Fire frequency and species associations in perennial grasslands of south-west Ethiopia

Fires play an important role in shaping species composition and associations in East African grasslands. Grassland plains of Omo National Park (ONP), Ethiopia, which are dominated by perennial grass species, exist in a fire-prone environment. Our objective was to determine if the current pattern of plant species composition in ONP's grassland plains was correlated with the historical pattern of fire frequency. Species composition was determined at 160 plots along 30 west-trending transects, approximately 2 km apart. Fire frequency for each plot was estimated using eleven Landsat satellite images that spanned a 23-year period. The Mantel and partial Mantel tests were used to test for correlation between species composition and fire frequency.
Plots in the northern grassland plain appear to burn every other year, while plots in the southern grassland plain burn once every 4–5 years. However, no significant correlation was found between patterns in species composition and fire frequency. Likewise, a selective analysis by functional group (i.e. grass, shrubs) revealed no relationship with fire frequency. It appears that fire does play a role in dictating species composition in ONP, but only in the sense that species that can tolerate the current fire regime persist. Species distribution, however, appears to be under the influence of other factors.     

Past climate changes and ecophysiological responses recorded in the isotope ratios of saguaro cactus spines

The stable isotope composition of spines produced serially from the apex of columnar cacti has the potential to be used as a record of changes in climate and physiology. To investigate this potential, we measured the δ¹⁸O, δ¹³C and F¹⁴C values of spines from a long-lived columnar cactus, saguaro (Carnegiea gigantea). To determine plant age, we collected spines at 11 different heights along one rib from the stem apex (3.77 m height) to the base of a naturally occurring saguaro. Fractions of modern carbon (F¹⁴C) ranged from 0.9679 to 1.5537, which is consistent with ages between 1950 and 2004. We observed a very strong positive correlation (r = 0.997) between the F¹⁴C age of spines and the age of spines determined from direct and repeated height measurements taken on this individual over the past 37 years. A series of 96 spines collected from this individual had δ¹⁸O values ranging from 38‰ to 50‰ [Vienna standard mean ocean water (VSMOW)] and δ¹³C values from ?11.5‰ to ?8.5‰ [Vienna Peedee belemnite (VPDB)]. The δ¹⁸O and δ¹³C values of spines were positively correlated (r = 0.45, P < 0.0001) and showed near-annual oscillations over the ～15-year record. This pattern suggests that seasonal periods of reduced evaporative demand or greater precipitation input may correspond to increased daytime CO₂ uptake. The lowest δ¹⁸O and δ¹³C values of spines observed occurred during the 1983 and 1993 El Niño years, suggesting that the stable isotope composition recorded in spine tissue may serve as a proxy for these climate events. We compared empirical models and data from potted experimental cacti to validate these observations and test our hypotheses. The isotopic records presented here are the first ever reported from a chronosequence of cactus spines and demonstrate that tissues of columnar cacti, and potentially other long-lived succulents, may contain a record of past physiological and climatic variation.     

Additional evidence for bone technology in the southern African Middle Stone Age

Few Middle Stone Age sites have yielded convincing evidence for a complex bone technology, a behavior often associated with the emergence of modern cultures. Here, we review the published evidence for Middle Stone Age bone tools from southern Africa, analyze an additional nine bone artifacts recently recovered from Middle Stone Age levels at Blombos Cave, describe an unpublished bone tool from probable Middle Stone Age levels at Peers Cave, examine a single bone awl found at Blombosch Sands (an open site near Blombos Cave), and reappraise marked bone artifacts and a bone point recovered from Klasies River. To determine the chronological and cultural attribution of these artifacts, document bone-manufacturing techniques associated with the southern African MSA, and discuss the symbolic significance of the markings present on some of these objects we use (1) available contextual information; (2) morphometric comparison of Later Stone Age, Modern San, and purported Middle Stone Age projectile points; (3) analysis of the carbon/nitrogen content of bone tools and faunal remains from Peers and Blombos caves; and (4) microscopic analysis of traces of manufacture and use. Previously undescribed bone artifacts from Blombos Cave include a massive point manufactured on weathered bone, two complete awls and two awl tips manufactured on small-sized mammal and bird bone, a probable projectile point with a tang manufactured by knapping and scraping, a shaft fragment modified by percussion, used as retoucher and bearing a set of incised lines on the middle of the periosteal surface, and two fragments with possible engravings. The point from Peers Cave can be assigned to the Middle Stone Age and bears tiny markings reminiscent of those recorded on projectile points from Blombos and used as marks of ownership on San arrow points. The awl from Blombosch Sands and the bone point from Klasies River can be attributed to the Later Stone Age. Two notched objects from Klasies are attributed to the Middle Stone Age and interpreted as tools used on soft material; a third object bears possible deliberate symbolic engravings. Although low in number, the instances of bone artifacts attributable to the Middle Stone Age is increasing and demonstrates that the bone tools from Blombos Cave are not isolated instances. New discoveries of bone tools dating to this time period can be expected.     

