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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.
21

Ecologia alimentar de morcegos frugívoros em uma área de restinga do nordeste do Brasil e comportamento germinativo de espécies pioneiras após passagem pelo sistema digestório

Oliveira, Tamiris da Silva 27 February 2018 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The knowledge of the trophic interactions of fruit bats is fundamental to understand the role of these animals in the organization of tropical ecosystems. The present study, the fauna of fruit bats and food items that composed the diet of the species in the “Resting” of Northeast Brazil were determined. Similarity in the diet of the bats and the influence of seasonality and sex on the consumption of the resources were avaluated. Subsequently, the species of plants and seeds that passed through the digestive tract of the bats were identified for the evaluation of the germinative behavior (percentage, mean germination time, germination speed and synchronization index) of the seeds of four pioneer plant species (Cecropia pachystachya, Passiflora silvestris, Solanum asperum and Vismia guianensis). Seeds consumed by bats Artibeus lituratus and Carollia perspicillata were compared to unconsumed seeds (collected from fruits). Between October 2016 and September 2017, eight species of fruit bats were captured and nine species of plants identified in their fecal samples. The association between species based on diet content showed that these can be divided into three groups: specialists in Cecropia (A. lituratus and A. planirostris), specialist in Solanum (D. cinerea) and generalist (C. perspicillata). Carollia perspicillata contributed with seed samples throughout the year, having its diet influenced by seasonality. However, differences in the diet of males and females of this species were not observed. It was observed that the germination of C. pachystachya was significantly benefited after ingestion by A. lituratus. Seeds of S. asperum, P. silvestris and V. guianensis consumed by C. perspicillata presented neutral and negative effects on germinability in relation to seeds collected from fruits. The results of the present study indicated that the species seem to adapt to the different conditions of food supply during the dry and rainy periods, modifying their diet or moving to other areas where they can consume fruits of their preference. In addition, the same species of bat can produce distinct effects on the germinative behavior of seeds consumed, as well as different bats can contribute in a differentiated way in the establishment rates of plants in the restinga, mainly in the initial stages of succession. / Conhecer as interações tróficas dos morcegos frugívoros é fundamental para se entender o papel desses animais na organização dos ecossistemas. No presente estudo, a fauna de morcegos frugívoros e os itens alimentares que compunham a dieta das espécies na restinga do Nordeste do Brasil foram determinados. Também foi avaliada a similaridade na dieta dos quirópteros e a influência da sazonalidade e do sexo no consumo dos recursos. Subsequentemente, as espécies de plantas e sementes que passaram pelo trato digestório dos morcegos foram identificadas para a avaliação do comportamento germinativo (porcentagem, tempo médio de germinação, velocidade de germinação e índice de sincronização) das sementes de quatro espécies de plantas pioneiras (Cecropia pachystachya, Passiflora silvestris, Solanum asperum e Vismia guianensis). Sementes consumidas pelos morcegos Artibeus lituratus e Carollia perspicillata foram comparadas com sementes não consumidas (coletadas dos frutos). Entre outubro de 2016 e setembro de 2017, oito espécies de morcegos frugívoros foram capturadas e nove espécies de plantas identificadas em suas amostras fecais. A associação entre espécies com base no conteúdo da dieta mostrou que estas podem ser divididas em três grupos: especialistas em Cecropia (A. lituratus e A. planirostris), especialista em Solanum (D. cinerea) e generalista (C. perspicillata). Carollia perspicillata contribuiu com amostras de sementes durante todo o ano, tendo sua dieta influenciada pela sazonalidade. Entretanto, diferenças na dieta de machos e fêmeas dessa espécie não foram constatadas. Foi observada que a germinação de C. pachystachya foi significativamente beneficiada após a ingestão por A. lituratus. Sementes de S. asperum, P. silvestris e V. guianensis consumidas por C. perspicillata apresentaram efeitos neutros e negativos na germinabilidade em relação às sementes coletadas dos frutos. Os resultados do presente estudo indicaram que as espécies parecem adequar-se às diferentes condições de oferta de alimentos durante os períodos seco e chuvoso, modificando sua dieta ou deslocando-se para outras áreas onde possam consumir frutos de sua preferência. Além disso, uma mesma espécie de morcego pode produzir efeitos distintos no comportamento germinativo das sementes consumidas, assim como morcegos diferentes podem contribuir de forma diferenciada nas taxas de estabelecimento de plantas na restinga, principalmente nos estádios iniciais de sucessão. / São Cristóvão, SE
22

How vertebrate communities affect quality and yield of macadamia farms in Levubu, South Africa

