scholarly journals Estimating the abundance of duiker (Cephalophus spp.) populations in African rainforests: an overview of relevant methods

2019 ◽  
Author(s):  
Gaius Bolumbu Entanga Elenga ◽  
Jean-Michel Gaillard ◽  
Dieudonné Eyul’Anki Musibono ◽  
Séraphin Ndey Bibula Ifuta ◽  
Christophe Bonenfant
Keyword(s):  
Nous Avons ◽  
Large Scale ◽  
Distance Sampling ◽  
Central Africa ◽  
Biological Information ◽  
Population Abundance ◽  
Large Herbivores ◽  
Afrique Centrale ◽  
Implementation Costs ◽  
Funding Information

AbstractDuikers are among the most sought after antelope species for bush meat in central Africa. Estimates of population abundance of duikers based on reliable methods is therefore of prime importance for their sustainable management. Here we retrieved 31 studies from the literature and compared methods used to estimate the abundance of duiker populations in African rainforests. Implemented methods all derived from seven main combinations of sampling designs and population abundance estimators. We then evaluated the relevance of those seven methods by scoring them based on eight criteria selected according to their pros and cons reported in the litterature for large-scale population management of wildlife. For management purposes, methods derived from distance sampling offer the best compromise between the implementation costs and the biological information collected. In particular, both diurnal and nocturnal distance sampling can be recommended. Hunter calls and drive-netting are less reliable, but can be used in association with other measurements in the framework of indicators of ecological changes, a monitoring approach that has been successfully used in temperate ecosystems for managing large herbivores.Funding informationMinistère de l’Environnement et du Développement Durable de la République Démocratique du Congo, Campus France and Centre National de la Recherche Scientifique (CNRS).RésuméLes céphalophes sont parmi les espèces d’antilopes les plus recherchées pour la viande de brousse en Afrique centrale. L’estimation de l’abondance des populations de céphalophes revêt donc une importance primordiale pour leur gestion durable et adaptative. Nous avons extrait 31 études de la littérature et comparé les méthodes utilisées pour estimer l’abondance des populations de céphalophes dans les forêts tropicales africaines. Les méthodes employées dérivent de sept combinaisons principales de plans d’échantillonnage et d’estimateurs d’abondance. Nous avons évalué la pertinence de ces sept méthodes sur la base de critères sélectionnés en fonction de leurs avantages et inconvénients pour une gestion à grande échelle de la population. Les méthodes dérivées de l’échantillonnage par distance offrent le meilleur compromis entre les coûts de mise en œuvre et les informations biologiques collectées. Les méthodes d’échantillonnage diurne et nocturne se sont montrées les plus satisfaisantes. Les méthodes d’appel par les chasseurs et de battue au filet sont moins fiables, mais peuvent être utilisées en association avec d’autres mesures biologiques comme indicateurs de changements écologiques, une approche qui a été utilisée avec succès dans les écosystèmes tempérés pour la gestion des grands herbivores.Mots-clés:gestion durable, grands herbivores, indicateurs de changement écologique, méthode de recensement, viande de brousse

Regional integration and free movement in Central Africa Integración regional y libre circulación en África Central L'intégration régionale et la libre circulation en Afrique centrale

2013 ◽  
Vol 3 (3) ◽  
pp. 123-140 ◽  
Author(s):  
Guy Marcel Nono
Keyword(s):  
Social Policy ◽  
Regional Integration ◽  
Central Africa ◽  
Regional Level ◽  
Free Movement ◽  
African Union ◽  
Colonial History ◽  
Political Debate ◽  
Politique Sociale ◽  
Afrique Centrale