New age constraints on the Middle Stone Age occupations of Kharga Oasis, Western Desert, Egypt

Spring-deposited carbonate rocks, or tufas, exposed along the flanks of the Libyan Plateau near Kharga Oasis, Western Desert, Egypt, can provide a directly datable stratigraphic context for Middle Stone Age/Middle Paleolithic (MSA/MP) archaeological material, if such material can be found in situ within tufa strata. Two such localities (Mata'na Site G and Bulaq Wadi 3 Locus 1) described by Caton-Thompson were revisited and sampled for uranium-series analysis. At Mata'na Site G (KH/MT-02), Middle Stone Age ("Upper Levalloisian") material is underlain by tufa with a uranium-series age of 127.9+/-1.3 ka, and overlain by tufa with an age of 103+/-14 ka. At Bulaq Wadi 3 Locus 1, a uranium-series age of 114.4+/-4.2 ka on tufa capping a small collection of Middle Stone Age artifacts also provides a minimum age constraint on that material. Tufa underlying an MSA workshop (KH/MD-10) indicates that this assemblage, characterized by use of several Levallois reduction methods, was deposited after approximately 124 ka. Furthermore, uranium-series ages averaging approximately 133 ka on a Wadi Midauwara tufa (WME-10) without associated archaeological material suggest that one period of spring flow in the region began during the Marine Isotope Stage 6/5e transition, prior to the warmest portion of the last interglacial period. The dated archaeological material suggests that the distinction that has been identified between Nubian and non-Nubian complexes in the Nile Valley may hold for the Western Desert, although local complexity has yet to be fully described.     

Paleogeographic variations of pedogenic carbonate delta13C values from Koobi Fora, Kenya: implications for floral compositions of Plio-Pleistocene hominin environments

Plio-Pleistocene East African grassland expansion and faunal macroevolution, including that of our own lineage, are attributed to global climate change. To further understand environmental factors of early hominin evolution, we reconstruct the paleogeographic distribution of vegetation (C(3)-C(4) pathways) by stable carbon isotope (delta(13)C) analysis of pedogenic carbonates from the Plio-Pleistocene Koobi Fora region, northeast Lake Turkana Basin, Kenya. We analyzed 202 nodules (530 measurements) from ten paleontological/archaeological collecting areas spanning environments over a 50-km(2) area. We compared results across subregions in evolving fluviolacustrine depositional environments in the Koobi Fora Formation from 2.0-1.5 Ma, a stratigraphic interval that temporally brackets grassland ascendancy in East Africa. Significant differences in delta(13)C values between subregions are explained by paleogeographic controls on floral composition and distribution. Our results indicate grassland expansion between 2.0 and 1.75 Ma, coincident with major shifts in basin-wide sedimentation and hydrology. Hypotheses may be correct in linking Plio-Pleistocene hominin evolution to environmental changes from global climate; however, based on our results, we interpret complexity from proximate forces that mitigated basin evolution. An approximately 2.5 Ma tectonic event in southern Ethiopia and northern Kenya exerted strong effects on paleography in the Turkana Basin from 2.0-1.5 Ma, contributing to the shift from a closed, lacustrine basin to one dominated by open, fluvial conditions. We propose basin transformation decreased residence time for Omo River water and expanded subaerial floodplain landscapes, ultimately leading to reduced proportions of wooded floras and the establishment of habitats suitable for grassland communities.     

