• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 200
  • 114
  • 49
  • 34
  • 11
  • 10
  • 9
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 622
  • 157
  • 123
  • 89
  • 79
  • 64
  • 60
  • 60
  • 59
  • 51
  • 48
  • 39
  • 38
  • 37
  • 35
  • 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.
391

A organização e a ritmicidade no forrageamento e na enxameação de Plebeia remota (Holmberg, 1903) (Hymenoptera, Apidae, Meliponini) / The organization and rhythm in the foraging and swarming of Plebeia remota (Holmberg, 1903) (Hymenoptera, Apidae, Meliponini)

Patricia Nunes Silva 19 June 2007 (has links)
Os meliponíneos são abelhas que ocorrem nas regiões tropicais e subtropicais da Terra. Neste momento em que as mudanças globais atraem tanto interesse científico, consideramos oportuno o estudo detalhado da organização social de Plebeia remota, espécie de abelha que apresenta diapausa reprodutiva no outono e inverno. Embora outras pesquisas tenham sido realizadas nesta espécie, indicando principalmente os efeitos dos fatores abióticos sobre a atividade de vôo, a divisão de trabalho entre as operárias durante o forrageamento não tinha sido estudada, tanto no período de diapausa quanto no período em que ocorre oviposição pela rainha. A ausência da construção de células de cria durante alguns meses na colônia, e o reinício desta atividade em agosto, implicam em profundas alterações fisiológicas em um grupo de operárias e na rainha, aumentando a complexidade da divisão de trabalho e da organização social. Analisamos as atividades de operárias individualmente nos dois períodos, e tratamos do comportamento individual na construção do coletivo nas atividades de forrageamento. Uma das abordagens foi a ritmicidade das forrageiras nesses dois períodos. Também estudamos o efeito da temperatura e da umidade relativa no padrão de forrageamento. Além disso, outro processo de grande importância para a reprodução das colônias foi estudado, a enxameação. Tanto a biologia dos enxames quanto a ritmicidade da construção de células e do POP no início do estabelecimento das colônias recém-enxameadas foram estudadas. Também discutimos os fatores que podem estar envolvidos no crescimento inicial das colônias e seu estabelecimento. O forrageamento e a enxameação são processos muito importantes para o crescimento e reprodução das colônias, e a compreensão deles são importantes para o desenvolvimento de técnicas de manejo e de medidas para a promoção da conservação das abelhas. / The meliponine are bees that occur in the tropical and subtropical regions of the Earth. In this moment that the global changes attract so much scientific interest, we consider opportune the detailed study of the social organization of Plebeia remota, a bee species that present reproductive diapause in autumn and winter. Although other researches had been made in this species, indicating mainly the effects of abiotic factors on the flight activity, the division of labor among the workers during the foraging had not been studied either in the diapause period or in the queen oviposition period. The absence of brood cells construction during some months in the colony, and the restart of this activity in august, imply profound physiologic alterations in a group of workers and in the queen, increasing the complexity of the division of labor and social organization. We analyzed the workers activities individually in the two periods and considered the individual behavior in the construction of the collective on the foraging activities. One of the approaches was the rhythm of the foragers in these two periods. We also studied the effect of temperature and relative humidity on the foraging pattern. Furthermore, another process of great importance to the reproduction of the colonies was studied, the swarming. Either the biology of the swarms as the rhythm of the construction of brood cells and of the POP in the beginning of the establishment of the colonies was studied. We also discussed the factors that may have been involved in the initial growth of the colonies and their establishment. The foraging and the swarming are processes very important to the growth and the reproduction of the colonies, and their comprehension is important to the development of management techniques and measurements to the promotion of conservation of bees.
392

O papel de Apis Mellifera l. como polinizador da mamoneira (Ricinus Communis L.): avaliaÃÃo da eficiÃncia de polinizaÃÃo das abelhas e incremento de produtividade da cultura / The role of Apis Mellifera L. how polinizador of mamoneira (Ricinus Communis L.): assessment of efficiency of bee polinizaÃÃo and enhancement of productivity of culture

