostras foram negativas. Os resultados sugerem que esses patógenos têm menor importância epidemiológica nesta população de MLCD de Niterói. Acreditamos que os presentes resultados são inesperados e surpreendentes, considerando todo o ambiente e a biologia alteradas dos MLCDs constituintes da população invasora presente em Niterói. Ainda, consideramos que esses dados são importantes para entender a ecologia das doenças na região, bem como para servir como dados testemunhos com fins de acompanhar o projeto de translocação, especialmente com vistas a estudos futuros com os animais translocados.
309

Invasão biológica de Casuarina equisetifolia na Restinga da Massambaba: Estrutura, Riqueza e Regeneração / Biological invasion of Casuarina equisetifolia at Restinga da Massambaba: structure, richness and regeneration

Alessandro Henrique Nunes Branth Fontes 24 April 2013 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A invasão biológica é vista como o processo de introdução e adaptação de espécies que não fazem parte, naturalmente, de um determinado ecossistema e é considerada a segunda maior causa de perda de biodiversidade. Casuarina equisetifolia é uma angiosperma bem adaptada a ambientes com alto teor de salinidade e baixo teor hídrico representando uma grande ameaça a perda de biodiversidade em ambientes costeiros ao colonizar rapidamente áreas degradadas nesses ambientes. O presente trabalho procurou avaliar os efeitos da invasão de C. equisetifolia na diversidade de espécies e estrutura da comunidade em um trecho na Restinga da Massambaba. Foram distribuídas 46 parcelas de 10m x 10m em cinco diferentes tratamentos próximas entre si denominadas: manejo, queimada, invasão, restinga e controle. Através do escalonamento multidimensional não métrico (NMDS) verificou-se que existe diferença na composição florística entre os tratamentos invadidos e não invadidos, mas que entre os tratamentos invadidos a composição é a mesma. Mesmo os tratamentos sendo próximos entre si, a ANOVA mostrou que existe diferença na densidade de C. equisetifolia mostrando que fatores externos influenciam a estrutura da população nesses tratamentos. O hábito herbáceo foi predominante nos tratamentos de invasão diferindo do tratamento controle onde o hábito arbustivo é o mais significativo. A síndrome de dispersão predominante foi a zoocórica em todos os tratamentos, exceto no tratamento de fogo e de invasão, onde a anemocoria obteve o mesmo número numero de espécies. A ANOVA indicou que a riqueza do tratamento controle é muito maior do que a riqueza nos tratamentos de invasão. Os tratamentos de invasão possuem um índice de Shannon variando de 0,23 a 1,4, enquanto a tratamento controle possui um índice de 2,49, mostrando o quanto C. equisetifolia homogeneíza a flora, fazendo com que poucas espécies consigam colonizar esses ambientes como Pilosocereus arrabidae, Schinus terebinthifolius e Varronia curassavica. A regressão linear realizada indica que a riqueza de espécies diminui com o aumento da densidade de C. equisetifolia / Biological invasion is seen as the process of introduction and adaptation of species that are not part of a particular ecosystem and is considered the second greatest cause of biodiversity loss. Casuarina equisetifolia is an angiosperm well adapted to environments with high salinity levels and low water content representing a major threat to biodiversity loss in coastal environments cause it rapidly colonize degraded areas in these environments. This study aimed to assess the effects of the invasion of C. equisetifolia in species diversity and community structure in a fragment at the Restinga da Massambaba. Were allocated 46 plots of 10m x 10m in five different areas near to each other called: management, fire, intrusion, restinga and control. Through the Non Metric Multidimensional Scaling (NMDS) found that there is difference in floristic composition between invaded and non-invaded areas, but between areas invaded the composition is the same. Even the treatments being close to each other, ANOVA showed a significant difference in density of C. equisetifolia showing that external factors influence the structure of the population in these treatments. The herbaceous habit was prevalent in areas of differing invasion of the area where the shrubby habit control is the most significant. Zoochory was the dispersion syndrome predominant in all areas, except in the area of fire and invasion, where anemochory obtained the same number of species. The ANOVA indicated that the richness of the control area is much greater than the richness in the areas of invasion. The invasion areas have a Shannon index ranging from 0.23 to 1.4, while the control region has an index of 2.49, showing how C. equisetifolia lets the flora homogeneous, enabling a few species able to colonize these environments as Pilosocereus arrabidae, Schinus terebinthifolius and Varronia curassavica. Linear regression indicated that the richness decreases with increasing density C. equisetifolia.
310

