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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

Fishery and ecological interactions for selected cetaceans, off the northeast United States of America

Waring, Gordon Thayer 01 January 1995 (has links)
Conservation and management of marine mammal populations requires information on direct and indirect affects of anthropogenic activities, population dynamics, habitat requirements and behavioral ecology. For most populations, particularly the non-hunted smaller whales and dolphins, programs designed to collect these data are relatively new (i.e., two decades old or less). This study utilizes data collected from several recent research programs to address some specific scientific and management issues. Pilot whale by-catch relative to distant-water fleet Atlantic mackerel fishing operations was examined. Although incidental mortality was not correlated to mackerel catch and effort statistics, it was associated with fishing season and depth. By-catch is highest during spring in shelf edge waters when mackerel, fishing activity, and pilot whales are concentrated along a linear habitat. Further, pilot whale behavior in the vicinity of fishing trawlers is an important component of the by-catch problem. Seasonal and spatial overlap patterns between selected cetaceans and prey resources off the northeast U.S. indicate trophic relationships are likely broader than previously hypothesized. The degree of overlap suggests that cetacean trophic requirements are likely buffeted from stock collapse of one or more prey species. However, broad scale correlations were not observed between most cetaceans and prey spatial and temporal abundance data. A dynamic patch model incorporating energetic requirements, probability of mortality "by-catch" and finding food, food value, and habitat type was used to simulate the behavioral ecology of a hypothetical pilot whale in mid-Atlantic shelf edge waters. The model suggested that the forager will make risky decisions at low state (i.e., fat reserves) levels. The general trend was to select the safer patches at high state levels. Reducing food gain versus increasing mortality or travel costs produced the most variability in model results. This variability provides some insight into pilot whale foraging around fishing vessels, since it is assumed that, although the risk of mortality is higher, the energetic costs are lower.
2

Impacts of habitat disturbance, including ecotourism activities, on breeding behavior and success of the pitta-like ground roller, Atelornis pittoides, an endangered bird species in the eastern rainforest of Ranomafana National Park, Madagascar

Razafimahaimodison, Jean Claude Rolland Andrianantenaina 01 January 2004 (has links)
Although ecotourism is touted as a tool to promote sustainable development and conservation of protected areas, it can have a negative impact on some species that it intends to protect. This dissertation explores the impacts of tourism on the breeding behavior and success of Atelornis pittoides , Madagascar's endemic pitta-like ground roller. Another goal is to understand the foraging and nesting requirements of this endangered bird. From 2000 to 2003, I studied the morphology, habitat use, distribution, foraging behavior, nesting-habitat selection, breeding behavior, and breeding success of Atelornis pittoides (Brachypteraciidae, Coraciiformes) at three different study localities in the Ranomafana National Park. Data were collected using line transects, point counts, mist netting, and direct observation. Characteristics of preferred and rejected habitats were measured at each of the three study localities. Habitat disturbance was evaluated by direct observation and park records. Talatakely forest had suffered the greatest disturbance; Vohiparara had suffered moderate disturbance, and Parcelle 1 had suffered little disturbance (and supported no ecotourism). The breeding success of Atelornis was found to be jeopardized by natural- and human-induced habitat disturbance. It decreased in areas of heavy tourism, in years marked by heavy tourism, and for nests built close to tourist trails. Nest predation rates increased with increasing tourism. There were differences in the calling behavior of birds at the three localities; in the most disturbed habitats, the birds called less frequently, particularly in the middle of the day (when tourists are likely to draw predators to their nesting sites). Atelornis was found to be selective in its choice of nesting sites. There were significant differences in vegetation structure and composition, as well as other habitat characteristics (e.g., soil exposure, presence of fallen trees, local topography), between preferred and rejected habitats. In general, nesting habitat selection is related to predator avoidance, access to ideal foraging habitat, and avoidance of competition with conspecifics. Long-term pair bonding and nest habitat fidelity (from year to year) was demonstrated, for the first time, in this study. A minor but statistically significant amount of sexual dimorphism was also demonstrated, and interpreted within the context of foraging and breeding adaptations.
3