RÃmulo Augusto Guedes Rizzardo 28 February 2007 (has links)
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A pesquisa foi realizada no NÃcleo de ProduÃÃo ComunitÃria Santa Clara, idealizado e administrado pela Brasil Ecodiesel IndÃstria e ComÃrcio de BiocombustÃveis e Ãleos vegetais S. A., localizado no municÃpio de Canto do Buriti, estado do Piau, e na Universidade Federal do CearÃ, localizada em Fortaleza, no estado do CearÃ. A coleta de dados ocorreu durante o perÃodo de Abril de 2006 a Janeiro de 2007 com o objetivo de investigar a polinizaÃÃo da mamoneira (Ricinus communis L.), o papel de agentes polinizadores biÃticos e a utilizaÃÃo de abelhas Apis mellifera na sua polinizaÃÃo, visando contribuir para minimizar as perdas de produtividade desta cultura. Foram avaliados a biologia floral e requerimento de polinizaÃÃo da mamoneira; eficiÃncia da polinizaÃÃo por Apis mellifera e comportamento de pastejo de Apis mellifera e Scaptotrigona bipunctata H.(canudo) em inflorescÃncia de mamoneira, bem como os frutos e sementes produzidas na cultura. Os resultados mostraram que as abelhas coletam pÃlen e nÃctar durante todo o dia, tendo a abelha canudo, preferÃncia pelo pÃlen. A mamoneira aceita polinizaÃÃo cruzada, porÃm vingando significativamente (p<0,05) menos que a autopolinizaÃÃo. O vento mostrouse o principal vetor de pÃlen na plantaÃÃo. Ãreas com introduÃÃo de abelhas melÃferas produziram marginalmente (p = 0,08) mais frutos que Ãreas sem a introduÃÃo de abelhas. De forma semelhante, tambÃm levaram a significativa (p<0,05) produÃÃo de racemos com mais frutos (22,39) e sementes mais pesadas (0,54g) com maior percentual de Ãleo (54,48%) e maior energia bruta (9006,81kcal/kg) do que o obtido em Ãreas sem abelhas (15,84, 0,47g, 49,94% e 8843,29kcal/kg, respectivamente). A avaliaÃÃo fisiolÃgica das sementes nÃo encontrou diferenÃas entre os dois tratamentos, ambos apresentaram mÃdia de 84% de germinaÃÃo. Pode-se concluir que o principal agente polinizador da mamoneira à o vento e que a espÃcie pode ser polinizada, vingando seus frutos tanto por meio de autopolinizaÃÃo quanto polinizaÃÃo cruzada, embora apresente melhores resultados com autogamia. A introduÃÃo de colÃnias de Apis mellifera em cultivos de mamona contribui para incremento significativo de produtividade da cultura, tanto ao aumentar o nÃmero de frutos por cacho quanto o rendimento de Ãleo dos mesmos, provavelmente porque ao coletar pÃlen as abelhas melÃferas aumentam a quantidade de autopÃlen em suspensÃo no ar nas proximidades da panÃcula, favorecendo uma maior percentagem de autopolinizaÃÃo. Palavras-chave: polinizaÃÃo da mamoneira, rendimento de Ãleo, anemofilia, comportamento de pastejo, biodiesel. / The research was carried out in the NÃcleo de ProduÃÃo ComunitÃria Santa Clara, idealized and administered by the Brasil Ecodiesel IndÃstria e ComÃrcio de BiocombustÃveis e Ãleos vegetais S. A., county of Canto do Buriti, state of PiauÃ, Brazil, and at the Universidade Federal do CearÃ, located in Fortaleza, state of CearÃ. Data were collected from April 2006 to January 2007 investigating castor bean (Ricinus communis L.) pollination, the role of biotic pollinating agents and the use of the honey bee Apis mellifera in its pollination. The study aimed to contribute in mitigating yield productivity losses in this crop. The following parameters were evaluated: floral biology, castor bean pollination requirements, A.mellifera pollination efficiency, foraging behavior of A.mellifera and Scaptotrigona bipunctata in castor bean inflorescences, and physiological evaluation of fruits and seeds produced. Results showed that both bee species harvested pollen and nectar throughout the day, but S. bipunctata prefers pollen much more than nectar. The castor bean plant accepts cross pollination, but it sets significantly (p<0.05) less fruits than self-pollination. The wind appeared as the main pollen vector in the plantation. Areas where honey bee colonies were introduced produced marginally (p = 0.08) more fruits than areas where no colony was made available. Similarly, they also led to significantly (p<0.05) more fruits per raceme (22.39) heavier seeds (0,54g) greater oil percentage (54.48%) and greater gross energy (9006.81kcal/kg) than those produced in areas without introduction of honey bee colonies (15.84, 0.47g, 49.94% e 8843.29kcal/kg, respectively), Physiological evaluation of seeds found no significant differences among treatments and produced an average 84% germination. It is concluded that the wind is the major pollinator of castor bean, and this species can be pollinated and set fruits both by means of cross and self-pollination, though showing better results under autogamy. The introduction of A. mellifera colonies in castor bean plantations contributes to increase crop productivity significantly, both increasing the number of fruits set per raceme and their oil content, probably because when collecting pollen honey bees increase the amount of self-pollen floating in the air around the panicles, favoring greater proportion of self-pollination.
393

