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Tropical Africa (tropical + africa)
Selected AbstractsPollen,plant,climate relationships in sub-Saharan AfricaJOURNAL OF BIOGEOGRAPHY, Issue 3 2007Julie Watrin Abstract Aim, To demonstrate that incorporating the bioclimatic range of possible contributor plants leads to improved accuracy in interpreting the palaeoclimatic record of taxonomically complex pollen types. Location, North Tropical Africa. Methods, The geographical ranges of selected African plants were extracted from the literature and geo-referenced. These plant ranges were compared with the pollen percentages obtained from a network of surface sediments. Climate-response surfaces were graphed for each pollen taxon and each corresponding plant species. Results, Several patterns can be identified, including taxa for which the pollen and plant distributions coincide, and others where the range limits diverge. Some pollen types display a reduced climate range compared with that of the corresponding plant species, due to low pollen production and/or dispersal. For other taxa, corresponding to high pollen producers such as pioneer taxa, pollen types display a larger climatic envelope than that of the corresponding plants. The number of species contained in a pollen taxon is an important factor, as the botanical species included in a taxon may have different geographical and climate distributions. Main conclusions, The comparison between pollen and plant distributions is an essential step towards more precise vegetation and climate reconstructions in Africa, as it identifies taxa that have a high correspondence between pollen and plant distribution patterns. Our method is a useful tool to reassess biome reconstructions in Africa and to characterize accurately the vegetation and climate conditions at a regional scale, from pollen data. [source] DIVERSIFICATION OF THE AFRICAN GENUS PROTEA (PROTEACEAE) IN THE CAPE BIODIVERSITY HOTSPOT AND BEYOND: EQUAL RATES IN DIFFERENT BIOMESEVOLUTION, Issue 3 2010Luis M. Valente The Cape region of South Africa is a hotspot of flowering plant biodiversity. However, the reasons why levels of diversity and endemism are so high remain obscure. Here, we reconstructed phylogenetic relationships among species in the genus Protea, which has its center of species richness and endemism in the Cape, but also extends through tropical Africa as far as Eritrea and Angola. Contrary to previous views, the Cape is identified as the ancestral area for the radiation of the extant lineages: most species in subtropical and tropical Africa are derived from a single invasion of that region. Moreover, diversification rates have been similar within and outside the Cape region. Migration out of the Cape has opened up vast areas, but those lineages have not diversified as extensively at fine spatial scales as lineages in the Cape. Therefore, higher net rates of diversification do not explain the high diversity and endemism of Protea in the Cape. Instead, understanding why the Cape is so diverse requires an explanation for how Cape species are able to diverge and persist at such small spatial scales. [source] The mechanisms of resistance to antimalarial drugs in Plasmodium falciparumFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 2 2003Jacques Le Bras Abstract Drug-resistant malaria is primarily caused by Plasmodium falciparum, a species highly prevalent in tropical Africa, the Amazon region and South-east Asia. It causes severe fever or anaemia that leads to more than a million deaths each year. The emergence of chloroquine resistance has been associated with a dramatic increase in malaria mortality among inhabitants of some endemic regions. The rationale for chemoprophylaxis is weakening as multiple-drug resistance develops against well-tolerated drugs. Plasmodium falciparum drug-resistant malaria originates from chromosome mutations. Analysis by molecular, genetic and biochemical approaches has shown that (i) impaired chloroquine uptake by the parasite vacuole is a common characteristic of resistant strains, and this phenotype is correlated with mutations of the Pfmdr1, Pfcg2 and Pfcrt genes; (ii) one to four point mutations of dihydrofolate reductase (DHFR), the enzyme target of antifolates (pyrimethamine and proguanil) produce a moderate to high level of resistance to these drugs; (iii) the mechanism of resistance to sulfonamides and sulfones involves mutations of dihydropteroate synthase (DHPS), their enzyme target; (iv) treatment with sulphadoxine,pyrimethamine selects for DHFR variants Ile(51), Arg(59), and Asn(108) and for DHPS variants Ser(436), Gly(437), and Glu(540); (v) clones that were resistant to some traditional antimalarial agents acquire resistance to new ones at a high frequency (accelerated resistance to multiple drugs, ARMD). The mechanisms of resistance for amino-alcohols (quinine, mefloquine and halofantrine) are still unclear. Epidemiological studies have established that the frequency of chloroquine resistant mutants varies among isolated parasite populations, while resistance to antifolates is highly prevalent in most