- Email: [email protected]
Human occupation in southern Namibia during the Late Pleistocene – A geoarchaeological approach
186
Abstracts / Quaternary International 404 (2016) 174e213
Geosciences, University of Bremen, Germany; 2 Department of Environmental and Geographical Science, University of Cape Town, South Africa. E-mail address: [email protected].
To better understand Holocene vegetation and hydrological changes of South Africa, we analyzed pollen and microcharcoal of marine sediment core GeoB8331-4 from the inner continental-shelf south of the Orange River mouth covering the last 9800 years. Most pollen is from the Orange River catchment area, which lies largely in the summer rainfall zone (SRZ). Pollen from the Cape region in the winter rainfall zone (WRZ) is continuously delivered by the southeast trade winds. During the early Holocene (prior to 8900 cal. yr BP), the presence of Renosterbos vegetation indicates a relatively northward extension of the WRZ, and a percentage minimum of grass pollen suggests low summer rainfall in the SRZ. Towards the mid-Holocene (8900e3100 cal. yr BP), Renosterbos vegetation decreases indicating a southward retraction of the WRZ. At the same time, a rather moist savanna rich in grasses implies increased summer rainfall in the SRZ, suggesting a southward shift of the SRZ. Effects of human activities such as overgrazing are apparent during approximately the last 300 years. Based on the different pollen sources from the SRZ and WRZ respectively, contrasting climate developments are evident in the SRZ and WRZ during the last 9800 years. For the SRZ, the records suggest relatively arid conditions during the early Holocene. The climate in the SRZ gradually became more humid towards the mid-Holocene resulting from increased austral summer insolation. The opposite trend was found in the WRZ. The early Holocene humid conditions in the WRZ may be attributed to an equatorward shift of the southern westerlies. Keywords: pollen, vegetation change, climate variability, Holocene, South Africa
EARLY HOLOCENE CHARCOALS FROM STRATUM 4D OF WONDERWERK CAVE, NORTHERN CAPE M. Bamford. Evolutionary Studies Institute, University of the Witwatersrand, South Africa. E-mail address: [email protected].
Wonderwerk Cave in the Northern Cape Province of South Africa has a record of occupation spanning some 2 million years comprising flora, fauna and cultural artefacts, and therefore has the most complete macrobotanical record associated with hominin/human activities in southern Africa. Here the charcoals from Stratum 4d of excavation 1, (dated about 12 200 e 8 600 years ago) are identified and a preliminary vegetation reconstruction has been done. As there are thousands of pieces of charcoal a selection of them has been taken and studied. Some pieces were not identifiable. Although the number of pieces assigned to each taxon cannot be taken as a direct measure of abundance because charcoal fragment distribution can assist in interpreting abundance. Some of the taxa identified are Searsia lancea (Anacardiaceae); Commiphora cf. schimperi. (Burseraceae); Strychnos sp. (Loganiaceae) and Dombeya rotundifolia (Sterculioideae, Malvaceae). Assuming that the firewood was of local origin, the climate during the latest Pleistocene would have been slightly more mesic than today's arid to semi-arid climate. Keywords: charcoal, Holocene
EVIDENCE OF VEGETATION CHANGE IN LATE QUATERNARY DEPOSITS OF THE NAMIB DESERT AND BOUNDARY REGION L. Scott 1, *, G. Gil-Romera 2, E. Marais 3, G.A. Brook 4. 1 Department of Plant Sciences, University of the Free State, South Africa; 2 Department of Geoenvironmental Processes and Global Change, Pyrenean Institute of Ecology, Spain; 3 National Museum, Windhoek, Namibia; 4 Department of Geography, University of Georgia, Athens, USA. E-mail address: [email protected].
* Corresponding author.