A pillar of African emergence and an important issue of political debate that is central to regional integration, free movement is however not yet acquired in Central Africa. Yet a glance at the pre colonial history invites us to believe that Central Africa has been an area of free movement. The recognition of a right that cannot be realized only by an agreement leads to the Central African states pledging to work together in the context of regional integration by recognizing their citizens' right to full mobility. This contribution highlights the efforts, challenges and prospects of free movement in Central Africa by reference to the African Union framework, and asks if the legal and institutional framework of free movement in Central Africa has led to the emergence of a social policy supportive of free movement at the sub regional level. Spanish La libre circulación de personas es un pilar del África emergente, un tema importante en el debate político, un punto central de la integración regional, y sin embargo todavía intangible en África Central. No obstante, una mirada a la historia precolonial nos invita a pensar que África Central ha sido un espacio de libre circulación. El reconocimiento de un derecho que no puede realizarse sólo por un acuerdo, conduce a que los Estados de África Central se comprometan a trabajar juntos en el marco de la integración regional para reconocer el derecho de sus ciudadanos a la movilidad total. Esta contribución destaca los esfuerzos, desafíos y perspectivas de la libre circulación en África Central en referencia con el marco de la Unión Africana, y se pregunta si el marco legal e institucional de la libre circulación en África Central ha llevado a la aparición de una política social que apoye la libre circulación a nivel subregional. French Pilier de l'émergence de l'Afrique, enjeu des débats politiques et de l'intégration, la libre circulation n'est pas encore un acquis en Afrique Centrale. Pourtant, un regard porté sur l'histoire précoloniale nous invite à croire que l'Afrique centrale a été un espace de libre circulation. La reconnaissance d'un droit ne pouvant se faire que par l'objet d'un accord, les États d'Afrique Centrale se sont engagés dans le choix d'une histoire à réaliser ensemble dans le cadre de l'intégration, en consacrant dans des pactes communautaires la pleine mobilité de leurs ressortissants. Cette contribution met en évidence les efforts, défis et perspectives de la libre circulation en Afrique centrale par référence au cadre de l'Union africaine, et pose la question de savoir si le cadre juridique et institutionnel de la libre circulation en Afrique centrale a conduit à l'émergence d'une politique sociale en faveur de la libre circulation au niveau sous régional.

scholarly journals Within-Season Changes in Land-Use Impact Pest Abundance in Smallholder African Cassava Production Systems

Insects ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 269 ◽  
Author(s):  
Andrew Kalyebi ◽  
Sarina Macfadyen ◽  
Andrew Hulthen ◽  
Patrick Ocitti ◽  
Frances Jacomb ◽  
...  
Keyword(s):  
Land Use ◽  
Bemisia Tabaci ◽  
Large Scale ◽  
Production Systems ◽  
Smallholder Farmers ◽  
Negative Relationship ◽  
Central Africa ◽  
Sub Saharan Africa ◽  
Smallholder Farming ◽  
Manihot Esculenta Crantz

Cassava (Manihot esculenta Crantz), an important commercial and food security crop in East and Central Africa, continues to be adversely affected by the whitefly Bemisia tabaci. In Uganda, changes in smallholder farming landscapes due to crop rotations can impact pest populations but how these changes affect pest outbreak risk is unknown. We investigated how seasonal changes in land-use have affected B. tabaci population dynamics and its parasitoids. We used a large-scale field experiment to standardize the focal field in terms of cassava age and cultivar, then measured how Bemisia populations responded to surrounding land-use change. Bemisia tabaci Sub-Saharan Africa 1 (SSA1) was identified using molecular diagnostics as the most prevalent species and the same species was also found on surrounding soybean, groundnut, and sesame crops. We found that an increase in the area of cassava in the 3–7-month age range in the landscape resulted in an increase in the abundance of the B. tabaci SSA1 on cassava. There was a negative relationship between the extent of non-crop vegetation in the landscape and parasitism of nymphs suggesting that these parasitoids do not rely on resources in the non-crop patches. The highest abundance of B. tabaci SSA1 nymphs in cassava fields occurred at times when landscapes had large areas of weeds, low to moderate areas of maize, and low areas of banana. Our results can guide the development of land-use strategies that smallholder farmers can employ to manage these pests.