malarial endemic countries. Established and strong drug pressure combined with low antiparasitic immunity probably explains the multidrug-resistance encountered in the forests of South-east Asia and South America. In Africa, frequent genetic recombinations in Plasmodium originate from a high level of malaria transmission, and falciparum chloroquine-resistant prevalence seems to stabilize at the same level as chloroquine-sensitive malaria. Nevertheless, resistance levels may differ according to place and time. In vivo and in vitro tests do not provide an adequate accurate map of resistance. Biochemical tools at a low cost are urgently needed for prospective monitoring of resistance. [source] When and where to fuel before crossing the Sahara desert , extended stopover and migratory fuelling in first-year garden warblers Sylvia borinJOURNAL OF AVIAN BIOLOGY, Issue 2 2008Thord Fransson Large numbers of passerine migrants cross the Sahara desert every year on their way to-and-from wintering areas in tropical Africa. In the desert, hardly any fuelling opportunities exist and most migrants have to prepare in advance. A central question is how inexperienced birds know where to fuel. Inexperienced garden warblers Sylvia borin were studied in Greece just before the desert crossing in autumn. Body mass data collected at two sites indicate that most birds do not fuel for the desert crossing further north. For the first time, detailed information about stopover duration close to the Sahara desert was studied by using light weight radio-transmitters. Results from Crete show that most first-year garden warblers arrive with relatively small fuel loads in relation to lean body mass (<30%), stay for 13,20 d and depart with an average fuel load of about 100%. Radio-tagged birds performed small scale movements initially and took advantage of fig fruits. Birds trapped at fig trees were heavier than birds trapped with tape lures, showing that tape lures can bias the sample of migrants trapped. The precise fuelling pattern found indicates that first-year migrants must also include external spatial cues to make the preparation for crossing the desert in the right area. [source] ORIGINAL ARTICLE: Freshwater paths across the ocean: molecular phylogeny of the frog Ptychadena newtoni gives insights into amphibian colonization of oceanic islandsJOURNAL OF BIOGEOGRAPHY, Issue 1 2007G. John Measey Abstract Aim, Amphibians are a model group for studies of the biogeographical origins of salt-intolerant taxa on oceanic islands. We used the Gulf of Guinea islands to explore the biogeographical origins of island endemism of one species of frog, and used this to gain insights into potential colonization mechanisms. Location, São Tomé and Príncipe, two of the four major islands in the Gulf of Guinea, West Africa, are truly oceanic and have an exceptionally high biodiversity. Methods, Mitochondrial DNA is used to test the endemic status of a frog from São Tomé and compare it with congeneric taxa from tropical Africa. Existing data on surface currents, surface salinity, atmospheric circulation and bird migration in the Gulf of Guinea are summarized to address hypotheses concerning colonization mechanisms. Results, The endemic status of Ptychadena newtoni (Bocage) is supported here by mitochondrial DNA sequences, and analysis of this and other molecular data indicates that an East African species close to Ptychadena mascareniensis (Duméril and Bibron) is its nearest relative. We refute the possibility that this population was anthropogenically introduced, in favour of a natural dispersal mechanism. Main conclusions, With six endemic frogs and one caecilian, the Gulf of Guinea islands harbour a diverse amphibian fauna. Five of these species appear to have their closest relatives in East Africa. Insufficient evidence exists for transportation by storms, birds or rafts alone. However, we propose a synergy of rafting, favourable surface currents and a reduction in salinity of surface waters. Catastrophic events, or wet periods in climatic history, could allow freshwater paths to open far enough to enable continental flora and fauna to reach these and other isolated oceanic islands. [source] Plant diversity and endemism in sub-Saharan tropical AfricaJOURNAL OF BIOGEOGRAPHY, Issue 2 2001Linder Aim This paper has as its central aim the location of centres of species richness and endemism in the sub-Saharan African flora. Previous postulation of these centres has been based on an intuitive interpretation of distributional data; this paper provides a test of these centres. A second aim is to establish whether the two indices, richness and endemism, locate the same centres. Thirdly the relationship between species richness and endemism, and latitude and rainfall are explored. Location The study area includes much of sub-Saharan Africa, but excludes the species-poor southern margin of the Sahara and the Namib,Kalahari regions. Methods Analyses were based on 1818 species, scored on a 2.5 × 2.5 degree grid. Species richness was inferred from a simple grid-diversity count; endemism was determined by three measures: the