A review of palynological sequences from various deposits provides evidence for plant cover and patterns of past vegetation change in Namibia for the late Quaternary despite the scarcity of suitable deposits, complexity of environmental factors, diverse settings and spatially and temporally scattered nature of data. In this dry region fossil hyrax dung deposits had the most potential. The oldest pollen from the Brandberg (Damaraland) of between 49e39 ka, suggests relatively warm dry conditions with a tree-rich pollen assemblage of Rhus, Dombeya, Combretaceae, Euclea in a grassy vegetation that included succulent Aizoaceae. A marked difference is seen in pollen composition at ca. 43 ka and ca. 21 ka with prominent Asteraceae pollen of the Pentzia, Stoebe and Artemisia types, and Passerina, grass and Olea pollen, suggesting cool conditions with available moisture probably coming in winter from the west coast. At Mirabib (central Namibia, almost 200 km south of Brandberg), increased Stoebe type also occurred ca. 43 ka but the assemblage differs by a stronger presence of grass pollen indicating relatively wet conditions in this part of the desert. The transition from OIS 2-1 is not recorded in Namibia but the period between ca. 10 and 8 ka at Blasskranz and Mirabib (central Namib) had high proportions of grass pollen suggesting relatively moist conditions with some Stoebe type and occasional tree pollen, showing a slight offset with spring and bat guano data from Windhoek (ca. 8e7.6 ka). Generally lower grass pollen ratios at Blasskranz ca. 7.4e7.2 ka, less than at Mirabib, indicates dryness. To the north along the Huab River (Damaraland) at ca. 7 ka, prominent Commiphora occurred corresponding with a similar development at Blasskranz but not at Mirabib. Between about 7 and 6.5 ka different Asteraceae and Acanthaceae types alternated at Blasskranz with less grass pollen suggesting dry conditions. By 6.4 e5.2 ka grassy conditions occurred here with increasing arboreal pollen of Salvadora, Mimosoideae and Searsia, and later Combretaceae, representing a major change in the Blasskranz sequence after 5.5 ka to an environment of summer-rain seasonality and C4 photosynthesis. This was followed by a short decline in grass pollen indicating a relatively dry phase (ca. 5e4.3 ka). Grass pollen numbers recovered during the subsequent phase but Combretaceae declined gradually in favour of Grewia, Commiphora and Capparaceae ca. 2 ka. At Blasskranz, microscopic charcoal peak at times when savanna is prominent. Burning seems to be controlled by interplay between fuel cover, seasonality and moisture availability. To the north ca. 6e1 ka, at Huab River and further to Orupembe in Kaokoland, grassy vegetation occurred corresponding in part with the Otjikoto Lake and Blasskranz records to the east and south respectively. Different patterns at Blasskranz and the nearby Kuiseb River over the last 2 ka may be related to the proximity of the latter to the coast. After 1 ka mopane woodland developed at the northern sites with a parallel dry fluctuation without mopane at Blasskranz and the Kuiseb River. Keywords: hyrax dung, pollen, Namibia, seasonality, grassland
HUMAN OCCUPATION IN SOUTHERN NAMIBIA DURING THE LATE PLEISTOCENE e A GEOARCHAEOLOGICAL APPROACH I. Schmidt 1, *, G. Ossendorf 1, 2, A. Bolten 3, O. Bubenzer 3. 1 Institute of Prehistoric Archaeology, University of Cologne, Germany; 2 School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, South Africa; 3 Institute of Geography, University of Cologne, Germany. E-mail address: [email protected].
Southern Namibia holds a rich Late Pleistocene archaeological record, known from research along the escarpment as well as within the coastal mining sperrgebiet. The area, situated between the Orange River and Namib Sand Sea, between the Atlantic coast and the Huib Plateau, comprises a diverse set of geological and geomorphological features. Although little is known about the impact of Pleistocene global climatic developments on this region, it probably provided an arid, but relatively stable environment for Pleistocene occupants. Recent archaeological investigations at the archaeological site of Apollo 11, however, indicate that the local settlement history took place in a discontinuous manner during the Late Pleistocene. Given the still scarce data on regional palaeo-climate/-environment as well as almost absence of geoarchaeological on-site investigations, the observations allow for the formulation three (not necessarily mutually exclusive) hypotheses for the discontinuous occupation pattern: a) the pattern reflects
Abstracts / Quaternary International 404 (2016) 174e213
187
demographic changes related to environmental changes; b) it is caused by geogenic site formation processes; c) it is related to culturally/socially embedded changes in land-use systems. A project recently funded at the University of Cologne intends to investigate these preliminary observations on a regional scale. The project focuses on the interdisciplinary study of a Late Pleistocene archaeological sequence in the vicinity of Apollo 11. By gaining information on site-formation processes, the environmental context as well as chrono-cultural developments, results will contribute to test the above mentioned hypotheses. Here, we present the first general results of our interdisciplinary geoarchaeological study of the southern Namibian Pleistocene landscape, using geostatistical methods to explore and investigate available spatiotemporal data. Incentives are planned to better understand and identify cultural/behavioural and environmental variables leading to the success or failure of Late Pleistocene populations in this region.
