Rainforests Of Cameroon Research Articles

Demographic rates and diversity vary with tree stature and ontogenetic stage in an African tropical rainforest

AbstractThe vertical gradient of light in closed‐canopy forests selects for trees with different adult statures, but our understanding of how stature affects forest diversity and demography is unclear. In a species‐rich rainforest in Cameroon, we quantified the contributions of four growth forms of increasing adult stature (treelet, understory, canopy, emergent species) to forest structure and diversity, and investigated variation in life history trade‐offs across growth forms. Treelets had the highest stem density, contributed the most to forest diversity, and diverged from larger statured species in terms of demographic trade‐offs. Growth rates were slower for smaller statured than for larger statured species, and at the adult stage, treelets had significantly lower mortality than other growth forms. We observed significant interspecific trade‐off relationships between staure and demographic rates that often differed between growth forms. Recruitment rate strongly declined with adult stature for all growth forms, but recruitment per reproductive adult declined only for emergents. While we observed a significant growth‐mortality trade‐off across all species, the trade‐off was similar across growth forms. Smaller statured species in our study are not light‐demanding but rather treelet and understory species that live entirely in the shaded understory. Differences in how historical biogeography has shaped species pools may ultimately cause variation in how adult stature contributes to tropical forest diversity.

Ant-following behavior is correlated with plumage traits in African understory birds

Ant-following behavior is a common phenomenon in birds of Neotropical and Afrotropical rainforests but yet little is known from Central Africa. We here report on the phenomenon in lowland rainforest in Cameroon, quantifying the strength of the interaction of different ant-following bird species with driver ants and test the hypothesis that higher levels of specialization in ant-following behavior are associated with dominance or aggression-dependent plumage and other morphological traits. Flock size varied between 1 and 11 individuals with a mean size of 5.34 ± 2.68 (mean ± SD) individuals occurring at the same time. The maximum number of species present during one raid observed was ten, whereas the minimum number was four with an overall species richness of 6.89 ± 2.1 species. The 21 attending bird species strongly varied in the degree of ant-following behavior. In an interspecific comparison, plumage traits such as the presence of a colored crown, eyespots, and bare skin around the eye, in combination with metatarsus length and weight, were significantly correlated with ant-following behavior. These results suggest that—in size and identity of species—ant-following bird assemblages in Central Africa are similar to those reported from East Africa. They also suggest that ant following favors the selection of traits that signal dominance in interactions between individuals struggling for valuable food resources in the forest understory.

Concurrent Clade I and Clade II Monkeypox Virus Circulation, Cameroon, 1979-2022.

During 1979-2022, Cameroon recorded 32 laboratory-confirmed mpox cases among 137 suspected mpox cases identified by the national surveillance network. The highest positivity rate occurred in 2022, indicating potential mpox re-emergence in Cameroon. Both clade I (n = 12) and clade II (n = 18) monkeypox virus (MPXV) were reported, a unique feature of mpox in Cameroon. The overall case-fatality ratio of 2.2% was associated with clade II. We found mpox occurred only in the forested southern part of the country, and MPXV phylogeographic structure revealed a clear geographic separation among concurrent circulating clades. Clade I originated from eastern regions close to neighboring mpox-endemic countries in Central Africa; clade II was prevalent in western regions close to West Africa. Our findings suggest that MPXV re-emerged after a 30-year lapse and might arise from different viral reservoirs unique to ecosystems in eastern and western rainforests of Cameroon.

The influence of vegetation structure on sleeping site selection by chimpanzees (Pan troglodytes troglodytes).

