@phdthesis{Gebert2022,
  author    = {Gebert, Friederike},
  title     = {Mammals and dung beetles along elevational and land use gradients on Mount Kilimanjaro: diversity, traits and ecosystem services},
  doi       = {10.25972/OPUS-19195},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-191950},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Despite belonging to the best described patterns in ecology, the mechanisms driving biodiversity along broad-scale climatic gradients, like the latitudinal gradient in diversity, remain poorly understood. Because of their high biodiversity, restricted spatial ranges, the continuous change in abiotic factors with altitude and their worldwide occurrence, mountains constitute ideal study systems to elucidate the predictors of global biodiversity patterns. However, mountain ecosystems are increasingly threatened by human land use and climate change. Since the consequences of such alterations on mountainous biodiversity and related ecosystem services are hardly known, research along elevational gradients is also of utmost importance from a conservation point of view. In addition to classical biodiversity research focusing on taxonomy, the significance of studying functional traits and their prominence in biodiversity ecosystem functioning (BEF) relationships is increasingly acknowledged. In this dissertation, I explore the patterns and drivers of mammal and dung beetle diversity along elevational and land use gradients on Mt. Kilimanjaro, Tanzania. Furthermore, I investigate the predictors of dung decomposition by dung beetles under different extinction scenarios. Mammals are not only charismatic, they also fulfil important roles in ecosystems. They provide important ecosystem services such as seed dispersal and nutrient cycling by turning over high amounts of biomass. In chapter II, I show that mammal diversity and community biomass both exhibited a unimodal distribution with elevation on Mt.Kilimanjaro and were mainly impacted by primary productivity, a measure of the total food abundance, and the protection status of study plots. Due to their large size and endothermy, mammals, in contrast to most arthopods, are theoretically predicted to be limited by food availability. My results are in concordance with this prediction. The significantly higher diversity and biomass in the Kilimanjaro National Park and in other conservation areas underscore the important role of habitat protection is vital for the conservation of large mammal biodiversity on tropical mountains. Dung beetles are dependent on mammals since they rely upon mammalian dung as a food and nesting resource. Dung beetles are also important ecosystem service providers: they play an important role in nutrient cycling, bioturbation, secondary seed dispersal and parasite suppression. In chapter III, I show that dung beetle diversity declined with elevation while dung beetle abundance followed a hump-shaped pattern along the elevational gradient. In contrast to mammals, dung beetle diversity was primarily predicted by temperature. Despite my attempt to accurately quantifiy mammalian dung resources by calculating mammalian defecation rates, I did not find an influence of dung resource availability on dung beetle richness. Instead, higher temperature translated into higher dung beetle diversity. Apart from being important ecosystem service providers, dung beetles are also model organisms for BEF studies since they rely on a resource which can be quantified easily. In chapter IV, I explore dung decomposition by dung beetles along the elevational gradient by means of an exclosure experiment in the presence of the whole dung beetle community, in the absence of large dung beetles and without any dung beetles. I show that dung decomposition was the highest when the dung could be decomposed by the whole dung beetle community, while dung decomposition was significantly reduced in the sole presence of small dung beetles and the lowest in the absence of dung beetles. Furthermore, I demonstrate that the drivers of dung decomposition were depend on the intactness of the dung beetle community. While body size was the most important driver in the presence of the whole dung beetle community, species richness gained in importance when large dung beetles were excluded. In the most perturbed state of the system with no dung beetles present, temperature was the sole driver of dung decomposition. In conclusion, abiotic drivers become more important predictors of ecosystem services the more the study system is disturbed. In this dissertation, I exemplify that the drivers of diversity along broad-scale climatic gradients on Mt. Kilimanjaro depend on the thermoregulatory strategy of organisms. While mammal diversity was mainly impacted by food/energy resources, dung beetle diversity was mainly limited by temperature. I also demonstrate the importance of protected areas for the preservation of large mammal biodiversity. Furthermore, I show that large dung beetles were disproportionately important for dung decomposition as dung decomposition significantly decreased when large dung beetles were excluded. As regards land use, I did not detect an overall effect on dung beetle and mammal diversity nor on dung beetle-mediated dung decomposition. However, for the most specialised mammal trophic guilds and dung beetle functional groups, negative land use effects were already visible. Even though the current moderate levels of land use on Mt. Kilimanjaro can sustain high levels of biodiversity, the pressure of the human population on Mt. Kilimanjaro is increasing and further land use intensification poses a great threat to biodiversity. In synergy wih land use, climate change is jeopardizing current patterns and levels of biodiversity with the potential to displace communities, which may have unpredictable consequences for ecosystem service provisioning in the future.},
