Scaling of Animal Communities: From Local and Landscape to Global Processes
by Kristy Udy
Date of Examination:2017-07-11
Date of issue:2017-12-12
Advisor:Prof. Dr. Teja Tscharntke
Referee:Dr. Christoph Scherber
Referee:Prof. Dr. Kreft Holger
Persistent Address:
http://dx.doi.org/10.53846/goediss-6634
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Abstract
English
Animal communities are influenced by processes changing from the local to global scale. Local processes include resource and habitat availability, while landscape processes are often driven by habitat availability and heterogeneity that shapes the species pool and population size. At the global scale, area and environmental heterogeneity are major processes influencing animal communities. I determined the influence of local and landscape scale processes on plant-pollinator communities at different levels of urbanisation (farmland, villages and cities). The influence of landscape was separated from that of the sampling unit by conducting pollinator observations on phytometer plants experimentally placed in the different landscapes (grassy field margins in farmland and gardens in villages and cities). Pollinator diversity and abundance was highest in farmland and villages, but species group identity changed with a number of wild bee species only present in gardens in villages and cities. Plant-pollinator interaction networks in farmland sites were more robust with higher interaction strength compared with networks in villages and cities. Bumblebee movement patterns were analysed using the same landscapes as the plant-pollinator experiment, but with farmhouse gardens added. I examined how local resources and landscape type affect bumblebee foraging behaviour and colony performance. I placed 32 Bombus terrestris colonies along the farmland to urban gradient and analysed local and long-range movement patterns of bumblebees to assess where pollinators forage in urban areas. Additionally, I measured if B. terrestris colony growth depends on resource availability in the direct surroundings of the colony or on landscape type. B. terrestris workers visited plants providing floral resources in the direct surroundings of the colonies. Furthermore, the workers foraged in greater distances to their colonies, if the mass flowering crop oilseed rape was flowering. I investigated the influence of urban area size by studying arthropod communities along an urbanisation gradient from small villages to cities. I sampled arthropods in gardens and public green spaces at the edge and centre of urban areas to determine the relative importance of local and landscape influence on community composition. Arthropods sampled were from different taxa: Coleoptera, Araneae and Hymenoptera. Araneae and Hymenoptera were influenced only by the local surroundings (green space type and position in an urban area), whereas Coleoptera communities were influenced by both local and landscape effects (urban area size). I also investigated whether environmental heterogeneity (niche processes) or space (neutral processes) are better predictors of mammal species richness patterns at the global scale. The relative influence of these two processes has not been tested at the global level. I used a burning algorithm to increase both area and environmental heterogeneity simultaneously. Niche processes explain global species richness relationships better than neutral processes. The environmental factors that explain most variation in species richness were either the range in elevation or in precipitation. In conclusion, local and landscape scale processes influenced arthropod community structure in urban areas. Abundance and diversity respond to local resources and habitat type, while community composition was influenced by the heterogeneity of the surrounding landscape in a taxon-specific way. The importance of environmental heterogeneity scales up to the entire globe as I found it is also an important predictor of mammal species richness. By determining at which scale species richness and animal communities are influenced, this study increases our understanding of how the ecological world is structured.
Keywords: Urban Ecology; Invertebrates; Plant-pollinator network; Global mammal richness