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African Forests (african + forest)
Selected AbstractsA Catastrophic Destruction of African Forests about 2,500 Years Ago Still Exerts a Major Influence on Present Vegetation FormationsIDS BULLETIN, Issue 1 2002Jean Maley First page of article [source] Book review: Science and Conservation in African Forests: The Benefits of Long-Term ResearchAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2010W. Scott McGraw No abstract is available for this article. [source] Spatial patterns in species,area relationships and species distribution in a West African forest,savanna mosaicJOURNAL OF BIOGEOGRAPHY, Issue 4 2005Thomas Hovestadt Abstract Aim, To investigate the relationship between the slope z of the species,area relationship (SAR) and the intensity of spatial patterns in species number and dissimilarity for woody plants with different modes of seed dispersal. According to island theory we expect, for any given archipelago, steeper slopes and more pronounced spatial patterns for groups of less dispersive species. Location, Ivory Coast, West Africa. Methods, In a West African forest,savanna mosaic we collected presence,absence data for woody plant species in 49 forest islands. The parameters of the SARs were fitted by nonlinear regressions and then compared for plant species aggregated according to their mode of seed dispersal. We used the Mantel test to calculate the intensity of spatial patterns in species number, i.e. residual deviation from SAR, and species dissimilarity. Results, The z -value for bird-dispersed species was lower (0.11) than that for wind-dispersed species (0.27), with mammal-dispersed species taking an intermediate value (0.16). This result suggests that, as a group, bird-dispersed species are better colonizers. The spatial pattern in species number as well as species similarity was more pronounced for bird- compared with wind-dispersed species. Main conclusions, The standard interpretation of the theory of island biogeography claims that shallow slopes in the SAR imply low isolation of islands, i.e. good dispersal abilities of species. The results of our study appear to contradict this statement. The contradiction can eventually be resolved by a more detailed account of the colonization process, i.e. by distinguishing between dispersal and consecutive establishment of populations. [source] A molecular diagnostic for identifying central African forest artiodactyls from faecal pelletsANIMAL CONSERVATION, Issue 1 2010S. Ntie Abstract Small to medium-sized central African forest artiodactyls constitute a diverse yet heavily hunted group composed primarily of species within the genera Cephalophus, Neotragus, Tragelaphus and Hyemoschus. Of these genera, Cephalophus is the richest with as many as seven sympatric species known to occur in central African forests. However, differentiating species from their faeces or from tissue where the whole carcass is unavailable is very difficult. In order to develop a robust molecular diagnostic for species identification, a database of mitochondrial cytochrome b (553 bp) and control region (,675 bp) sequences was compiled from all forest Cephalophus species and other similarly sized, sympatric Tragelaphus, Neotragus and Hyemoschus species. Reference phylogenies from each marker were then used to recover the identity of sequences obtained from unknown faecal samples collected in the field. Results were then compared to determine which region best recovered species identity with the highest statistical support. Restriction fragment length polymorphisms (RFLPs) were also assessed as an alternative method for rapid species identification. Of the methods examined, tree-based analyses built on a geographically comprehensive database of control region sequences was the best means of reliably recovering species identity from central African duikers. However, three sister taxa appear indistinguishable (Cephalophus callipygus, Cephalophus ogilbyi and Cephalophus weynsi) and not all species were monophyletic. This lack of monophyly may be due to incomplete lineage sorting commonly observed in recently derived taxa, hybridization or the presence of nuclear translocated copies of mitochondrial DNA. The high level of intra-specific variation and lack of robust species-specific diagnostic sites made an RFLP-based approach to duiker species identification difficult to implement. The tree-based control region diagnostic presented here has many important applications including fine-scale mapping of species distributions, identification of confiscated tissue and environmental impact assessments. [source] Forest fragmentation relaxes natural nest predation in an Afromontane forestANIMAL CONSERVATION, Issue 4 2009T. Spanhove Abstract Nest predation is widely regarded as a major driver underlying the population dynamics of small forest birds. Following forest fragmentation and the subsequent invasion by species from non-forested landscape matrices, shifts