Multinational Enterprises and the Globalization of Medicine: Siemens and the Business of X-ray Equipment in Non-Western Markets, 1900–1939

2014 ◽  
Vol 15 (4) ◽  
pp. 820-848
Author(s):  
Pierre-Yves Donzé
Keyword(s):  
International Organizations ◽  
Multinational Enterprises ◽  
Large Scale ◽  
Multinational Enterprise ◽  
Central Africa ◽  
Great Difficulty ◽  
X Ray ◽  
Hospital Development ◽  
Slight Growth ◽  
The 19Th Century

Whereas the globalization of medicine since the middle of the 19th century has primarily been approached as the sociopolitical and cultural outcome of imperialism, this article argues that Western big business also played a major role through the worldwide export of standardized medical technologies. It focuses on the expansion of Siemens on the X-ray equipment market in non-Western countries during the first half of the twentieth century. This German multinational enterprise experienced slight growth from the mid-1920s onwards but relied mainly on two markets (Argentina and Brazil). It specialized in providing large-scale equipment to a few urban hospitals and engaged during the 1930s in large-scale hospital development together with local authorities and international organizations in various countries (China, Peru, and Central Africa). However, Siemens had great difficulty in expanding its business to include private doctors and inland outlets, where it faced intense competition from other Western X-ray producers. This paper emphasizes that this shortcoming stemmed from a direct application of the European strategy (high-quality, expensive equipment for hospitals) to non-Western markets, where health systems differed.

Large-Scale Movements of Large Herbivores Livestock following changes in seasonal forage supply

2008 ◽  
pp. 187-206 ◽  
Author(s):  
Randall B. Boone ◽  
Shauna B. Burnsilver ◽  
Jeffrey S. Worden ◽  
Kathleen A. Galvin ◽  
N. Thompson Hobbs
Keyword(s):  
Large Scale ◽  
Large Herbivores

scholarly journals Assessing the measurement transfer function of single-cell RNA sequencing

2016 ◽  
Author(s):  
Hannah R. Dueck ◽  
Rizi Ai ◽  
Adrian Camarena ◽  
Bo Ding ◽  
Reymundo Dominguez ◽  
...  
Keyword(s):  
Transfer Function ◽  
Single Cell ◽  
Rna Sequencing ◽  
Large Scale ◽  
Transfer Functions ◽  
Single Cells ◽  
Biological Information ◽  
Gene Detection ◽  
Single Cell Rna Sequencing ◽  
Scale Control

AbstractRecently, measurement of RNA at single cell resolution has yielded surprising insights. Methods for single-cell RNA sequencing (scRNA-seq) have received considerable attention, but the broad reliability of single cell methods and the factors governing their performance are still poorly known. Here, we conducted a large-scale control experiment to assess the transfer function of three scRNA-seq methods and factors modulating the function. All three methods detected greater than 70% of the expected number of genes and had a 50% probability of detecting genes with abundance greater than 2 to 4 molecules. Despite the small number of molecules, sequencing depth significantly affected gene detection. While biases in detection and quantification were qualitatively similar across methods, the degree of bias differed, consistent with differences in molecular protocol. Measurement reliability increased with expression level for all methods and we conservatively estimate the measurement transfer functions to be linear above ~5-10 molecules. Based on these extensive control studies, we propose that RNA-seq of single cells has come of age, yielding quantitative biological information.

A multifrequency method to classify and evaluate fisheries acoustics data

2006 ◽  
Vol 63 (10) ◽  
pp. 2225-2235 ◽  
Author(s):  
J Michael Jech ◽  
William L Michaels
Keyword(s):  
Clupea Harengus ◽  
Biological Information ◽  
Classification Algorithms ◽  
Atlantic Herring ◽  
Population Abundance ◽  
Acoustic Data ◽  
Video Images ◽  
Abundance Estimates ◽  
Fisheries Acoustics ◽  
Acoustic Surveys

