ORAL PRESENTATIONS

Keynote - Understanding tropical forest ecology through biogeochemistry

Marijn Bauters

Ghent University, CAVElab - Computational & Applied Vegetation Ecology

Tropical forests are a key component in the global carbon cycle and host an important share of global biodiversity. However, they are in peril, with changing climate and intensifying land-use change increasingly putting pressure on this biome. Understanding the functioning of these forests is essential to accurately predict future trajectories of forest ecosystems across the tropics. In my talk, I will argue that building this understanding should be done 1) from a multi-disciplinary perspective, and 2) without overly relying on generalizations across regions. To exemplify this, I will show how studying central African forests – by combining biogeochemistry and ecology - have led us to rethink long-standing paradigms of tropical forest functioning. These advances are not only essential for our fundamental understanding of tropical forest functioning, but can also greatly impact the practical decision making to optimize conservation efforts.

Do the immediate effects of whole genome duplication facilitate polyploid establishment in stressful environments?

Quinten Bafort ^1,2, Tian Wu ², Annelore Natran ², Olivier De Clerck ¹, Yves Van de Peer ^1,2,3,4

¹ Ghent University, ² VIB-UGent Center for Plant Systems Biology, ³ Nanjing Agricultural University, ⁴ University of Pretoria

Polyploidisation or genome duplication is one of the main drivers of plant evolution. Often such a duplication coincides with considerable morphological, physiological and even phytochemical changes. Polyploid plants are often larger and sturdier than diploids, and some are more resistant to abiotic stress e.g. drought. Not surprisingly, many economically important crops are polyploid e.g. common wheat, cotton, sweet potatoes, coffee, banana, oat, watermelon, strawberries. Nevertheless being polyploid comes at a cost. Neopolyploids face many challenges e.g. interploidy competition, low genetic diversity, minority cytotype exclusion, genomic shock and meiotic/mitotic irregularities. As if that were not enough, most neopolyploids have a lower fitness than their diploid ancestors. Consequently polyploid establishment is one of the biggest mysteries in polyploidy research. There is increasing evidence that the fate of neopolyploids depends strongly on the environment. We used a common garden experiment on genetically diverse neopolyploid strains of the greater duckweed Spirodela polyrhizha to investigate the phenotypic effects of polyploidisation, and its impact on fitness (growth) over a range of environmental conditions.

Invasion dynamics of the neotropical tree Cecropia peltata L. (Urticaceae) in Cameroon

Claire Baudoux ¹, Célia Paris ², Olivier Hardy ³, Achille Biwolé ⁴, Narcisse Kamdem ⁵, Patrick Heuret ⁶

¹ Université Libre de Bruxelles, ² École normale supérieure Paris-Saclay, ³ Université Libre de Bruxelles, ⁴ Université de Douala, ⁵ Université de Yaoundé I, ⁶ Institut national de la recherche agronomique, Université de Montpellier.

Cecropia peltata, a neotropical tree listed as one of the "100 most invasive species in the world", became invasive in Cameroon after it was introduced around 1900 to the Limbe Botanical Garden, on the southwest coast of the country. Since then, this species has spread throughout the coastal region and some scientists have speculated that it may replace Musanga cecropioides, a native Central African tree with similar ecology. In this study, we aimed to (i) establish the current distribution of the invasive Cecropia and assess the possibility that it replaces the native species by comparing their abundance in areas where they coexist, between 1988, 2008 and 2018, (ii) reconstruct the invasion dynamics of C. peltata in Cameroon through population genetic analyses. Using 19 microsatellite loci previously developed for this species, a total of approximately 300 trees were genotyped. Through a field study conducted in 2018, a distribution map of the invasive species C. peltata in Cameroon was established, showing that it has spread up to 100 km from Limbé. Furthermore, the comparison of the relative abundance of C. peltata versus M. cecropioides over time shows a progressive relative increase of the invasive species in the coastal area. In addition, demographic inferences about the invasive population in Cameroon suggest that only a dozen individuals were introduced into Cameroon about 120 years ago and that a demographic expansion followed about 40 years ago. Moreover, genetic signatures of the invasion processes confirm that the population expansion would have started from the botanical garden of Limbé and suggests that the spread of the species have occurred by diffusion, which is common for invasive species, with very limited loss of genetic diversity during the expansion and the apparition of new mutations at the microsatellite markers.