  subject      = {Kilimandscharo},
  language  = {en}
}
@phdthesis{Fricke2022,
  author    = {Fricke, Ute},
  title     = {Herbivory, predation and pest control in the context of climate and land use},
  doi       = {10.25972/OPUS-28732},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287328},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Chapter 1 - General introduction Anthropogenic land-use and climate change are the major drivers of the global biodiversity loss. Yet, biodiversity is essential for human well-being, as we depend on the availability of potable water, sufficient food and further benefits obtained from nature. Each species makes a somewhat unique contribution to these ecosystem services. Furthermore, species tolerate environmental stressors, such as climate change, differently. Thus, biodiversity is both the "engine" and the "insurance" for human well-being in a changing climate. Here, I investigate the effects of temperature and land use on herbivory (Chapter 2), predation (Chapter 3) and pest control (Chapter 4), and at the same time identify features of habitats (e.g. plant richness, proximity to different habitat types) and landscapes (e.g. landscape diversity, proportion of oilseed rape area) as potential management targets in an adaptation strategy to climate change. Finally, I discuss the similarities and differences between factors influencing herbivory, predation and pest control, while placing the observations in the context of climate change as a multifaceted phenomenon, and highlighting starting points for sustainable insect pest management (Chapter 5). Chapter 2 - Plant richness, land use and temperature differently shape invertebrate leaf-chewing herbivory on major plant functional groups Invertebrate herbivores are temperature-sensitive. Rising temperatures increase their metabolic rates and thus their demand for carbon-rich relative to protein-rich resources, which can lead to changes in the diets of generalist herbivores. Here, we quantified leaf-area loss to chewing invertebrates among three plant functional groups (legumes, non-leguminous forbs and grasses), which largely differ in C:N (carbon:nitrogen) ratio. This reseach was conducted along spatial temperature and land-use gradients in open herbaceous vegetation adjacent to different habitat types (forest, grassland, arable field, settlement). Herbivory largely differed among plant functional groups and was higher on legumes than forbs and grasses, except in open areas in forests. There, herbivory was similar among plant functional groups and on legumes lower than in grasslands. Also the presence of many plant families lowered herbivory on legumes. This suggests that open areas in forests and diverse vegetation provide certain protection against leaf damage to some plant families (e.g. legumes). This could be used as part of a conservation strategy for protected species. Overall, the effects of the dominant habitat type in the vicinity and diverse vegetation outweighed those of temperature and large-scale land use (e.g. grassland proportion, landscape diversity) on herbivory of legumes, forbs and grasses at the present time. Chapter 3 - Landscape diversity and local temperature, but not climate, affect arthropod predation among habitat types Herbivorous insects underlie top-down regulation by arthropod predators. Thereby, predation rates depend on predator community composition and behaviour, which is shaped by temperature, plant richness and land use. How the interaction of these factors affects the regulatory performance of predators was unknown. Therefore, we assessed arthropod predation rates on artificial caterpillars along temperature, and land-use gradients. On plots with low local mean temperature (≤ 7°C) often not a single caterpillar was attacked, which may be due to the temperature-dependent inactivity of arthropods. However, multi-annual mean temperature, plant richness and the dominant habitat type in the vicinity did not substantially affect arthropod predation rates. Highest arthropod predation rates were observed in diverse landscapes (2-km scale) independently of the locally dominanting habitat type. As landscape diversity, but not multi-annual mean temperature, affected arthropod predation rates, the diversification of landscapes may also support top-down regulation of herbivores independent of moderate increases of multi-annual mean temperature in the near future. Chapter 4 - Pest control and yield of winter oilseed rape depend on spatiotemporal crop-cover dynamics and flowering onset: implications for global warming Winter oilseed rape is an important oilseed crop in Europe, yet its seed yield is diminished through pests such as the pollen beetle and stem weevils. Damage from pollen beetles depends on pest abundances, but also on the timing of infestation relative to crop development as the bud stage is particularly vulnerable. The development of both oilseed rape and pollen beetles is temperature-dependent, while temperature effects on pest abundances are yet unknown, which brings opportunities and dangers to oilseed rape cropping under increased temperatures. We obtained measures of winter oilseed rape (flowering time, seed yield) and two of its major pests (pollen beetle, stem weevils) for the first time along both land-use and temperature gradients. Infestation with stem weevils was not influenced by any temperature or land-use aspect considered, and natural pest regulation of pollen beetles in terms of parasitism rates of pollen beetle larvae was low (< 30\%), except on three out of 29 plots. Nonetheless, we could identify conditions favouring low pollen beetle abundances per plant and high seed yields. Low pollen beetle densities were favoured by a constant oilseed rape area relative to the preceding year (5-km scale), whereas a strong reduction in area (> 40\%) caused high pest densities (concentration effect). This occurred