Sleep is an important aspect of great ape life; these animals build sleeping platforms every night. In a community of chimpanzees, each subgroup selects a sleeping site where each individual builds a sleeping platform, mostly on a tree. Previous studies have measured the heights of sleeping platforms and sleeping trees to test the predation avoidance and thermoregulation hypotheses of sleeping site selection. However, it remains unclear how components of vegetation structure (vertical and horizontal) together determine the selection of sleeping sites by chimpanzees. Using botanical inventories around sleeping sites in a tropical rainforest of Cameroon, we found that chimpanzees preferentially sleep in trees measuring 40-50 cm in diameter. Regarding height, on average, sleeping trees measured 26 m and sleeping platforms were built at 16 m. To build sleeping platforms, chimpanzees preferred four tree species, which represent less than 3% of tree species in the study area. We demonstrate that the variation in abundance of tree species and the vertical and horizontal structure of the vegetation drive chimpanzee sleeping site selection. It was previously thought that preference for vegetation types was the driver of sleeping site selection in chimpanzees. However, results from this study indicate that the importance of vegetation types in sleeping site selection depends on their botanical characteristics including the variation in tree size, the abundance of all trees, the abundance of sleeping trees, and the occurrence of preferred sleeping tree species, which predict sleeping site selection. The height and diameter of trees are considered by chimpanzees when selecting a particular tree for sleeping and when selecting a site with a specific vertical structure. In addition to tree height, the abundance of smaller neighboring trees may also play a role in the chimpanzee antipredation strategy. Our results demonstrate that chimpanzees consider several vegetation parameters to establish sleeping sites.

Indications of an Achaea sp. caterpillar outbreak disrupting fruiting of an ectomycorrhizal tropical tree in Central African rainforest

Background and aims – Where one or several tree species come to dominate patches of tropical forest, as many masting ectomycorrhizal legumes do in Central Africa, ecological theory predicts they may be prone to herbivory, which might alter their reproductive output. This was indirectly investigated in lowland rainforest in Cameroon for Tetraberlinia korupensis, whose crowns were attacked in 2008 by an outbreaking black caterpillar—identified as an Achaea sp., probably A. catocaloides—in Korup National Park. Material and methods – Field-collected data on tree-level seed and fruit (pod) production of T. korupensis in its 2008 masting event were compared with that of its two co-dominant neighbours (T. bifoliolata, Microberlinia bisulcata), whose populations masted in 2007 (and 2010). To do this, bivariate regression models (linear, polynomial, ZiG [zero-inflated gamma model]), contingency table analysis, and non-parametric measures of dispersion were used. Key results – Assuming T. korupensis is prone to Achaea caterpillar attacks, empirical data support the hypothesized lower proportion of adults participating in its masting (54% in 2008) than for either masting population of M. bisulcata (98% in 2007, 89% in 2010) or T. bifoliolata (96% in 2007, 78% in 2010). These fruiting T. korupensis trees were about one-third larger in stem diameter than conspecific non-fruiters and produced as many pods and seeds per capita as T. bifoliolata. However, regressions only modestly support the hypothesis that the positive tree size–fecundity relationship for T. korupensis was weaker (i.e. lower adj. R2) than for M. bisulcata (whose leaves are morphologically similar) or T. bifoliolata, with mostly similar dispersion about the median among these species. Conclusion – Altogether, the findings suggest a role for tolerance in nutrient-poor forests. It is postulated that instead of conferring resistance to herbivores, the ectomycorrhizas associated with these trees may enable them to more quickly recover from potential yet unpredictable insect outbreaks.

Interaction and resource exploitations between invasive and native ants in cocoa and surronding farmlands in southern Cameroon rainforest

Interaction and resource exploitations between invasive and native ants in cocoa and surronding farmlands in southern Cameroon rainforest

Predicting bushmeat biomass from species composition captured by camera traps: Implications for locally based wildlife monitoring

Abstract Facing the bushmeat crisis, tropical forests require effective monitoring for sustainable wildlife management. To gain credibility with local people and conservation officials, the monitoring needs indicators that comply with local knowledge and predict the available faunal resources. This study explores predictive indicators for bushmeat biomass—the total biomass of five main hunted mammals—in a Cameroonian rainforest. We employed camera trapping and the Random Encounter and Staying Time (REST) model to estimate the spatial variation in each species' population density and bushmeat biomass at three sites. We then calculated six indicators from camera‐trap capture rate estimates and assessed their predictive performance for the total wild meat amount. Duikers generally increased with distance from the public road, but two red duiker species were more markedly affected by the distance than blue duikers. Spatial density patterns of brush‐tailed porcupines and Emin's pouched rats differed between sites. Consequently, bushmeat biomass displayed exponential growth away from the road with varying degrees among the sites. Of the six indicators, the R/B ratio (red‐to‐blue duiker ratio) and the D/R ratio (duiker‐to‐rodent ratio) exhibited positive linear‐like correlations to bushmeat biomass at all sites. The correlation lines were moderately similar across sites in the R/B ratio but largely different in the D/R ratio, suggesting that the latter is unsuitable for sharing information between neighbouring communities. Synthesis and applications. The two indicators based on captured animal composition may effectively predict the total biomass of the main target species for bushmeat hunting, given a reasonably large sample size. The R/B ratio (red duikers/blue duikers) is recommended as a first choice; the D/R ratio (duikers/rodents) can be a good alternative when information sharing is not essential. Because local hunters are aware of depletion‐related changes in species composition of caught animals, these indices may be effectively incorporated into community‐based wildlife monitoring.

