Global ETD Search

51	Drivers of macrophyte assemblages in South African freshwater systems Martin, Grant Douglas January 2013 (has links) Potentially damaging submerged invasive freshwater macrophytes have been identified in South African freshwater systems, but have received less attention than their floating counterparts. To ascertain the changes and effects that these species may have on macrophyte ecology, an understanding of the drivers of macrophyte assemblages is essential. The aims of this thesis were to investigate select abiotic and biotic factors driving introduction, establishment and spread of submerged macrophytes in South Africa. Surveys on the status of submerged plant species in South Africa were conducted to find out the distribution and diversity of the species present, imported to, and traded in South Africa. Numerous submerged indigenous and invasive macrophyte locality records were collected during field surveys, of which many were first time records. Pet stores and aquarist trading activities were identified as potential vectors for the spread of submerged macrophytes through online surveys and personal interviews. These results highlighted the potential these species have for continuing to enter, and spread within South African water bodies. Maximum Entropy (MAXENT) is a general-purpose method used to predict or infer distributions from incomplete information, and was used here to predict areas suitable for the establishment of five of these invasive macrophytes. Many systems throughout South Africa, particularly those in the subtropical coastal regions, were found to be climatically suitable for the establishment of Elodea canadensis Michx., Egeria densa Planch., Hydrilla verticillata (L.f.) Royle (all Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae), and Cabomba caroliniana Gray (Cabombaceae). Despite the high probability of invasion, facilitated by vectors and suitable climate, South Africa’s rich indigenous submerged aquatic flora may be preventing the establishment of these submerged invasive species. Studies on the competitive interactions between a common indigenous submerged macrophytes, Lagarosiphon major (Roxb.) (Hydrocharitaceae) and M.spicatum, an invasive native to Eurasia, were conducted to ascertain which conditions influence competitive superiority. High sediment nutrient conditions significantly increased the growth rate and competitive ability of both species, while clay sediments significantly increased the competitive ability of L. major over M. spicatum, but sandy sediments improved the competitive ability of M. spicatum. These results highlighted the dynamic changes in competition between submerged species driven by abiotic factors, but did not take into consideration the effect that herbivory, a biotic factor, could have on competition between the two species. The effect of herbivory by phytophagous insects of submerged plant species has been regarded as negligible. To find out what this effect is, multiple field surveys were undertaken throughout South Africa to find natural enemies of indigenous Lagarosiphon species with the aim of identifying such species, and quantifying their influence on plant growth dynamics. Several new phytophagous species were recorded for the first time. An ephydrid fly, Hydrellia lagarosiphon Deeming (Diptera: Ephydridae) was ascertained to be the most ubiquitous and abundant species associated with L. major in South Africa. The influence of herbivory by this fly on the competitive ability of L. major in the presence of M. spicatum was investigated using an inverse linear model, which showed that herbivory by H. lagarosiphon reduced the competitive ability of L. major by approximately five times in favour of M. spicatum. This study served to highlight the importance of herbivory as a driver of submerged aquatic plant dynamics. Current ecological theory emphasises the importance of investigating beyond plant-herbivore interactions, by including multitrophic interactions in community dynamics. Therefore, the potential of parasitism by a parasitoid wasp, Chaenusa luteostigma sp. n. Achterberg (Hymenoptera: Braconidae: Alysiinae) on H. lagarosiphon to shift the competitive interactions between the two plant species was also examined. The addition of the parasitoid reduced the effect of herbivory by the fly on L. major by half, thereby shifting the competitive balance in favour of L. major over M. spicatum. This