more frequently in warmer regions, due to drought around sowing, which contributed to increased pollen beetle numbers in those regions. Yet, in warmer regions, oilseed rape flowered early, which possibly led to partial escape from pollen beetle infestation in the most vulnerable bud stage. This is also suggested by higher seed yields of early flowering oilseed rape fields, but not per se at higher temperatures. Thus, early flowering (e.g. cultivar selection) and the interannual coordination of oilseed rape area offer opportunities for environmental-friendly pollen beetle management. Chapter 5 - General discussion Anthropogenic land-use and climate change are major threats to biodiversity, and consequently to ecosystem functions, although I could show that ecosystem functions such as herbivory and predation barely responded to temperature along a spatial gradient at present time. Yet, it is important to keep several points in mind: (i) The high rate of climate warming likely reduces the time that species will have to adapt to temperature in the future; (ii) Beyond mean temperatures, many aspects of climate will change; (iii) The compensation of biodiversity loss through functional redundancy in arthropod communities may be depleted at some point; (iv) Measures of ecosystem functions are limited by methodological filters, so that changes may be captured incompletely. Although much uncertainty of the effects of climate and land-use change on ecosystem functions remains, actions to halt biodiversity loss and to interfere with natural processes in an environmentally friendly way, e.g. reduction of herbivory on crops, are urgently needed. With this thesis, I contribute options to the environment-friendly regulation of herbivory, which are at least to some extent climate resilient, and at the same time make a contribution to halt biodiversity loss. Yet, more research and a transformation process is needed to make human action more sustainable. In terms of crop protection, this means that the most common method of treating pests with fast-acting pesticides is not necessarily the most sustainable. To realize sustainable strategies, collective efforts will be needed targeted at crop damage prevention through reducing pest populations and densities in the medium to long term. The sooner we transform human action from environmentally damaging to biodiversity promoting, the higher is our insurance asset that secures human well-being under a changing climate.},
  subject      = {{\"O}kologie},
  language  = {en}
}
@phdthesis{Boetzl2022,
  author    = {B{\"o}tzl, Fabian Alexander},
  title     = {The influence of crop management and adjacent agri-environmental scheme type on natural pest control in differently structured landscapes},
  doi       = {10.25972/OPUS-24140},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-241400},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Summary Chapters I \& II: General Introduction \& General Methods Agriculture is confronted with a rampant loss of biodiversity potentially eroding ecosystem service potentials and adding up to other stressors like climate change or the consequences of land-use change and intensive management. To counter this 'biodiversity crisis', agri-environment schemes (AES) have been introduced as part of ecological intensification efforts. These AES combine special management regimes with the establishment of tailored habitats to create refuges for biodiversity in agricultural landscapes and thus ensure biodiversity mediated ecosystem services such as pest control. However, little is known about how well different AES habitats fulfil this purpose and whether they benefit ecosystem services in adjacent crop fields. Here I investigated how effective different AES habitats are for restoring biodiversity in different agricultural landscapes (Chapter V) and whether they benefit natural pest control in adjacent oilseed rape (Chapter VI) and winter cereal fields (Chapter VII). I recorded biodiversity and pest control potentials using a variety of different methods (Chapters II, V, VI \& VII). Moreover, I validated the methodology I used to assess predator assemblages and predation rates (Chapters III \& IV). Chapter III: How to record ground dwelling predators? Testing methodology is critical as it ensures scientific standards and trustworthy results. Pitfall traps are widely used to record ground dwelling predators, but little is known about how different trap types affect catches. I compared different types of pitfall traps that had been used in previous studies in respect to resulting carabid beetle assemblages. While barrier traps collected more species and deliver more complete species inventories, conventional simple pitfall traps provide reliable results with comparatively little handling effort. Placing several simple pitfall traps in the field can compensate the difference while still saving handling effort.   Chapter IV: How to record predation rates? A plethora of methods has been proposed and used for recording predation rates, but these have rarely been validated before use. I assessed whether a novel approach to record predation, the use of sentinel prey cards with glued on aphids, delivers realistic results. I compared different sampling efforts and showed that obtained predation rates were similar and could be linked to predator (carabid beetle) densities and body-sizes (a proxy often used for food intake rates). Thus, the method delivers reliable and meaningful predation rates. Chapter V: Do AES habitats benefit multi-taxa biodiversity? The main goal of AES is the conservation of biodiversity in agricultural landscapes. I investigated how effectively AES habitats with different temporal continuity fulfil this goal in differently structured landscapes. The different AES habitats investigated had variable effects on local biodiversity. Temporal continuity of AES habitats was the most