Controle biológico de Brachiaria decumbens Stapf em área de reserva legal em processo de recuperação, na região do Pontal do Paranapanema, São Paulo, Brasil /

Rodrigues, Elisangela Ronconi. January 2010 (has links)
Orientador: Reinaldo Monteiro / Banca: Alessandro Camargo Angelo / Banca: Osmar Cavassan / Banca: Fábio Socolowski / Banca: Marco Antonio de Assis / Resumo: O Pontal do Paranapanema, a segunda região mais pobre do Estado de São Paulo, tem histórico de devastação florestal recente: até 1942, toda a região possuía cobertura florestal nativa protegida por lei, a chamada "Grande Reserva do Pontal", a qual foi transformada em grandes fazendas de pastagem por meio de desmatamentos ilegais e grilagem de terras, transformando a área num mosaico altamente fragmentado. No entanto, é no Pontal do Paranapanema que encontramos a maior área contínua de Floresta Estacional Semidecidual, contida no Parque Estadual Morro do Diabo. Este histórico torna claro que ações que promovam a restauração de áreas degradadas na região tem importância indiscutível na conservação e perpetuação do bioma Floresta Estacional e sua biodiversidade, que inclui espécies raras e ameaçadas de extinção, como o mico-leão preto (Leontophitecus chrysopygus). Diante do exposto esta pesquisa teve por objetivos: caracterizar florísticamente um plantio realizado para restauração de reserva legal e testar o uso de espécies nas entrelinhas deste plantio para controle das invasoras, hoje citadas como um dos maiores empecilhos aos projetos de restauração. Para tal, foram demarcadas 16 parcelas de 20 x 30 metros, representando quatro tratamentos em três repetições, com uma testemunha par cada tratamento. Os quatro tratamentos correspondem a espécies de leguminosas que foram testadas nas entrelinhas, sendo elas: Lab-lab (Dolichos lablab), Crotalária (Crotalaria spectabilis) Mucuna-Preta (Mucuna aterrina), e Java, leguminosa híbrida obtida do cruzamento e seleção de dois cultivares de Macrotyloma axillare. Os resultados mostraram que as leguminosas tem efeito sobre o desenvolvimento de Brachiaria decumbens apenas no início de seu ciclo de vida. Duas espécies de leguminosas (Mucuna aterrina e Macrotyloma axillare) foram eficientes no controle... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Pontal do Paranapanema, the second poorest region in the state of São Paulo, has a history of recent forest destruction: up to 1942, the entire region had native forest protected by law, the "Grande Reserva do Pontal", which was transformed on grazing on large farms by illegal logging and land grabbing, transforming the region into a highly fragmented mosaic. However, it is in the Pontal that it is found the largest continuous area of seasonal semideciduous forest, contained in the Morro do Diabo State Park. This history makes clear that actions to promote the restoration of degraded areas in the region has a key importance in the preservation and perpetuation of seasonal forest biome and its biodiversity, including rare and endangered species such as the black lion tamarin (Leontophitecus chrysopygus). This study aimed to characterize floristically an area of restoration for a legal reserve and test the use of some species for weed control, today cited as one of the biggest impediments to restoration projects. For this purpose, 16 plots with 20 x 30 meters each were demarcated, representing four treatments and a control in three replicates . The four treatments correspond to legumes species that were tested, namely: Dolichos lablab, Crotalaria spectabilis, Mucuna aterrima, "Java", a legume hybrid obtained from crossing and selection of two cultivars of Macrotyloma axillare. The results show that the pulses have an effect on the development of Brachiaria decumbens in the beginning of its life cycle. Two species of legumes (Mucuna aterrima and Macrotyloma axillare) were efficient in controlling B.decumbens during the whole period of analyses, but also led to death of all tree species in these plots, showing the need for management of these species when used in biological control / Doutor

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