Browsing by Author "Bronner, Gary N"

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    Facilitating golden mole conservation in South African highland grasslands : a predictive modelling approach
    (2016) Rampartab, Chanel; Bronner, Gary N; Bennett, Nigel C; Bloomer, Paulette; Robertson, M P
    Golden moles are subterranean mammals endemic to sub-Saharan Africa and threatened by anthropogenic habitat loss. At present, little is known about the biology, taxonomy, distribution and severity of threats faced by many of these taxa. In an attempt to raise awareness of these elusive grassland flagship taxa, the Endangered Wildlife Trust's Threatened Grassland Species Programme (EWT-TGSP) identified the need for more information on the distributions and conservation status of four poorly-known golden mole taxa (Amblysomus hottentotus longiceps, A. h. meesteri, A. robustus, A. septentrionalis) that are endemic to the Grassland Biome, and which may be heavily impacted by anthropogenic habitat alteration in the Highveld regions of Mpumalanga Province. This study employed species distribution modelling to predict the distributional ranges of these taxa, and involved four main processes: (i) creating initial models trained on sparse museum data records; (ii) ground-truthing field surveys during austral spring/summer to gather additional specimens at additional localities; (iii) genetic analyses (using cytochrome-b) to determine the species identities of the newly-acquired specimens, as these taxa are morphologically indistinguishable; and (iv) refining the models and determining the conservation status of these Highveld golden moles. Initial species distribution models were developed using occurrence records for 38 specimens, based on interpolated data for 19 bioclimatic variables, continuous altitude data, as well as categorical spatial data for landtypes, WWF ecoregions and vegetation types. These initial models helped to effectively focus survey efforts within a vast study area, with surveying during the austral spring-summer of 2013-4 resulting in the acquisition of 25 specimens from across Mpumalanga, nine individuals of which (A. h. meesteri n = 2; A. septentrionalis n = 5; unknown n = 2) were captured in five new quarter-degree-squares (QDSs) where no previous golden moles have been recorded. Additionally, observed activity was also recorded in nine new QDSs (see Appendix 3), showing that the model refinement methods used (variable selection, auto-correlation, non-repeated versus cross-validated models, jackknife of variable importance and localities, independent data testing) were effective in locating golden mole populations. By using genetically-identified historical golden mole records, predictive distribution models were calibrated in maximum entropy (MaxEnt) software to focus ground-truthing efforts.
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    Phylogeography of a morphologically cryptic golden mole assemblage from South-Eastern Africa
    (Public Library of Science, 2015) Mynhardt, Samantha; Maree, Sarita; Pelser, Illona; Bennett, Nigel C; Bronner, Gary N; Wilson, John W; Bloomer, Paulette
    The Greater Maputaland-Pondoland-Albany (GMPA) region of southern Africa was recently designated as a centre of vertebrate endemism. The phylogeography of the vertebrate taxa occupying this region may provide insights into the evolution of faunal endemism in south-eastern Africa. Here we investigate the phylogeographic patterns of an understudied small mammal species assemblage ( Amblysomus ) endemic to the GMPA, to test for cryptic diversity within the genus, and to better understand diversification across the region. We sampled specimens from 50 sites across the distributional range of Amblysomus , with emphasis on the widespread A . hottentotus , to analyse geographic patterns of genetic diversity using mitochondrial DNA (mtDNA) and nuclear intron data. Molecular dating was used to elucidate the evolutionary and phylogeographic history of Amblysomus . Our phylogenetic reconstructions show that A . hottentotus comprises several distinct lineages, or evolutionarily significant units (ESUs), some with restricted geographic ranges and thus worthy of conservation attention. Divergence of the major lineages dated to the early Pliocene, with later radiations in the GMPA during the late-Pliocene to early-Pleistocene. Evolutionary diversification within Amblysomus may have been driven by uplift of the Great Escarpment c. 5-3 million years ago (Ma), habitat changes associated with intensification of the east-west rainfall gradient across South Africa and the influence of subsequent global climatic cycles. These drivers possibly facilitated geographic spread of ancestral lineages, local adaptation and vicariant isolation. Our study adds to growing empirical evidence identifying East and southern Africa as cradles of vertebrate diversity.