Aspectos ecol?gicos e comportamentais do cupim subterr?neo Asi?tico Coptotermes gestroi Wasmann (Isoptera: Rhinotermitidae / Ecological and behavioral aspects of Asian subterraneous termite, Coptotermes gestroi Wasmann (Isoptera: Rhinotermitidae). Serop?dica: UFRRJ, 2004. 84p. (MSc. dissertatio).

Brito, Henrique Noronha Figueiredo de 15 June 2004 (has links)
Made available in DSpace on 2016-04-28T14:58:32Z (GMT). No. of bitstreams: 1 2004-Henrique Noronha Figueredo de Brito.pdf: 2218652 bytes, checksum: 99b76927025a1c7d2189d065209f2c9b (MD5) Previous issue date: 2004-06-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work was a conducted at the campus of the Universidade Federal Rural do Rio de Janeiro, objectifying to study the behavior of the Asian subterraneous termite Coptotermes gestroi under various aspects to find new strategies to manage this insect through the knowledge its ecology. The first experiment remained in the field from June 04th to July 28th, 2003 having as objective to monitor environmental variables that could be influencing the foraging of this termite in 13 selected areas with distinct visual characteristics, according to the type of vegetation, luminosity, proximity of constructed areas and humidity. The environmental variables considered were: morning and afternoon brightness; temperature of the soil in the morning and afternoon and soil moisture. The absence of foraging during the dry period of the year indicated that drought is one of the main factors for the movement of this subterraneous termite species. The subsequent experiments were performed in laboratory under dark environment and designed, as a randomized complete block design with split-plots. Each block consisted of a central container with humid substrate (vermiculite), linked to five other containers by tubes. Laborers and soldiers of C. gestroi were introduced in the interior of the central container, on the ratio of 5:1, totalizing 120 individuals. One of the experiments had as objective to verify their attractiveness to four woods, the survival of these individuals and the consumption of each. The odor of the wood exerted basic role in the consumption; the density of each one influenced on the period of permanence of the individuals while that the flavor was an important factor for the consumption, mainly, in longer periods. The second study evidenced the influence of two nitrogen sources (nitrate and ammonia) and three concentrations (0, 0.5 and 1 molar) on the attractiveness and the consumption of treated wood. Positive influence in the wood consumption exists when nitrogen was applied. On the other hand, nitrogen. also exerted great influence in the mortality , caused by the entomopathogenic fungus Metarhizum anisoplae on the wood. However, nitrogen under ammonium form, resulted in lower comsumption preference and