in predator communities may increase nest predation near forest edges. However, effects of human-driven habitat change on nest predation have mainly been inferred from studies with artificial nests, despite being regarded as poor surrogates for natural ones. We studied variation in predation rates, and relationships with timing of breeding and characteristics of microhabitats and fragments, on natural white-starred robin Pogonocichla stellata nests during three consecutive breeding seasons (2004,2007) in a Kenyan fragmented cloud forest. More than 70% of all initiated nests were predated during each breeding season. Predation rates nearly quadrupled between the earliest and the latest nests within a single breeding season, increased with distance to the forest edge, and decreased with the edge-to-area ratio of forest fragments. These spatial relationships oppose the traditional perception of edge and fragmentation effects on nest predation, but are in line with results from artificial nest experiments in other East African forests. In case of inverse edge and fragmentation effects on nest predation, such as shown in this study, species that tolerate edges for breeding may be affected positively, rather than negatively, by forest fragmentation, while the opposite can be expected for species restricted to the forest interior. The possibility of inverse edge effects, and its conservation implications, should therefore be taken into account when drafting habitat restoration plans. [source] Forest Elephants: Tree Planters of the CongoBIOTROPICA, Issue 4 2009Stephen Blake ABSTRACT The abundance of large vertebrates is rapidly declining, particularly in the tropics where over-hunting has left many forests structurally intact but devoid of large animals. An urgent question then, is whether these ,empty' forests can sustain their biodiversity without large vertebrates. Here we examine the role of forest elephant (Loxodonta africana cyclotis) seed dispersal in maintaining the community structure of trees in the Ndoki Forest, northern Congo. Analysis of 855 elephant dung piles suggested that forest elephants disperse more intact seeds than any other species or genus of large vertebrate in African forests, while GPS telemetry data showed that forest elephants regularly disperse seeds over unprecedented distances compared to other dispersers. Our analysis of the spatial distribution of trees from a sample of 5667 individuals showed that dispersal mechanism was tightly correlated with the scale of spatial aggregation. Increasing amounts of elephant seed dispersal was associated with decreasing aggregation. At distances of<200 m, trees whose seeds are dispersed only by elephants were less aggregated than the random expectation, suggesting Janzen,Connell effects on seed/seedling mortality. At the landscape scale, seed dispersal mode predicted the rate at which local tree community similarity decayed in space. Our results suggest that the loss of forest elephants (and other large-bodied dispersers) may lead to a wave of recruitment failure among animal-dispersed tree species, and favor regeneration of the species-poor abiotically dispersed guild of trees. [source] Combining Biogeographic and Phylogenetic Data to Examine Primate Speciation: An Example Using Cercopithecin MonkeysBIOTROPICA, Issue 4 2009Jason M. Kamilar ABSTRACT We combined phylogenetic and biogeographic data to examine the mode of speciation in a group of African monkeys, the Cercopithecini. If allopatric speciation is the major force producing species, then there should be a positive relationship between the relative divergence time of taxa and their degree of geographic range overlap. Alternatively, an opposite relationship between divergence time and geographic range overlap is consistent with sympatric speciation as the main mechanism underlying the cercopithecin radiation. We collected biogeographic and phylogenetic data for 19 guenon species from the literature. We digitized geographic range maps and utilized three different phylogenetic hypotheses based on Y chromosome, X chromosome, and mitochondrial (mtDNA) data. We used regressions with Monte Carlo simulation to examine the relationship between the relative time since divergence of taxa and their degree of geographic range overlap. We found that there was a positive relationship between relative divergence time and the proportion of geographic range overlap between taxa using all three molecular data sets. Our findings provide evidence for allopatric speciation being the common mode of diversification in the cercopithecin clade. Because most of these primates are forest adapted mammals, the cyclical contraction and expansion of African forests from the late Miocene to the present has likely been an important factor driving allopatric speciation. In addition, geographic barriers such as the Congo and Sanaga rivers have probably played a complementary role in producing new species within the clade. [source] | |||||||||||||