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Rock hyrax middens are important palaeoenvironmental archives in southern Africa. Carbon and nitrogen isotope measurements on middens (hyraceum) are key components of climate reconstructions, but their interpretations require refinement. Although δ 15 N in hyraceum often correlates with independent proxies for palaeo-aridity, the impacts of dietary and physiological controls on hyraceum δ 15 N remain to be resolved. We analyse δ 13 C and δ 15 N in plant foliage, hyrax faecal pellets and hyraceum from 21 sites across southern Africa. Faeces are generally depleted in 13 C (δ 13 C typically < −20‰), suggesting significant browsing. Grazing is rarely dominant and probably occurs only when palatable grass is available. Variability in faecal and foliar δ 15 N is large, but foliar δ 15 N is positively correlated with faecal δ 15 N. The diet-faeces δ 15 N offset is uncorrelated with climate (aridity), but is correlated with %N in faeces. Faecal δ 15 N is positively correlated with modern hyraceum δ 15 N, and the relationships with aridity index for foliar and faecal (body tissue) δ 15 N are comparable. These observations implicate diet as a significant control on hyraceum δ 15 N and we observe no strong evidence for metabolic controls on hyraceum δ 15 N. More data are required to refine these relationships, but these observations are consistent with current palaeoenvironmental interpretations of midden δ 15 N and δ 13 C. [ABSTRACT FROM AUTHOR]

Abstract: Like many of the world''s subtropical regions, southern Africa is highly sensitive to changes in the earth''s climate system, but a dearth of reliable palaeoenvironmental records means that relatively little is known about how regional environments have been affected over centennial to multi-millennial timescales. To a large extent this sensitivity is a function of the position of these regions at the interface between temperate and tropical circulation systems. The resulting seasonality and irregularity of rainfall have limited the development of suitable archives, such as lakes and wetlands, for the preservation of palaeoenvironmental proxies. This paper reviews and evaluates the value of rock hyrax middens as novel palaeoenvironmental archives in southern Africa. Considered are (1) the contemporary taxonomy, distribution and ecology of hyraxes, (2) the mechanisms of hyrax midden development, their physical and chemical structure, rates of accumulation and age; and (3) the palaeoenvironmental proxies preserved within hyrax middens, including fossil pollen, stable isotopes and biomarkers. The interpretive constraints and opportunities offered by these various midden characteristics are assessed with a view to demonstrating the potential of these deposits, widespread as they are through arid and semi-arid southern Africa, in providing a more detailed and chronologically resolved view of late Quaternary palaeoenvironments across the subcontinent. [Copyright &y& Elsevier]

Abstract: Presented here are stable nitrogen isotope data from a rock hyrax (Procavia capensis) middens from northwestern Namibia that record a series of rapid aridification events beginning at ca. 3800cal yr BP, and which mark a progressive decrease in regional humidity across the Holocene. Strong correlations exist between this record and other terrestrial and marine archives from southern Africa, indicating that the observed pattern of climate change is regionally coherent. Combined, these data indicate hemispheric synchrony in tropical African climate change during the Holocene, with similar trends characterising the termination of the ‘African Humid Period’ (AHP) in both the northern and southern tropics. These findings run counter to the widely accepted model of direct low-latitude insolation forcing, which requires an anti-phase relationship to exist between the hemispheres. The combined dataset highlights: 1) the importance of forcing mechanisms influencing the high northern latitudes in effecting low-latitude climate change in Africa, and 2) the potential importance of solar forcing and variations in the Earth''s geomagnetic shield in determining both long-term and rapid centennial-scale climate changes, identifying a possible mechanism for the variations marking the AHP termination in both the southern and northern tropics. [Copyright &y& Elsevier]

Abstract: It has long been understood that as ephemeral landscape features sand dunes are highly sensitive to environmental change, and thus their distribution and the timing of their development may provide clues to past climate dynamics. The relationship between climate and dune activity, however, is neither simple nor straightforward, with a range of controls affecting the balance between erodibility (the availability of sediment for deflation) and erosivity (the potential for sediment transport). To explore such complex systems over large spatial and temporal scales, a number of dune activity indices (DAI) have been created that incorporate wind speed and moisture balances to calculate the potential for, and degree of dune mobilisation. Using modern weather station data, these indices have generally been shown to provide reasonable indications of dune activity potential. Until recently, however, the detailed quantitative data required to inform these equations has not been available for past climate scenarios, and attempts to determine the relative importance of the various controls of dune activity have relied on rough estimations of climatic parameters. This paper combines data from monthly general circulation model (GCM) outputs from the coupled Ocean-Atmosphere GCMs for 21ka with the most detailed DAI equation presently available to calculate the potential for dune reactivation in southern Africa during the Last Glacial Maximum (LGM, 18–24ka). Based on these data and calculations it is indicated that there was significantly less potential for dune activity across southern Africa at 21ka. When compared to the aeolian sediment records from the region, this study poses serious and fundamental questions about: 1) the reliability of the model outputs, 2) the degree to which DAIs are able to account for the complexity and dynamics of aeolian systems, and/or 3) the interpretation of dune records as palaeoclimatic proxies at millennial time scales. [Copyright &y& Elsevier]