resources are highly variable during the late Quaternary. That this basin was, at times, a key resource for Stone Age populations is evident from the extensive occurrence of stone tools, most notably in association with the fluvial networks and lake sumps of the ZambeziOkavango system. Today, these riparian corridors link the semi-arid desert region to the southern sub-tropics and, in the past, drove environmental change in the Kalahari, potentially impacting the occupation and dispersal of hominins within the interior southern African basin. Here we report new ages on previously undated Stone Age archaeological assemblages along the upper Zambezi valley and examine the broader relevance of these sites within the context of palaeoenvironmental change.
Keywords: Namibia, Late Pleistocene, geoarchaeology, landscape, human settlement
THE EVOLUTIONARY PRESSURE OF GLACIAL ARIDIFICATION AND THE USE OF POLLEN-eOVULE RATIO AS A PREDICTIVE PROXY OF POLLEN TRANSFER EFFICIENCY (PTE) IN PERIPLOCOIDEAE (APOCYNACEAE)
COMPARING THE LARGE MAMMAL FOSSIL RECORD AND THE ARCHAEOLOGICAL RECORD DURING THE MID TO LATE QUATERNARY IN SOUTHERN AFRICA
J.C.L. de Jager*, L. Joubert. Department of Plant Sciences, University of the Free State, South Africa.
J. Brink 1,2, *. 1 Florisbad Quaternary Research Dept., National Museum, South Africa; 2 Centre for Environmental Management, University of the Free State, South Africa.
E-mail address: [email protected].
E-mail address: [email protected].
The mammalian fossil record in southern Africa reflects a long-term trend towards drier climates. It is a trend that is generally shared with East Africa and is reflected in the number of arid and semi-arid adapted taxa shared between the two subregions, both in the past and in the present. However, this biogeographic connection appears to have become diminished to some extent towards the end-Early Pleistocene, when in the south the appearance of wetlands on a sub-regional scale contributes to a distinctive faunal character. In faunal terms this time is known as the Florisian Land Mammal Age and it spans between c. 0.6 Ma and the beginning of the Holocene. The trend towards wetter conditions on a sub-regional scale is a deviation from the longer-term trend towards aridity. The wetland faunal signal extended across modern biome boundaries and intersected the open habitat of the central interior and surrounding savannah areas, but excluded the Cape montane and coastal areas. In this contribution the coincidence of major changes in the large mammal fossil record and the archaeological record in southern Africa is explored. Keywords: large mammal evolution, southern endemism, wetlands, archaeological record References: BRINK, J.S. in press. Faunal evidence for mid- and late Quaternary environmental change in southern Africa. In: Knight, J. and Grab, S.W. (eds) Quaternary environmental change in southern Africa: physical and human dimensions. Cambridge University Press. VRBA, E. S. 1995. On the connections between palaeoclimate and evolution. In E.S. Vrba, G.H. Denton, T.C. Partridge & L.H. Burckle (eds.) Palaeoclimate and evolution. Yale University Press, New Haven, pp. 24e45.
AN OSL CHRONOLOGY FOR STONE AGE ARCHAEOLOGICAL SITES IN THE UPPER ZAMBEZI VALLEY S. Burrough*, D.S.G. Thomas. School of Geography and Environment, University of Oxford, UK. E-mail address: [email protected].
Theories concerning the distribution of early people in the landscape place great importance on the temporal dynamics of water availability, and may be particularly relevant in the Kalahari basin where water
* Corresponding author.