The ecology of painted ringtails (Pseudochirulus forbesi larvatus) at Mt. Stolle, Papua New Guinea and contributions to the conservation of New Guinean mammals

Stephens, Suzette A 01 January 2005 (has links)
Many areas of New Guinea remain poorly sampled, hindering conservation planning efforts. Endemic species significantly contribute to explaining a peak in non-flying mammal diversity at mid-elevations, even after removal of boundary effects. When corrected for area, effects of diet and body size become relevant. Diversity of non-eutherians declines with elevation similar to rodents. Folivores drop in diversity with elevation more markedly than carnivores. Smaller-bodied mammals drop in diversity more markedly than larger-bodied ones. Field surveys at Mt. Stolle produced 3 new species records for Sandaun Province of Papua New Guinea, and 5 new species records for the Telefomin area. I collected data on radio-collared painted ringtails, including: body measurements, home range sizes, survival rates, waking hours spent eating, walking and resting, hours of activity and activity levels. Male painted ringtails are larger than females; males are more active and heavier males return later. Males walk more than females, and heavier males walk more. The male survival rate is one-sixth that of females. Male home ranges overlap with those of two or more females. Painted ringtails are almost entirely folivorous, consuming at least 75 tree species. Bark is consumed from at least five species, two of which were sought significantly beyond their abundance at the site. Selectivity in foliage consumed is present at both the species and family levels of trees, and proximity of diet trees to dreys plays a role in selection. The top 10 species most frequently consumed by males and females do not differ, but the top 10 families do differ. The painted ringtail diet is more folivorous and the tree species composition is significantly different than that of the larger sympatric coppery ringtail and mountain cuscus. Bark consumed by painted ringtails contained calcium, potassium and magnesium levels significantly higher than that found in control trees (conspecifics and other species). Significantly more adult male painted ringtails (14 of 21) were captured at bark trees than adult females (three of 17) or juvenile males (one of six); juvenile females were equally captured at and away from these trees (six of 12).
4

Elephant versus other browsers' long-term influences on savanna woodland dynamics : synergistic influences of elephant and other large mammalian herbivores on the structure and composition of woody plant communities in Hluhluwe-iMfolozi Park, South Africa

O'Kane, Christopher Anthony John January 2012 (has links)
A crucial question in the debate about reintroducing elephant culling is whether the long-term effects of elephants and mesobrowsers on woodlands are similar. Sufficiently high biomass-densities of mesobrowsers may, following reduction or removal of elephants, continue to heavily impact earlier life-history stages of a similar suite of woody plants that elephant impacted, preventing these species from maturing. Thus a similar end-point for woodland structure and composition is achieved. No study exists in the literature where woody plant and habitat utilisation of the savanna browser guild has been determined in the same locality over the same period. A review of 49 years of literature implied that the two groups impact the same core woody-species in the same habitats. Dietary and habitat utilisation of guild members was determined in Hluhluwe-iMfolozi Park, South Africa. A small suite (n = 8) of woody species formed the core diet of all guild members. Herbivores’ densities were determined using a novel GIS approach; all members of the guild showed extensive overlap in habitat use. GPS collars and a GIS were then used to detect zones of different density of impala in the landscape, thus defining, for the first time, a natural fine-grain browsing gradient. Densities of woody seedlings were significantly less (average 48% reduction) in areas of high versus low impala density. A simple browse-browser model, incorporating, in a novel approach, functional groups of plant species, was parameterised from these results and an extensive review of the literature. Outputs suggest that over the long-term (100 years), impala will have a similar impact on woodland structure as elephant. An apparently strong synergistic effect between impala and elephant impact, suggests that reduction or removal of either impala or elephant will radically reduce long-term destruction of woodlands. In smaller or medium sized reserves, where control of mesobrowser populations is practical, profitable and more acceptable than elephant culling, these findings imply a re-direction of management efforts. Management should consider the biomass-density of both groups, rather than just focus on the system’s perceived ‘keystone’ species. Such principles may also apply to temperate and other systems.
5