study provides valuable insight into a selection of drivers of submerged macrophyte assemblages of South Africa. It highlights the precarious position of South African freshwater systems with regard to the potential invasion by damaging submerged invasive species. It also provides interesting insights into the effect of competition, herbivory and parasitism on the establishment and spread of species within submerged freshwater systems. Understanding the different influences could assist managers and policy makers to make validated decisions ensuring the integrity of South African freshwater systems. Freshwater plants -- South Africa Aquatic weeds -- South Africa Invasive plants -- South Africa Freshwater ecology -- South Africa Biotic communities -- South Africa Maximum entropy method Lagarosiphon major -- South Africa Phytophagous insects -- South Africa Hydrellia -- South Africa Parasitoids -- South Africa
52	Pflanze-Herbivore-Parasitoid Interaktionen auf Wildrosenarten und ihren Hybriden entlang eines geographischen Gradienten / Plant-herbivore-parasitoid interations on dog rose species and their hybrids along a geographic gradient Klinge, Katrin 19 January 2006 (has links) No description available. 590 Tiere (Zoologie) WN Mathematics and Natural Science Hundsrosen Phänotyp Rhagoletis alternata Diplolepis rosae Phragmidium phytophage Insekten Hybridisierung Allozyme genetische Differenzierung multitrophische Interaktionen geographischer Gradient Fressbarkeit Spodoptera littoralis Rosa canina Rosa corymbifera Rosa rubiginosa dog roses phenotyp Rhagoletis alternata <si>Diplolepis rosae Phragmidium phytophagous insects hybridisation allozymes genetic differentiation multitrophic interactions geographic gradient palatability Spodoptera littoralis Rosa canina Rosa corymbifera Rosa rubiginosa 42.65 Tiergeographie Tierökologie
53	Biogéographie du microclimat foliaire : mécanismes et conséquences sur les relations plantes-insectes / Biogeography of the leaf microclimate : mechanisms and consequences on insect-plant interactions Caillon, Robin 29 January 2016 (has links) Les performances du végétal et des arthropodes dont il constitue le microhabitat dépendent des températures de surface foliaire. Celles-ci peuvent dévier fortement de la température de l’air et présenter des niveaux d’hétérogénéité différents selon l'échelle spatiale considérée. La feuille atténue les températures extrêmes en rapprochant son amplitude de variation journalière de celle de la température de l’air. Cependant, cette réponse diminue l’hétérogénéité des températures de surface foliaire et les capacités de thermorégulation comportementale des arthropodes à l'échelle de la feuille. Les températures moyennes de surface foliaire atténuent peu le réchauffement, et déterminent localement la performance photosynthétique du végétal. De l’échelle de la feuille à celle de la canopée, les plantes montrent des réponses différentes au réchauffement. Ce type de changement d'échelle est primordial pour améliorer notre compréhension de l'impact des changements climatiques. / Plant performance and leaf-dwelling arthropods are impacted by leaf surface temperatures. Leaf surface temperatures can show important deviation from air temperature and present different levels of heterogeneity depending on the spatial scale. The leaf buffers temperature extremes by getting closer in amplitude to air temperature. However, this physiological response decreases the heterogeneity of temperatures at the leaf surface and the opportunities for arthropods to behavioraly thermoregulate in this microclimate. Mean temperatures at the leaf surface show low buffering abilities in response to warming and locally determine photosynthetic performance. From the leaf to the canopy scale, plants show different responses to warming and scaling is crucial to increase our understanding of the impact of global warming. Acariens Canopée Changement climatique Échelle spatiale Écologie biophysique Écologie quantitative Extrêmes Feuille Gradient latitudinal Hétérogénéité Microclimat Microhabitat Moyenne Photosynthèse Plasticité physiologique Phytophages Pucerons Réchauffement Relations plantes-arthropodes Résistance thermique Température Température corporelle Température létale Thermorégulation comportementale Variance Aphids Behavioural thermoregulation Biophysical ecology Body temperature Canopy Climate change Extremes Heterogeneity Latitudinal gradient Leaf Lethal temperature Mean Microclimate Microhabitat Photosynthesis Physiological plasticity Phytophagous Plant-arthropods relationship Quantitative ecology Spatial scale Spider mites Temperature Thermal resistance Variance Warming