important predictor with older, more temporally continuous habitats harbouring higher overall biodiversity and different species assemblages in most taxonomic groups than younger AES habitats. Results however varied among taxonomic groups and natural enemies were equally supported by younger habitats. Semi-natural habitats in the surrounding landscape and AES habitat size were of minor importance for local biodiversity and had limited effects. This stresses that newly established AES habitats alone cannot restore farmland biodiversity. Both AES habitats as well as more continuous semi-natural habitats synergistically increase overall biodiversity in agricultural landscapes. Chapter VI: The effects of AES habitats on predators in adjacent oilseed rape fields Apart from biodiversity conservation, ensuring ecosystem service delivery in agricultural landscapes is a crucial goal of AES. I therefore investigated the effects of adjacent AES habitats on ground dwelling predator assemblages in oilseed rape fields. I found clear distance decay effects from the field edges into the field centres on both richness and densities of ground dwelling predators. Direct effects of adjacent AES habitats on assemblages in oilseed rape fields however were limited and only visible in functional traits of carabid beetle assemblages. Adjacent AES habitats doubled the proportion of predatory carabid beetles indicating a beneficial role for pest control. My results show that pest control potentials are largest close to the field edges and beneficial effects are comparably short ranged. Chapter VII: The effects of AES habitats on pest control in adjacent cereal fields Whether distance functions and potential effects of AES habitats are universal across crops is unknown. Therefore, I assessed distance functions of predators, pests, predation rates and yields after crop rotation in winter cereals using the same study design as in the previous year. Resulting distance functions were not uniform and differed from those found in oilseed rape in the previous year, indicating that the interactions between certain adjacent habitats vary with habitat and crop types. Distance functions of cereal-leaf beetles (important cereal pests) and parasitoid wasps were moreover modulated by semi-natural habitat proportion in the surrounding landscapes. Field edges buffered assemblage changes in carabid beetle assemblages over crop rotation confirming their important function as refuges for natural enemies. My results emphasize the beneficial role of field edges for pest control potentials. These findings back the calls for smaller field sizes and more diverse, more heterogeneously structured agricultural landscapes. Chapter VIII: General Discussion Countering biodiversity loss and ensuring ecosystem service provision in agricultural landscapes is intricate and requires strategic planning and restructuring of these landscapes. I showed that agricultural landscapes could benefit maximally from (i) a mixture of AES habitats and semi-natural habitats to support high levels of overall biodiversity and from (ii) smaller continuously managed agricultural areas (i.e. smaller field sizes or the insertion of AES elements within large fields) to maximize natural pest control potentials in crop fields. I propose a mosaic of younger AES habitats and semi-natural habitats to support ecosystem service providers and increase edge density for ecosystem service spillover into adjacent crops. The optimal extent and density of this network as well as the location in which AES and semi-natural habitats interact most beneficially with adjacent crops need further investigation. My results provide a further step towards more sustainable agricultural landscapes that simultaneously allow biodiversity to persist and maintain agricultural production under the framework of ecological intensification.},
  subject      = {{\"O}kologie},
  language  = {en}
}
@phdthesis{Krimmer2021,
  author    = {Krimmer, Elena},
  title     = {Agri-environment schemes and ecosystem services: The influence of different sown flower field characteristics on pollination, natural pest control and crop yield},
  doi       = {10.25972/OPUS-20657},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206577},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Insects are responsible for the major part of the ecosystem services pollination and natural pest control. If insects decline, these ecosystem services can not longer be reliably delivered. Agricultural intensification and the subsequent loss and fragmentation of habitats has among others been identified to cause insect decline. Ecological intensification aims to promote alternative and sustainable management practices in agricultural farming, for example to decrease the use of external inputs such as pesticides. Agri-environment schemes make amends for farmers if they integrate ecologically beneficial measures into their farming regime and can therefore promote ecological intensification. There is a wide variety of agri-environment schemes, but the implementation of sown flower fields on crop fields is often included. Flower fields offer foraging resources as well as nesting sites for many different insect species and should be able to support insect populations as well as to increase ecosystem services to adjacent fields. However, the potential of flower fields to exhibit these effects is depending on many factors. Among others, the age and size of the flower field can influence if and how different insects profit from the measure. Additionally, the complexity of the surrounding landscape and therefore the existing biodiversity is influencing the potential of flower fields to increase ecosystem services locally. The goal of this study is to disentangle to which degree these factors influence the ecosystem services pollination and natural pest control and if these factors interact with each