Daily and seasonal rhythms of stem shrinkage and swelling in Luki rainforest

Basile Luse Belanganayi ^1,2, Bhely Angoboy Ilondea ³, Fils Mbungu Phaka ³, Félix Laurent ^2,4, Brice Y. Djiofack ^2,4, Tom De Mil ¹, Richard L. Peters ⁵, Hans Beeckman ²

¹ Gembloux Agro-Bio Tech, University of Liege, Passage des Déportés, 2, 5030 Gembloux, Belgium, ² Service of Wood Biology, Royal Museum for Central Africa (RMCA), Leuvensesteenweg 13, 3080 Tervuren, Belgium, ³ Institut National pour l’Etudes et la Recherche Agronomiques, Avenue des Cliniques 13, Kinshasa, D.R. Congo, ⁴ Department of Forest and water Management, Gent University, Coupure Links 653, 9000, Ghent, Belgium, ⁵ Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf 8903, Switzerland.

The evidence of climate change on tropical ecosystems is becoming increasingly clear. It is predicted that tropical forest ecosystems could be exposed to higher temperatures and more frequent droughts, with a reduction in their carbon storage capacity and possible vegetation dieback. Given the large amounts of carbon that tropical forests recycle and store, it is therefore a priority to understand how they are already responding and predict their future responses. The radial growth of a tree is a widely used proxy for whole tree growth and can be measured on varying timescales. This research focused on seasonal stem growth, deduced from daily rhythms of shrinkage and swelling, and its relation with climatic seasonality. It was conducted in UNESCO-MAB reserve of Luki, in D.R. Congo, between October 2013 to November 2015 and between September 2018 to March 2020. We examined: (1) When do trees grow and how long does the growing season last? (2) How do weather conditions determine tree’s secondary growth on daily and seasonal basis? To answer these questions, radial stem size-change have been measured on 17 trees belonging to 13 species, using high-precision point dendrometers. Dendrometer’s raw data had been cleaned and processed, then plotted as boxplots to show tree’s daily and seasonal evolution of growth rate (GR), contribution to growth (CG), and probability of growth (PG). On daily basis, the tree’s GR, CG, and PG increase at night, when the daily temperature and VPD are lowest, and decreases during the day. On an annual basis, growth starts around October. GR, CG, and PG increase from this period until December. They decrease in the first half of January and begin to increase again, peaking in April and decreasing to a minimum in July. The dry season (from July to September) is characterized by almost no growth.

The role of climate and fungal taxonomy in the lichenized Trentepohliales communities

Luca Borgato ^1,2, Damien Ertz ^2,3, Fabienne Van Rossum ^2,3, Annemieke Verbeken ¹

¹ Ghent University, Research Group Mycology. KL Ledeganckstraat 35, 9000 Gent, Belgium, ² Meise Botanic Garden, Research Department. Nieuwelaan 38, 1860 Meise, Belgium, ³ Fédération Wallonie-Bruxelles, Direction Générale de l'Enseignement non obligatoire et de la Recherche scientifique, Rue A. Lavallée 1, 1080 Bruxelles, Belgium

Global warming is considered responsible for the increase of lichens associated with trentepohlioid algae in temperate regions. However, little is known about the diversity of Trentepohliales, a group of essentially tropical free-living and lichenized algae. A detailed study of the diversity of lichenized Trentepohliales was carried out in three forests of Western Europe. Additional samples of trentepohlioid lichens from other regions in the world were also used. A phylogenetic analysis using rbcL locus was performed, and associations between phylogenetic distances of photobionts and ecological factors (climate, geographic location, mycobiont host taxonomy and substratum) were tested by variation partitioning and phylogenetic signal analyses. Results highlighted an unexpected high diversity of the Trentepohliales in extratropical regions. The phylogenetic patterns showed selectivity of some algae in the mycobiont choice and vice-versa, while others had the ability to associate with several partners. Photobionts seemed to be less selective than mycobionts. The main factors influencing lichenized algal communities were fungal taxa and climate. Photobiont switching between mycobiont species as well as between lichenized and free-living lifestyles appeared to drive the evolution of Trentepohliales and might explain the high cryptic diversity observed.

