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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/9768 |
| Date | January 2012 |
| Creators | Delcros, Gwenaelle. |
| Contributors | Schoeman, Corrie M., Taylor, Peter John. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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