@article{LaswayKinaboMremietal.2021, author = {Lasway, Julius V. and Kinabo, Neema R. and Mremi, Rudolf F. and Martin, Emanuel H. and Nyakunga, Oliver C. and Sanya, John J. and Rwegasira, Gration M. and Lesio, Nicephor and Gideon, Hulda and Pauly, Alain and Eardley, Connal and Peters, Marcell K. and Peterson, Andrew T. and Steffan-Dewenter, Ingolf and Njovu, Henry K.}, title = {A synopsis of the Bee occurrence data of northern Tanzania}, series = {Biodiversity Data Journal}, volume = {9}, journal = {Biodiversity Data Journal}, doi = {10.3897/BDJ.9.e68190}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265018}, year = {2021}, abstract = {Background Bees (Hymenoptera: Apoidea: Anthophila) are the most important group of pollinators with about 20,507 known species worldwide. Despite the critical role of bees in providing pollination services, studies aiming at understanding which species are present across disturbance gradients are scarce. Limited taxononomic information for the existing and unidentified bee species in Tanzania make their conservation haphazard. Here, we present a dataset of bee species records obtained from a survey in nothern Tanzania i.e. Kilimanjaro, Arusha and Manyara regions. Our findings serve as baseline data necessary for understanding the diversity and distribution of bees in the northern parts of the country, which is a critical step in devising robust conservation and monitoring strategies for their populations. New information In this paper, we present information on 45 bee species belonging to 20 genera and four families sampled using a combination of sweep-netting and pan trap methods. Most species (27, ~ 60\%) belong to the family Halictidae followed by 16 species (35.5\%) from the family Apidae. Megachilidae and Andrenidae were the least represented, each with only one species (2.2\%). Additional species of Apidae and Megachilidae sampled during this survey are not yet published on Global Biodiversity Information Facility (GBIF), once they will be available on GBIF, they will be published in a subsequent paper. From a total of 953 occurrences, highest numbers were recorded in Kilimanjaro Region (n = 511), followed by Arusha (n = 410) and Manyara (n = 32), but this pattern reflects the sampling efforts of the research project rather than real bias in the distributions of bee species in northern Tanzania.}, language = {en} } @phdthesis{Lasway2022, author = {Lasway, Julius Vincent}, title = {Impact of human land use on bee diversity and plant-pollinator interactions in Tanzania savannah ecosystems}, doi = {10.25972/OPUS-25772}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257726}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {One of the pronounced global challenges facing ecologists is how to feed the current growing human population while sustaining biodiversity and ecosystem services. To shed light on this, I investigated the impact of human land use on bee diversity and plant-pollinator interactions in Tanzania Savannah ecosystems. The thesis comprises the following chapters: Chapter I: General Introduction This chapter provides the background information including the study objectives and hypotheses. It highlights the ecological importance of bees and the main threats facing bee pollinators with a focus on two land-use practices namely livestock grazing and agriculture. It also highlights the diversity and global distribution of bees. It further introduces the tropical savannah ecosystem, its climate, and vegetation characteristics and explains spectacular megafauna species of the system that form centers of wildlife tourism and inadequacy knowledge on pollinators diversity of the system. Finally, this chapter describes the study methodology including, the description of the study area, study design, and data collection. Chapter II: Positive effects of low livestock grazing intensity on East African bee assemblages mediated by increases in floral resources The impact of livestock grazing intensity on bee assemblage has been subjected to research over decades. Moreover, most of these studies have been conducted in temperate Europe and America leaving the huge tropical savannah of East Africa less studied. Using sweep netting and pan traps, a total of 183 species (from 2,691 individuals) representing 55 genera and five families were collected from 24 study sites representing three levels of livestock grazing intensity in savannah ecosystem of northern Tanzania. Results have shown that moderate livestock grazing slightly increased bee species richness. However, high livestock grazing intensity led to a strong decline. Besides, results revealed a unimodal distribution pattern of bee species richness and mean annual temperature. It was also found that the effect of livestock grazing and environmental temperature on bee species richness was mediated by a positive effect of moderate grazing on floral resource richness. The study, therefore, reveals that bee communities of the African savannah zone may benefit from low levels of livestock grazing as this favors the growth of flowering plant species. A high level of livestock grazing intensity will cause significant species losses, an effect that may increase with climatic warming. Chapter III: Agricultural intensification with seasonal fallow land promotes high bee diversity in Afrotropical drylands This study investigated the impact of local agriculture intensification on bee diversity in the Afro tropical drylands of northern Tanzania. Using sweep netting and pan traps, a total of 219 species (from 3,428 individuals) representing 58 genera and six families were collected from 24 study sites (distributed from 702 to 1708 m. asl) representing three levels of agriculture intensity spanning an extensive gradient of mean annual temperature. Results showed that bee species richness increased with agricultural intensity and with