SMARTWOOD ID: Smart classification of Congolese timbers – On the why and how of digitizing wood collections

Ruben De Blaere ¹, Kévin Lievens ², Hans Beeckman ³, Jan Van den Bulcke ⁴, Jan Verwaeren ⁵, Wannes Hubau ⁶, Tom De Mil ⁷, Joris Van Acker ⁸

Africamuseum Tervuren, Ghent University, ULiège

Wood identification is a key step in the enforcement of laws and regulations aiming at combatting illegal timber trade. It is a major concern especially for countries with species-rich forest resources, with a high demand for automatized wood identification systems. Robust wood identification tools depend on a solid database of reference material. Reference material for wood identification is typically curated in botanical collections (xylaria) of wood, which mostly consists of secondary xylem. Specimens from the Tervuren xylarium are used as source of data of tree species with potential use as timber. A database has been created of high-resolution optical scans of the end-grain surfaces enriched with expert wood anatomical descriptions of macroscopical features. These can serve as annotated training data to develop interactive identification keys and an artificial intelligence for computer vision based wood identification. A first version of the database consists of images of 1190 species, with 4 or more images for every species, from the Democratic Republic of the Congo, potentially usable as timber. Every image comes from a different specimen and thereby from a different tree.

The association between rainforest disturbance and recovery, tree community composition, and community traits in the Yangambi area in the Democratic Republic of the Congo

Jonas Depecker ^1,2,3

¹ KU Leuven, ² Meise Botanic Garden, ³ KU Leuven Plant Institute

Despite their key role in biodiversity conservation, forests in the Congo Basin are increasingly threatened by human activities, but it remains challenging to assess the impact of forest deg- radation under a more or less intact canopy. Likewise, forest recovery following agricultural abandonment remains poorly understood in the Congo Basin. Here, we surveyed 125 vegetation quadrats across 25 forest inventory plots in the Yangambi area. We aimed to find associations between both selective logging and forest recovery, and a range of forest community and tree community trait characteristics, as compared to reference undisturbed old-growth forest. We found that plots in undisturbed old-growth forest harboured both more tree individuals and tree species with a higher wood density as compared to plots in disturbed old-growth forest. In addition, their tree community composition was significantly different, whereas species diversity recovered since relatively recent agricultural abandonment (< 60 years), community com- position and forest structure remained significantly different from the plots in undisturbed old- growth forest. Our study provides some insights into the rate of forest recovery in the Congo basin after agricultural abandonment and highlights the need of proper conservation of the remaining relatively undisturbed old-growth forests. Finally, we stress the need for more extensive vegetation surveys in the Congo Basin to further unravel the effects of anthropogenic disturbance.

Generation time explains molecular evolutionary pace in Annonaceae

Luiz Fonseca ¹, Timothy R. Baker ², R. Toby Pennington ³, Silke Sercu ¹, Robbe Strybol ¹, Lars Chatrou ¹

¹ Ghent University, ² University of Leeds, ³ University of Exeter

Generation time is widely considered the main force behind extensive molecular evolutionary patterns. It shapes differences in nucleotide substitutions between species and lineages, confounding the molecular clock. Here we assemble a comprehensive phylogenetic tree of Annonaceae and use this tree as source of molecular substitution rates. We use the mean branch length, or sum of the branch lengths from tip to root divided by the number of branches, and the path length, or sum of the branch lengths from tip to root, as variables for each species. Using these two variables, we confirm previous results showing significant difference in substitution rates between the subfamilies Annonoideae and Malmeoideae. Combining the two rate variables with generation time obtained from demographic studies, we demonstrate a negative and significant correlation between generation time and the differences in substitution rates between the two subfamilies of Annonaceae. The subfamily Annonoideae has species with significantly longer life cycles compared to the subfamily Malmeoideae. To support our findings, simulations were implemented, which provide statistical support for our results.

Variation in onset of leaf unfolding and wood formation in a Central African tropical tree species

Bhely Angoboy Ilondea ^1,2,3, Jan Van den Bulcke ³, Hans Beeckman ², Joris Van Acker ³, Camille Couralet ^2,3, Adeline Fayolle ⁴, Wannes Hubau ^2,3, Chadrack Kafuti ^2,3,5, Mélissa Rousseau ², Emmanuel Kasongo Yakusu ^2,3,9, Alain Kaka di-Makwala ¹, Nils Bourland ^2,6,7, Victor Deklerck ^2,8, Corneille Ewango ⁹, Tom De Mil ^2,3