Geographic distribution, diversity and conservation status of giant millipedes in southern Cameroon rainforest

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Local-scale structuration of species-habitat association in the semi-deciduous tropical rainforest in eastern Cameroon

Tropical forests are hyperdiverse, and although broad-scale variation in diversity can be reasonably well explained, local-scale variation in diversity is harder to understand. It has been revealed that species may show species-habitats associations. However, how the assembled species are associated with local habitats and how community-habitat associations vary regarding species abundance and class size remains unclear. Here, we analyzed the community-habitat associations by applying the multivariate regression trees (MRT) technique on data of 22,064 trees distributed across 30 1-ha plots varying in topography and soil conditions in a semi-deciduous tropical rainforest of Cameroon. Further, the indicator species analysis was used to determine the most important species for structuring assemblages.The MRT divides the whole tree community inventoried into four habitats types: Habitat 1 (H1) sandy loamy, acidic soil with a low Na concentration (pH ≤ 6.245 and [Na] < 4.535 cmol kg−1); H2 equal to neutral sandy soil with a small Na concentration (7 ≤ pH > 6.245 and [Na] < 4.535 cmol kg−1); H3 equal to Loamy sandy soil with average Na concentration (4.535 ≤ [Na] < 6.243 cmol kg−1) and; H4 equal to Loamy sandy soil with high nutrients concentration ([Na] ≥ 6.243 cmol kg−1). Coincidentally, the same habitat types were also generated for the understorey and large trees classes taken separately, although a difference was somehow recorded for the small stems class. Among investigated environmental variables, soil Na content and, to a lesser extent, soil pH were identified as the primary responsible for the first split for habitat types for understorey and large trees classes. By contrast, the most determinant for discrimination habitat types for small stems was soil cation exchange capacity, followed by soil moisture content. Overall, 29 species were found as indicators characterizing the four habitat types for the whole tree community, with index values varying between 33% and 99 %. But specifically, the number of indicators species for large trees was 28. Intriguingly, some indicator species within the large trees class changed to either non-indicator or intermediate indicator species in the understorey trees class that was best represented by as less as 16 species. A comparable species richness was recorded across all plots of the studied area; however, significant variability was found regarding species abundance, with habitats H1 and H4 with higher average abundance values. This study highlights that soil variables adding to topographical habitat filtering were important in shaping the composition of local species.

The effect of climatic factors on the number of malaria cases in an inland and a coastal setting from 2011 to 2017 in the equatorial rain forest of Cameroon

BackgroundWeather fluctuation affects the incidence of malaria through a network of causuative pathays. Globally, human activities have ultered weather conditions over time, and consequently the number of malaria cases. This study aimed at determining the influence of humidity, temperature and rainfall on malaria incidence in an inland (Muyuka) and a coastal (Tiko) settings for a period of seven years (2011–2017) as well as predict the number of malaria cases two years after (2018 and 2019).MethodsMalaria data for Muyuka Health District (MHD) and Tiko Health District (THD) were obtained from the Regional Delegation of Public Health and Tiko District Health service respectively. Climate data for MHD was obtained from the Regional Delegation of Transport while that of THD was gotten from Cameroon Development Coorporation. Spearman rank correlation was used to investigate the relationship between number of malaria cases and the weather variables and the simple seasonal model was used to forecast the number of malaria cases for 2018 and 2019.ResultsThe mean monthly rainfall, temperature and relative humidity for MHD were 200.38 mm, 27.050C, 82.35% and THD were 207.36 mm, 27.57 °C and 84.32% respectively, with a total number of malaria cases of 56,745 and 40,160. In MHD, mean yearly humidity strongly correlated negatively with number of malaria cases (r = − 0.811, p = 0.027) but in THD, a moderate negative yearly correlation was observed (r = − 0.595, p = 0.159). In THD, the mean seasonal temperature moderately correlated (r = 0.599, p = 0.024) positively with the number of malaria cases, whereas MHD had a very weak negative correlation (r = − 0.174, p = 0.551). Likewise mean seasonal rainfall in THD moderately correlated (r = − 0.559, p = 0.038) negatively with malaria cases, contrary to MHD which showed a very weak positive correlation (r = 0.425, p = 0.130). The simple seasonal model predicted 6,842 malaria cases in Muyuka, for 2018 and same number for 2019, while 3167 cases were observed in 2018 and 2848 in 2019. Also 6,738 cases of malaria were predicted for MHD in 2018 likewise 2019, but 7327 cases were observed in 2018 and 21,735 cases in 2019.ConclusionHumidity is the principal climatic variable that negatively influences malaria cases in MHD, while higher seasonal temperatures and lower seasonal rain fall significantly increase malaria cases in THD.