increasing temperature. However, the effects of agriculture intensity and temperature on bee species richness were mediated by the positive effects of agriculture and temperature on floral resource richness used by bee pollinators. Moreover, results showed that variation of bee body sizes increases with agricultural intensification, "that effect", however, diminished in environments with higher temperatures. This study reveals that bee assemblages in Afrotropical drylands benefit from agriculture intensification in the way it is currently practiced. Further intensification, including year-round irrigated crop monocultures and extensive use of agrochemicals, is likely to exert a negative impact on bee diversity and pollination services, as reported in temperate regions. Moreover, several bee species were restricted to natural savannah habitats. Therefore, to conserve bee communities in Afro tropical drylands and guarantee pollination services, a mixture of savannah and agriculture, with long periods of fallow land should be maintained. Chapter IV: Impact of land use intensification and local features on plants and pollinators in Sub-Saharan smallholder farms For the first time in the region, this study explores the impact of land-use intensification on plants and pollinators in Sub-Saharan smallholder farms. The study complemented field surveys of bees with a modern DNA metabarcoding approach to characterize the foraged plants and thus built networks describing plant-pollinator interactions at the individual insect level. This information was coupled with quantitative traits of landscape composition and floral availability surrounding each farm. The study found that pollinator richness decreased with increasing impervious and agricultural cover in the landscape, whereas the flower density at each farm correlated with pollinator richness. The intensification of agricultural land use and urbanization correlated with a higher foraging niche overlap among pollinators due to the convergence of individuals' flower-visiting strategies. Furthermore, within farms, the higher availability of floral resources drove lower niche overlap among individuals, greater abundance of flower visitors shaped higher generalization at the networks level (H2I), possibly due to increased competition. These mechanistic understandings leading to individuals' foraging niche overlap and generalism at the network level, could imply stability of interactions and the pollination ecosystem service. The integrative survey proved that plant-pollinator systems are largely affected by land use intensification and by local factors in smallholder farms of Sub-Saharan Africa. Thus, policies promoting nature-based solutions, among which the introduction of more pollinator-friendly practices by smallholder farmers, could be effective in mitigating the intensification of both urban and rural landscapes in this region, as well as in similar Sub-Saharan contexts. Chapter V: A synopsis of the Bee occurrence data of northern Tanzania This study represents a synopsis of the bee occurrence data of northern Tanzania obtained from a survey in the Kilimanjaro, Arusha, and Manyara regions. Bees were sampled using two standardized methods, sweep netting and colored pan traps. The study summed up 953 species occurrences of 45 species belonging to 20 genera and four families (Halictidae, Apidae, Megachilidae, and andrenidae) A. This study serves as the baseline information in understanding the diversity and distribution of bees in the northern parts of the country. Understanding the richness and distribution of bees is a critical step in devising robust conservation and monitoring strategies for their populations since limited taxonomic information of the existing and unidentified bee species makes their conservation haphazard. Chapter VI: General discussion In general, findings obtained in these studies suggest that livestock grazing and agriculture intensification affects bee assemblages and floral resources used by bee pollinators. Results have shown that moderate livestock grazing intensity may be important in preserving bee diversity. However, high level of livestock grazing intensity may result in a strong decline in bee species richness and abundance. Moreover, findings indicate that agriculture intensification with seasonal fallow lands supports high floral resource richness promoting high bee diversity in Afrotropical drylands. Nonetheless, natural savannahs were found to contain unique bee species. Therefore, agriculture intensification with seasonal fallow should go in hand with conserving remnant savannah in the landscapes to increase bee diversity and ensure pollination services. Likewise, findings suggest that increasing urbanization and agriculture cover at the landscape level reduce plant and pollinator biodiversity with negative impacts on their complex interactions with plants. Conversely, local scale availability of floral resources has shown the positive effects in buffering pollinators decline and mitigating all detrimental effects induced by land-use intensification. Moreover, findings suggest that the impact of human land use (livestock grazing and agriculture) do not act in isolation but synergistically interacts with climatic factors such as mean annual temperature, MAT. The impact of MAT on bee species richness in grazing gradient showed to be more detrimental than in agriculture habitats. This could probably be explained by the remaining vegetation cover following anthropogenic disturbance. Meaning that the remaining vegetation cover in the agricultural gradient probably absorbs the solar radiations hence reducing detrimental effect of mean annual temperature on bee species richness. This one is not the case in grazing gradient since the impact of livestock grazing is severe, leaving the bare land with no vegetation cover. Finally, our findings conclude that understanding the interplay of multiple anthropogenic activities and their interaction with MAT as a consequence of ongoing climate change is necessary for mitigating their potential consequences on bee assemblages and the provision of ecosystem services. Morever, future increases in livestock grazing and agriculture intensification (including year-round crop irrigated monocultures and excessive use of agrochemicals) may lead to undesirable consequences such as species loss and impair provision of pollination services.