worse conditions for the development of M. anisoplae. / Este trabalho foi realizado no campus da Universidade Federal Rural do Rio de Janeiro, objetivando estudar o comportamento do cupim subterr?neo asi?tico Coptotermes gestroi sob diversos aspectos para encontrar novos mecanismos de manejo atrav?s do conhecimento da ecologia desse inseto. O primeiro trabalho permaneceu no campo durante o per?odo de 04 de junho a 28 de julho de 2003, tendo como objetivo monitorar quais vari?veis ambientais estariam influenciando o forrageamento desse cupim em 13 ?reas selecionadas a partir de caracter?sticas visuais distintas relacionadas, ao tipo de vegeta??o, luminosidade, proximidade de ?reas constru?das e umidade. As vari?veis ambientais avaliadas foram: luminosidade de manh? e ? tarde; temperatura do solo, pela manh? e ? tarde; umidade do solo pela manh?. A aus?ncia de forrageamento durante o per?odo seco do ano indicou que a falta de umidade ? um dos fatores principais para a movimenta??o do cupim subterr?neo. Os experimentos subseq?entes foram realizados em laborat?rio com ambiente escurecido e montados, seguindo um mesmo modelo experimental de blocos ao acaso com arranjo em parcelas subdivididas no tempo. Cada bloco constituiu-se de um recipiente central preenchido com substrato ?mido (vermiculita) e interligado a outros cinco recipientes por interm?dio de tubula??es. No interior do recipiente central foram introduzidos oper?rios e soldados de C. gestroi, mantendo a propor??o de 5:1, totalizando 120 indiv?duos. Um dos experimentos teve como objetivo verificar a atratividade de quatro ess?ncias florestais ? sobreviv?ncia desses indiv?duos e o consumo de cada madeira. O odor da madeira exerceu papel fundamental no consumo e a densidade de cada uma influenciou no per?odo de perman?ncia dos indiv?duos sobre as mesmas enquanto que a palatabilidade foi fator preponderante para o consumo, mormente, em per?odos mais longos. O segundo estudo permitiu constatar a influ?ncia de duas fontes de nitrog?nio (nitrato e am?nia) em tr?s doses (0, 0.5 e 1 molar) sobre a atratividade e o consumo da madeira tratada. O estudo permite ainda verificar que existe influ?ncia positiva no consumo de madeira quando o nitrog?nio ? aplicado. Em contrapartida, esse mesmo nitrog?nio exerceu maior influ?ncia na mortalidade dos indiv?duos submetidos ao tratamento, em virtude da presen?a do fungo entomopatog?nico Metarhizum anisoplae sobre as estacas. No entanto, o nitrog?nio sob a forma amoniacal, apresentou menor prefer?ncia de consumo e piores condi??es para o desenvolvimento do M. anisoplae.
394

A organização e a ritmicidade no forrageamento e na enxameação de Plebeia remota (Holmberg, 1903) (Hymenoptera, Apidae, Meliponini) / The organization and rhythm in the foraging and swarming of Plebeia remota (Holmberg, 1903) (Hymenoptera, Apidae, Meliponini)