Keywords: Stone-age archaeology, Zambezi, Holocene, Kalahari basin
The influence of climate change on the evolution of pollination mechanisms and floral morphology is poorly understood, even though angiosperm pollination and reproductive success is strongly influenced by extrinsic factors such as climate, habitat integrity and pollinator activity. In southern Africa the Periplocoideae (Apocynaceae) is represented by seven genera namely; Cryptolepis R.Br, Ectadium E.Mey, Mondia Skeels, Petopentia Bullock, Raphionacme Harv., Stomatostemma N.E.Br. and Tacazzea Decne. Periplocoideae are characterized by pollen aggregated in tetrads which are shed onto sticky spoon-shaped translators at anthesis. Pollen aggregation in the Apocynaceae has been shown to cause elevated pollen transfer efficiency (PTE) and as a result, reduced pollen production and low pollen-eovule ratios. It is therefore postulated that low polleneovule ratio is associated with pollen aggregation and can be used as a measure to test the relationship between PTE and pollen aggregation. Livshultz et al. (2011) propose that the various degrees of pollen aggregation in the Apocynaceae developed in reaction to aridification during glacial periods of the Tertiary, which resulted in a pronounced pollinator allee effect. This suggests that all Periplocoideae genera, which have the same degree of pollen aggregation, should have similar PTE's and consequently similar pollen-eovule ratios. We determined the polleneovule ratios of representatives of all seven southern African Periplocoideae genera and mapped these onto the Periplocoideae phylogeny modified from Ionta & Judd (2007) and Joubert et al. (in prep). We show that there is much variation in pollen-eovule ratio among the seven Periplocoideae genera and therefore postulate significant differences in the PTE of the seven genera. We investigate differences in floral structure and habitat of the seven genera as possible causes of this variation in PTE. Understanding how pollen-eovule ratios changed during the evolution of Periplocoideae, in reaction to changing environments, provide a basis for predicting plant evolutionary trends in reaction to anthropogenic climatic change. Keywords: Apocynaceae, Periplocoideae, pollen-eovule ratio, pollen transfer efficiency (PTE), pollen aggregation References: Ionta, G.M. & Judd, W.S. 2007. Phylogenetic relationships in Periplocoideae (Apocynaceae s.l.) and insights into the origin of pollinia. Annals of the Missouri Botanical Garden 94: 360 e 375 Joubert, L., Klak, C., Venter, A.M., Bruyns, P.V. & Venter, H.J.T. In prep. Phylogenetic and Biographic Relationships in Cryptolepis R.Br. (Apocynaceae, Periplocoideae) Livshults, T., Mead, J.V., Goyder, D.J. & Brannin, M. 2011. Climate niches of the milkweeds with plesiomorphic traits (Secamonoideae; Apocynaceae) and the milkweed sister group link ancient African climates and floral evolution. American Journal of Botany 98: 1966 e 1977
Abstracts / Quaternary International 404 (2016) 174e213
Geosciences, University of Bremen, Germany; 2 Department of Environmental and Geographical Science, University of Cape Town, South Africa. E-mail address: [email protected].
To better understand Holocene vegetation and hydrological changes of South Africa, we analyzed pollen and microcharcoal of marine sediment core GeoB8331-4 from the inner continental-shelf south of the Orange River mouth covering the last 9800 years. Most pollen is from the Orange River catchment area, which lies largely in the summer rainfall zone (SRZ). Pollen from the Cape region in the winter rainfall zone (WRZ) is continuously delivered by the southeast trade winds. During the early Holocene (prior to 8900 cal. yr BP), the presence of Renosterbos vegetation indicates a relatively northward extension of the WRZ, and a percentage minimum of grass pollen suggests low summer rainfall in the SRZ. Towards the mid-Holocene (8900e3100 cal. yr BP), Renosterbos vegetation decreases indicating a southward retraction of the WRZ. At the same time, a rather moist savanna rich in grasses implies increased summer rainfall in the SRZ, suggesting a southward shift of the SRZ. Effects of human activities such as overgrazing are apparent during approximately the last 300 years. Based on the different pollen sources from the SRZ and WRZ respectively, contrasting climate developments are evident in the SRZ and WRZ during the last 9800 years. For the SRZ, the records suggest relatively arid conditions during the early Holocene. The climate in the SRZ gradually became more humid towards the mid-Holocene resulting from increased austral summer insolation. The opposite trend was found in the WRZ. The early Holocene humid conditions in the WRZ may be attributed to an equatorward shift of the southern westerlies. Keywords: pollen, vegetation change, climate variability, Holocene, South Africa
EARLY HOLOCENE CHARCOALS FROM STRATUM 4D OF WONDERWERK CAVE, NORTHERN CAPE M. Bamford. Evolutionary Studies Institute, University of the Witwatersrand, South Africa. E-mail address: [email protected].