other. Furthermore, it will be examined if and how flower fields and ecosystem services influence crop yield. Additional factors examined in this study are distance decay and pesticide use. The abundance of beneficial insects can decrease strongly with increasing distance to suitable habitats. Pesticide use in turn could abrogate positive effects of flower fields on beneficial insects. To examine these different aspects and to be able to make recommendations for flower field implementation, field experiments were conducted on differently composed sown flower fields and adjacent oilseed rape fields. Flower fields differed in their age and continuity as well as in their size. Additionally, flower and oilseed rape fields were chosen in landscapes with different amounts of semi-natural habitat. Oilseed rape fields adjacent to calcareous grasslands and conventional crop fields served as controls. Pollinator observations and pollen beetle and parasitism surveys were conducted in the oilseed rape fields. Additionally, different yield parameters of the oilseed rape plants were recorded. Observations were conducted and samples taken in increasing distance to the flower fields to examine distance decay functions. Spray windows were established to inspect the influence of pesticides on ecosystem services and crop yields. Linear mixed models were used for statistical analysis. The results show, that newly established flower fields with high amounts of flower cover are very attractive for pollinators. If the flower fields reached a certain size (> 1.5ha), the pollinators tended to stay in these fields and did not distribute into the surroundings. High amounts of semi-natural habitat in the surrounding landscape increased the value of small flower fields as starting points for pollinators and their subsequent spillover into crop fields. Additionally, high amounts of semi-natural habitat decreased the decay of pollinators with increasing distance to the flower fields. Based on these results, it can be recommended to establish many small flower fields in landscapes with high amounts of semi-natural habitat and large flower fields in landscapes with low amounts of semi-natural habitat. However, it is mentionable that flower fields are no substitute for perennial semi-natural habitats. These still must be actively conserved to increase pollination to crop fields. Furthermore, the lowest amount of pollen beetle infestation was found on oilseed rape fields adjacent to continuous flower fields aged older than 6 years. Flower fields and calcareous grasslands in general increased pollen beetle parasitism in adjacent oilseed rape fields compared to conventional crop fields. The threshold for effective natural pest control could only be reached in the pesticide free areas in the oilseed rape fields adjacent to continuous flower fields and calcareous grasslands. Parasitism and superparasitism declined with increasing distance to the adjacent fields in pesticide treated areas of the oilseed rape fields. However, they remained on a similar level in spray windows without pesticides. Large flower fields increased parasitism and superparasitism more than small flower fields. Flower fields generally have the potential to increase pollen beetle parasitism rates, but pesticides can abrogate these positive effects of flower fields on natural pest control. Last but not least, effects of flower fields and ecosystem services on oilseed rape yield were examined. No positive effects of pollination on oilseed rape yield could be found. Old and continuous flower fields increased natural pest control in oilseed rape fields, which in turn increased seed set and total seed weight of oilseed rape plants. The pesticide treatment had negative effects on natural pest control, but positive effects on crop yield. Pollination and natural pest control decreased with increasing distance to the field edge, but fruit set slightly increased. The quality of the field in terms of soil and climatic conditions did not influence the yield parameters examined in this study. Yield formation in oilseed rape plants is a complex process with many factors involved, and it is difficult to disentangle indirect effects of flower fields on yield. However, perennial flower fields can promote ecological intensification by increasing crop yield via natural pest control. This study contributes to a better understanding of the effects of differently composed flower fields on pollination, natural pest control and oilseed rape yield.},
  subject      = {{\"O}kologie},
  language  = {en}
}
@article{GrosHovestadtPoethke2006,
  author    = {Gros, Andreas and Hovestadt, Thomas and Poethke, Hans Joachim},
  title     = {Evolution of local adaptions in dispersal strategies},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-45406},
  year      = {2006},
  abstract  = {The optimal probability and distance of dispersal largely depend on the risk to end up in unsuitable habitat. This risk is highest close to the habitat's edge and consequently, optimal dispersal probability and distance should decline towards the habitat's border. This selection should lead to the emergence of spatial gradients in dispersal strategies. However, gene flow caused by dispersal itself is counteracting local adaptation. Using an individual based model we investigate the evolution of local adaptations of dispersal probability and distance within a single, circular, habitat patch. We compare evolved dispersal probabilities and distances for six different dispersal kernels (two negative exponential kernels, two skewed kernels, nearest neighbour dispersal and global dispersal) in patches of different size. For all kernels a positive correlation between patch size and dispersal probability emerges. However, a minimum patch size is necessary to allow for local adaptation of dispersal strategies within patches. Beyond this minimum patch area the difference in mean dispersal distance between center and edge increases linearly with patch radius, but the intensity of local adaptation depends on the dispersal kernel. Except for global and nearest neighbour dispersal, the evolved spatial pattern are qualitatively similar for both, mean dispersal probability and distance. We conclude, that inspite of the gene-flow originating from dispersal local adaptation of dispersal strategies is possible if a habitat is of sufficient size. This presumably holds for any realistic type of dispersal kernel.},
