Biodiversity and conservation value of an Atlantic central African forest: the Ngovayang Massif (Cameroon)

A total of 7967 individuals with dbh ≥ 10 cm were recorded, belonging to 583 species, 267 genera and 71 families. The mean number of stems was 532 ± 75 stems ha-1. The mean Fisher's alpha index was 42.4 ± 6.5. Taking into account other data available, the list of vascular plants known in the Massif reaches a total of 1497 species. We found 224 species of high conservation value, including Cameroon endemics and other rare and threatened species. Species richness and endemism are comparable to those of the richest known sites in Central African forests. Topographic heterogeneity, high precipitation and atmospheric humidity owing to the proximity of the ocean, and permanence of a forest cover during past geological times probably all contribute to explaining the Massif's high tree diversity and endemism. This study highlights the botanical importance of the poorly studied Ngovayang forest within the Lower Guinea region, justifying efforts for improved assessment of this value and for the development of suitable national conservation strategies

Submontane forests, their ecology, history and contribution to African biodiversity: what do ant/plant symbioses tell us?

Much work on the impact of past climatic fluctuations on the structure, distribution and genesis of biodiversity in Central Africa has focused on contrasts between rainforest and savannah biomes, and to a lesser extent on montane vs. lowland rainforests. Each of these biomes is characterized by different dominant plant taxa: grasses in savannahs, diverse tree species in lowland rainforests, and a relatively small number of tree species, distinct often at the familial level, in montane rainforests. These dominant taxa are in turn characterized by distinctive macro- and microfossils, and in the case of savannah and forest by different carbon isotopic signatures. Shifts in their distribution in space and time are thus evident in the fossil record. In contrast, much less is known about the historical biogeography of two more subtly contrasting kinds of communities, namely the lowland and submontane Guineo-Congolian rainforests. Floras and faunas of these two elevational zones include many related, but ecologically distinct, species, subspecies or ecotypes, and the broader application of molecular phylogeography is likely to reveal many further cases of cryptic genetic differentiation in relation to elevation. Whereas many submontane taxa have vicariant species essentially in lowland forests (e.g., Allanblackia, Pterygota, Scaphopetalum), some have more relatives at higher altitudes (e.g., Ocotea, Syzygium), suggesting different evolutionary histories. Pollen grains of related lowland and submontane plants are usually indistinguishable, and pollen spectra of lowland and submontane plant assemblages may be difficult to distinguish at best. Thus, the fossil record is largely silent on how climatic fluctuations have affected the distribution of lowland and submontane forests and their distinctive biodiversity, and palynologists and paleoecologists have accorded relatively little attention to the question. Nevertheless, this component of the biotic response to climatic change is most interesting in evolutionary terms, for its study often reveals speciation events that are recent, or even still in progress. After a brief review of biogeographical patterns in African submontane forests, we examine in detail how the different responses of ants to plants to elevational gradients has promoted the diversification of symbiotic ant/plant mutualisms within Guineo-Congolian rainforests, contributing to both the genesis of biodiversity (in speciation-engine "cradles") and its preservation against extinction (in refugial "museums"). (Texte intégral

Phylogenetic relationships in two African Cedreloideae genera (Meliaceae) reveal multiple rain/dry forest transitions