Wonderwerk Cave in the Northern Cape Province of South Africa has a record of occupation spanning some 2 million years comprising flora, fauna and cultural artefacts, and therefore has the most complete macrobotanical record associated with hominin/human activities in southern Africa. Here the charcoals from Stratum 4d of excavation 1, (dated about 12 200 e 8 600 years ago) are identified and a preliminary vegetation reconstruction has been done. As there are thousands of pieces of charcoal a selection of them has been taken and studied. Some pieces were not identifiable. Although the number of pieces assigned to each taxon cannot be taken as a direct measure of abundance because charcoal fragment distribution can assist in interpreting abundance. Some of the taxa identified are Searsia lancea (Anacardiaceae); Commiphora cf. schimperi. (Burseraceae); Strychnos sp. (Loganiaceae) and Dombeya rotundifolia (Sterculioideae, Malvaceae). Assuming that the firewood was of local origin, the climate during the latest Pleistocene would have been slightly more mesic than today's arid to semi-arid climate. Keywords: charcoal, Holocene
EVIDENCE OF VEGETATION CHANGE IN LATE QUATERNARY DEPOSITS OF THE NAMIB DESERT AND BOUNDARY REGION L. Scott 1, *, G. Gil-Romera 2, E. Marais 3, G.A. Brook 4. 1 Department of Plant Sciences, University of the Free State, South Africa; 2 Department of Geoenvironmental Processes and Global Change, Pyrenean Institute of Ecology, Spain; 3 National Museum, Windhoek, Namibia; 4 Department of Geography, University of Georgia, Athens, USA. E-mail address: [email protected].
* Corresponding author.
A review of palynological sequences from various deposits provides evidence for plant cover and patterns of past vegetation change in Namibia for the late Quaternary despite the scarcity of suitable deposits, complexity of environmental factors, diverse settings and spatially and temporally scattered nature of data. In this dry region fossil hyrax dung deposits had the most potential. The oldest pollen from the Brandberg (Damaraland) of between 49e39 ka, suggests relatively warm dry conditions with a tree-rich pollen assemblage of Rhus, Dombeya, Combretaceae, Euclea in a grassy vegetation that included succulent Aizoaceae. A marked difference is seen in pollen composition at ca. 43 ka and ca. 21 ka with prominent Asteraceae pollen of the Pentzia, Stoebe and Artemisia types, and Passerina, grass and Olea pollen, suggesting cool conditions with available moisture probably coming in winter from the west coast. At Mirabib (central Namibia, almost 200 km south of Brandberg), increased Stoebe type also occurred ca. 43 ka but the assemblage differs by a stronger presence of grass pollen indicating relatively wet conditions in this part of the desert. The transition from OIS 2-1 is not recorded in Namibia but the period between ca. 10 and 8 ka at Blasskranz and Mirabib (central Namib) had high proportions of grass pollen suggesting relatively moist conditions with some Stoebe type and occasional tree pollen, showing a slight offset with spring and bat guano data from Windhoek (ca. 8e7.6 ka). Generally lower grass pollen ratios at Blasskranz ca. 7.4e7.2 ka, less than at Mirabib, indicates dryness. To the north along the Huab River (Damaraland) at ca. 7 ka, prominent Commiphora occurred corresponding with a similar development at Blasskranz but not at Mirabib. Between about 7 and 6.5 ka different Asteraceae and Acanthaceae types alternated at Blasskranz with less grass pollen suggesting dry conditions. By 6.4 e5.2 ka grassy conditions occurred here with increasing arboreal pollen of Salvadora, Mimosoideae and Searsia, and later Combretaceae, representing a major change in the Blasskranz sequence after 5.5 ka to an environment of summer-rain seasonality and C4 photosynthesis. This was followed by a short decline in grass pollen indicating a relatively dry phase (ca. 5e4.3 ka). Grass pollen numbers recovered during the subsequent phase but Combretaceae declined gradually in favour of Grewia, Commiphora and Capparaceae ca. 2 ka. At Blasskranz, microscopic charcoal peak at times when savanna is prominent. Burning seems to be controlled by interplay between fuel cover, seasonality and moisture availability. To the north ca. 6e1 ka, at Huab River and further to Orupembe in Kaokoland, grassy vegetation occurred corresponding in part with the Otjikoto Lake and Blasskranz records to the east and south respectively. Different patterns at Blasskranz and the nearby Kuiseb River over the last 2 ka may be related to the proximity of the latter to the coast. After 1 ka mopane woodland developed at the northern sites with a parallel dry fluctuation without mopane at Blasskranz and the Kuiseb River. Keywords: hyrax dung, pollen, Namibia, seasonality, grassland
HUMAN OCCUPATION IN SOUTHERN NAMIBIA DURING THE LATE PLEISTOCENE e A GEOARCHAEOLOGICAL APPROACH I. Schmidt 1, *, G. Ossendorf 1, 2, A. Bolten 3, O. Bubenzer 3. 1 Institute of Prehistoric Archaeology, University of Cologne, Germany; 2 School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, South Africa; 3 Institute of Geography, University of Cologne, Germany. E-mail address: [email protected].
