Predation and abiotic processes rather than competition should influence the community structure of rodents and shrews with life histories characterised by high fecundity, short longevity and unstable populations. I investigated the influence of abiotic processes, predation and competition on three parameters of community structure (species composition, phenotypic and phylogenetic niches) of rodents and shrews at Mkhuze and Kube Yini, two game reserves in KwaZulu-Natal, South Africa, using null models and multivariate analyses. Rodents and shrews were sampled between 2007 and 2009. Sample-based rarefaction curves indicated that rodent species richness was higher at Mkhuze than at Kube Yini, while shrew species richness was identical at both reserves. Species richness estimators indicated that estimates of species richness were fairly accurate, hence strengthening the results from my null model analyses. I found evidence that immigration and extinction operating at a regional scale influenced rodent species composition. Moreover, habitat filtering operating at a local scale influenced rodent and shrew species composition. These processes produced nested assemblages: species present at species-poor sites were subsets of species present at species-rich sites. Habitat filtering also influenced the phenotypic niche of rodents and shrews: sympatric species showed similar phenotypic adaptations (phenotypic niches were underdispersed), probably in response to similar food requirements. Furthermore, shrew phenotypic traits showed a convergent evolution, and local assemblages comprised distantly related species (phylogenetic evenness), suggesting the influence of habitat filtering on the phylogenetic niche structure of shrews. Predation influenced shrew phenotypes. Bullae and ears were underdispersed and larger than expected by chance, probably to reduce predation risk through increased hearing sensitivity. In contrast, I found no evidence that predation influenced the rodent phenotypic niche. Competition influenced the phenotypic niches of rodents and shrews in species-rich assemblages (phenotypic niches were overdispersed). In these assemblages, the coexistence of species was facilitated by dietary and microhabitat partitioning. Competition also influenced the phylogenetic niche of rodents: phenotypic traits showed a convergent evolution, and local assemblages comprised closely related species (phylogenetic clustering). In conclusion, both abiotic and biotic processes influenced different parameters of the community structure of rodents and shrews. However, despite similar life-history traits, the community structure of local assemblages differed between rodents and shrews. Comparing patterns and processes of community structure across taxa would help find general trends of community organisation. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.

The identification of non-random species composition patterns predicted by assembly rules is a central theme in community ecology. Based on life history characteristics, species composition patterns of rodents and shrews should be consistent with predictions from nestedness rather than competition hypotheses. This study investigated the seasonal changes in rodent and shrew assemblages in eleven savanna vegetation types in a protected reserve in South Africa. Rodents and shrews were sampled between 2009 and 2010 at Phinda Private Game Reserve (PPGR), KwaZulu-Natal. Sample-based rarefaction curves showed that rodent and shrew abundance and richness varied among seasons and vegetation types. Species richness estimators indicated that inventories for rodents (80%) and shrews (100%) were fairly complete. Null-model analyses found no evidence that species co-occurrence patterns in the reserve were non-random with respect to predictions from Diamond’s Assembly rules, niche limitation hypothesis and nestedness hypothesis. I also investigated seasonal changes in species richness and abundance of rodent and shrew assemblages on cattle, pineapple and former cattle farms surrounding PPGR, and used cluster analyses to compare the species composition of rodents and shrews at farm and PPGR study sites. Small mammal assemblages exhibited a heterogeneous distribution and species composition patterns changed between seasons. Sample-based rarefaction curves showed that rodent and shrew abundance and richness varied among seasons and study sites. Species richness estimators indicated that inventories for the rodents (91%) and shrews (100%) on the farms were essentially complete. Rodent and shrew species composition patterns did not group study sites according to land use, nor could species composition patterns be explained by vegetation characteristics. My results suggest that complex biotic and abiotic processes other than competition, nestedness, land use and vegetation characteristics operate at different spatial and temporal scales to structure rodent and shrew assemblages. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.