¹ Institut National pour l’Etude et la Recherche Agronomiques, Kinshasa, Democratic Republic of Congo, ² Royal Museum for Central Africa, Wood Biology Service, Tervuren, Belgium, ³ Laboratory of Wood Technology (UGent-Woodlab), Department of Environment, Ghent University, Ghent, Belgium, ⁴ Forest is Life, TERRA Teaching and Research Centre, Gembloux Agro Bio-Tech, University of Liège, Liège, Belgium, ⁵ Department of Natural Resources Management, Faculty of Agricultural Sciences, University of Kinshasa, Kinshasa, Democratic Republic of Congo, ⁶ Center for International Forestry Research, Bogor, Indonesia, ⁷ Resources & Synergies Development Pte., Ltd., Singapore, Singapore, ⁸ Royal Botanic Gardens, Kew, Richmond, United Kingdom, ⁹ Faculty of Renewable Natural Resources Management, University of Kisangani, Kisangani, Democratic Republic of Congo, Forest is Life, TERRA Teaching and Research Centre, Gembloux Agro Bio-Tech, University of Liège, Liège, Belgium

A diversity of phenological strategies has been reported for tropical tree species. Defoliation and seasonal dormancy of cambial activity inform us on how trees cope with water stress during the dry season, or maximize the use of resources during the rainy season. We study the matching between defoliation and cambial activity for Prioria balsamifera, a key timber species in the DRDC. We (i) evaluated the seasonality of cambial activity and synchrony of phenology among trees in response to climate and (ii) identified the seasonality of leaf phenology and its relation with cambial phenology. Historic defoliation data were collected every ten days in the Luki Man and Biosphere Reserve using weekly crown observations whereas recent observations involved time-lapse cameras. Cambial pinning was performed on ten trees during 20 months and radius dendrometers were installed on three trees during 13 months. Tree rings were measured on cores from 13 trees and growth synchrony was evaluated. We found that P. balsamifera defoliates annually with a peak observed at the end of the dry season and the beginning of the rainy season. The new leaves unfolded shortly after shedding of the old leaves. The peak defoliation dates varied across years from 12 September to 14 November and the fraction of number of trees that defoliated at a given time was found to be negatively correlated with annual rainfall and temperature; during the dry season when precipitation and temperatures are the lowest. Wood formation (radial growth), was found to be highly seasonal, with cambial dormancy occurring during the dry season and growth starting at the beginning of the rainy season. Individual ring-width series don’t cross date well. The within species variability of leaf phenology and cambial rhythms provides information on resistance of the population against climate changes.

Preliminary results on the revision of the African Laetiporus

Jean-Claude Rizinde ^{1, 2}, Mario Amalfi ^3,4, Cony Decock ¹

¹ Mycothèque de l’Université catholique de Louvain (BCCM/MUCL), Belgique, ² Université de Goma, Faculté des Sciences Agronomiques, RD Congo ³ Meise Botanic Garden, Nieuwelaan 38, 1860 Meise, Belgium, ⁴ Service Général de l’Enseignement Supérieur et de la Recherche Scientifique/Belgique

The tropical African Laetiporus species are revised. The status of L. discolor, described from Mauritius, remains uncertain. The small fragments left from type specimen do not allow for a clear circumscription of the species. Laetiporus oboensis and Laetiporus tenuiculus are described as new from the African insular equatorial of island of São Tomé based on phylogenetic, morphological, and distribution data. Laetiporus oboensis and L. tenuiculus are sympatric in the afromontane forest of the Western Africa, insular São Tomé. Laetiporus oboensis is characterized by compound basidiomes, with densely imbricated pilei in orange tint, a lobed margin, large pores, and basidiospores averaging 4.8 × 3.7 μm, whereas L. tenuiculus has mostly solitary, small, thin basidiomes, with pale flesh to pale orange pileus, an incised margin, smaller pores, and basidiospores averaging 5.4 × 4.2 µm. A third potential species (or species complex), Laetiporus sp. also inhabits the eastern African mountain range. It is characterized by white to very light brown imbricated pileus, xx pores / mm, and basidiospores yy. The three species are phylogenetically closely related.