An experimental and observational study of interspecific territoriality between the blackcap Sylvia atricapilla (Linnaeus) and the garden warbler Sylvia borin (Boddaert)

Garcia, Ernest January 1981 (has links)
Ecological divergence between Blackcaps and Garden Warblers appears to be incomplete. They resemble each other closely in morphology and their foraging behaviour and food (in the breeding season) are at least broadly similar. Nevertheless, they are sympatric and occur together in a wide range of habitats although Garden Warblers are proportionately commoner in lower, denser vegetation. The two species are strongly interspecifically territorial where they occur together. However, Blackcaps are more interspecifically aggressive than Garden Warblers and are clearly dominant to them in interactions. Blackcaps respond just as strongly to playback of Garden Warbler song as they do to that of Blackcap song. They sometimes intrude into Garden Warbler territories and seek- out and chase the territory holders. In contrast, with rare exceptions, any Garden Warblers which intrude into Blackcap territories are attacked and chased until they leave the area. Also, during song playback experiments, Garden Warblers approach the loudspeaker less closely in response to Blackcap song than they do to Garden Warbler song. Many Blackcaps arrive on the breeding grounds before the earliest Garden Warblers do. A removal experiment, in which such established Blackcaps were systematically removed, showed that some of them had been keeping-out potential Garden Warbler settlers, since the latter then readily established territories and bred in a large part of the Blackcap-free zone. Normally, Garden Warblers have their territories outside Blackcat>-occupied habitat, partly because they are prevented by the aggressiveness of the Blackcaps from settling elsewhere. However, observation and song playback experiments have shown that, once established, Garden Warblers do defend their territories against both conspecifics and Blackcaps. Blackcaps have recently increased dramatically in Britain and Garden Warblers have decreased simultaneously. However, although Blackcaps can limit the local breeding densities of Garden Warblers in any one year, it is not yet clear whether Blackcap numbers are a significant factor in determining the total sizes of Garden Warbler populations.
6

A demographic perspective on trait heritability and sex differences in life history

Barthold, Julia A. January 2015 (has links)
Biologists have long used demographic approaches to answer questions in ecology and evolution. The utility of these approaches has meant a constant development and refinement of methods. A key milestone has been the development of phenotype structured population models that link ecology and evolution. Moreover, biostatistical research steadily improves methods to coax demographic information from scarce data. In this thesis, I build upon some of the recent advances in the field. My first three studies focus on the consequences of sex differences in life history for population dynamics. Firstly, I test whether males matter for the dynamics of African lion (Panthera leo) populations via a previously unquantified mechanism: the inheritance of phenotype from father to offspring. Secondly, I develop a method to estimate age-specific mortality rates for both sexes in species where one of the sexes disperses around the age of maturity. Thirdly, I apply this method to study variation in mortality between the sexes and between two populations of African lions. After these three chapters, which make contributions to the field of sex-structured population dynamics, I focus on the integration of phenotype structured modelling and quantitative genetics. I illustrate how heritability of a quantitative character that develops with age depends on (i) viability selection, (ii) fertility selection, (iii) the development of the phenotype with age, and (iv) phenotype inheritance from parents to offspring. Our results question the adequacy of quantitative genetics methods to obtain unbiased estimates of heritability for wild populations. This thesis advances our understanding of population development over ecological time scales. This knowledge has applications in conservation and population management, but also contributes to untangling evolutionary processes in wild animals.
7