Wangia profunda gen. nov., sp. nov., a novel marine bacterium of the family Flavobacteriaceae isolated from southern Okinawa Trough deep-sea sediment

An orange-pigmented, Gram-negative, nonmotile, strictly aerobic and oxidase- and catalase-positive bacterium (SM-A87(T)) was isolated from the deep-sea sediment of the southern Okinawa Trough area. The main fatty acids were i15 : 0, i17 : 0 3OH, i15 : 1 G, i17 : 1 omega 9c, 15 : 0, i15 : 0 3OH and summed feature 3 (comprising i-15 : 0 2OH and/or 16 : 1 omega 7c). MK-6 was the predominant respiratory quinone. DNA G+C content was 35.8 mol%. Flexirubin-type pigments were absent. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain SM-A87(T) formed a distinct lineage within the family Flavobacteriaceae, with <93% sequence similarity to the nearest strain of genus Salegentibacter. Moreover, strain SM-A87(T) could be distinguished from the nearest phylogenetic neighbors by a number of chemotaxonomic and phenotypic properties. On the basis of polyphasic analyses, it is proposed that strain SM-A87(T) be classified in a novel genus and a new species in the family Flavobacteriaceae, designated Wangia profunda gen. nov., sp. nov. The type strain is SM-A87(T) (CCTCC AB 206139(T)=DSM 18752).     

Agglutinated conical foraminifera from the Lower-Middle Eocene of the Trentinara Formation (southern Italy)

Five taxa of agglutinated conical foraminifera were recorded for the first time in the Trentinara Formation, and two of them are new. Barattolites trentinarensis n. gen. n. sp. shows high conical shape, an eccentric proloculus, trochospiral early chambers, two orders of radial subepidermal partitions and columnar pillars. It is recorded in the Ypresian of Panno Bianco Mt. (Calabria) and in the Ypresian-Lower Lutetian of Serra Pastorella (Basilicata). Pseudochrysalidina (?) variospira n. sp. shows a high conical test, a trochospiral juvenile growth stage, a megalosphere in apical position, and low pillars and chambers in the adult stage. It is known in the Ypresian of Serra Pastorella. Agglutinated conical foraminifera fill the late Lower to early Middle Eocene gap in their Paleogene record. Their very intermittent record is due to their extremely narrow ecological range.     

Coping Strategies in Livestock-dependent Households in East and Southern Africa: A Synthesis of Four Case Studies

Integrated assessment seeks to combine models of the ecological as well as the social system to allow different scenarios to be tested in terms of their likely impacts on ecological functioning and household well-being. We outline such work undertaken in four case studies in East and southern Africa: pastoralist communities in northern Tanzania, agro-pastoralists in southern Kenya, communal and commercial ranchers in South Africa, and mixed crop-livestock farmers in western Kenya. Results from these case studies are synthesised to test the hypothesis that households’ capacity to adapt in the face of increasing external stresses is governed by flexibility in livelihood options. The results support this hypothesis. There is considerable variation in how households in these places cope with external stresses. Options include intensification, diversification, and increasing off-farm economic activities, and these depend on household objectives and attitudes as well as on access to natural resources, inputs and output markets. The results also indicate that generally it is the poorer households that can gain the most from implementing such options for coping and managing risk. Quantifying likely household and ecosystem impacts of different options is a crucial step in targeting appropriate technology, policy and adaptation interventions in the face of considerable system changes. We conclude with some research needs to improve integrated assessment tools that may allow us to represent more realistically the highly complex decision-making milieu of householders in sub-Saharan Africa who are dependent on ecosystem goods and services for a large part of their livelihoods.     

Use of phylogeny to resolve the taxonomy of the widespread and highly polymorphic African giant shrews (Crocidura olivieri group, Crocidurinae, Mammalia)

The aim of this study is to provide a better understanding of the genetic relationships within the widespread and highly polymorphic group of African giant shrews (Crocidura olivieri group). We sequenced 769 base pairs (bp) of the mitochondrial cytochrome b gene and 472 bp of the mitochondrial control region over the entire geographic range from South Africa to Morocco. The analyses reveal four main clades associated with different biomes. The largest clade occurs over a range covering Northwest and Central Africa and includes samples of C. fulvastra, C. olivieri, and C. viaria. The second clade is composed of C. goliath from Gabon, while South African C. flavescens, and C. hirta form two additional clades. On the basis of these results, the validity of some taxa in the C. olivieri group should be re-evaluated.