Acoustic surveys have been conducted on Georges Bank from 1998 to present to estimate Atlantic herring (Clupea harengus) population abundance. Acoustic data were collected with a 12 or 18, 38, and 120 kHz Simrad EK500 scientific echo sounder. A pelagic trawl and underwater video images were used to collect biological information and to verify the species composition of acoustic backscatter. A multifrequency classification method was developed to improve the efficiency and accuracy of classifying species from acoustic echograms. In this method, a volume backscatter (Sv) threshold was applied equivalently to all echograms, and then a composite echogram was created based on which frequencies had Sv greater than or less than the Sv threshold. The results of this method were compared with the standard method of visually scrutinizing regions, and metrics were developed to evaluate the accuracy of classification algorithms relative to current methods, as well as to assess the effects of classification methods on population abundance estimates. In general, this method matched visually scrutinized Atlantic herring regions, but with consistent biases in classifying 38 kHz backscatter. The metrics highlighted spatial and temporal changes in the acoustic landscape, which may be indicative of intra- and inter-annual biological changes.

The Origin, Formation and Early History of the Chikunda of South Central Africa

1972 ◽  
Vol 13 (3) ◽  
pp. 443-461 ◽  
Author(s):  
Allen Isaacman
Keyword(s):  
Nineteenth Century ◽  
Historical Linguistic ◽  
Cultural Differences ◽  
Ethnic Groups ◽  
Large Scale ◽  
Central Africa ◽  
Military History ◽  
Early History ◽  
South Central ◽  
History Of

Although historians have examined the process of pre-colonial political integration, little attention has been paid to the complementary patterns of ethnic and cultural assimilation. The Chikunda, who were initially slaves on the Zambezi prazos, provide an excellent example of this phenomenon. Over the course of several generations, captives from more than twenty ethnic groups submerged their historical, linguistic, and cultural differences to develop a new set of institutions and a common identity. The decline of the prazo system during the first half of the nineteenth century generated large scale migrations of Chikunda outside of the lower Zambezi valley. They settled in Zumbo, the Luangwa valley and scattered regions of Malawi where they played an important role in the nineteenth-century political and military history of south central Africa.

scholarly journals NETWORKS FROM GENE EXPRESSION TIME SERIES: CHARACTERIZATION OF CORRELATION PATTERNS

2007 ◽  
Vol 17 (07) ◽  
pp. 2477-2483 ◽  
Author(s):  
D. REMONDINI ◽  
N. NERETTI ◽  
C. FRANCESCHI ◽  
P. TIERI ◽  
J. M. SEDIVY ◽  
...  
Keyword(s):  
Gene Expression ◽  
Time Series ◽  
Large Scale ◽  
Molecular Mechanisms ◽  
Single Gene ◽  
Biological Information ◽  
Reconstruction Method ◽  
Gene Expression Time Series ◽  
Expression Time

We address the problem of finding large-scale functional and structural relationships between genes, given a time series of gene expression data, namely mRNA concentration values measured from genetically engineered rat fibroblasts cell lines responding to conditional cMyc proto-oncogene activation. We show how it is possible to retrieve suitable information about molecular mechanisms governing the cell response to conditional perturbations. This task is complex because typical high-throughput genomics experiments are performed with high number of probesets (103–104 genes) and a limited number of observations (< 102 time points). In this paper, we develop a deepest analysis of our previous work [Remondini et al., 2005] in which we characterized some of the main features of a gene-gene interaction network reconstructed from temporal correlation of gene expression time series. One first advancement is based on the comparison of the reconstructed network with networks obtained from randomly generated data, in order to characterize which features retrieve real biological information, and which are instead due to the characteristics of the network reconstruction method. The second and perhaps more relevant advancement is the characterization of the global change in co-expression pattern following cMyc activation as compared to a basal unperturbed state. We propose an analogy with a physical system in a critical state close to a phase transition (e.g. Potts ferromagnet), since the cell responds to the stimulus with high susceptibility, such that a single gene activation propagates to almost the entire genome. Our result is relative to temporal properties of gene network dynamics, and there are experimental evidence that this can be related to spatial properties regarding the global organization of chromatine structure [Knoepfler et al., 2006].