Indirect interactions structuring ecological communities

da Silva, Milton Barbosa January 2016 (has links)
Ecological communities are collections of species bound together by their influences on one another. Community structure, therefore, refers to the way in which these influences are organised. As a result, ecologists are mainly interested in the factors driving the structure, functioning, and persistence of communities. The traditional focus, however, has been on the feeding relationships among species (direct trophic interactions), whereas relationships mediated by a third species or the environment (indirect interactions) have been largely overlooked. I investigated the role of indirect interactions in structuring communities through a series of field experiments in a diverse assemblage of arthropods living on a Brazilian shrub species. I experimentally reduced the abundance of the commonest galler on the shrub and found that the perturbation resonated across the food web, affecting its structure and robustness. Since there was no potential for these effects to be propagated directly or indirectly via the documented trophic links, the effects must have spread non-trophically and/or through trophic links not included in the web. Thus, I investigated non-trophic propagation of effects in the system. I demonstrate that hatched galls of the commonest galler, which serve as habitat for other species, can mediate non-trophic interactions that feedback to the galler modifying its interactions with parasitoids and inquiline aphids. I performed further manipulative experiments, excluding ants, live galls and hatched galls, to reveal mechanisms for the non-trophic interaction modifications observed in this system. Finally, I explored how non-trophic interaction modification could affect the structure and stability of a discrete ecological community in the field. I investigated how the densities of certain pairs of groups relate to each other, and how their relationship changes in relation to a third group. Then, I assembled an "effect network" revealing, for the first time in an empirical community, a hidden web of non-trophic indirect interactions modifying the direct interactions and modifying each other. Overall, the thesis presents evidence that communities are strongly interconnected through non-trophic indirect interactions. This is one of the first empirical demonstrations of the context-dependent modification of interactions via non-trophic interactions. However, determining the mechanisms behind such interaction modifications may be unfeasible. Understanding how the observed effects relate to community structuring requires shifting our focus from bipartite interaction networks to a more holistic approach.
8

Genetic control of the diamondback moth (Plutella xylostella L.)

Harvey-Samuel, Timothy January 2015 (has links)
Insect pests represent major threats to food production, biodiversity conservation, and human and animal health. Currently, the most widespread strategy to control their populations is through the spraying of synthetic chemical insecticides. However, the overuse of these compounds has had significant negative environmental consequences. Additionally, our reliance on insecticides has resulted in major reductions in their efficacy through pest-evolved resistance. To successfully manage insect pests, while avoiding environmental degradation, thus requires the development of novel, more sustainable, pest management strategies. Recent advances in our understanding of recombinant DNA methods and molecular biology have allowed the application of transgenic tools to pest management. Here, synthetic genes can be engineered, transformed into the genomes of pest species, and transported into wild target populations through the natural mating behaviour of the insect. A strategy in which these transgenes are lethal to those insects inheriting them in the field is known as RIDL – Release of Insects carrying a Dominant Lethal. A variant of RIDL limits this lethality to females – female specific RIDL (fsRIDL) – which explicitly targets the reproductive capacity of a target population. The aim of this thesis is to investigate the application of such an fsRIDL strategy to the diamondback moth (Plutella xylostella L.). This economically important pest of brassica crops is highly adept at developing resistance to insecticides and is considered extremely difficult to manage effectively. I present findings which demonstrate the power of diamondback moth lines transformed with fsRIDL transgenes to eliminate target pest populations, and combine synergistically with other transgenic control strategies such as Bt crops in counteracting the evolution of pesticide resistance. Additionally, an exploration into an alternative gene expression system to that used in current RIDL strategies – the Q system – suggests that not all expression systems will be suitable for transgene control within this highly specific framework. It is hoped that this work will contribute towards the effective control of the diamondback moth, and form a model for the sustainable control of other lepidopteran species through genetic pest management.
9

Mapping and understanding the distributions of potential vector mosquitoes in the UK : new methods and applications