Silva, Patricia Nunes 19 June 2007 (has links)
Os meliponíneos são abelhas que ocorrem nas regiões tropicais e subtropicais da Terra. Neste momento em que as mudanças globais atraem tanto interesse científico, consideramos oportuno o estudo detalhado da organização social de Plebeia remota, espécie de abelha que apresenta diapausa reprodutiva no outono e inverno. Embora outras pesquisas tenham sido realizadas nesta espécie, indicando principalmente os efeitos dos fatores abióticos sobre a atividade de vôo, a divisão de trabalho entre as operárias durante o forrageamento não tinha sido estudada, tanto no período de diapausa quanto no período em que ocorre oviposição pela rainha. A ausência da construção de células de cria durante alguns meses na colônia, e o reinício desta atividade em agosto, implicam em profundas alterações fisiológicas em um grupo de operárias e na rainha, aumentando a complexidade da divisão de trabalho e da organização social. Analisamos as atividades de operárias individualmente nos dois períodos, e tratamos do comportamento individual na construção do coletivo nas atividades de forrageamento. Uma das abordagens foi a ritmicidade das forrageiras nesses dois períodos. Também estudamos o efeito da temperatura e da umidade relativa no padrão de forrageamento. Além disso, outro processo de grande importância para a reprodução das colônias foi estudado, a enxameação. Tanto a biologia dos enxames quanto a ritmicidade da construção de células e do POP no início do estabelecimento das colônias recém-enxameadas foram estudadas. Também discutimos os fatores que podem estar envolvidos no crescimento inicial das colônias e seu estabelecimento. O forrageamento e a enxameação são processos muito importantes para o crescimento e reprodução das colônias, e a compreensão deles são importantes para o desenvolvimento de técnicas de manejo e de medidas para a promoção da conservação das abelhas. / The meliponine are bees that occur in the tropical and subtropical regions of the Earth. In this moment that the global changes attract so much scientific interest, we consider opportune the detailed study of the social organization of Plebeia remota, a bee species that present reproductive diapause in autumn and winter. Although other researches had been made in this species, indicating mainly the effects of abiotic factors on the flight activity, the division of labor among the workers during the foraging had not been studied either in the diapause period or in the queen oviposition period. The absence of brood cells construction during some months in the colony, and the restart of this activity in august, imply profound physiologic alterations in a group of workers and in the queen, increasing the complexity of the division of labor and social organization. We analyzed the workers activities individually in the two periods and considered the individual behavior in the construction of the collective on the foraging activities. One of the approaches was the rhythm of the foragers in these two periods. We also studied the effect of temperature and relative humidity on the foraging pattern. Furthermore, another process of great importance to the reproduction of the colonies was studied, the swarming. Either the biology of the swarms as the rhythm of the construction of brood cells and of the POP in the beginning of the establishment of the colonies was studied. We also discussed the factors that may have been involved in the initial growth of the colonies and their establishment. The foraging and the swarming are processes very important to the growth and the reproduction of the colonies, and their comprehension is important to the development of management techniques and measurements to the promotion of conservation of bees.
395

Cattle Browsing Sagebrush Steppe During Fall: Effects On Plant Community Structure and Influence of Experience On Cattle Foraging Behavior and Body Weights

Petersen, Charles A. 01 May 2012 (has links)
Disturbances such as fire and grazing can degrade landscapes, but they can also rejuvenate them. I evaluated: 1) the practicality of strategically timed (fall), high intensity browsing of sagebrush (Artemisia tridentata ssp. tridentata, ssp. wyomingensis) by cattle; 2) the foraging behavior and body weights of cattle with varying levels of experience browsing sagebrush; and 3) the ensuing responses of grasses, forbs, and sagebrush to cattle grazing. In spatially and temporally replicated trials from 2007 to 2009, fall grazing by cattle reduced the abundance of sagebrush and promoted production of grasses and forbs. The cattle used in these trials were challenged to learn to eat sagebrush in the unfamiliar circumstance of confinement in small pastures. Throughout the trials from 2007 to 2009, pregnant cows with calves (2007), bred yearling heifers (2008), and first-calf heifer/calf pairs (2009) supplemented with protein and energy – to mitigate the effects of terpenes in big sagebrush – learned to select sagebrush as a significant portion of their diet. In virtually every case, experienced animals consistently used more sagebrush and lost less weight, or actually gained more weight, than naive animals in 2008 and 2009. My research suggests grazing by cattle during fall can be effective, biologically and economically, and can lead to habitat renovation and resilience. Moreover, grazing can create locally adapted systems in ways that landscape manipulations with chemical and mechanical treatments and prescribed fire cannot. These “technological fixes” are increasingly impractical due to environmental concerns, the high costs of fossil fuels, and the need to repeat outcome-based treatments rather than incorporating process-based approaches into managing landscapes. Rather than attempting to convert sagebrush steppe landscapes to grass at extravagant costs, as we have done historically, we must now consider ways to create locally adapted herds of livestock and complementary management practices to ensure long-term health of sagebrush steppe. As many ranchers already feed hay to cows during winter, using sagebrush steppe vegetation as an additional forage resource would allow ranchers to feed roughly half the hay, which would greatly reduce winter feed costs. In addition to financial savings in hay, the secondary benefits from improving sagebrush steppe condition and productivity would result in habitat improvements for both livestock and wildlife.
396

