Diversity patterns and resource use of bats on the slopes of Mt. Kilimanjaro, Tanzania

Landscape alterations through, e.g., agriculture, climate change and the constant decline of water resources are threatening the global biodiversity. Species become extinct while new species are still described almost on a daily basis. The intricate networks of species interactions and their roles for our ecosystems are frequently yet to be unraveled and therefore the consequences of species loss are largely unknown. The challenges are to identify the species occurring in a habitat, to describe parameters effecting their distribution, to analyze their roles in the ecosystem and ultimately in many cases also to find measures for the conservation of species and their roles as, e.g., seed dispersers, predators of pest insects or pollinators. In this context the species-rich, highly mobile and crucial ecosystem services-providing bats form a highly interesting study group. Especially in the Paleotropics there are still severe gaps in the knowledge of bat species richness, distribution and especially in the corresponding interaction networks. Hence, my thesis addresses the effects of land use as well as the biotic and abiotic factors influencing the distribution of these flying vertebrates and particularly the interactions of the seed-dispersing fruit bats with their food plants. With Mt. Kilimanjaro we chose a tropical mountain system as study area that provided unique opportunities to gain insights in the consequences of elevation and temperature shifts, as well as the effects of disturbed and undisturbed habitats, on flying vertebrates. For this we captured bats in five different habitats with different elevation and degree of disturbance: the natural habitats savanna and lower montane forest, and the disturbed habitats, maize, coffee plantations, homegardens. Additionally, we obtained fecal material from the frugivorous species in order to get information on their food plants. My first chapter assesses species diversity and abundance of frugivorous bats within different land use types on the slopes of Mt. Kilimanjaro and the factors driving these differences along the elevational gradient. The species accumulation curves confirmed that the sampling effort was adequate for all habitats. Fruit bat guilds showed a niche partitioning influenced by water availability, elevation and canopy height. As we recorded a distinctively higher capture rate of females, we suggest that maternity colonies may profit in some way from the agricultural habitats, as they were not only often found near bodies of water but also in proximity to promising foraging areas, e.g., planted trees, such as Ficus spp. within plantations. My second chapter examines the association between vegetation structure and temperature on species richness of frugivorous and insectivorous bats and birds. LiDAR-derived vegetation structure and temperature described over 90 % of the variability in bat and bird species richness, with high canopy density enhancing species richness of bats and birds, probably by providing more food resources and more microhabitats. LiDAR data allowed the collection of reliable, fine-scaled data on vegetation structure over large areas, which permits a better understanding of animal-habitat relationships. Bird and bat species richness were significantly associated with temperature, which influences insectivorous prey, and in combination with precipitation drives vegetation growth as well as flower and fruit development, and therefore might indirectly influence also frugivorous species through the effect on their food plants. In my third chapter I examined the richness and complexity of bat assemblages between riparian and non-riparian sites along the slopes of Mt. Kilimanjaro and investigated how species composition of different natural habitats were influenced by abiotic factors. Canopy closure and elevation were the best explaining parameters for overall bat community structure and abundance. Water availability on the other hand best explained bat community composition. Riparian areas provide drinking water and roosting options for bat species and act as connecting corridors between habitats. The amount of available fig trees best explained fruit bat abundance and species richness, as they provide a reliable year-round food resource with their special fruiting phenology and presentation. Ripe figs may also attract insect prey such as moths and therefore support insectivorous bats. Overall, riparian areas provide a higher availability of food, water resources and roosting spots compared e.g., to the surrounding savanna habitat. The last chapter highlights the essential ecosystem function of frugivorous pteropodid bats as seed dispersers, using newly developed barcoding-techniques to gain insights into the bat-plant interaction networks and thus into their value in preserving genetic connectivity within and among habitats. I also compared these molecular results with conventional microhistological identification of food items and obtained a much more detailed insight into the diet of the species through the use of DNA-barcoding. The vast majority of seeds was not dispersed by the pteropodid bats using endozoochory but by consuming larger-seeded fruits. The low specialization of the encountered interaction-networks shows that all bat species used a rather broad spectrum of fruiting plants. Moraceae, however, were the primary food resource of all bat species, while the genus Epomophorus also presented a high interaction rate with several exotic plant species, such as Psidium guajava or Eriobotrya japonica. My thesis presents the first detailed assessment of the frugivorous bats living along the slopes of Mt. Kilimanjaro. Fruit bats showed a niche partitioning based on morphological traits and in their habitat use. Disturbed landscapes were not just perceived as hostile matrix, but were often used as flyways for passing to more suitable roosting and foraging habitats, and also increased the dietary options through the presence of food resources, native and cultivated, respectively. Vegetation structure and temperature were the best explaining variables for the occurrence of both bats and birds, while water availability and fig trees were the main components promoting frugivorous species in all habitats. My study also provides clear evidence that riparian stripes are highly important microhabitats in the savanna habitat that can be used as highways to move between different elevational zones. The wide distribution of bats along the slopes of Mt. Kilimanjaro underlines the importance of these highly mobile animals for the ecosystems of the region, particularly as the area is under increasing pressure through an ongoing human habitat fragmentation