For all researches, please visit our "Peer-reviewed publications" page.
Congrains C, Carvalho A, Miranda E, Cumming G, Henry D, Manu S et al. (2016)
Genetic and paleomodelling evidence of the population expansion of the cattle egret Bubulcus ibis in Africa during the climatic oscillations of the Late Pleistocene
Journal of Avian Biology.
Increasing aridity during glacial periods produced the retraction of forests and the expansion of arid and semi-arid environments in Africa, with consequences for birds. Cattle egret (Bubulcus ibis) is a dispersive species that prefers semiarid environments and requires proximity to bodies of water. We expected that climatic oscillations led to the expansion of the range of the cattle egret during arid periods, such as the Last Maximum Glacial (LGM) and contraction of distribution during the Last Interglacial (LIG) period, resulting in contact of populations previously isolated. We investigated this hypothesis by evaluating the genetic structure and population history of 15 cattle egret breeding colonies located in West and South Africa using the mitochondrial DNA (mtDNA) control region, mtDNA ATPase 8 and 6, and an intron of nuclear gene transforming growth factor beta-2. Occurrence data and bioclimatic information were used to generate ecological niche models of three periods (present, LGM and LIG). We used the genetic and paleomodelling data to assess the responses of the cattle egret from Africa to the climatic oscillations during the late Pleistocene. Genetic data revealed low levels of genetic differentiation, signs of isolation-by-distance, as well as recent increases in effective population size that started during the LGM. The observed low genetic structure may be explained by recent colonization events due to the demographic expansion following the last glacial period and by dispersal capacity of this species. The paleomodels corroborated the expansion during the LGM, and a more restricted potential distribution during the LIG. Our findinds supports the hypothesis that the species range of the cattle egret expanded during arid periods and contracted during wet periods.
Iloh* A, Ogundipe O (2016)
Using ecological niche modelsto plan conservation in a changing environment: A case for the plant Chasmanthera dependens Hochst (Menispermaceae) in West Africa
Journal of Ecology and The Natural Environment 8(1) 1-8.
Climatic envelope modeling techniques implemented in two algorithms, Genetic Algorithm for Rule-set Production (GARP) and bioclimatic variables (BIOCLIM) were used to assess effects of climatic conditions on distributions of plants and anticipate how climate would have delimited their distribution under future conditions using a liana species Chasmanthera dependens as a case example. In all, 120 geo-referenced plant records generated from fieldwork and drawn from data served by the Global Biodiversity Information Facility (GBIF). Environmental variables were derived from monthly temperature and rainfall data from WorldClim; eliminating environmental variables with correlations of 0.75 and left eight (8) variables for analysis. Results show that the current suitable range (ecological niche) of the model plant was broad across the tropical rain forest regions. Predictions to future climate scenarios (2050), predicted a significant reduction of suitable distributional areas for the species suggesting possible loss of plant species. Indeed, ex-situ conservation may be the most appropriate conservation tool for this species and others in similar situations. Key words: Bioclimatic variables (BIOCLIM), climate change, conservation, ecological niche models, genetic algorithm for rule-set production (GARP).
Keywords: Bioclimatic variables (BIOCLIM), climate change, conservation, ecological niche models, genetic algorithm for rule-set production (GARP)
Gabriel S, Bennett C, Ba A, Henry S (2015)
Modeling the Suitability Index of Selected Conifers on Mambilla Plateau Taraba State, Nigeria: Implication on Planted Forest
International Journal of Agroforestry Remote Sensing and GIS pp. 1-9.
The Mambilla Plateau is a semi temperate highland region found within the broader tropical savannah of northeast Nigeria which supported the growing of cold tolerant fruits such as apple and pears was explored to determine its suitability for growing of cold tolerant conifers in contrasts to the surrounding tropical ecosystems. The authors conducted an exploratory work using both modeling and seedling germination tests to determine the feasibility of survival and suitability of conifers on the Mambilla plateau. The work investigated growth factors such as water availability (maximum average rainfall for optimum growth, minimum rainfall for survival) and temperature (maximum average temperature for optimum growth and minimum temperature required for survival). A climate envelope model (CEM) of species distribution and pre validated germination test were conducted on the selected species in Diva GIS software and on the field respectively to identify the potentially suitable sites on the plateau. Of the four conifer species under investigation Pinus ponderosa of Pacific Northwest, USA origin and Pinus caribaea of Nicaragua var. honduresis origin were found to be potentially suitable to the Mambilla Plateau environment. However, relatively robust and longer field trials were suggested on the two species before any conclusive action is taken.