}, subject = {Human land use}, language = {en} } @phdthesis{Kindeketa2014, author = {Kindeketa, William Joseph}, title = {Pollination in wild plant communities along altitudinal and land use gradients Mount Kilimanjaro, Tanzania}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-100136}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2014}, abstract = {1. Pollination of sexually reproducing plants requires pollen transfer agents, which can be biotic, abiotic or a combination of biotic and abiotic agents. The dominance of one of pollination system in wild plant communities depends on climatic factors and/or degrees of anthropogenic influences, which have effects on pollinator diversity and pollination function. Anthropogenic activities and climate change are also considered as main causes of ongoing invasion of invasive species into wild and managed habitats which can bring up competition for pollinators with possible negative consequences for the reproduction of co-occurring native plant species. 2. The study aimed to determine pollination systems and pollination limitation of invasive and native plant communities in natural savannah between 870 - 1130 m and semi-natural (managed) grassland between 1300 - 1750 m above sea level; effects of flower density and pollinator abundance on seed production of cross-pollinated and self-pollinated plants; and relationships of bee abundance and the proportion of cross- pollinated plants at the southern slope of Mount Kilimanjaro, Tanzania. 3. Pollinator-exclusion, open pollination and supplemental hand-pollination treatments were applied to 27 plant species in savannah and grassland habitats. Flowers were counted in each clusters based upon their species. Pollinators were sampled by using pan traps. Information-theory-based multi-model averaging and generalized linear mixed effects models were used to identify and analyze the effects of flower density, pollinator abundance, pollination treatments and habitat types on seed production. Regression models were used to determine relationships of altitude with bee abundance, and with proportion of cross-pollinated plants. 4. My results show that mean seed numbers of native plants were significantly lower in pollinator-exclusion treatments than in open-pollination treatments, indicating their reliance on pollinators for reproductive success. In contrast, seed numbers of invasive plants were similar in pollinator-exclusion and open-pollination treatments, demonstrating an ability of reproduction without pollinators. Despite of higher levels of self-pollination in invasive plants, supplemental hand-pollination treatments revealed pollen limitation in grassland and marginally in savannah habitats. There were no significant difference in seed numbers between supplemental hand pollination and open pollination treatments of native plant communities in savannah and grassland, which indicates no pollination limitation in the studied ecological system for native communities. Besides, grassland plants produced comparatively more seeds than savannah plants, however seeds in grasslands were lighter than those of the savannah which may be due to nutrient limitation in grassland. 5. I found 12 cross-pollinated and 15 self-pollinated plants along altitudinal gradient after comparing seeds from pollinator-excluded and open-pollinated experiments. I also found that proportions of cross-pollinated plants and bee abundance simultaneously decreased with increasing altitude. All cross-pollinated plants were native and grew in savannah habitats, with an exception of one species. 6. Neither effects of focal flower density nor a significant interaction between focal flower densities and bee abundance for self-pollinated plants were observed. However, there were effects of focal flower densities and interactions of flower density with bee abundance for cross-pollinated plants. Non-focal flower density has no significant effects on seed production of cross-pollinated and self-pollinated plants. 7. The results show that native plants depend more on cross-pollination than invasive plants, despite of most native plants in managed habitat (grassland) rely on self-pollination for reproduction. The tendency of having more cross-pollinated plants in natural savannah which are in low altitude coincides with other finding that the cross-pollinated plants and bee abundance simultaneously decrease with increasing altitude. Therefore, our findings support the hypotheses that self-fertilization of flowering plants increases with increasing altitude, and pollinator limitation is most pronounced in managed or disturbed habitats. Despite of reduction of pollinators in grassland, only invasive plants experience pollen limitation, which may be due to poor integration with available pollinator networks. 8. I also found bee abundance and flower density are not the main pollination factors required by self-pollinated plants during reproduction. However, focal flower density, which influences pollinator diversity, is more applicable to cross-pollinated plants. Climate change and anthropogenic activities in natural habitats are factors that influence pollinator abundance and functioning, which lead to a shift of mating systems in plant communities so as to assure their reproduction.}, subject = {Best{\"a}ubungs{\"o}kologie}, language = {en} }