Complementary allometric model of understory tree biomass in the semi-deciduous rainforest of Cameroon

Forest understorey contains remarkable plant diversity, contributing to the heterogeneous environments for other biotic gatherings and soil supplement aggregations. Nonetheless, the biomass of the understorey vegetation is neglected because of the lack of appropriate allometric equations without which there are uncertainties in biomass estimation. This study was aimed at developing multispecies allometric equations that will be used to estimate the aboveground biomass of different compartments (trunk, crown, and leaves) of understorey trees in the semi-deciduous rainforest of Cameroon. Understorey tree diameter (1.0-10.0 cm), height, and crown diameter were measured on 1023 trees as biomass predictors. The results showed that the fit of the model improves with more predictive variables, four of which were considered in all studied compartments (trunk, crown, and leaves). Existing specific and pantropic allometries based on diameter tend to overestimate the aboveground biomass of understorey trees when compared to the allometry developed in this study. This study highlighted the importance of a specific aboveground biomass allometric equation for understorey trees. Furthermore, the multispecies allometric equation developed for understorey trees complements those recently developed for overstorey trees, thereby contributing to the total aboveground woody biomass estimation in semi-deciduous forest in the Congo Basin.

Four new threatened species of Rinorea (Violaceae), treelets from the forests of Cameroon

SummaryFour species of Rinorea are described as new to science; all four species are endemic to evergreen rain forest in Cameroon. Rinorea villiersii Achound. and R. amietii Achound are placed in Rinorea [unranked] Crassiflorae M.Brandt, while, R. dewildei Achound. and R. faurei Achound. fall in Rinorea [unranked] Dentatae Engl. The first species appears to be endemic to the Solé Forest Reserve northeast of Yabassi in Littoral Region. The second and the third species are found mainly in Littoral and South Regions, R. amietii extending to South West Region and R. dewildei extending to Central Region. The fourth species, R. faurei is an endemic of the Santchou Forest Reserve at the foot of Dschang Plateau in West Region. The taxonomic affinities of the four species are discussed, illustrations and a distribution map are provided, and their conservation status is assessed. All four species are threatened with extinction according to the 2012 IUCN categories and criteria.

Alcohol, drugs and sexual abuse in Cameroon's rainforest

Due to global socio-economical and ecological changes, indigenous societies are exposed to an increased risk of alcohol and substance abuse. Most research on this topic has been done on indigenous communities in Canada, Australia, the US, parts of Europe and New Zealand, leaving indigenous communities in other parts of the world largely unrepresented. This study focuses on alcohol and drug consumption among the Baka: a former hunter-gatherer society in southeastern Cameroon that has been facing drastic socio-ecological changes in the last five decades. During long-term fieldwork we collected ethnographic and empirical data by means of group and individual interviews among four Baka communities. By using a multivariable approach, we describe psychoactive substance use behaviors, its socio-cultural and political context, and consequences. Our findings show that 48% of men, 24% of women and 11% of children between five and 16 years old reported alcohol intake in the past 24 h. The use of Tramadol was also reported, including by children as young as five years old. Psychoactive substances were used for recreational purposes, as painkillers, and energy boosters. Substance abuse was related to health issues, especially problems with fertility, and to several household and social conflicts. Other factors related to substance abuse were Baka's marginalization and sexual exploitation of Baka women and girls. By discussing these matters, we hope to stimulate more research on similar problems in small-scale societies and to invite governments, human rights activists, and other important parties to take action.