  subject      = {Ausbreitung},
  language  = {en}
}
@phdthesis{Pfrommer2009,
  author    = {Pfrommer, Albrecht},
  title     = {Seed dispersal ecology of Leonia cymosa (Violaceae) in the rain forest of Eastern Ecuador},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37129},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {Leonia cymosa (Violaceae) ist ein Baum der unteren Waldschicht im Amazonischen Regenwald. Meine Probenfl{\"a}chen befanden sich in der „Reserva Faunistica Cuyabeno" im nord-{\"o}stlichen Ecuador: Meine Untersuchung hatte das Ziel, die Variation von Baummerkmalen zu beschreiben und zu kl{\"a}ren, ob und wie die Fruchtentnahme aus den einzelnen B{\"a}umen durch Fruchtfresser mit den Baummerkmalen zusammenh{\"a}ngt. Die mittlere H{\"o}he einer fruchttragenden L. cymosa war 6,6 m (Min. 2 m, Max. 12,6 m). Der Median der Individuendichte lag bei 11,8 B{\"a}umen pro Hektar. Die B{\"a}ume wuchsen {\"u}berwiegend in Gruppen, die aus B{\"a}umen verschiedener H{\"o}he bestanden. L. cymosa bl{\"u}hte zwei Mal im Jahr, sowohl im sp{\"a}ten Februar bis M{\"a}rz, als auch im Oktober. Die daraus jeweils folgenden Fruchtsaisons erstreckten sich auf die Monate August/September und M{\"a}rz bis Mai. Das Fruchtfleisch von L. cymosa enthielt die Zucker Fruktose, Glucose und Saccharose, Proteine, aber keine Lipide. Es gab es signifikante Unterschiede zwischen B{\"a}umen bei allen untersuchten N{\"a}hrstoffbestandteilen. Die saisonale Produktivit{\"a}t der {\"u}berwachten B{\"a}ume lag im Median bei 45 (1999, n= 57) bzw. bei 36 (2000, n=92) reifen Fr{\"u}chten. Das maximale Fruchtangebot eines Baumes zum Zeitpunkt einer Fruchtz{\"a}hlung lag bei 324 reifen Fr{\"u}chten Schwarzr{\"u}ckentamarine (Saguinus nigricollis, Callitrichidae) und Totenkopf{\"a}ffchen (Saimiri sciureus, Cebidae), sowie m{\"o}glicherweise eine unidentifizierte nachtaktive Tierart, konsumierten die Fr{\"u}chte von L. cymosa in meinem Untersuchungsgebiet. Fr{\"u}chte, die von den B{\"a}umen auf den Boden herabgefallen waren, wurden von Gr{\"u}nen Zwergagutis (Myoprocta pratti, Dasyproctidae) gefressen. Schwarzr{\"u}ckentamarine und Totenkopf{\"a}ffchen unterschieden sich stark in ihrer Effektivit{\"a}t als Samenausbreiter. Schwarzr{\"u}ckentamarine waren zuverl{\"a}ssige Ausbreiter, Totenkopf{\"a}ffchen nicht. Jede meiner Studienfl{\"a}chen war Teil des Kern-Wohngebietes von jeweils einer Gruppe von Schwarzr{\"u}ckentamarinen, und fiel in das Streifgebiet einer Gruppe von Totenkopf{\"a}ffchen. In einer Stichprobe von 6 B{\"a}umen vergleichbarer und hoher saisonaler Fruchtproduktion war die Gesamtanzahl an reifen Fr{\"u}chten eines jeweiligen Baums, die durch den zuverl{\"a}ssigen Samenausbreiter S. nigricollis im Verlauf einer Fruchtsaison geerntet wurden, mit keinem der gemessenen N{\"a}hrstoffbestandteile des Fruchtfleischs signifikant korreliert. Der zuverl{\"a}ssige Samenausbreiter von L. cymosa scheint keinen Selektionsdruck auf den N{\"a}hrstoffgehalt der Fr{\"u}chte von L. cymosa auszu{\"u}ben. Die saisonale Fruchtproduktion eines L. cymosa -Baums war die haupts{\"a}chliche Vorhersagevariable f{\"u}r alle Aspekte der Fruchtentnahme durch den effektiven Samenausbreiter, Saguinus nigricollis, sowie auch durch den Nicht-Samenausbreiter, Saimiri sciureus. B{\"a}ume mit gr{\"o}ßerer saisonaler Fruchtproduktion hatten eine h{\"o}here Wahrscheinlichkeit der Fruchtentnahme durch den Samenausbreiter als B{\"a}ume mit kleinerer saisonaler Fruchtproduktion. Von B{\"a}umen mit gr{\"o}ßerer saisonaler Fruchtproduktion ernteten die Samenausbreiter ebenfalls mehr Fr{\"u}chte. Diese B{\"a}ume hatten also einen gr{\"o}ßeren Ausbreitungserfolg. Der prozentuale Anteil der vom Samenausbreiter entnommenen Fr{\"u}chte an der gesamten saisonalen Fruchtproduktion eines Baums sank jedoch mit wachsender Fruchtproduktion. Im Gegensatz dazu stieg der prozentuale Anteil der vom Nicht-Samenausbreiter abgeernteten Fr{\"u}chte an der gesamten saisonalen Fruchtproduktion mit gr{\"o}ßer werdender saisonaler Fruchtproduktion. Ebenso stieg die Wahrscheinlichkeit der Fruchtentnahme durch den Nicht-Samenausbreiter und die Anzahl der von ihm geernteten Fr{\"u}chte mit gr{\"o}ßer werdender saisonaler Fruchtproduktion. Die beobachteten Unterschiede zwischen Samenausbreiter und Nicht-Samenausbreiter sind auf Unterschiede in der jeweiligen Nahrungsaufnahmekapazit{\"a}t, der Gruppengr{\"o}ße und des Fouragierverhaltens zur{\"u}ckzuf{\"u}hren. Tamarine ernteten mit geringerer Wahrscheinlichkeit L. cymosa B{\"a}ume, die nicht oder nur wenig von umgebender Vegetation gedeckt waren. Dies reflektiert wahrscheinlich ein Verhalten der Tamarine zur Vermeidung von Angriffen von Wald-Raubv{\"o}geln. Bei hoher Dichte von L. cymosa-Fr{\"u}chten in der Nachbarschaft einzelner B{\"a}ume verringerte sich der Anteil der Fr{\"u}chte an der saisonalen Fruchtproduktion, die von Tamarinen geerntet wurden. Dies spricht f{\"u}r Konkurrenz von B{\"a}umen um Samenausbreiter. Meine Studie hat Selektionsdr{\"u}cke der Samenausbreiter auf die saisonale Fruchtproduktion von L. cymosa aufgedeckt. Meine Ergebnisse best{\"a}tigen die Vorhersagen der „fruit crop size-Hypothese". Meine Ergebnisse zeigen ebenfalls, dass es auch Faktoren außerhalb der Kontrolle eine Baumindividuums gibt, die die Fruchtentnahme von L. cymosa B{\"a}umen beeinflussen. Selektion durch Samenausbreiter k{\"o}nnte durch Nachbarschaftsbedingungen begrenzt.},
