Diversity of lobate phytoliths in grass leaves from the Sahel region, West Tropical Africa: Tribe Paniceae

Phytoliths are microscopic amorphous silicon dioxide (SiO2.H2O) particles occurring in leaves, internodes, glumes and inflorescence within all members of the grass family Poaceae. Phytoliths of grasses are of particular interest, as they possess morphological features which have encouraged many investigators to identify these plants from which fossil phytoliths might have originated. The present study is a step towards preparing a systematic inventory of grass phytoliths in western tropical Africa. Morphology and dimensions of phytoliths from 66 species belonging to the tribe Paniceae have been studied. Four shape categories of lobate phytoliths have been determined in leaf blade spodograms: bilobate, nodular bilobate, polylobate, quadra-lobate. Bilobate shaped phytoliths are frequently represented in all genera of Paniceae. 13 groups of lobate phytoliths have been distinguished based on significant morphological criteria like shape of outer margins, shape of the shank and number of lobes. A size category system of lobate phytolith dimensions (length, width; length and width of shanks) has been developed by the analysis of average, minimum and maximum values of these dimensions. Application of the size category system results on classifying the major groups into 25 subgroups. The study proves that size and shape can be used to assign some of the lobate phytoliths to their respective genera. Some rarely produced lobate shapes like nodular bilobate and polylobate types could be used together on assemblage basis as markers for definite genera in the tribe Paniceae, e.g. Brachiaria, Panicum, Pennisetum and Setaria. Also, bilobate phytoliths with concave margins have been recorded in five species. Bilobate phytoliths with flattened and convex margins and quadra-lobate shapes are produced by almost all species which therefore resulted in an inconsistent and indefinite relationship with the taxa that produce them. The study shows a correlation between width dimensions of bilobate shapes and their shanks. Greater width dimensions usually connected to thick shanks while short ones are attached to thin shanks. A spectrum on percentages of species producing each type of lobate phytolith has been designed. It is recommended that such spectrum should be carried out for all tribes of Poaceae on phyto-geographical basis which might eliminate the effect of redundancy and multiplicity on the classification of grass phytoliths.     

Limnological studies of two contrasting but closely linked springs in Nigeria,West Africa

ABSTRACT

An account is presented of the chemistry and algal flora of two streams in Ekiti State, Nigeria. The two streams, one of which is much warmer than the other, are separate upstream but subsequently merge. A comparison of the springs revealed that while they differed markedly in temperature, colour, turbidity, conductivity, solids, total alkalinity, total hardness, Ca, SiO₃, SO₄, Mg, Cl^- and dissolved oxygen, they showed some similarities in pH, Fe, Na, K, PO₄ and NO₃. In the cold spring, while total alkalinity, conductivity and silicate increased in the wet season, total hardness decreased slightly and other variables exhibited fluctuations with season. For the warm spring, except for increased total alkalinity and total hardness, dissolved oxygen and pH decreased in the wet season. However, most parameters of the warm spring were unaffected by season. Floristically, the springs were rich in species with a total of 84 taxa: 56 in the warm spring, 33 in the cold spring, 44 at the confluence and 40 beyond the confluence. The warm spring was dominated mainly by blue-green algae such as Lyngbya birgei, Synechococcus aequalis and Oscillatoria spp.; the cold spring was dominated by Rhizoclonium hieroglyphicum and Navicula spp. The confluence was dominated by Terpsinoe musica, R. hieroglyphicum and Lyngbya birgei, while the site downstream of the confluence was dominated entirely by R. hieroglyphicum. In most cases, the confluence and downstream area beyond the confluence of the springs exhibited intermediate characteristics between the two springs. This study is a contribution to the dearth of information on streams in West Africa.     