Establishing phylogenetic relationships allows investigating how species diversity has evolved in various ecosystems. The genera Entandrophragma and Khaya contain tree species distributed in different African biomes (lowland rain forest, lowland dry forest, mountain forest), allowing to examine how (single or multiple events) and when the processes of diversification led to biome transitions. Based on the sequencing of plastid genome (pDNA: c. 160,000 bp) and ribosomal DNA (rDNA: c. 7,000 bp) and habitat characteristic data for each species, we have: (1) reconstructed phylogenetic relationships between species and estimated the dates of divergence between the main lineages, and (2) reconstructed ancestral states regarding biome preferences. The globally consistent phylogenetic tree topologies obtained with both markers in Entandrophragma show five main clades that are quite consistent with previously-defined sections based on reproductive characters of flowers. By contrast, in Khaya, pDNA and rDNA show divergent topologies, possibly due to a more recent diversification involving incomplete lineage sorting and/or recurrent hybridization events. Two major periods of diversification were highlighted: one for Entandrophragma species during the Oligo- Miocene, and a second, during the Pleistocene, concerned both genera at the intraspecific level for Entandrophragma and at the interspecific level for Khaya. These different diversification periods coincide with three major biomes shifts in Entandrophragma. The first habitat transition from rain to dry forests occurred during the Oligo-Miocene and two other transitions were inferred during the Pleistocene, one from rain forest to dry forest and another from rain forest to high altitude mountain forest

Do the clothes make the criminal? The influence of clothing match on identification accuracy in showups

Showups, a single suspect identification, are thought to be a more suggestive procedure than traditional lineups by the U.S. Supreme Court and social science researchers. Previous research typically finds that a clothing match in showup identifications increases false identifications. However, these experiments do not allow for a determination of whether this increase arises from a change in response bias, reduced discriminability, or both. In the present study, participants viewed a mock crime video and made a showup identification with either a clothing match or mismatch. Contrary to prior research, the best discriminability occurred when the guilty and innocent suspects wore clothing that matched the clothing worn during the crime. A clothing match also resulted in a more liberal response bias. The results are consistent with the principle of encoding specificity and the outshining hypothesis, as instantiated in the item, context, ensemble theory. Practical implications are discussed

Stationary solutions of the one-dimensional nonlinear Schroedinger equation: I. Case of repulsive nonlinearity

All stationary solutions to the one-dimensional nonlinear Schroedinger equation under box and periodic boundary conditions are presented in analytic form. We consider the case of repulsive nonlinearity; in a companion paper we treat the attractive case. Our solutions take the form of stationary trains of dark or grey density-notch solitons. Real stationary states are in one-to-one correspondence with those of the linear Schr\"odinger equation. Complex stationary states are uniquely nonlinear, nodeless, and symmetry-breaking. Our solutions apply to many physical contexts, including the Bose-Einstein condensate and optical pulses in fibers.Comment: 11 pages, 7 figures -- revised versio

Measurement of one-particle correlations and momentum distributions for trapped 1D gases

van Hove's theory of scattering of probe particles by a macroscopic target is generalized so as to relate the differential cross section for atomic ejection via stimulated Raman transitions to one-particle momentum-time correlations and momentum distributions of 1D trapped gases. This method is well suited to probing the longitudinal momentum distributions of 1D gases in situ, and examples are given for bosonic and fermionic atoms.Comment: 4 pages, 2 .eps figure

A Study of Unemployment Insurance in Texas

This study is an attempt to provide a comprehensive review of the Texas unemployment insurance program that will yield a greater understanding of the factors that have brought the program to its present position and will give some insight into what can be done to improve the system

Speech Communication

Contains reports on five research projects.C.J. Lebel FellowshipNational Institutes of Health (Grant 5 T32 NSO7040)National Institutes of Health (Grant 5 R01 NS04332)National Institutes of Health (Grant 5 R01 NS21183)National Institutes of Health (Grant 5 P01 NS13126)National Institutes of Health (Grant 1 PO1-NS23734)National Science Foundation (Grant BNS 8418733)U.S. Navy - Naval Electronic Systems Command (Contract N00039-85-C-0254)U.S. Navy - Naval Electronic Systems Command (Contract N00039-85-C-0341)U.S. Navy - Naval Electronic Systems Command (Contract N00039-85-C-0290)National Institutes of Health (Grant RO1-NS21183), subcontract with Boston UniversityNational Institutes of Health (Grant 1 PO1-NS23734), subcontract with the Massachusetts Eye and Ear Infirmar