Keywords: Biogeoclimatic Ecosystems, Prediction, Species Distribution Model, Suitability Index
Moraga P, Cano J, Baggaley R, Gyapong J, Njenga S, Nikolay B et al. (2015)
Modelling the distribution and transmission intensity of lymphatic filariasis in sub-Saharan Africa prior to scaling up interventions: integrated use of geostatistical and mathematical modelling
Parasites & Vectors 8(1) 560.
BACKGROUND:Lymphatic filariasis (LF) is one of the neglected tropical diseases targeted for global elimination. The ability to interrupt transmission is, partly, influenced by the underlying intensity of transmission and its geographical variation. This information can also help guide the design of targeted surveillance activities. The present study uses a combination of geostatistical and mathematical modelling to predict the prevalence and transmission intensity of LF prior to the implementation of large-scale control in sub-Saharan Africa.METHODS:A systematic search of the literature was undertaken to identify surveys on the prevalence of Wuchereria bancrofti microfilaraemia (mf), based on blood smears, and on the prevalence of antigenaemia, based on the use of an immuno-chromatographic card test (ICT). Using a suite of environmental and demographic data, spatiotemporal multivariate models were fitted separately for mf prevalence and ICT-based prevalence within a Bayesian framework and used to make predictions for non-sampled areas. Maps of the dominant vector species of LF were also developed. The maps of predicted prevalence and vector distribution were linked to mathematical models of the transmission dynamics of LF to infer the intensity of transmission, quantified by the basic reproductive number (R 0 ).RESULTS:The literature search identified 1267 surveys that provide suitable data on the prevalence of mf and 2817 surveys that report the prevalence of antigenaemia. Distinct spatial predictions arose from the models for mf prevalence and ICT-based prevalence, with a wider geographical distribution when using ICT-based data. The vector distribution maps demonstrated the spatial variation of LF vector species. Mathematical modelling showed that the reproduction number (R 0 ) estimates vary from 2.7 to 30, with large variations between and within regions.CONCLUSIONS:LF transmission is highly heterogeneous, and the developed maps can help guide intervention, monitoring and surveillance strategies as countries progress towards LF elimination.
Keywords: Basic reproductive number, Bayesian geostatistical modelling, Lymphatic filariasis, Mathematical modelling, Sub-Saharan Africa, Wuchereria bancrofti
Borokini T (2014)
Okoubaka Aubrevillei (Pelleg & Norman): A Synthesis of Existing Knowledge for Research and Conservation in West and Central Africa
Journal of Biology and Life Science 6(1) 67.
Okoubaka aubrevillei is the largest parasitic plant known to man. It is a tropical tree species distributed within West and Central Africa. Concerns were drawn to the tree because of its rarity, disjunct distribution in all its native range, paucity of published scientific information and its hemi-parasitic potentials. This article gathered and synthesized all existing scientific information on the tree to provide a solid foundation for further research on the tree. This article provided detailed information on its name etymology, taxonomic history, and geographical distribution including new locations for the tree, ecological significance and behaviour within its range, supported with an updated map illustrating its distribution within West and Central Africa. The possible causes of its rarity in its range were identified and its hemi-parasitic behaviour was hypothesized. In addition, ethnobotanical uses of the tree, symbolism and dendrolatry, and its significance in modern medicine were extensively discussed. The paper concluded with highlights on prospects for immediate conservation, management and research focus areas for the tree species.
Keywords: Conservation, Hemi-parasitism, Okoubaka aubrevillei, Rarity., West and Central Africa
Hamid A, Aiyelaagbe O (2012)
Pharmacological investigation of Asystasia calyciana for its antibacterial and antifungal properties
International Journal of Chemical and Biochemical Sciences 1 99-104.
The phytochemical investigation of Asystasia calyciana (whole plant) extracts revealed the presence of saponins, tannins, steroids, glycosides, flavonoids and anthraquinones. The hexane, ethylacetate and methanol extracts of Asystasia calyciana were evaluated invitro to determine inhibition of human pathogenic microorganisms made up of six bacteria and six fungi. The plant metabolites inhibited the growth of twelve test organisms at different concentrations between 12.5 and 200mg/ml using agar diffusion plate method. The hexane extract exhibited higher antibacterial properties than both ethylacetate and methanol extracts of the plant. The hexane and ethylacetate extracts revealed higher antifungal properties than the methanol extract of A. calyciana, with activity of hexane and ethylacetate extracts comparable to that of the reference drug (tioconazole) against Candida albicans, Rhizopus stolon, Pneumonae notatum, Tricophyton rubrum and Epidermophyton floccosum and Candida albicans and Epidermophyton floccosum, respectively.
Keywords: A. calyciana, agar diffusion method, antibacterial and antifungal, ethnomedicine, phytochemical screening