Woody plant phenology in the West Africa savanna

In the savanna of West Africa the seasonality of rainfall, with a drought period of at least four months, strongly influences the vegetation. Rainfall is a very critical abiotic variable and therefore plant species must be well adapted to survive in this habitat.
In our research, phenological patterns of 120 woody plant species have been examined based on the presence of green leaves. According to the patterns found, these species can be classified in phenological groups, which represent different strategies for survival. Two extreme strategies are found to resist drought: (1) by using the waterstorage in the deeper soil layers and river beds and by restricting drought-damage through scleromorphic features, and (2) by avoiding the drought through foliage shedding in the dry period.
The first strategy is represented by the riparian and upland evergreens , and the semi-evergreens . The evergreens bear leaves the whole year, gradually replacing old leaves by new ones. The riparian evergreens are strictly bound to riverbeds and grow in or immediately adjacent to them. The semi-evergreens shed their leaves and start sprouting during a short period (one-two weeks) once a year. Because the evergreens and the semi-evergreens are in leaf in the dry period they have to protect themselves to drought damage by scleromorphic features.
Contrary to these species are the deciduous species which are bare for at least some months per year. When the dry season starts their leaves dry out and are subsequently shed. They start sprouting before or at the beginning of the first rains. Although much less in number, some deciduous trees also have scleromorphic features to resist drought-damage. The strategy of sprouting just before the rainy season begins indicates that certain water resources remain available to these deep-rooting woody plants throughout the year, providing them with a fully operating photosynthetic apparatus when favourable conditions arrive.     

Pyrethroid resistance in Culex quinquefasciatus from West Africa

Laboratoire de Lutte contre les Insectes Nuisibles, ORSTOM, Montpellier, France, *OCCGE, Institut Pierre Richet, BP 1500, Bouaké 01, Côte d'Ivoire, †INRA, Laboratoire de Biologie des Invertébrés, 123 Bd Meilland, 06606 Antibes, France, and ‡CNRS UMR 5554, Laboratoire de Génétique et Environnement, Institut des Sciences de l'Environnement, Université de Montpellier II (CC 065), 34095 Montpellier, France
Abstract .Pyrethroid resistance was investigated in thirty-three samples of Culex quinquefasciatus Say from twenty-five cities in Côte d'Ivoire and Burkina Faso. Permethrin resistance ratios at LC₅₀ ranged from 9.5- to 82-fold in Côte d'Ivoire and from 17- to 49-fold in Burkina Faso. For deltamethrin, resistance ratios were lower and ranged from nine to thirty-eight in both countries. A strain was selected with permethrin to investigate resistance mechanisms. After forty-two generations of selection, permethrin resistance level reached 3750-fold, but deltamethrin resistance remained unexpectedly unchanged. This indicated that a specific mechanism was involved in permethrin resistance. Synergist assays and biochemical tests indicated that resistance was partly due to P450-dependent oxidases. A target site insensitivity ( kdr ) was also involved, associated with DDT cross resistance and a dramatic loss of permethrin knockdown effect on adults. This resistance should be taken into consideration when planning the use of pyrethroid-impregnated materials in urban areas, as Culex is by far the main source of nuisance. Any failure in nuisance control due to resistance is likely to demotivate people in using impregnated materials.     

松嫩草原典型群落植硅体碳汇

植硅体碳汇是草原碳汇的重要部分。本研究选取松嫩草原中禾本科群落、莎草科群落、菊科群落为对象,通过湿式灰化法提取植硅体,并通过碱溶分光光度法对植硅体碳量进行测定。根据植硅体含碳量估算了松嫩草原的植硅体碳封存速率,探讨了禾本科群落、莎草科群落、菊科群落植硅体碳封存能力的差异。结果表明:松嫩草原的植硅体碳封存速率为1.67 kg CO₂·hm^-2·a^-1。群落植硅体含碳量与植硅体含量之间有显著的负相关关系(P<0.05,R²=0.94)。不同群落植硅体碳封存能力存在显著的差异,群落植硅体碳封存速率分别为:莎草科群落(2.151 kg CO₂·hm^-2·a^-1)、禾本科群落(1.716 kg CO₂·hm^-2·a^-1)、菊科群落(1.218 kg CO₂·hm^-2·a^-1)。群落植硅体碳封存能力受到群落组成...     

Establishment of a General Medicine Residency Training Program in Rural West Africa

Ghana, a developing country in West Africa, has major medical burdens in taking care of a large population with limited resources. Its three medical schools produce more than 200 graduates per year, but most emigrate to developed lands after training. Ghana is working to educate and retain locally trained physicians, but it is difficult to get them to work in rural settings where the need is greatest. This article details the establishment of a General Medicine residency at a 150-bed hospital in rural Ghana. Early training comprises 6 months each in Medicine, Surgery, OB/GYN, and Pediatrics; the hospital in Techiman also has a Surgery residency. House officers choose the program for more hands-on experience than they can get in larger centers. They perform many tasks, including surgery, sooner and more independently than do residents in developed countries. The training program includes a morning report, clinical teaching rounds, and rotations on in-patient wards and in the Emergency Department and clinics. Teaching focuses on history, physical examination, good communication, and proper follow-up, with rigorous training in the OR and some clinical research projects pertinent to Ghana. Trainees work hard and learn from one another, from a dedicated faculty, and by evaluating and treating very sick patients. Ghana’s rural residencies offer rigorous and attractive training, but it is too soon to tell whether this will help stem the “brain drain” of young physicians out of West Africa.     