Assessing the determinants of Ebola virus disease transmission in Baka Community of the Tropical Rainforest of Cameroon

BackgroundEbola virus disease (EVD) is a severe, often fatal illness in humans and nonhuman primates caused by the Ebola virus. The recently approved rVSV-EBOV vaccine is not available in many high-risk countries hence prevention is paramount. The design of effective prevention interventions requires an understanding of the factors that expose communities at risk. It was based on this that we investigated the Baka community of Abong-Mbang Health District in tropical rain forest of Cameroon.MethodsA cross-sectional study was conducted with participants randomly selected from 13 villages in Abong-Mbang by multi-stage cluster sampling. A questionnaire was administered to them to collect demographic information, data on knowledge of EVD, their feeding and health-seeking behaviour. Data was analyzed using the chi-square test. Knowledge of EVD was assessed using an 8 item Morisky Scale. An adapted Threat Capability Basic Risk Assessment Guide was used to determine their risk of exposure to infection.ResultsA total of 510 participants, most of whom were hunters (31.4%), farmers (29.8%), and had primary education (62.7%), were included in this study. Although 83.3% participants had heard of EVD, most (71%) did not know its cause. Their source of information was mainly informal discussions in the community (49%). Misconceptions were identified with regards to the cause and mode of transmission. Only 43.1% accepted EVD could be transmitted from human-to-human. Generally, participants’ knowledge of EVD was poor. Demographic factors such as level of education, occupation and ethnic group significantly affected knowledge of EVD. The majority of participants were at a very high risk of exposure to infection as they consumed various forms of bush meat and were involved in other risky practices such as scarification and touching of corpses. Although over half of participants seek medical care, most of them preferred traditional medicine. Socio-cultural and service-related factors were deterrent factors to medical care.ConclusionParticipants generally had poor knowledge of EVD and were at high risk of infection. We recommend rigorous sensitization campaigns in the study area to educate the population on EVD and clarify the misconceptions identified. EVD surveillance is recommended particularly as outbreaks have often been reported in the Congo Basin.

Plant diversity and conservation concerns in a semi-deciduous rainforest in Cameroon: implications for sustainable forest management

Plant diversity and conservation concerns in a semi-deciduous rainforest in Cameroon: implications for sustainable forest management

Wood Density of Lower Stratum Trees in a Semi-Deciduous Tropical Forest of Cameroon

The lower forest stratum is often neglected in trees wood density studies. The aim of this study was to investigate wood density of lower stratum forest in a semi-deciduous rain forest of Cameroon. The data was collected from 30 random squares plots of 100m² and 200m. The wood density was assessed using immersion method. Wood samples were collected at three levels including: the base, the trunk and branches of trees. Measurement variables collected include the diameter, height and crown diameter. These variables were correlated to wood density using the Pearson coefficient. A total of 1498 samples from 136 tree species were collected. The wood density from these samples varied from 0.156 g.cm-³ to 0.914 g.cm-³, with an average of 0.561 g.cm-³. ANOVA test showed that, wood density decreased significantly from 0.609 to 0.571 and then to 0.509 g.cm-³ for the base, trunk and branches respectively. Interspecific analysis showed that wood density was significantly different between species (ANOVA, p˂0.001). With respect of biological type, the mean wood density of 27 understory tree species (exclusively) found was 0.562 g.cm-³. Wood density of 56 tropical forest tree species hitherto unknown in the literature were determined. The Pearson correlation between measurement variables and wood density was close to zero; nevertheless, it varied in function of the tree species. This study suggested that more investigations of wood density of tropical forest trees should be conducted, particularly in the Congo Basin forests where an important diversity of medium and lower forest stratum trees is expected.