Golding, Nicholas January 2013 (has links)
A number of emerging vector-borne diseases have the potential to be transmitted in the UK by native mosquitoes. Human infection by some of these diseases requires the presence of communities of multiple vector mosquito species. Mitigating the risk posed by these diseases requires an understanding of the spatial distributions of the UK mosquito fauna. Little empirical data is available from which to determine the distributions of mosquito species in the UK. Identifying areas at risk from mosquito-borne disease therefore requires statistical modelling to investigate and predict mosquito distributions. This thesis investigates the distributions of potential vector mosquitoes in the UK at landscape to national scales. A number of new methodological approaches for species distri- bution modelling are developed. These methods are then used to map and understand the distributions of mosquito communities with the potential to transmit diseases to humans. Chapter 2 reports the establishment of substantial populations of the West Nile virus (WNV) vector mosquito Culex modestus in wetlands in southern England. This represents a drastic shift in the species’ known range and an increase in the risk of WNV transmission where Cx. modestus is present. Chapter 3 develops and applies a new species interaction distribution model which identifies fish and ditch shrimp of the genus Palaemonetes as predators which may restrict the distribution of the potential WNV vector community in these wetlands. Chapter 4 develops a number of methods to make robust predictions of the probability of presence of a species from presence-only data, by eliciting and applying estimates of the species’ prevalence. Chapter 5 introduces a new Bayesian species distribution modelling approach which outperforms existing methods and has number of useful features for dealing with poor- quality data. Chapter 6 applies methods developed in the previous two chapters to produce the first high-resolution distribution maps of potential vector mosquitoes in the UK. These maps identify several wetland areas where vector communities exist which could maintain WNV transmission in birds and transmit it to humans. This thesis makes significant contributions to our understanding of the distributions of UK mosquito species. It also provides methods for species distribution modelling which could be widely applied in ecology and epidemiology.
10

Área de biodiversidade: adversidades na avaliação da produção científica / Difficulties in the evaluation of scientific production.

Lapido, Fabiana Montanari 04 November 2013 (has links)
Conhecer as especificidades da comunicação científica em biodiversidade, por meio da avaliação dos periódicos que veiculam resultados de pesquisa na área. O estudo partiu dos periódicos científicos, nacionais e estrangeiros, classificados pelo Programa Qualis da Área de Biodiversidade, referente ao ano 2012, pertencentes às áreas de botânica, oceanografia, zoologia e ecologia. Para a avaliação dos periódicos, definiu-se um plano metodológico composto por duas etapas. A primeira incluiu a análise dos periódicos a partir dos indicadores bibliométricos, realizada a partir da porcentagem captada pela janela de citações de dois anos do Fator de Impacto e do próprio Fator de Impacto no período de 2007 a 2011, utilizando quartis para identificação dos periódicos de maior e menor posição no ranking da área, segundo cada um destes indicadores. A segunda etapa teve como objetivo realizar a análise dos aspectos formais dos periódicos, e considerou: tempo de existência ou duração, pontualidade, periodicidade, quantidade de artigos publicados por ano, porcentagem de artigos de pesquisa, datas de recebimento e aprovação, revisão por pares e idiomas de publicação. Dentre os principais resultados obtidos a partir da análise dos indicadores biblométricos, estão: os periódicos classificados pelo Qualis Biodiversidade apresentam uma baixa média, tanto da porcentagem da janela de citação, como do próprio Fator de Impacto; e 75% dos periódicos BOZE possuem índices abaixo de 20% para a janela de citação de dois anos. A análise dos aspetos formais não revelou diferenças significativas entre os periódicos, porém revelou a necessidade de uma revisão da qualidade dos periódicos classificados nos estratos B3 e B4. Constatou-se que as áreas BOZE apresentam diferenças significativas quanto à dinâmica de citações da produção científica, com destaque para as áreas de ecologia (maior obsolescência da literatura) e zoologia (menor obsolescência da literatura) que demonstraram desempenhos extremos. / Knowing the specifics of scientific communication in biodiversity, through the evaluation of journals that present research results in the area. The study was based on scientific journals, domestic and foreign, sorted by the 2012 Qualis Program for Biodiversity pertaining to the areas of botany, oceanography, zoology and ecology. A two steps method for the evaluation of journals was defined. The first included the analysis of the journals from the bibliometric indicators, carried out based on the citation percentage by quartile in a two year window of citations measuring the variation in impact factors over the years. The second aims to perform the analysis of the formal aspects of the journals, in particular: time of existence or duration, punctuality, frequency, number of articles published per year, percentage of research articles, dates of receipt and approval, review by peers and number of languages it is published in. Among the results of the study, it was found that the areas BOZE significant differences in the dynamics of scientific citations, highlighting the areas of ecology (greater obsolescence of literature) and zoology (lower obsolescence of literature) who demonstrated extreme performances.

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