number of species restricted to two grids, the sum of the inverse of the ranges of the component species of each grid, and the proportion of the species in each grid that have restricted ranges. Results The African flora shows a remarkably profound patterning, both in species richness and endemism. The two measures locate largely the same centres, although the rank order among them differs. These centres are: the Cape Floristic Region, East Coast, Congo-Zambezi watershed, Kivu, Upper and Lower Guinea. Richness is strongly related to maximum rainfall, but there are no obvious correlations between modern climate and endemism. Species richness and endemism north of the equator is much more concentrated into centres than south of the equator. Main conclusions There are strongly developed refugia in sub-Saharan Africa. North of the equator, these refugia are sharply delimited and rather small, separated by large areas of very low endemism. South of the equator endemism tends to be more generally distributed. Variation in species richness in sub-Saharan Africa can be explained largely by modern rainfall, while endemism may be related to palaeoclimatic fluctuations. Both species richness and endemism show a strong skewing towards the south, indicating that the fluctuations in the Sahara might have influenced the modern distribution of plants in Africa. [source] Environment and host-plant genotype effects on the seasonal dynamics of a predatory mite on cassava in sub-humid tropical AfricaAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2009Christine Zundel Abstract 1,In tropical dry seasons, survival of small arthropods such as predatory mites is often negatively affected by low relative humidity (RH). For species that do not diapause or migrate to refuges, the ability of the habitat to mitigate climatic conditions becomes crucial. 2,The relative effect of macro-habitat (dry grassland hill, humid multiple cropping area, humid riparian forest) and microhabitat (host-plant genotypes with hairy, semi-hairy and glabrous apices) on the seasonal dynamics of the phytoseiid mite Typhlodromalus aripo, a predator of Mononychellus tanajoa on cassava, was examined in a field experiment during a dry season. The effect of RH and plant genotype on T. aripo egg survival was determined in an environment control chamber. 3,Predator abundance was higher in humid multiple cropping areas and on hairy cassava compared with the other habitat types and cassava genotypes. 4,Discriminant and regression analyses showed that the predator's dry season persistence was related to high RH, high plant vigour and hairy apices, but not to prey abundance. 5,In the controlled climate experiment, the effect of host-plant morphology was evident only at the intermediate RH level of 55%. An effect of apex hairiness was not found. 6,It is concluded that the effect of genotype on T. aripo persistence diminishes under low RH conditions, and that supportive effects of apex hairs become effective only in the field, probably through protection from wind and/or intraguild predation. Humid multiple cropping areas planted with hairy and vigorous cassava genotypes are suitable dry season reservoirs for T. aripo. [source] Rising African cassava production, diseases due to high cyanide intake and control measuresJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 12 2008Dulce Nhassico Abstract Cassava is the staple food of tropical Africa and its production, averaged over 24 countries, has increased more than threefold from 1980 to 2005, and the population has more than doubled over that time compared with a 1.5 times increase worldwide. Agriculturally, cassava performs very well but the roots and leaves contain cyanogenic glucosides that are dangerous to human health. These cyanogens sometimes produce acute intoxication leading to death, they exacerbate goitre and cretinism in iodine-deficient regions, cause konzo and are implicated in the occurrence of tropical ataxic neuropathy and stunting of children. Konzo is an irreversible paralysis of the legs with many thousands of cases, mainly amongst children, in Mozambique, Tanzania, Democratic Republic of Congo, Cameroon, Central African Republic and probably other tropical African countries. Attempts to alleviate cassava cyanide toxicity have included the development of an information network and distribution in developing countries of picrate kits, which measure total cyanide in cassava and urinary thiocyanate. A simple wetting method that reduces total cyanide in cassava flour three- to sixfold has been successfully field tested and is being introduced in Mozambique. Transgenic technology shows promise in increasing the rate of loss of cyanide from roots during processing. World health and agricultural bodies should pay more attention to emerging health problems associated with toxicity of cyanogens in cassava. Copyright © 2008 Society of Chemical Industry [source] The Efficacy of Chemoprophylaxis against Malaria with Chloroquine plus Proguanil, Mefloquine, and Atovaquone plus Proguanil in Travelers from DenmarkJOURNAL OF TRAVEL MEDICINE, Issue 3 2003Kristian Kofoed