Amanita in the Guineo-Congolian rainforest: Epitypes and new species from the Dja Biosphere Reserve, Cameroon

ABSTRACT Four epitypes and three new species of Amanita (Amanitaceae, Agaricales, Agaricomycetes, Basidiomycota) are described from Guineo-Congolian rainforests of Cameroon. Amanita echinulata, A. fulvopulverulenta, A. robusta, and A. bingensis are epitypified based on collections that are the first since the species were described nearly a century ago. Morphological features of the epitypes are described and enumerated. Amanita minima, Amanita luteolamellata, and A. goossensfontanae are described as new and added to the known macromycota of tropical Africa. Habit, habitat, and known distribution are provided for each species. Sequence data for the internal transcribed spacer (ITS) locus are provided for types and other collections of all taxa, and a molecular phylogenetic analysis across the genus Amanita corroborates morphology-based infrageneric placement for each.

A concise comparison of two rainfall onset definitions using convective properties derived from TRMM precipitation radar data

Most rainfall onset definitions in West Africa were estimated using station-based data. These data and hence the rainfall onset definitions may, however, not be a good representative for the entire climatic zone of the station. Based on existing definitions, a new rainfall onset definition is developed from the Tropical Rainfall Measurement Mission 3B42 gridded rainfall observations. 16 years of data were analyzed, which were taken between mid-April to mid-July over rainforest zones (west coast rainforest, dry rainforest and Nigeria–Cameroon rainforest) and between mid-May to mid-August over savannah zones (Nigeria savannah, and “Central African and South Sudan savannah”). While both definitions yield rather similar results in west coast rainforest, Nigeria–Cameroon rainforest and Nigeria savannah zones; results differ, however, substantially over dry rainforest and the Central African and South Sudan savannah. The new onset definition is further justified using an event-based analysis of mesoscale convective systems, flash counts and other convective parameters. Results have proved the new onset definition to be reliable and relevant for applications in agricultural productivity.

Crop genotype and stem cutting portion affect infestation pressure of the cassava root scale Stictococcus vayssierei Richard (Hemiptera: Stictococcidea) in a rainforest in Cameroon

African root and tuber scale (ARTS) Stictococcus vayssierei Richard is a serious constraint to the production of cassava (Manihot esculenta Crantz) in Central Africa, and the food and income security for smallholder farmers. Therefore, to improve the production of cassava it is urgent to determine the appropriate cultural practices that lower ARTS infestation pressure. This study tests the single and combined effects of stem cutting portion and crop variety on ARTS infestation levels’. A split-plot design with four cassava varieties (TMS 96/0023, Excel, Miboutou and Douma) as the main plots and three stem cuttings portions of these varieties (lower, middle and upper portions of the mother plant) as sub-plots was used. The results showed that at 12 months after planting (MAP), lower portions of the local variety Douma showed the highest fresh shoots (2.95 ± 0.13 kg) than the upper portions (2.08 ± 0.09 kg) of the Excel variety. The portions at lower of the Excel variety were the most infested (118-158.38 and 126.75 ARTS) at 3, 6 and 9 MAP respectively. The yield of local variety Douma was higher (20.00-20.11 t ha− 1) in plots planted with portions at middle and lower, followed by yields of TMS 96/0023 variety (19.00 t ha− 1) in plots planted with the lower portions. Overall, irrespective of the cassava variety, the lower portion 16.49 t ha− 1 resulted in higher yield than those the upper portion 10.81 t ha− 1.

Patterns of host-parasite associations in tropical lice and their passerine hosts in Cameroon.

Coevolutionary processes that drive the patterns of host–parasite associations can be deduced through congruence analysis of their phylogenies. Feather lice and their avian hosts have previously been used as typical model systems for congruence analysis; however, such analyses are strongly biased toward nonpasserine hosts in the temperate zone. Further, in the Afrotropical region especially, cospeciation studies of lice and birds are entirely missing. This work supplements knowledge of host–parasite associations in lice using cospeciation analysis of feather lice (genus Myrsidea and the Brueelia complex) and their avian hosts in the tropical rainforests of Cameroon. Our analysis revealed a limited number of cospeciation events in both parasite groups. The parasite–host associations in both louse groups were predominantly shaped by host switching. Despite a general dissimilarity in phylogeny for the parasites and hosts, we found significant congruence in host–parasite distance matrices, mainly driven by associations between Brueelia lice and passerine species of the Waxbill (Estrildidae) family, and Myrsidea lice and their Bulbul (Pycnonotidae) host species. As such, our study supports the importance of complex biotic interactions in tropical environments.