Southern Namibia holds a rich Late Pleistocene archaeological record, known from research along the escarpment as well as within the coastal mining sperrgebiet. The area, situated between the Orange River and Namib Sand Sea, between the Atlantic coast and the Huib Plateau, comprises a diverse set of geological and geomorphological features. Although little is known about the impact of Pleistocene global climatic developments on this region, it probably provided an arid, but relatively stable environment for Pleistocene occupants. Recent archaeological investigations at the archaeological site of Apollo 11, however, indicate that the local settlement history took place in a discontinuous manner during the Late Pleistocene. Given the still scarce data on regional palaeo-climate/-environment as well as almost absence of geoarchaeological on-site investigations, the observations allow for the formulation three (not necessarily mutually exclusive) hypotheses for the discontinuous occupation pattern: a) the pattern reflects
Abstracts / Quaternary International 404 (2016) 174e213
187
demographic changes related to environmental changes; b) it is caused by geogenic site formation processes; c) it is related to culturally/socially embedded changes in land-use systems. A project recently funded at the University of Cologne intends to investigate these preliminary observations on a regional scale. The project focuses on the interdisciplinary study of a Late Pleistocene archaeological sequence in the vicinity of Apollo 11. By gaining information on site-formation processes, the environmental context as well as chrono-cultural developments, results will contribute to test the above mentioned hypotheses. Here, we present the first general results of our interdisciplinary geoarchaeological study of the southern Namibian Pleistocene landscape, using geostatistical methods to explore and investigate available spatiotemporal data. Incentives are planned to better understand and identify cultural/behavioural and environmental variables leading to the success or failure of Late Pleistocene populations in this region.
resources are highly variable during the late Quaternary. That this basin was, at times, a key resource for Stone Age populations is evident from the extensive occurrence of stone tools, most notably in association with the fluvial networks and lake sumps of the ZambeziOkavango system. Today, these riparian corridors link the semi-arid desert region to the southern sub-tropics and, in the past, drove environmental change in the Kalahari, potentially impacting the occupation and dispersal of hominins within the interior southern African basin. Here we report new ages on previously undated Stone Age archaeological assemblages along the upper Zambezi valley and examine the broader relevance of these sites within the context of palaeoenvironmental change.
Keywords: Namibia, Late Pleistocene, geoarchaeology, landscape, human settlement
THE EVOLUTIONARY PRESSURE OF GLACIAL ARIDIFICATION AND THE USE OF POLLEN-eOVULE RATIO AS A PREDICTIVE PROXY OF POLLEN TRANSFER EFFICIENCY (PTE) IN PERIPLOCOIDEAE (APOCYNACEAE)
COMPARING THE LARGE MAMMAL FOSSIL RECORD AND THE ARCHAEOLOGICAL RECORD DURING THE MID TO LATE QUATERNARY IN SOUTHERN AFRICA
J.C.L. de Jager*, L. Joubert. Department of Plant Sciences, University of the Free State, South Africa.
J. Brink 1,2, *. 1 Florisbad Quaternary Research Dept., National Museum, South Africa; 2 Centre for Environmental Management, University of the Free State, South Africa.
E-mail address: [email protected].
E-mail address: [email protected].