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    Seed predation and potential dispersal of Ceratocaryum argenteum (Restionaceae) nuts by the striped mouse (Rhabdomys pumilio) / Joseph Douglas Mandla White
    (2013) White, Joseph Douglas Mandla; Bronner, Gary N; Midgley Jeremy J
    This study aimed to better understand the role of rodents as seed predators and dispersers in the fynbos biome at De Hoop Nature Reserve, South Africa in May and June, 2013. Based on previous studies I hypothesised that the large, nut-like seeds of Ceratocaryum argenteum (Restionaceae) are scatter-hoarded by rodents and that rodent seed choices and seed fates are affected by seed size and hull thickness. Field trials using three seed types showed that smaller seeds with a high reward and low processing cost were consumed significantly(p<0.01) more than large, thick hulled seeds. Application of wire tags to facilitate discovery of relocated seeds had no significant influence on seed choice (p>0.05), but further research should be conducted to determine if spooling of C. argenteum seeds influences rodent seed choice. Smaller seeds with a high-reward and low processing cost showed a significantly greater percentage of usage (p<0.01) where seed stations were encountered and exploited. Rhabdomys pumilio was confirmed as being the most common murid at the study site, however, it seems unlikely that it scatter-hoards C. argenteum seeds, as no consumption or burial of seeds was observed. However, R. pumilio did show an interest in C. argenteum seeds and attempted to consume some seeds or carried seeds over distances not significantly different (p>0.05) from the observed distances between nearest neighbour C.argenteum plants before discarding them on the soil. Additionally, the maximum distance R. pumilio moved C. argenteum seeds was commensurate with the maximum distance between nearest neighbour C. argenteum stands, so the end fate of the seeds remains unknown. Further research should account for seasonal variability in scatter-hoarding behaviour.
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    Terrestrial small mammal community composition in the Volcanoes National Park, Rwanda
    (2010) Tuyisingize, Deogratias; Bronner, Gary N; Peterhans, Julian C Kerbis; Fawcett, Katie A
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    The natural history, sensory ecology and biogeography of the seed dispersal of large fruits in Fynbos
    (2019) White, Joseph D M; Midgley, Jeremy J; Bronner, Gary N
    Seed dispersal is a crucial life-history stage for the regeneration of all reseeding plants. In the Fynbos Biome of the Greater Cape Floristic Region (GCFR) of South Africa, at least 100 plant species have seed traits that suggest they are scatterhoarded by small mammals. The aims of this thesis were to investigate the dispersal biology of large-fruited Fynbos plants by: 1) determining the spatial and taxonomic extent of scatter-hoarding through seed trials, investigating both dry, nut-like and semi-fleshy fruits; 2) trait-based analyses investigating selective drivers of seed colour polymorphisms in flat-winged, serotinous Leucadendron and 3) modeling the relative influence of environmental, biological and disturbance drivers in predicting the distributions of serotinous and scatterhoarded Leucadendron. Seed predation and scatter-hoarding by small mammals was widespread, yet locally patchy. Four new fynbos species with large, nut-like fruits were confirmed to be scatter-hoarded, by either Acomys subspinosus or Gerbilliscus paeba. Many species with small, nut-like fruits, with no clear dispersal or defense strategies, suffered intense seed predation by the nonhoarding small mammals, Rhabdomys pumilio and Micaelamys namaquensis. The large, dry, nut-like fruits of Ceratocaryum argenteum have a globally unique, alternative strategy for effective dispersal. The nuts emit a strong scent that mimics the scent of herbivore dung and exploits the olfactory sensory perception of dung beetles, which rolled and buried the seeds. The semi-fleshy fruits of the rock-restricted Heeria argentea were dispersed by the mutualistic M. namaquensis, which consumed only the pericarp, allowing for germination, as well as moving fruits to fire-protected, rocky outcrops. Many flat-winged Leucadendron seeds, with polymorphic brown or black seed coats, displayed background matching with post-fire soils. This plant defense likely reduces predation by visually cued avian granivores. Finally, modeling results suggest that the distributions of both serotinous and scatter-hoarded plants are strongly negatively and positively influenced by more intense seasonal drought and longer fire return interval in the GCFR, respectively. Overall, this thesis advances our understanding of large-fruited Fynbos plants, providing unique insights into their natural history, ecology, evolution, conservation and biogeography.