Linden, Valerie M. G. 15 May 2019 (has links)
PhD (Zoology) / Department of Zoology / Ecosystem services and disservices are important features in agro-ecosystems and both can have relevant economic impacts on farmers. While there has been much research on the value of ecosystem services, especially that of pest control by bats and birds, ecosystem disservices are often overlooked or estimated separately. Both, services and disservices, however, change with landscape and may be supported by natural vegetation. It is hence inevitable to assess them together to uncover their relative value and importance. Habitat loss and fragmentation are major threats to biodiversity and ecosystem services. Agricultural intensification can cause habitat loss and can negatively affect natural ecosystems and their services. However, the removal of natural vegetation can also reduce ecosystem disservices that origin from natural areas. This study focused on the economic trade-off between biocontrol by bats and birds and crop raiding by vervet monkeys in South African macadamia orchards, using vertebrate exclusion experiments. Crop quality and yield were assessed and extrapolated to income values. The study furthermore focused in more detail on the impact of orchard edge habitat and farm management on bats as ecosystem service providers as well as the arthropod community, which can provide both services (pollination, biocontrol) as well as disservices (crop damage). The macadamia industry is highly profitable and plantings are expanding worldwide. South Africa is currently the largest macadamia producer in the world and the study area, Levubu, holds some of the oldest macadamia plantings in the country. The subtropical climate and high annual rainfall make this area an intensively farmed landscape. Levubu lies at the foothills of the Soutpansberg, a centre of biodiversity and patches of natural vegetation wind through orchards of macadamia, avocado, banana and timber. Insect pest pressure is high in the macadamia industry, with several stink bug species (Hemiptera) and two moth species (Lepidoptera) accounting for most of the damage to the crop. Chapter One provides a detailed overlook over the South African macadamia industry, describes the major pest insect species and their impact on the crop and highlights the role of ecosystem services and disservices and the potential importance of remaining natural areas. Over three consecutive seasons, between September 2015 and May 2018, bats, birds and monkeys were excluded, using cages with nets, from a total of 96 macadamia trees. Four treatments were applied (Full, Day, Night, Control) to distinguish between effects of the different functional groups. Exclusions took place at orchard edges with natural or human-modified edge habitat to assess the impact of vicinity to natural vegetation on pest control and crop raiding. Results presented in Chapter Two showed that biocontrol by bats and birds was stronger near natural vegetation and significantly impacted crop quality as well as yield. Effects of bats and birds were still significant at human-modified edges, whereas crop raiding by monkeys is limited to the natural orchard edges. The economic impact analysis shows that the benefits of biocontrol through bats and birds outweighed the income losses due to crop-raiding monkeys. The value of bats and birds was as high as USD 5000 per hectare per year through prevented insect damage and a 60% crop increase. Crop-raiding affected the yield, which dropped by about 26% and resulted in losses of about USD 1500 per hectare. These results highlight the importance of integrating natural areas into agricultural landscapes, even if they incur the risk of being disadvantageous. Farmers need to be made aware of the enormous economic benefits. Effective crop raiding mitigation strategies still need to be researched to avoid negative association with natural areas. These can, however, possibly also limit access for biocntrol agents, like bats and birds and thereby reduce their economic impact. Especially the removal of natural areas or establishment of buffer zones of unpalatable crops between agricultural land and forests is not advisable. Integrative research in agro-ecosystems on trade-offs between a variety of ecosystem services and disservices is necessary in future, rather than assessing them separately. The bat community on macadamia farms was monitored monthly and compared between orchard edges. Stationary bat detectors were placed at each set of exclosures for two consecutive nights a month, automatically recording from sunset to sunrise. Recorded bat calls were identified manually to species level and activity converted to Miller’s activity index, which counts the number of active minutes per species per night. We analysed the activity per feeding guild over season and landscape setting, estimated species richness and diversity (Hill’s numbers) and species turnover between farms, season and landscape setting, using diversity partitioning. The bat community was mostly influenced by seasonality with season turn-over accounting for 21% of total bat diversity (21.25 species). Edge habitat on the other hand only accounted for 5%. We found higher species richness and activity in the high season compared to the low. While there was no difference in diversity in the high season between the two orchard edge types, species diversity at the human-modified edge was lower than in the natural during the low season. Natural habitat might therefore be more important in the low season, while its effect is overwritten by high food availability during the high season. Clutter-edge species furthermore were more active at the natural orchard edges than open-air feeders, which were in turn more active at human-modified edges. Both activities dropped significantly during the low season. Chapter Three concludes that the macadamia landscape is able to support a high bat species diversity, which is affected by seasonal differences, probably due to food availability. Natural areas are important to be maintained to support sensitive species, relying on clutter habitat and natural roosts. Habitat features as well as farm management can also influence arthropod communities. Visual observations took place each month for 20 minutes per tree. Observations were counted and identified to at least order level. Chapter Four concentrates on the impact of orchard edge habitat and insecticide treatment on honey bees (83% of Hymenoptera observations) abundance. Honey bees were the only taxon significantly responding to both variables, with higher abundance close to natural areas and increasing abundance with increasing time since pesticide application. Honey bees furthermore seemed to recover slightly quicker from population crashes after insecticide treatments at natural edges than they did at human-modified edges. Hymenoptera can be highly beneficial to macadamia farmers, as farmers are heavily relying on pollination by honey bees and parasitoids are known to feed on major macadamia pest insect species. These ecosystem service providers were mostly affected by habitat and management practices, which may compromise their ecosystem service provision. Although commercial bee hives are exposed throughout macadamia orchards, they do not appear to fully replace the pollination and biocontrol services provided by feral species, which can be enhanced through resource supplementation by patches of nearby natural vegetation. Chapter Five concludes with emphasizing the general importance of natural vegetation in landscape planning of agricultural areas. This study proved confidently that benefits through ecosystem services largely outweigh negative impacts of ecosystem disservices, both stemming from these natural areas. Through the inclusion, maintenance and restoration of such patches of natural vegetation, farmers can potentially increase the value and effectiveness of biocontrol by bats and birds or other services. Seasonality largely determined bat species diversity, and a general high species diversity was observed in the macadamia landscape, possibly due to a certain degree of landscape heterogeneity and high food availability. Activity patterns of clutter-edge and open-air feeding bats varied with edge habitat, while clutter-dependent bat species / NRF

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