Ecology and conservation of the swift parrot - an endangered austral migrant

Saunders, Debra, debbie.saunders@anu.edu.au January 2008 (has links)
The swift parrot (Lathamus discolor, Psittacidae) is an endangered, austral migrant that inhabits forests and woodlands of south-eastern Australia. With a small population size (2500 birds), broad winter distribution (1 250 000 km2) and often cryptic nature, the swift parrot is a challenging species to study. In autumn they migrate north from their Tasmanian breeding grounds in search of suitable food resources throughout their winter range on mainland Australia. They are therefore dependent on a combination of suitable wintering, migration and breeding habitats. Although they spend a large proportion of their lives within winter habitats, the spatial and temporal dynamics of habitat use in this part of their range is poorly understood. This thesis aims to provide a greater understanding of large-scale winter habitat use by swift parrots, in both historic and current contexts, and provide a basis for future conservation management. ¶ Swift parrots, or red-shouldered paroquets as they were previously known, were among the first Australian birds to be scientifically described and illustrated following European settlement in 1788. However, within 60 years of settlement, habitats throughout the range of the species were being impacted upon. An important aspect of this habitat loss is the speed and spatial extent with which it occurred throughout the parrots’ broad distribution. Although the most extensive habitat loss in some areas occurred during colonial times, habitats continue to be lost as a result of various land management practices. Such impacts are also likely to be exacerbated by the ongoing cumulative impact with rapid climate change. As a result the swift parrot is an endangered species and is the subject of an ongoing national recovery program, to which this thesis contributes. ¶ Conserving habitat for the swift parrot, and other wide-ranging fauna species, is challenging since impacts in one area tend to be dismissed based on the assumption that there is sufficient habitat in other areas. These conservation challenges are discussed in regard to the national swift parrot recovery program. Although recovery program implementation for this species has been successful in identifying and protecting some important habitats, there are still many gaps in our knowledge that need to be addressed through a continuing and adaptive recovery effort, including an understanding of variable habitat use throughout their winter range. ¶ A study of swift parrot winter habitat use was therefore conducted at 53 sites across New South Wales over five years (2001-2005). Swift parrots used a diversity of winter foraging habitats in coastal and/or western slopes regions of New South Wales each year, including several habitats that occur in endangered ecological communities. Landscapes containing winter foraging habitat included scattered trees, remnant vegetation and continuous forests, and swift parrots foraged extensively on lerp and nectar from a diversity of tree species within these. The occurrence of swift parrots at foraging sites was primarily associated with the abundance of lerp, nectar and non-aggressive competitors. Although swift parrot abundance fluctuated significantly between years and regions, over half of all foraging sites were used repeatedly, highlighting their likely importance for conservation. ¶ Patterns of habitat use throughout the species’ winter range were also studied across five states/territories using volunteer data from 4140 surveys. These surveys were conducted by up to 300 volunteers twice a year, for seven years (1998-2004) with swift parrots detected in 19% of surveys. As a result, this study provided the first demonstration of large-scale drought related movements by a migratory population throughout their winter range. It also demonstrated the dynamic spatial and temporal patterns of winter habitat use, including repeated use of sites, by an austral migrant. Four regions in central Victoria were used most consistently, although the birds also visited other regions each year. ¶ During drought swift parrot abundance was significantly correlated with rainfall, whereby most of the population either concentrated in a few regions or migrated longer distances (up to 1000km) to drought refuges in wetter coastal areas. However, swift parrot abundance was not associated with specific climate variables during years of average to high rainfall throughout most of their range. Instead they appeared to prefer habitats within particular regions. Importantly this study emphasises that conservation measures need to be implemented throughout the distribution of migratory species, including drought refuge habitats and areas outside conservation reserves.
397