  subject      = {Samenverbreitung},
  language  = {en}
}
@phdthesis{Ernst2006,
  author    = {Ernst, Raffael},
  title     = {Anuran communities on the cutting edge : Analysing patterns and processes in anthropogenically altered tropical forests - Studies from the Guiana Shield and West Africa},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-18373},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2006},
  abstract  = {Summary Timber harvesting is currently the most common commercial utilisation activity in tropical forests. Assessing the effects of logging on different aspects of biodiversity and general ecosystem properties is hence of prime importance if the few remaining areas of intact tropical forest are to be protected effectively and efficiently. Tropical amphibian communities are an appropriate model system for studies on the impacts of human-induced environmental changes on the dynamics of complex biological systems. This thesis elaborates on patterns of diversity changes in tropical forest amphibian communities facing habitat alterations associated with selective logging in two globally important eco-regions (C{\^o}te d'Ivoire, Upper Guinea, West Africa and Guyana, the Guiana Shield, northern South America). The thesis is organised along two main themes. After a general introduction, a section on general methodology and an introduction to the model systems studied, the first theme moves from general patterns to underlying processes. A second theme running through both chapters carries from undisturbed systems to disturbed systems. A final section integrates findings and addresses implications for conservation management of anthropogenically altered tropical forests. Several case studies at the species- population and community level are being presented and data on the direct and indirect impacts of anthropogenic habitat alteration on respective organizational levels are provided. A key statement that is stressed on throughout the studies is the fact that common measures of diversity, such as species richness and species-diversity only inadequately reflect processes of diversity change following anthropogenic disturbance. They also fail to describe actual impacts on the dynamics of complex biological systems. It is argued that commonly used measures produce an incoherent and insufficient picture of diversity patterns and the underlying processes that shape these patterns. Thus, an understanding of higher levels of diversity, such as \&\#946;-diversity and functional diversity (and hence compositional patterns) appears to be the key to effectively mitigating the impacts of human-induced disturbance on amphibian communities. It is shown that the predictability of amphibian community composition depends on the respective level of anthropogenic disturbance imposed on a particular habitat. Hence, human activities that lead to changes in the structure of a forest, such as logging, not only alter simple system descriptors, such as the number of species in a given community, but rather alter the dynamics of the entire system. In this context, functional diversity is shown to be an important aspect underlying the actual mechanism that leads to the observed change of predictability patterns. Functional differences between species, rather than number of species per se appear to be the decisive factor in sustaining desirable ecosystem states and thus in maintaining important ecosystem services. Because biological diversity appears to play a substantial role in ecosystem resilience required to safeguard essential ecosystem functions in the face of environmental change, the thesis calls for a critical revision of common diversity assessments approaches. The studies advocate the reconsideration of the uncritical use of widespread measures and descriptors of biodiversity on grounds of inconsistent patterns found throughout numerous studies, including those presented herein.},
  subject      = {Tropischer Regenwald},
  language  = {en}
}
@phdthesis{Glos2006,
  author    = {Glos, Julian},
  title     = {Amphibian communities of the dry forest of Western Madagascar : taxonomy, ecology and conservation},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-18146},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2006},
  abstract  = {In meiner Arbeit habe ich taxonomische, gemeinschafts{\"o}kologische und aut{\"o}kologische Aspekte im westmadagassischen Trockenwald untersucht. Ziel dieser Arbeit war es Antworten auf die Fragen zu geben wie die einzelnen Arten die Habitate in Raum und Zeit nutzen, welchen Einfluss abiotische Parameter, Austrocknungsrisiko der Laichgew{\"a}sser und Mikrohabitat haben und wie Pr{\"a}datoren die Gemeinschaft und das Verhalten einzelner Arten beeinflussen. Somit tr{\"a}gt diese Arbeit dazu bei die grundlegenden Mechanismen zu verstehen, die die Zusammensetzung einer Lebensgemeinschaft bestimmen. Im Einzelnen untersuchte ich hierzu folgende Fragestellungen: Aus welchen Arten bestehen die Anurengemeinschaften des westmadagassischen Trockenwaldes, und wie lassen sich diese Arten morphologisch voneinander abgrenzen? Welche Unterschiede finden sich zwischen den Arten bez{\"u}glich ihres Paarungssystems, ihrer life-history und ihrer Habitatwahl bzw. den Anpassungen an ihr Habitat? Gibt es spezifische Kaulquappengemeinschaften, die sich anhand biotischer und abiotischer Umweltvariablen vorhersagen lassen? Unterscheiden sich die Muster der Vorhersagbarkeit von Gemeinschaften zwischen unterschiedlichen Habitattypen innerhalb eines lokalen r{\"a}umlichen Skalenniveaus? Wie beeinflusst das Vorkommen von Raubfeinden die Verteilung von Kaulquappen und deren Verhalten auf der r{\"a}umlichen Skalenebene einzelner Laichgew{\"a}sser? Anhand welcher Umweltvariablen l{\"a}sst sich die Laichplatzwahl von Anuren in diesem Habitat vorhersagen? Wie lassen sich die Ergebnisse nutzen, um Empfehlungen zum Schutz