Background The risk of malaria infection in travelers is seldom known in detail and neither is the efficacy of different prophylactic regimens, due to a lack of controlled trials. Surveillance of malaria diagnosed after return can provide data on risk and efficacy. Methods An open case-control study was initiated. Imported cases were notified to our department and were studied in 320 permanent residents in Denmark, returning from abroad with malaria from 1997 to 1999. These were compared with a group of 600 travelers who were not infected with malaria and matched by age, sex, and destination. Information on the use of chemoprophylaxis and the length of stay in malarious areas were obtained by questionnaire. Results Two hundred cases of Plasmodium falciparum malaria were notified of which 103 had used chloroquine and proguanil, 16 mefloquine, and 3 atovaquone and proguanil as prophylaxis, whereas the rest had taken other drugs or no prophylaxis. This study showed that the risk increased with increasing exposure and that compliance was lower especially for mefloquine users in malaria cases compared with controls. The study provided the first comprehensive data on the use of atovaquone/proguanil to travelers. The estimated efficacy of chloroquine and proguanil, mefloquine, and atovaquone and proguanil in fully compliant users was 1:599, 1:2,232, and 1:1,943, respectively, P. falciparum cases per prescription. The country specific risk data showed that the risk of getting malaria varied from 1 per 140 travelers to Ghana to almost 1 per 40,000 to Thailand, providing data that allow the use of prophylaxis to be restricted to high-risk areas. Conclusion There was a considerable variation in risk between the countries with the highest risk in tropical Africa. Chloroquine and proguanil was less efficient compared with mefloquine. Atovaquone/proguanil (Malarone) was at least as efficient as mefloquine, but breakthroughs were observed. [source] Contributions of Anopheles larval control to malaria suppression in tropical Africa: review of achievements and potentialMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2007K. WALKER Abstract Malaria vector control targeting the larval stages of mosquitoes was applied successfully against many species of Anopheles (Diptera: Culicidae) in malarious countries until the mid-20th Century. Since the introduction of DDT in the 1940s and the associated development of indoor residual spraying (IRS), which usually has a more powerful impact than larval control on vectorial capacity, the focus of malaria prevention programmes has shifted to the control of adult vectors. In the Afrotropical Region, where malaria is transmitted mainly by Anopheles funestus Giles and members of the Anopheles gambiae Giles complex, gaps in information on larval ecology and the ability of An. gambiae sensu lato to exploit a wide variety of larval habitats have discouraged efforts to develop and implement larval control strategies. Opportunities to complement adulticiding with other components of integrated vector management, along with concerns about insecticide resistance, environmental impacts, rising costs of IRS and logistical constraints, have stimulated renewed interest in larval control of malaria vectors. Techniques include environmental management, involving the temporary or permanent removal of anopheline larval habitats, as well as larviciding with chemical or biological agents. This present review covers large-scale trials of anopheline larval control methods, focusing on field studies in Africa conducted within the past 15 years. Although such studies are limited in number and scope, their results suggest that targeting larvae, particularly in human-made habitats, can significantly reduce malaria transmission in appropriate settings. These approaches are especially suitable for urban areas, where larval habitats are limited, particularly when applied in conjunction with IRS and other adulticidal measures, such as the use of insecticide treated bednets. [source] Systematics and phylogeny of the Asclerosibutia -group of genera (Coleoptera, Oedemeridae), with description of a new genus and seven new species from tropical AfricaMITTEILUNGEN AUS DEM MUSEUM FUER NATURKUNDE IN BERLIN-DEUTSCHE ENTOMOLOGISCHE ZEITSCHRIFT, Issue 1 2004Xavier A. Vázquez Abstract The phylogenetic relationships of the Asclerosibutia-group are studied, based on the examination of the type species of all genera previously described. The phylogenetic hypothesis supports that the Asclerosibutia-group is a monophyletic assemblage. On the base of the cladistic analysis, three genera can be recognized, i.e., Idgiomimula Blair, 1926, gen. rediv., Monosigynes gen. n. and Asclerosibutia Pic, 1914, with the following relationships: Idgiomimula (Monosigynes (Asclerosibutia)). Seven new species are described: Idgiomimula uhligi sp. n., Monosigynes difformis sp. n., Monosigynes marci sp. n., Monosigynes zarazagai sp. n., Monosigynes sphyrninus sp. n., Asclerosibutia girardi sp. n. and Asclerosibutia beardae sp. n. Danerces semipicea Karsch. 