Resource variation and the evolution of phenotypic plasticity in fishes

Ruehl, Clifton Benjamin 30 September 2004 (has links)
Resource variation and species interactions require organisms to respond behaviorally, physiologically, and morphologically within and among generations to compensate for spatial and temporal environmental variation. One successful evolutionary strategy to mitigate environmental variation is phenotypic plasticity: the production of alternative phenotypes in response to environmental variation. Phenotypic plasticity yields multiple characters that may enable organisms to better optimize phenotypic responses across environmental gradients. In this thesis, I trace the development of thought on phenotypic plasticity and present two empirical studies that implicate phenotypic plasticity in producing morphological variation in response to resource variation. The first empirical study addresses trophic plasticity, population divergence, and the effect of fine-scale environmental variation in western mosquitofish (Gambusia affinis). Offspring from two populations were fed either attached or unattached food items offered in three orientations: (1) water surface, (2) mid-water, (3) benthic, and (4) a daily rotation of the former three (fine-grained variation). Attached food induced wide heads, blunt snouts and rounded pectoral fins relative to morphology in the unattached treatment. Mid-water feeding induced elongated heads and deeper mid-bodies relative to benthic and surface feeding induced morphologies. The rotating treatment produced intermediate morphologies. Population divergence seemed related to both trophic and predation ecology. Ecomorphological consequences of induced morphologies and the need for inclusion of greater ecological complexity in studies of plasticity are discussed. The second study examines induced morphological plasticity and performance in red drum (Sciaenops ocellatus). I fed hatchery fish either hard or soft food for two months. Performance trials were designed to measure their ability to manipulate and consume hard food items. External morphology and the mass of pharyngeal crushing muscles were assessed for variation among treatments. A hard food diet induced deeper bodies and larger heads, more massive pharyngeal muscles, and initially more efficient consumption of hard food than fish receiving soft food. The observed morphological variation is in accordance with variation among species. Determining evolutionary mechanisms operating within red drum populations should eventually aid in developing and optimizing conservation efforts and ease the transition from hatchery facilities to estuaries.
398

Effects of Habitat Quality on Behavioural Decisions and Population Dynamics in the Siberian Jay

Nystrand, Magdalena January 2006 (has links)
The dynamics of natural populations may be influenced by a variety of factors, ranging from feeding interference and territoriality to the risk of predation and climatic effects. The relative influence of these factors may be contingent upon the quality of the habitat in which individuals reside. A factor that can largely affect population dynamics and that often covaries with habitat structure is predation risk. However, the combined effect of habitat and predation risk can vary according to the social context and intrinsic characteristics that affect individual behavioural responses. This thesis investigates the effects of habitat quality at the level of the population and the individual, and examines how it relates to the above factors in Siberian jays (Perisoreus infaustus), a territorial, group-living species in which the main cause of mortality is predation. The results demonstrate a strong effect of habitat on survival, reproduction and behaviour. Mortality was generally higher in open areas and managed forests and reproductive success decreased after forest management. Breeding females were more sensitive to environmental factors than males, possibly because of higher reproductive costs. Estimates of spatial demography suggested that there were more sinks than sources, and that they were located in open, managed forests. Behavioural decisions confirmed that open forests were associated with higher predation risks. However, decisions depended on social context; immigrants took highest risks and were the recipients of most aggression, largely an effect of social subordination. Also, parents provide their offspring with benefits that are withheld from immigrants. As a result, first-year survival was higher in retained offspring. Investigating the effects of multi-scale habitat quality on individual behaviour and population dynamics has generated an increased understanding of the effects of forest management on the dynamics of this population. This approach should facilitate development of an effective conservation management policy for this species.
399