Impact of Climate Variability on Infectious Disease in West Africa

The importance of infectious disease as a determinant (as well as an outcome) of poverty has recently become a prominent argument for international and national investment in the control of infectious disease, as can be seen in the recently articulated United Nations (UN) Millennium Development Goals (MDGs). Climate variability and land use change have an enormous impact on health in West Africa, and may yet undermine the potential for achieving the MDGs, in certain economic-ecological zones. However, their underlying role in determining the burden of disease in the region on a yearly or decadal basis has never been systematically studied. In order to improve our understanding of the future impacts of climate change, it may be more effective to start by investigating the impact of inter-annual climate variability, and short-term shifts in climate (e.g., decadal), on disease transmission dynamics. This information may inform both current and future policy decisions with regard to prediction, prevention, and management of adverse climate-related health outcomes. This article reviews current knowledge of changes in the epidemiology of infectious diseases associated with climate variability in West Africa over the last 40 years. Selected examples are considered from bacterial (meningococcal meningitis), protozoan (malaria), and filarial (onchocerciasis and lymphatic filariasis) infections where spatial and temporal disease patterns have been directly influenced by seasonal, inter-annual, or decadal changes in climate.The views expressed herein are those of the authors and do not necessarily reflect the views of the National Oceanic and Atmospheric Administration (NOAA) or any of its sub-agencies.     

Ebola virus disease: a highly fatal infectious disease reemerging in West Africa

Ebolavirus can cause a highly fatal and panic-generating human disease which may jump from bats to other mammals and human. High viral loads in body fluids allow efficient transmission by contact. Lack of effective antivirals, vaccines and public health infrastructures in parts of Africa make it difficult to health workers to contain the outbreak.     

Disturbances in semi-arid shrubland and arid grassland in the Karoo, South Africa: mammal diggings as germination sites

Mammals (mainly aardvark Orycteropus ufer , porcupine Hystrix austro-africanae , bat-eared fox Otocyon megalotis and Cape fox Vulpes chama ) which excavate holes in hard-capped soils in Karoo shrubland and inter-dune pans create microsites where seeds, detritus and water accumulate, and seeds germinate. Holes with seedlings were significantly deeper (6.7 ± 0.4 cm) than holes without seedlings (4.5 ± 0.3 cm). In open, inter-shrub sites, significantly more seedlings germinated in diggings than on the flat soil surface, but there was no difference in the proportion of seedlings germinating under shrubs and in diggings. In inter-dune pans, 96% of all seedlings found were growing in diggings.

Résumé

Les mammifères (surtout l'oryctérope Orycreropus afer , le porcépic Hystrix austro-ajricanae , l'otocyon Otocyion megalotis , et le renard du Cap Vulpes chama ) qui creusent des trous dans les régions buissonneuses du Karoo et dans les creux entre les dunes créent des microsites où les semences, les déchets et l'eau se rassemblent, et les semences germent. Les trous où elles germent sont significativement plus profonds (6,7 ± 0,4 cm) que ceux où elles ne germent pas (4,5± 0,3 cm). Aux endroits buissonneux ouverts, il pousse plus de jeunes plantes dans des creux qu'à la surface du sol, mais il n'y a pas de différence entre les proportions de celles qui poussent sous les buissons et dans les creux. Dans les creux entre les dunes, 96% des jeunes pousses croissent dans les excavations.     

Vegetation structure and greenness in Central Africa from Modis multi-temporal data

African forests within the Congo Basin are generally mapped at a regional scale as broad-leaved evergreen forests, with the main distinction being between terra-firme and swamp forest types. At the same time, commercial forest inventories, as well as national maps, have highlighted a strong spatial heterogeneity of forest types. A detailed vegetation map generated using consistent methods is needed to inform decision makers about spatial forest organization and their relationships with environmental drivers in the context of global change. We propose a multi-temporal remotely sensed data approach to characterize vegetation types using vegetation index annual profiles. The classifications identified 22 vegetation types (six savannas, two swamp forests, 14 forest types) improving existing vegetation maps. Among forest types, we showed strong variations in stand structure and deciduousness, identifying (i) two blocks of dense evergreen forests located in the western part of the study area and in the central part on sandy soils; (ii) semi-deciduous forests are located in the Sangha River interval which has experienced past fragmentation and human activities. For all vegetation types enhanced vegetation index profiles were highly seasonal and strongly correlated to rainfall and to a lesser extent, to light regimes. These results are of importance to predict spatial variations of carbon stocks and fluxes, because evergreen/deciduous forests (i) have contrasted annual dynamics of photosynthetic activity and foliar water content and (ii) differ in community dynamics and ecosystem processes.     

