Vitenskapelig sammendrag
The overall objective of SPHERE is to explore the role of spatial heterogeneity of resources as a mediator of large herbivore population stability in African savannas. Recent studies predict that the increased variability in rainfall that is predicted under local climate change scenarios and the resulting temporal variability in resource availability will lead to severe declines in African herbivore populations. However, new theory predicts that spatial heterogeneity of resources can act as a buffer against such temporal heterogeneity. Up to now this theory awaits empirical testing. African savanna grasslands are an ideal system to test this theory, with characteristic grazing lawns as a clearly visible aspect of spatial resource heterogeneity. Several grazer species concentrate foraging in these lawns but it is unclear how lawn abundance and spatial distribution affects grazer population dynamics on a larger scale. SPHERE will use this system to investigate the hypothesized effect of resource heterogeneity on population stability. Moreover, SPHERE will advance current theory by including interspecific differences, specifically body mass and digestive physiology. Both strongly influence herbivore resource requirement. Finally, it will link population-level responses to demographic processes by testing how resource heterogeneity affects survival of different age-classes. To this end SPHERE will quantify lawn distribution in two South-African reserves and relate it to spatially explicit demographic and long-term census data of six herbivore species that differ in body mass and digestive system. The fellow will be based at the Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo. CEES will provide the candidate with excellent training opportunities in population biology, ungulate ecology and advanced statistics. In addition, the complementary skills of European collaborators will further ensure the feasibility and high quality of the fellowship.
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