Untangling forest history in the Yangambi Biosphere Reserve (Tshopo, D.R. Congo) through fossil charcoal analysis

Alain Kadorho ^1,2,3, John Tshibamba ⁴, Seintsheng Ntamwira ³, Jean-Pierre Messina ⁵, Jan Van den Bulcke ¹, Wannes Hubau ^1,2

¹ UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, B-9000 Gent, Belgium, ² Royal Museum for Central Africa, Wood Biology Service, Leuvensesteenweg 13, B-3080 Tervuren, Belgium, ³ Université Officielle de Bukavu, Faculté des Sciences, Département de Biologie, B.P. 570, Bukavu, Democratic Republic of Congo, ⁴ Université de Mbujimayi, Faculté des Sciences appliquées, Mbujimayi, Democratic Republic of Congo, ⁵ Université Notre Dame du Kasayi, Kasayi, Democratic Republic of Congo.

Considering the period of the third millennium forest crisis around 2500 years BP in the forests of the Congo Basin, forest units should converge today into mature and identical communities. The factors determining the current distribution of the supposedly mature tropical forests of Central Africa remain an enigma to be resolved. In Yangambi, the fragmentation of the forest massif into a forest mosaic remains unclarified. Furthermore, understanding of the resilience or long-term response of Central African forests to environmental change over the past millennia remains limited in this part of the world. Our main hypothesis is that past forest disturbances could explain the origin of the current forest mosaic in the canopy of Central African tropical forests. These disturbances were either anthropogenic in nature, or natural (e.g. climate change). Our main objective is to untangle the origin of the forest mosaic that constitutes the canopy of the Central African rainforest today. This study is conducted in permanent forest inventory plots in the Yangambi Biosphere Reserve, located in the central Congolese basin on the right bank of the Congo River. To achieve this objective, we will sample fossil charcoal and soil. These field data will allow us to make anthracomass estimate, dating and anatomical analysis of charcoal and geochemical analysis. With these analysis, we expect to find anthracomass and forest types relationship. Further analysis of our dataset will allow to obtain charcoal dating and forest types relationship or vegetation change over time. The Botanical identification of charcoal fragments or past vegetation will be known. We will find the influence of geochemical data on the past and actual forest types. The implications of these results for understanding long-term forest dynamic or resilience and management of tree species will be discussed.

Drivers of variations in height-diameter allometry of an emergent tropical tree species

Chadrack Kafuti ¹, Jan Van den Bulcke ¹, Hans Beeckman ², Joris Van Acker ¹, Wannes Hubau ¹, Tom De Mil ³, Hulda Hatakiwe ⁴, Brice Djiofack ¹, Adeline Fayolle ³, Grace Jopaul Loubota Panzou ⁵, Nils Bourland ²

¹ Ghent University, ² Royal Museum for Central Africa, ³ Gembloux AgroBioTech, ⁴ Center for International Forestry Research, ⁵ Université Marien Ngwabi

Reliable tree height-diameter (H-D) allometries are a key tool for the estimation of forest productivity and Above Ground Biomass (AGB). Most existing H-D allometries developed for the tropical region are based on large-scale multi-species datasets, and their use to derive information on productivity and AGB at the species level is prone to uncertainties. The single-species H-D allometric equations available are mainly focused on monocultures or stands with simple tree species mixtures and did not account for the site effects. Here we measured the height and diameter of 2,288 trees of the emergent tree species Pericopsis elata in DRC and in Cameroon. We first examined how accurate multispecies H-D allometric equations are in predicting the total height of P. elata. We then tested whether single-species H-D allometric equations vary between sites. We developed the first H-D allometry of P. elata and tested whether and how stand-level and environmental variables affect this H-D allometry at the regional level. We additionally evaluated whether tree-level variables are important at the local level where climate and stand development stage are expected to be less variable. We found that pantropical, regional and local H-D allometries significantly underestimate the total height of P. elata. The local multi-species H-D allometry developed for Yangambi showed the highest underestimation in all the studied sites. This result supports the need for an H-D allometry specific for P. elata. The species-level H-D allometry developed showed significant underestimations for trees from the disturbed and undisturbed forests in DRC, while overestimations were observed for similar sites in Cameroon. We showed that even within a single species, a substantial variation exists between sites. The basal area showed to be a significant covariate accounting for the site effects at the regional-scale where climate variables showed minor effects. However, at the local-scale, none of climate or stand variables showed to be significant. Local-scale variation showed to be associated with differences in light availability, highlighting the potential of management options that shape the local environment in driving species productivity.