Ecology of nitrogen-fixing cyanobacteria in dry tropical habitats of West Africa: A multivariate analysis

Summary Under specific conditions prevailing in dry tropical areas (high light intensities, dryness, extreme temperature change), studies of the composition and evolution of algal populations, primarily nitrogen-fixing cyanobacteria (N₂BGA), were conducted. Large scale sampling permitted interpretation using the statistical methods of principal component analysis and analysis of correspondences on the same data. On 86 stations, '49 biotic and abiotic factors were collected: the absolute and relative composition of algal communities were determined by serial dilution and physical-chemical composition of surface soil was analysed. A principal component analysis with a Bravais-Pearson matrix identified: i) four distinct algal groups in the algal communities; ii) similar algal compositions in distinct areas; iii) positive correlations between N₂BGA and pH, C, N, Ca, P, K, and sand. Factorial analysis allowed comparison between quantitative and qualitative factors (vegetal cover, fertilization, wetness, cultivation) indicating that in regard to nitrogen-fixation potential algal communities exist in three states: selective, active and accumulative. Change from one state to another depends mostly on water control. This paper was presented at the Third International Symposium on Nitrogen Fixation with Non-Legumes, Helsinki, 2–8 September 1984. See Plant and Soil 90, 1986.     

The significance of the oil palm (Elaeis guineensis Jacq.) in the late Holocene environments of west and west central Africa: A further consideration

Abundant archaeological evidence of the occurrence of the endocarp of the oil palm,Elaeis guineensis, in the rain forest and woodland savanna zones of west and central Africa from about 5000 B.P. has shown the tree to be an important element in the subsistence economy of the region; its pollen also has been recorded in most of the regional terrestrial sediments studied so far. The distinct and consistently sudden and more marked increases in this pollen during the late Holocene when compared with the late Tertiary and late Pleistocene frequencies strongly indicate that the late Holocene upsurges were due to both natural and human factors favourable for the expansion of this heliophytic tree. Reasons are given for suggesting that upsurges in oil palm pollen during the late Holocene period in this region can be used as indices of plant cultivation. While the oil palm is known from early Tertiary deposits in west Africa, its earliest palynological record from terrestrial sediments in the west central part dates back only to the early Holocene. More palynological studies of Tertiary and Quaternary terrestrial cores are required to establish with more certainty the antiquity ofE. guineensis in west central Africa.     

Fossil wood charcoal assemblages from Elands Bay Cave, South Africa: implications for Late Quaternary vegetation and climates in the winter-rainfall fynbos biome

Aim The aim of this paper is to analyse fossil charcoal deposits, largely identified to the species level and spanning a sequence from the late Holocene to < 40,000 BP , in order to reconstruct Late Quaternary vegetation and climatic patterns in the western (winter-rainfall) fynbos biome of South Africa. Location The charcoals were excavated from the Elands Bay Cave (32°19S, 18°20E) on the semiarid (200–250 mmyr^?1), winter-rainfall coastline of the western fynbos biome. Methods Patterns in the charcoal data set over time were sought by manual sorting of the charcoal×sample matrix, as well as by subjecting the data to multivariate analysis. Palaeoclimatic reconstruction was attempted by comparing the climatic controls on contemporary vegetation communities that resembled the fossil assemblages. Charcoal diversity was modelled using sample age and number of charcoal fragments as explanatory variables. Results The fossil assemblages ranged from xeric communities (similar to those presently occurring at the site) during the Holocene, to more mesic thicket and fynbos vegetation in the terminal Pleistocene, to Afromontane forest and riverine woodland communities after about 18,000 BP . Diversity of the charcoal samples increased monotonically with increasing sample age. Main conclusions The results suggest that, unlike the eastern fynbos biome, which is under fundamentally different climatic controls, soil moisture conditions in the western part of the biome were higher in the Last Glacial than during the Holocene. This scenario may help to explain the higher regional richness and associated diversification in the western than eastern part of the biome.     