1881. Microsessinia notatipennis Pic, 1922, Microsessinia rufithorax Pic, 1958, are transferred to the genus Monosigynes. Microsessinia cyanescens Pic, 1922 is transferred to Asclerosibutia and Asclerosibutia terminalis Blair, 1926 is transferred to Idgiomimula. The following new synonyms are established: Microsessinia Pic, 1922 (= Asclerosibutia Pic, 1914), Microsessinia notatipennis var. atrimembris Pic, 1935 (= Monosigynes notatipennis (Pic, 1922)), Asclerosibutia gabonica Pic, 1914. Nacerdes latenigra Pic, 1922, Asclerosibutia lineaticollis var. rufipennis Blair, 1926, Asclerosibutia reducta Pic, 1930, Asclerosibutia divisa Pic. 1952, Asclerosibutia lineaticollis var. ealensis Pic, 1952 (all synonyms of Asclerosibutia lineaticollis Pic, 1914). and Asclerosibutia abdominalis Blair, 1926 (= Asclerosibutia marshalli Blair, 1926). Keys to the genera and species are given. All descriptions are accompanied by male and female genital illustrations. Lectotypes for the following species are designated: Monosigynes rufithorax Pic, 1958, Asclerosibutia violacea Blair, 1926, and Asclerosibutia lineaticollis var. rufipennis Blair. 1926. [source] Screening for glucose-6-phosphate dehydrogenase deficiency using a modified formazan method: A pilot study on Filipino male newbornsPEDIATRICS INTERNATIONAL, Issue 1 2003CARMENCITA PADILLA AbstractBackground: Glucose-6-phosphate dehydrogenase (G6PD) deficiency has increased prevalence rates in tropical Africa, tropical and subtropical Asia and some parts of the Mediterranean. Earlier studies on G6PD deficiency in the Philippines have shown prevalence rates of 4.5% to 25.7%. Methods: In the present study, 3278 male newborns were screened for G6PD deficiency using the modified formazan method, a simple screening procedure affordable in the setting of a developing country. Subjects with positive screening results were recalled for confirmatory testing using a commercial assay kit for quantitative enzyme determination. Results: Of the 3278 boys studied, 186 revealed positive screening results. Of the 186, 65 boys had confirmatory testing. Of these 65 boys, 45 were confirmed to have G6PD deficiency and 20 had normal results. This study reveals an incidence of G6PD deficiency of 3.9% among male Filipinos. Conclusion: This study recommends the inclusion of G6PD deficiency in the panel of disorders for newborn screening among Filipino newborns. [source] The evolutionary ecology of detritus feeding in the larvae of freshwater DipteraBIOLOGICAL REVIEWS, Issue 1 2009Athol J. McLachlan Abstract Detritus (dead organic matter), largely of terrestrial origin, is superabundant in inland waters but because of its indigestible nature, would appear to be a poor food source for animals. Yet this unpromising material is widely used as food and indeed can be viewed as a defining characteristic of the freshwater environment. We here explore the relationships among animals, detritus and its associated micro-organism decomposers, taking a functional approach. We pose questions about interrelationships and attempt to arrive at new insights by disentangling them from an adaptive point of view. To do this we have been careful in selecting the habitats for detailed consideration. Rain pools on rock surfaces in tropical Africa and pools on peat moorland in the UK were chosen. Both examples have a relatively simple community structure and hence offer the prospect of achieving our aim. As model organisms for study we focus principally on the aquatic stages of selected holometabolous insects; that is, selected genera of the universally common midges, Ceratopogonidae and Chironomidae. We approach these case studies from an evolutionary ecology perspective and see detritus as a simple template upon which a beautiful complex of adaptations can evolve. [source] Morphological data indicates two major clades of the subtribe Gorteriinae (Asteraceae-Arctotideae)CLADISTICS, Issue 3 2006Per Ola Karis The phylogeny of subtribe Gorteriinae (Asteraceae-Arctotideae) is investigated by means of cladistic analysis of morphological characters. Two sister groups are formed, namely a Gorteria clade also containing Hirpicium and Gazania, and a Berkheya clade, which also contains Cullumia, Cuspidia, Didelta and Heterorhachis. The Gorteria clade has strong jackknife support and is diagnosed by four morphological characters (leaves with longitudinally striate hairs, fringed anther apical appendages, pollen of the "Gazania -type", and subulate-ensiform, ascending style sweeping hairs) that are unique within the Asteraceae. The Berkheya clade is moderately supported and diagnosed by two characters without contradiction (spiny leaves, and mamillate, large style sweeping hairs). Hirpicium and Berkheya are paraphyletic, with the other, morphologically more homogeneous genera (Gorteria, and Gazania, Cullumia, Cuspidia, Didelta and Heterorhachis, respectively) nested within them. There is some evidence for a radiation of species of the summer rainfall area of South Africa and tropical Africa and the corresponding species are nested within a grade confined to the Cape Floristic Region. © The Willi Hennig Society 2006. [source] | ||||||||||||||||||||||