Interactive analogical retrieval: practice, theory and technology

Vattam, Swaroop 24 August 2012 (has links)
Analogy is ubiquitous in human cognition. One of the important questions related to understanding the situated nature of analogy-making is how people retrieve source analogues via their interactions with external environments. This dissertation studies interactive analogical retrieval in the context of biologically inspired design (BID). BID involves creative use of analogies to biological systems to develop solutions for complex design problems (e.g., designing a device for acquiring water in desert environments based on the analogous fog-harvesting abilities of the Namibian Beetle). Finding the right biological analogues is one of the critical first steps in BID. Designers routinely search online in order to find their biological sources of inspiration. But this task of online bio-inspiration seeking represents an instance of interactive analogical retrieval that is extremely time consuming and challenging to accomplish. This dissertation focuses on understanding and supporting the task of online bio-inspiration seeking. Through a series of field studies, this dissertation uncovered the salient characteristics and challenges of online bio-inspiration seeking. An information-processing model of interactive analogical retrieval was developed in order to explain those challenges and to identify the underlying causes. A set of measures were put forth to ameliorate those challenges by targeting the identified causes. These measures were then implemented in an online information-seeking technology designed to specifically support the task of online bio-inspiration seeking. Finally, the validity of the proposed measures was investigated through a series of experimental studies and a deployment study. The trends are encouraging and suggest that the proposed measures has the potential to change the dynamics of online bio-inspiration seeking in favor of ameliorating the identified challenges of online bio-inspiration seeking.
400

Optimal Foraging Theory - OFT : Background, Problems and Possibilities / Optimal Foraging Theory - OFT : bakgrund, problem och möjligheter

Malmros, Ingegärd Enander January 2012 (has links)
Optimal Foraging Theory (OFT) has its origin in processualistic ideas in 1960s with traces back to the dawn of the archaeological science in the 19th century. The OFT model is based on the construction of an individual’s food item selection understood as an evolutionary construct that maximizes the net energy gained per unit feeding time. The most common variants are diet patch choice, diet breadth/prey choice models and Marginal Value Theorem (MVT). The theory introduced experimental studies combined with mathematically data analyses and computer simulations. The results visualized in the experimental diagrammed curve are possible to compare with the archaeological records. What is “optimal” is an empirical question not possible to know but still useful as a benchmark for measuring culture. The theory is common in USA but still not in Europe. OFT seems to be useful in hunter-gatherer research looking at human decisions, energy flow, depression of resources and extinction. This literature review concludes that the prey-choice/diet-breadth model seems to be useful for hunter-gatherer research on Gotland focusing on possible causes of the hiatus in archaeological records between 5000-4500 BC. / Optimal Foraging Theory (OFT) har sitt ursprung i de processualistiska ideérna under 1960-talet med spår tillbaka till arkeologins början som vetenskap under 1800-talet. OFT modellen baseras på konstruktionen av en individs födoämnesval som förstås som en evolutionär konstruktion som maximerar nettoenergiintaget per tidsenhet som gått åt för försörjningen. De vanligaste varianterna är patch-choice, diet breadth/prey choice modellerna och Marginal Value Theorem (MVT). Experimentella studier genomförs och data bearbetas matematiskt och visar datorsimulerade kurvdiagram möjliga att jämföra med arkeologiska källmaterial. Vad som är ”optimalt” är en empirisk fråga omöjlig att veta men användbar ändå som en slag referens för att mäta kultur. Teorin är vanlig i USA men ännu inte i Europa. OFT förefaller användbar inom forskning av jägare-samlare om man fokuserar på beslutsfattande, energiflöde, depression av resurser och utrotning av arter. Slutsatsen i denna litteraturöversikt är att prey choice/diet breadth modellen tycks vara användbar för gotländsk jägare-samlare-forskning som fokuserar på möjliga orsaker till de arkeologiska fyndens hiatus mellan 5000-4500 BC.

Page generated in 0.0827 seconds