The modern pollen-vegetation relationship of a tropical forest-savannah mosaic landscape, Ghana, West Africa

Transitions between forest and savannah vegetation types in fossil pollen records are often poorly understood due to over-production by taxa such as Poaceae and a lack of modern pollen-vegetation studies. Here, modern pollen assemblages from within a forest-savannah transition in West Africa are presented and compared, their characteristic taxa discussed, and implications for the fossil record considered. Fifteen artificial pollen traps were deployed for 1 year, to collect pollen rain from three vegetation plots within the forest-savannah transition in Ghana. High percentages of Poaceae and Melastomataceae/Combretaceae were recorded in all three plots. Erythrophleum suaveolens characterised the forest plot, Manilkara obovata the transition plot and Terminalia the savannah plot. The results indicate that Poaceae pollen influx rates provide the best representation of the forest-savannah gradient, and that a Poaceae abundance of >40% should be considered as indicative of savannah-type vegetation in the fossil record

Ecologie et gestion des espèces multi-usages du genre Erythrophleum (Fabaceae-Caesalpinioideae) en Afrique (synthèse bibliographique)

Ecology and management of the multipurpose Erythrophleum species (Fabaceae-Caesalpinioideae) in Africa. A review. Introduction. Widespread in Africa, the Erythrophleum genus includes four tropical tree species with a high economic and socio-cultural value: Erythrophleum ivorense, Erythrophleum suaveolens, Erythrophleum africanum and Erythrophleum lasianthum. Appropriate knowledge of the ecology and the distribution of these species is required for their sustainable management. This paper is based on an extensive literature review and summarizes the available information on the African Erythrophleum species in terms of botany, phylogeography, ecology, forestry and ethnobotany. Literature. Erythrophleum ivorense, E. suaveolens, E. africanum and E. lasianthum are morphologically different and occur in distinct climatic areas. They are non-pioneer light demander (E. ivorense and E. suaveolens) or pioneer species (E. africanum). Their primary mode of dispersal is via ballochore. The seeds have a dormancy period and can remain in the soil for several years. Their reproductive and foliar phenologies are regular and annual. Growth rate varies between species, ranging from 0.65 cm per year for E. ivorense to 0.16 cm per year for E. africanum. These trees are used in traditional medicine. Only E. ivorense and E. suaveolens (Tali) are mainly logged for timber. Conclusions. Erythrophleum species ecological data are better informed for E. ivorense and E. suaveolens because of their economic importance. This review highlights the existing lack of knowledge regarding the phenology (effects of climate, fructification periods), the minimum diameter of fructification and the mechanisms of natural seed dormancy breakage. Targeting such weaknesses is required to create or re-evaluate methods of conservation and/or enhancement of populations and logging practices

Evolution of the regular zone of histone H1 in Fabaceae plants

An analysis of the historic H1 subtype, H1-1, in eight legumes belonging to four genera of the tribe Vicieae (Pisum, Lathyrus, Lens, and Vicia), revealed an extended region consisting of the tandemly repeated AKPAAK motifs. We named this region the Regular zone (RZ). The AKPAAK motifs are organized into two blocks separated by a short (two or six amino acids) intervening sequence (IS). The distal block contains six AKPAAK motifs, while the number of repeats in the proximal block varies from six in V. faba to seven in the other species. In V. hirsuta, the first two repeated units of the proximal block are octapeptides AKAKPAAK. The apparent rate of synonymous substitutions in the blocks of RZ is much higher than in the rest of the gene. This can be explained by repeat shuffling within each block. In the C-domain of the orthologous H1 subtype froth Medicago truncatula (tribe Trifolieae), a region corresponding to the RZ of Vicieae species was found. It also consists of two blocks of AKPAAK motifs (four and three repeats in the proximal and distal blocks, respectively). These blocks are separated by a 20-amino acid IS. The first 20 amino acids of the Medicago RZ are not part of AKPAAK repeats. We hypothesise that the RZ has most probably evolved as a result of an expansion of AKPAAK repeats from two separate sites in the C-domain. This process started tens of millions of years ago and was most likely directed by positive selection