11C-Autoradiographs to image phloem loading

Generally, tree species load photoassimilates passively into the phloem, while herbaceous species load actively. These phloem loading strategies have implications for phloem sugar concentration and growth potential. Whereas, in previous research, phloem loading identification was performed with 14C-autoradiography, we suggest 11C-autoradiography, because of its compatibility with plant-PET (positron emission tomography) scans. Because 11C-autoradiography has been hardly used in plant sciences so far, it was tested in contrasting plant species: one temperate tree species, Populus tremula L., three tropical tree species, Erythrophleum suaveolens (Guill. & Perr.) Brenan, E. ivorense A. Chev., and Maesopsis eminii Engl., and two herbaceous crop species Solanum lycopersicum L. and S. tuberosum L. Our results confirmed that P. tremula is a passive loader, and Solanum spp. are active loaders. Erythrophleum spp. and young leaves of M. eminii showed the expected passive loading strategy, but the mature leaves of M. eminii showed an uncommon pattern. Images corrected for leaf tissue thickness supported that mature leaves of M. eminii used active phloem loading, which is linked to continuous investment in growth and new leaves, supporting the lower carbon storage levels often observed in tropical tree species. With this study, we demonstrate that 11C-autoradiography is a powerful tool to acquire detailed tracer distribution in leaves to typify phloem loading strategies in plant species

Biogéographie des forêts d'Afrique centrale : Déterminants, menaces et priorités de conservation des assemblages de mammifères

peer reviewedAim: Central Africa shelters diverse and iconic megafauna, which is threatened by climate and land-use changes and increased hunting-induced defaunation. Though crucial for coordinating regional conservation actions, how species assemblages are spatially structured remains poorly understood. This study aims to fill this knowledge gap for mammals across central African forests.Location: Tropical moist forests from Nigeria to the Albertine Rift. Methods: An extensive compilation of forest-dwelling mammal species lists was made from wildlife and bushmeat- related surveys across central Africa. A beta-diversity approach enabling the clustering of surveys composed of similar species was imple-mented to identify and delimit zoogeographic districts, separately for three well- documented mammal orders: carnivores, primates and artiodactyls. Random forest classification models were then used to identify the environmental determinants of the district's distribution and to produce a continuous zoogeographic map (and associ-ated uncertainties) critical to assess the conservation status of each district and their ongoing threats. Results: While carnivores do not present a clear spatial structure within central African forests, our findings highlight the structuring role of rivers on both primate and artiodactyl assemblages' distributions. We retained eight and six spatially congru-ent districts for primates and artiodactyls, respectively. These districts were shaped by the Ubangi-Congo River system, and the Cross and Sanaga Rivers, with a second-ary role of insularity and precipitation identified for primates. Highly threatened dis-tricts were highlighted, especially in Nigeria and in the Democratic Republic of Congo, the latter including vast areas that are understudied and poorly represented in the protected area network. Main Conclusions: Beyond refining our understanding of the diversity and uniqueness of mammalian assemblages across central African forests, our map of zoogeographic districts has far- reaching implications for the conservation of highly threatened taxa, allowing to target species and areas of interest for further sampling, conservation and rewilding efforts.PPECF - Programme de Promotion de l'Exploitation Certifiée des Forêts15. Life on lan

Climatic niche lability but growth form conservatism in the African woody flora

International audienceClimatic niche evolution during the diversification of tropical plants has received little attention in Africa. To address this, we characterised the climatic niche of >4000 tropical African woody species, distinguishing two broad bioclimatic groups (forest vs. savanna) and six subgroups. We quantified niche conservatism versus lability at the genus level and for higher clades, using a molecular phylogeny of >800 genera. Although niche stasis at speciation is prevalent, numerous clades individually cover vast climatic spaces suggesting a general ease in transcending ecological limits, especially across bioclimatic subgroups. The forest biome was the main source of diversity, providing many lineages to savanna, but reverse shifts also occurred. We identified clades that diversified in savanna after shifts from forest. The forest-savanna transition was not consistently associated with a growth form change, though we found evolutionarily labile clades whose presence in forest or savanna is associated respectively with climbing or shrubby species diversification

growth_common_garden

Growth in diameter in the common garden experiement for E. ivorense and E. suaveolens

AE_WP_Erythrophleum

Collected AE signals and water potential used to construct an acoustic vulnerability curves for E. ivorense ansd E. suaveolens. The AE signals were cumulated over the measurement period, and averaged over 5 minutes. The endpoint of the VCAE was based on the local maximum in the third derivative, following the strongest decrease in the first derivative. Cumulative acoustic emissions were then rescaled between zero and the defined endpoint to obtain a relative percentage of cavitation-related AE (%). The continuous water potential x-axis of the VCAE was obtained from a segmented linear regression relation between point measurements of xylem water potential, and xylem shrinkage monitored by dendrometers

Does metabolomic diversity correlate with neutral genetic diversity? The case of tropical trees

info:eu-repo/semantics/publishe

Connections between metabolic diversity and neutral genetic diversity. The case of a wild tree of African tropical forests

info:eu-repo/semantics/publishe

Study of connections between metabolic and neutral genetic diversities based on data integration on wild plants

info:eu-repo/semantics/publishe

Does the Phytochemical Diversity of Wild Plants Like the Erythrophleum genus Correlate with Geographical Origin?

Secondary metabolites are essential for plant survival and reproduction. Wild undomesticated and tropical plants are expected to harbor highly diverse metabolomes. We investigated the metabolomic diversity of two morphologically similar trees of tropical Africa, Erythrophleum suaveolens and E. ivorense, known for particular secondary metabolites named the cassaine-type diterpenoids. To assess how the metabolome varies between and within species, we sampled leaves from individuals of different geographic origins but grown from seeds in a common garden in Cameroon. Metabolites were analyzed using reversed phase LC-HRMS(/MS). Data were interpreted by untargeted metabolomics and molecular networks based on MS/MS data. Multivariate analyses enabled us to cluster samples based on species but also on geographic origins. We identified the structures of 28 cassaine-type diterpenoids among which 19 were new, 10 were largely specific to E. ivorense and five to E. suaveolens. Our results showed that the metabolome allows an unequivocal distinction of morphologically-close species, suggesting the potential of metabolite fingerprinting for these species. Plant geographic origin had a significant influence on relative concentrations of metabolites with variations up to eight (suaveolens) and 30 times (ivorense) between origins of the same species. This shows that the metabolome is strongly influenced by the geographical origin of plants (i.e. genetic factors).info:eu-repo/semantics/publishe