Establishment of the neotropical predator Amblyseius idaeus (Acari: Phytoseiidae) in Benin,West Africa

Populations of the phytoseiid predator Amblyseius(=Neoseiulus) idaeus (Denmark & Muma) from northeastern Brazil, have been successfully introduced into Benin, West Africa, as part of a classical biological control campaign to control the exotic cassava green mite Mononychellus tanajoa (Bondar). Monthly follow‐up surveys revealed the presence of A. idaeus in most release sites. Some populations have persisted for at least 18 months, including two cycles of potentially limiting wet and dry season conditions. In some sites A. idaeus has been the numerically dominant phytoseiid predator on cassava Manihot esculenta, where it is associated with the tetranychids M. tanajoa and Oligonychus gossypii Zacher. During periods of low M. tanajoa densities A. idaeus disappeared from cassava, but were found on weeds with O. gossypii until prey densities on cassava increased.     

Nut cracking by wild chimpanzees in Sierra Leone,West Africa

I report an incidence of chimpanzee (Pan troglodytes verus) cracking ofDetarium senegalense (Caesalpiniaceae) nuts on Tiwai Island, Sierra Leone. Similar behavior has been reported from other West African locations, but not from Central or East Africa.     

Heavy Metals in Sediments of the Gold Mining Impacted Pra River Basin,Ghana, West Africa

Total concentrations of Hg, Al, Fe, As, Pb, Cu, Cr, Ni, Mn, Co, V, and Zn were determined in surface sediments collected from 21 locations within the gold mining impacted Pra River basin in southwestern Ghana. Samples were collected during both the rainy and dry seasons. We hypothesized that in the rural southwestern portion of Ghana, the lack of industrial activities makes artisanal gold mining (AGM) by Hg amalgamation the main source of water resource contamination with heavy metals. Therefore, metals showing concentration trends similar to that of Hg in the studied system are likely impacted by AGM. We found that total-Hg (THg) concentrations in riverine sediments are rather low as compared to other aquatic systems that are impacted by similar mining activities. Measured THg concentrations ranged from 0.018 to 2.917 mg/kg in samples collected in the rainy season and from about 0.01 to 0.043 mg/kg in those collected during the dry season. However, the determination of the enrichment factor (EF) calculated using shale data as reference background values showed signs of severe contamination in most of the sampled sites. In the dry season, THg concentrations correlated positively and significantly to the concentrations of As (r = 0.864, p < 0.01), Cu (r = 0.691, p < 0.05), and Ni (r = 0.579, p < 0.05). Based on our previously stated hypothesis, this could then be an indication of the impact of AGM on ambient levels of these 3 elements. However, the determined concentrations of Cu, and Ni co-varied significantly with Al, suggesting that natural sources do account for the observed levels. Accordingly, both AGM and metal inputs from weathered natural deposits are likely co-responsible for the observed levels of Cu and Ni. In contrast, the lack of correlation between As and Al tends to suggest an impact of AGM on As levels. Overall, our data suggest that besides Hg and to some extent As, the impact of AGM on ambient levels of investigated metals in the gold mining impacted Pra River remains negligible. Finally, the increase in metal concentrations from the dry to the rainy season underlines the impact of changes in hydrologic conditions on levels and fate of metals in this tropical aquatic system.     

New genera,species and records of Phaneropterinae (Orthoptera,Phaneropteridae) from sub-Saharan Africa

The results of the study of many specimens preserved in different European museums are reported. The tribe Terpnistrini Brunner von Wattenwyl, 1878 is resurrected. The distribution of the following species is enhanced: Pardalota asymmetrica Karsch, 1896, Diogena denticulata Chopard, 1954, Diogena fausta (Burmeister, 1838), Plangiopsis adeps Karsch, 1896, Poreuomena sanghensis Massa, 2013 and Tylopsis continua (Walker, 1869). Further, for their peculiar characteristics, two African representatives of the American genus Symmetropleura Brunner von Wattenwyl, 1878 are included in two new genera: Symmetrokarschia africana (Brunner von Wattenwyl, 1878), comb. n. and Symmetroraggea dirempta (Karsch, 1889), comb. n. A new genus and species from the Democratic Republic of Congo, Angustithorax spiniger gen. n., sp. n., and a new genus and species from Tanzania, Arostratum oblitum gen. n., sp. n. are described. Finally Melidia claudiae sp. n. and Atlasacris brevipennis sp. n. are described and compared with related species.