Aim The high amount of species diversity concentrated in southern Africa has been attributed to palaeoclimatic factors, and the timing of radiations in some taxa corresponds to global palaeoclimatic trends. Using dwarf chameleons ( Bradypodion: Chamaeleonidae) as a model system, we explored the relationship between palaeoclimatic fluctuations and cladogenesis with respect to both temporal and spatial patterns in an effort to understand the process of speciation in southern Africa. Location South Africa, with particular emphasis on the Cape Floristic Region and the Maputaland–Pondoland–Albany hotspot. Methods Mitochondrial sequence data (ND2 and 16S) were used to estimate the timing of major radiations and to examine the number of lineages through time. A dated phylogeny was constructed using Bayesian phylogenetic reconstruction, and a Bayesian relaxed molecular clock was used to estimate divergence times. Spatial data and lineage-through-time plots were used to identify geographic regions that underwent diversification in connection with major climatic events. Both parsimony and likelihood optimizations of habitat type on the phylogeny were used to determine whether major habitat shifts have occurred. On a coarse scale (half-degree grid cells), phylogenetic diversity (sum of the branch lengths linking terminals) was compared with species richness (absolute number of species) to identify areas of conservation importance. Results The complete species phylogeny of dwarf chameleons shows that the timing and mode of diversification exhibit spatio-temporal patterns that link to phases in the evolution of southern Africa’s climate over the last 14 Myr. Optimizations of habitat on the phylogenetic tree show a progression from closed to open habitats since the Mid-Miocene, corresponding to the shift from C3 to C4 environments, and later with the development of south-western Africa’s winter-rainfall regime. These shifts are not simultaneous across the region, with different geographic centres of diversity generated during different time periods. Main conclusions Regions that are prominent centres of chameleon diversification are encompassed by the current biodiversity hotspots as shown by chameleon species richness and phylogenetic diversity. Diversity within the Cape Floristic Region appears to be the result of a Late Pliocene radiation, whereas the diversity encompassed within the Maputaland–Pondoland–Albany hotspot is an aggregate of asynchronous radiation events, probably influenced by lineage losses. Overall, dwarf chameleons have experienced a shift in habitat types, with recent radiations occupying open habitats, and older lineages persisting in relictual forested habitats, corresponding to the continental shift of vegetation types since the Miocene Climatic Optimum. [ABSTRACT FROM AUTHOR]

Abstract: Hyrax middens are unique environmental archives with the potential to provide unprecedented high-resolution palaeoenvironmental records, particularly in the arid regions of southern Africa. This study provides the first detailed characterisation of the organic matter composition of hyraceum and aims to identify biomarker evidence capable of providing new or supplementary palaeoenvironmental data from these novel archives. Pyrolysis gas chromatography mass spectrometry reveals hyraceum to be dominated by nitrogen-containing aromatic compounds, notably benzamide. This is almost certainly derived directly from the hyrax urine and is probably the main source of nitrogen as measured in bulk δ 15N measurements. Solvent-extractable lipids comprise homologous suites of long-chain n-alkanes (C24–C34) and n-alkanols (C16–C26), characteristic of higher plant leaf waxes, along with an abundance of animal-derived sterols, higher plant sterols and terpenoids; as well as the ubiquitous benzamide. n-alkane distributions and compound specific δ 13C clearly differentiate samples from the C3 vegetation dominated Cape Floristic Region, and the more arid, C4 grass-rich savannas of central Namibia (Klein Spitzkoppe). Distinct changes in n-alkane distribution and δ 13C are observed within the Spitzkoppe midden; most notably the mid to late Holocene period (c. 6000–2000calyr BP), which records a progressive reduction in grass-derived organic matter inputs. Based on the animal''s feeding behaviour and contemporary site ecology, a phase of increasing aridity is inferred, which is consistent with other proxy data from this site (e.g. bulk δ 15N). The excellent preservation of plant and animal biomarkers suggests that there is significant potential for midden-derived biomarkers to provide long-term palaeoenvironmental proxies. [Copyright &y& Elsevier]