bedrohter Arten auszusprechen? In dieser Arbeit beschreibe ich eine Froschart wissenschaftlich neu. Diese Art, Scaphiophryne menabensis, ist die seltenste Froschart in ihrem Verbreitungsgebiet, und aus meiner Arbeit resultiert die dringende Empfehlung, sie in ein bestehendes Schutzkonzept f{\"u}r den Kirindy-Wald und seine Umgebung mit einzubeziehen. Weiterhin beschreibe ich wissenschaftlich erstmalig in dieser Arbeit f{\"u}nf Kaulquappenarten und pr{\"a}sentiere Daten zu {\"O}kologie, life-history und Verhalten dieser Arten. Die wissenschaftliche Beschreibung weiterer Frosch- und Kaulquappenarten ist Gegenstand noch andauernder Studien (Scaphiophryne sp., Heterixalus carbonei und H. tricolor; Revision der Kaulquappen von Scaphiophryne). Die Ergebnisse dieser Arbeit stellen damit die Basis f{\"u}r alle weiteren {\"o}kologischen Studien an Fr{\"o}schen und Kaulquappen dieses {\"O}kosystems dar. FAZIT Die Amphibienfauna Madagaskars ist einzigartig, und sie stellt ein aufregendes Feld f{\"u}r {\"o}kologische Fragestellungen dar, sowohl als eigenst{\"a}ndiges System betrachtet als auch als Modell f{\"u}r andere Systeme. Umso mehr verwundert es, dass bislang kaum detaillierte {\"o}kologische Studien an diesem System durchgef{\"u}hrt wurden. Die vorliegende Arbeit schafft zun{\"a}chst mit der taxonomischen Beschreibung der vorkommenden Arten die Basis f{\"u}r {\"o}kologische Fragestellungen und zeigt dann auf den Ebenen sowohl der Gemeinschaft als auch einzelner Arten, wie verschiedene Umweltfaktoren die Verteilung von Anuren in Raum und Zeit beeinflussen. Es zeigt sich, dass sowohl statische Eigenschaften der Gew{\"a}sser als auch dynamische Faktoren wie Raubfeinde oder das Vorhandensein anderer Kaulquappen die Verteilung der Arten auf verschiedenen r{\"a}umlichen Skalenebenen sowie deren Verhalten beeinflussen. Somit tragen die Ergebnisse dieser Arbeit dazu bei, die grundlegenden Mechanismen zu verstehen, die die Zusammensetzung der Lebensgemeinschaften in diesem {\"O}kosystem bestimmen. Nicht zuletzt erm{\"o}glichen diese Erkenntnisse, geeignete, artenorientierte Schutzkonzepte f{\"u}r diese in ihrer Existenz stark bedrohte Anurengemeinschaft zu entwickeln und die Effekte von Habitatzerst{\"o}rung auf diese Gemeinschaft aufzuzeigen.},
  subject      = {Lurche},
  language  = {en}
}
@phdthesis{Lampert2001,
  author    = {Lampert, Kathrin P.},
  title     = {Alternative life history strategies in the West African reed frog, Hyperolius nitidulus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-1677},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2001},
  abstract  = {Distinct juvenile behaviour differences, changes in adult sizes and reproductive capacity and a long reproductive period triggered the working hypothesis of two alternative life-cycle strategies favouring aestivation or immediate reproduction. The hypothesis for the life-cycles of Hyperolius nitidulus that differed from the commonly assumed reproductive strategy for this species was confirmed by the results of this study. Aestivated juveniles start to mature at the beginning of the rainy season and reproduce subsequently. Their tadpoles grow until metamorphosis and either reproduce in this same season, in which case their offspring aestivates (one year - two generations), or they delay reproduction to the following year and aestivate themselves (one year - one generation). Juveniles trying to reproduce as fast as possible will invest in growth and differentiation and show no costly adaptations to aestivation, while juveniles delaying reproduction to the following rainy season will be well adapted to dry season conditions. Indirect evidence for the existence of a second generation was found in all three investigation years: adult size decreased abruptly towards the end of the rainy season, mainly due to the arrival of very small individuals, and clutch size decreased abruptly. Also at the end of the rainy season juveniles had two behavioural types: one hiding on the ground and clearly avoiding direct sunlight and another sitting freely above ground showing higher tolerance towards dry season conditions (high air temperatures and low humidity). Skin morphology differed between the types showing many more purine crystals in a higher order in the dry-season adapted juveniles. The final proof for the existence of a second generation came with the recapture of individuals marked as juveniles when they left the pond. The 45 recaptured frogs definitely came back to the pond to reproduce during the same season in 1999. Second generation frogs (males and females) were significantly smaller than the rest of all adults and egg diameter was reduced. Clutch size did not differ significantly. It was found that females did not discriminate against second generation males when coming to the ponds to reproduce. Second generation males had a similar chance to be found in amplexus as first generation males. Indirect and direct evidence for a second generation matched very well. The sudden size decrease in adults occurred just at the time when the first marked frogs returned. The observation that freshly metamorphosed froglets were able to sit in the sun directly after leaving the water led to the assumption that the decision whether to aestivate or to reproduce already happens during the frogs' larval period. Water chemistry and the influence of light was investigated to look for the factors triggering the decision, but only contaminated water increased the number of juveniles ready for aestivation. Whether the life history polymorphism observed in Hyperolius nitidulus is due to phenotypic plasticity or genetic polymorphism is still not known. Despite this uncertainty, there is no doubt that the optimal combination of different life histories is profitable and may be a reason for the wide range and high local abundance of Hyperolius nitidulus.},
  subject      = {Westafrika},
  language  = {en}
}