54	Untersuchungen zum Einfluß des Kots phytophager Insekten auf die Keimung und das frühe Wachstum von Kiefern (Pinus sylvestris L.), Birken (Betula pendula Roth.) und Eichen (Quercus robur L.) unter besonderer Berücksichtigung des Inhaltsstoff-Musters der Blattorgane / Investigation of the influence of insectfrass on the germination and the early growth of young pines (Pinus sylvestris L.), birches (Betula pendula Roth.) and oaks (Quercus robur L.) - especially on the patterns of the nutrients and inhibitors in the needles and leaves Jung, Peter 22 October 2004 (has links) No description available. 570 Biowissenschaften Biologie Forest Sciences and Forest Ecology phytophage Insekten Massenvermehrung Kiefer Birke Eiche Pinus Betula Quercus sekundäre Pflanzenstoffe Insektenkot Inhaltsstoffmuster Keimung Jugendwachstum phytophagous insects population explosion pine birch oak Pinus Betula Quercus The secondary plant substances insectfrass germination early growth 48.40 48.52 48.99 YP 000: Standortfaktoren YQE 000: Physiologie {Forstbotanik} YR 000: Forstzoologie YSH 000: Aufforstung Verjüngung und Bestandesgründung Auforstung
55	Birds, bats and arthropods in tropical agroforestry landscapes: Functional diversity, multitrophic interactions and crop yield Maas, Bea 20 November 2013 (has links) No description available. 630 birds bats arthropods multitrophic interactions agroforestry tropical landscape forest margin landscape functional diversity crop yield exclosure experiments experimental exclusion arthropod suppression avian predation ecosystem services mist netting point counts artificial plasticine caterpillar dummy experiment biological control monitoring mapping Lemon-bellied White-eye Grosbeak Starling Zosterops chloris Scissiostrum dubium Theobroma cacao cacao agroforestry cacao diseases cacao harvest cacao pests flying vertebrates aerial insectivores volant vertebrates logging breeding colony flower herbivory mesopredator release predatory insects ants spiders aphids Lepidoptera Coleoptera Lepidopteran larvae sustainable agriculture sustainable agroforestry management implications management recommendations applied managament extensive land use management landscape management conservation biodiversity-friendly dbh distance to forest forest proximity habitat conversion herbivory Indonesia insectivorous bats insectivorous birds invertebrates Central Sulawesi Napu valley leaf gleaning leaf herbivory pests insects phytophagous insects plant productivity remnant forest trees shade tree managament South-east Asia Paleotropics tropical landscape tree height landscape gradient local shade management Cacao Pod Borer Cherelle Wilt fruit abortion Helopeltis sulawesi deforestation habitat fragmentation land use intensification forest margin species critical decline predation experiment species-specific functions Southeast Asia biodiversity conservation mesopredators food security human welfare human well-being poverty alleviation poverty reduction smallholder cacao smallholder plantation cacao farmers sustainable cacao management landscape perspective landscape scale large scale field experiment long term field experiment human wellbeing economic importance economic value valuation ecosystem services landscape matrix yield quality yield quantity fruit productivity species identity species diversity species richness ecosystem functioning pesticide use chemical compounds complex food web tritrophic interactions wildlife-friendly rural livelihoods endangered bird species endangered bat species endemic endemic birds endemic bats beneficial impact IUCN Lore Lindu National Park bioindicator indicator species forest margin agricultural habitat agroforestry systems population density predation activity species activity cacao flower cacao pod Orthoptera linear mixed effect models Tukey Post Hoc Test AICc model selection generalized least squares restricted maximum likelihood model simplification species richness estimator species accumulation linear mixed-effects models Likelihood Ratio Test Maximum Likelihood nocturnal insects diurnal arthropods nocturnal arthropods diurnal insects landscape context Land- und Forstwirtschaft (PPN621302791)

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