Spatial distribution of Serengeti wildebeest in relation to resources

1999 ◽  
Vol 77 (8) ◽  
pp. 1223-1232 ◽  
Author(s):  
John F Wilmshurst ◽  
John M Fryxell ◽  
Brian P Farm ◽  
ARE Sinclair ◽  
Chris P Henschel
Keyword(s):  
Spatial Distribution ◽  
Energy Intake ◽  
Large Scale ◽  
Spatial Scales ◽  
Mechanistic Model ◽  
Large Herbivores ◽  
Serengeti Ecosystem ◽  
Dry Seasons ◽  
Behavioural Factors ◽  
Wet And Dry Seasons

We investigated the spatial distribution of radio-marked wildebeest (Connochaetes taurinus) in the Serengeti ecosystem in relation to the distribution of their food resources, comparing patterns in the wet and dry seasons and at local and landscape spatial scales. A mechanistic model of ruminant energy optimization predicted that wildebeest should maximize energy intake on swards 3 cm high and maintain energy balance on swards between 3 and 10 cm high. At the ecosystem scale, wildebeest preferred short and intermediate-height grass of moderate greenness during both the wet and dry seasons. This was consistent with the model prediction which suggests that large-scale movements by wildebeest are motivated, at least partially, by an energy-maximizing strategy. At the local scale, however, wildebeest showed spatial selectivity only on the basis of grass greenness, not on grass height. This differed from model expectations and may have resulted from wildebeest exploiting ephemeral green flushes of grass caused by localized rainfall in their movement radius. According to these results, the influence of other nutritional or behavioural factors on wildebeest distributions is not rejected, yet they suggest the potentially important role of an energy intake maximizing strategy on movement patterns. Our findings show that wildebeest movements are broadly similar to those of other large herbivores that migrate in response to resource gradients.

scholarly journals Dietary changes of large herbivores in the Turkana Basin, Kenya from 4 to 1 Ma

2015 ◽  
Vol 112 (37) ◽  
pp. 11467-11472 ◽  
Author(s):  
Thure E. Cerling ◽  
Samuel A. Andanje ◽  
Scott A. Blumenthal ◽  
Francis H. Brown ◽  
Kendra L. Chritz ◽  
...  
Keyword(s):  
Fossil Record ◽  
Central Africa ◽  
Mixed Feeding ◽  
Large Herbivore ◽  
Large Herbivores ◽  
Dietary Changes ◽  
Turkana Basin ◽  
Faunal Assemblages ◽  
The Past ◽  
Collection Sites

A large stable isotope dataset from East and Central Africa from ca. 30 regional collection sites that range from forest to grassland shows that most extant East and Central African large herbivore taxa have diets dominated by C4 grazing or C3 browsing. Comparison with the fossil record shows that faunal assemblages from ca. 4.1–2.35 Ma in the Turkana Basin had a greater diversity of C3–C4 mixed feeding taxa than is presently found in modern East and Central African environments. In contrast, the period from 2.35 to 1.0 Ma had more C4-grazing taxa, especially nonruminant C4-grazing taxa, than are found in modern environments in East and Central Africa. Many nonbovid C4 grazers became extinct in Africa, notably the suid Notochoerus, the hipparion equid Eurygnathohippus, the giraffid Sivatherium, and the elephantid Elephas. Other important nonruminant C4-grazing taxa switched to browsing, including suids in the lineage Kolpochoerus-Hylochoerus and the elephant Loxodonta. Many modern herbivore taxa in Africa have diets that differ significantly from their fossil relatives. Elephants and tragelaphin bovids are two groups often used for paleoecological insight, yet their fossil diets were very different from their modern closest relatives; therefore, their taxonomic presence in a fossil assemblage does not indicate they had a similar ecological function in the past as they do at present. Overall, we find ecological assemblages of C3-browsing, C3–C4-mixed feeding, and C4-grazing taxa in the Turkana Basin fossil record that are different from any modern ecosystem in East or Central Africa.

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