The mammalian fossil record in southern Africa reflects a long-term trend towards drier climates. It is a trend that is generally shared with East Africa and is reflected in the number of arid and semi-arid adapted taxa shared between the two subregions, both in the past and in the present. However, this biogeographic connection appears to have become diminished to some extent towards the end-Early Pleistocene, when in the south the appearance of wetlands on a sub-regional scale contributes to a distinctive faunal character. In faunal terms this time is known as the Florisian Land Mammal Age and it spans between c. 0.6 Ma and the beginning of the Holocene. The trend towards wetter conditions on a sub-regional scale is a deviation from the longer-term trend towards aridity. The wetland faunal signal extended across modern biome boundaries and intersected the open habitat of the central interior and surrounding savannah areas, but excluded the Cape montane and coastal areas. In this contribution the coincidence of major changes in the large mammal fossil record and the archaeological record in southern Africa is explored. Keywords: large mammal evolution, southern endemism, wetlands, archaeological record References: BRINK, J.S. in press. Faunal evidence for mid- and late Quaternary environmental change in southern Africa. In: Knight, J. and Grab, S.W. (eds) Quaternary environmental change in southern Africa: physical and human dimensions. Cambridge University Press. VRBA, E. S. 1995. On the connections between palaeoclimate and evolution. In E.S. Vrba, G.H. Denton, T.C. Partridge & L.H. Burckle (eds.) Palaeoclimate and evolution. Yale University Press, New Haven, pp. 24e45.
AN OSL CHRONOLOGY FOR STONE AGE ARCHAEOLOGICAL SITES IN THE UPPER ZAMBEZI VALLEY S. Burrough*, D.S.G. Thomas. School of Geography and Environment, University of Oxford, UK. E-mail address: [email protected].
Theories concerning the distribution of early people in the landscape place great importance on the temporal dynamics of water availability, and may be particularly relevant in the Kalahari basin where water
* Corresponding author.
Keywords: Stone-age archaeology, Zambezi, Holocene, Kalahari basin
The influence of climate change on the evolution of pollination mechanisms and floral morphology is poorly understood, even though angiosperm pollination and reproductive success is strongly influenced by extrinsic factors such as climate, habitat integrity and pollinator activity. In southern Africa the Periplocoideae (Apocynaceae) is represented by seven genera namely; Cryptolepis R.Br, Ectadium E.Mey, Mondia Skeels, Petopentia Bullock, Raphionacme Harv., Stomatostemma N.E.Br. and Tacazzea Decne. Periplocoideae are characterized by pollen aggregated in tetrads which are shed onto sticky spoon-shaped translators at anthesis. Pollen aggregation in the Apocynaceae has been shown to cause elevated pollen transfer efficiency (PTE) and as a result, reduced pollen production and low pollen-eovule ratios. It is therefore postulated that low polleneovule ratio is associated with pollen aggregation and can be used as a measure to test the relationship between PTE and pollen aggregation. Livshultz et al. (2011) propose that the various degrees of pollen aggregation in the Apocynaceae developed in reaction to aridification during glacial periods of the Tertiary, which resulted in a pronounced pollinator allee effect. This suggests that all Periplocoideae genera, which have the same degree of pollen aggregation, should have similar PTE's and consequently similar pollen-eovule ratios. We determined the polleneovule ratios of representatives of all seven southern African Periplocoideae genera and mapped these onto the Periplocoideae phylogeny modified from Ionta & Judd (2007) and Joubert et al. (in prep). We show that there is much variation in pollen-eovule ratio among the seven Periplocoideae genera and therefore postulate significant differences in the PTE of the seven genera. We investigate differences in floral structure and habitat of the seven genera as possible causes of this variation in PTE. Understanding how pollen-eovule ratios changed during the evolution of Periplocoideae, in reaction to changing environments, provide a basis for predicting plant evolutionary trends in reaction to anthropogenic climatic change. Keywords: Apocynaceae, Periplocoideae, pollen-eovule ratio, pollen transfer efficiency (PTE), pollen aggregation References: Ionta, G.M. & Judd, W.S. 2007. Phylogenetic relationships in Periplocoideae (Apocynaceae s.l.) and insights into the origin of pollinia. Annals of the Missouri Botanical Garden 94: 360 e 375 Joubert, L., Klak, C., Venter, A.M., Bruyns, P.V. & Venter, H.J.T. In prep. Phylogenetic and Biographic Relationships in Cryptolepis R.Br. (Apocynaceae, Periplocoideae) Livshults, T., Mead, J.V., Goyder, D.J. & Brannin, M. 2011. Climate niches of the milkweeds with plesiomorphic traits (Secamonoideae; Apocynaceae) and the milkweed sister group link ancient African climates and floral evolution. American Journal of Botany 98: 1966 e 1977