Taxonomic Review of the east Africa Ipomoea L. and Sweet Potato Wild Relatives (Convolvulaceae)

Samuel Paul Kagame ¹, Lars Chatrou ¹, Ana Rita Simoes ², Anne Muigai ³, Yang Jun ⁴

¹ Ghent University, ² Kew Gardens, ³ Jomo Kenyatta University of Agriculture and Technology, ⁴ Shanghai Chenshan Botanical Garden

Ipomoea L., the largest genus in Convolvulaceae family, comprises of approximately 900 species. This genus is widely distributed in the tropics and subtropics regions. They are characterized by their biglobular stigma, long corolla tube, pronounced midpetalline bands, among others. They have wide range of economic importance, ranging from ornamentals, medicine to food. Some species possess storage roots for example, Ipomoea batatas L. (sweet potato), which have edible storage roots. These roots are an important ecological strategy for plants as they reserve carbohydrates essential for plant survival during and after natural stress like droughts etc. Storage roots occur in at least 71 species of Convolvulaceae, with over half occurring in Africa. These numbers are likely, in reality, higher than documented ones, since roots are not consistently collected or recorded in botanical expeditions. Recent studies have looked at the systematics and evolution of Ipomoea, albeit with methodological and sampling limitations; for example, of the 128 Ipomoea species occurring in Kenya, only 79 species have been included in previous molecular studies. The level of conservation threat of Ipomoea is also largely unknown, whereby only 4% of species across tropical regions have so far been assessed; besides, the latest taxonomic works for the region pre-date molecular analysis of the group and it is also possible that targeted studies in this highly diverse area will reveal new species. We aimed at evaluating Ipomoea species found in the East Africa region and conducted taxonomic review of the group with a focus on ethnobotanical uses and finding some of the wild relatives of sweet potato native in the region. This study will form the basic foundation of subsequent studies that will be conducted on the Ipomoea species found in the East Africa Region.

Analysis of climate change in the forests of the Congo Basin: from local to regional scales

Emmanuel Kasongo Yakusu ^1,2,3, Joris Van Acker ¹, Nils Bourland ^2,4, Hans Beeckman ², Jan Van den Bulcke ¹, Marijn Bauters ^5,6, Pascal Boeckx ⁶, Wannes Hubau ^1,2

¹ UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium, ² Service of Wood Biology, Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium, ³ Faculté de Gestion des Ressources Naturelles Renouvelables, Université de Kisangani, B.P. : 2012, Avenue Kitima, 3, Kisangani, République Démocratique du Congo, ⁴ Center for International Forestry Research, Situ Gede Bogor Barat 16115, Indonesia, ⁵ Department of Green Chemistry and Technology, Isotope Bioscience Laboratory - ISOFYS, Ghent University, Coupure Links 653, 9000 Gent, Belgium, ⁶ UGent-CAVElab, Computational & Applied Vegetation Ecology, Ghent University, Coupure Links 653, 9000 Gent, Belgium.

Understanding the impacts of climate change on the forests of the Congo Basin and their unsustainable exploitation is essential for predicting the future of the Earth. Climate change studies in Central Africa are very weak (and almost rare in DRC). Climate data are often derived from satellites, which are not very efficient in equatorial Africa, or from interpolated gauge datasets, which have very low station coverage in the Congo Basin. Here we illustrate some results of climate change analysis from 61 years (1960-2020) of ground-based climate monitoring focusing on precipitation and temperature in the Yangambi reserve, located in the heart of the Congo Basin. Our newly digitised data from Yangambi represents a unique climate record in the central Congo Basin, a remarkably under-sampled and therefore enigmatic region in climate change research. The ground-based climate observations are then compared with those extracted from the World Rainfall Centre and the Tropical Rainfall Measurement Mission (a satellite product). Our results confirm a long-term increase in temperature and temperature extremes since the 1960s, with a strong acceleration of trends since the early 1990s. Our results also confirm a significant trend towards a drying of the dry season and an intensification of the wet season in the central Congo basin since the early 2000s. The continued intensification of rainfall seasonality in the central Congo Basin, with drier dry seasons and wetter rainy seasons, combined with increased extreme temperature events, will have a significant impact on local livelihoods, health and biodiversity. There is therefore an urgent need to develop nature-friendly forestry, agriculture and agroforestry systems and to establish early warning systems for vector-borne disease outbreaks and ecosystem degradation. To this end, systematic digitisation and recording of the climate in the Congo Basin will be essential, especially as existing satellite and interpolated climate products are not fully representative.

Photobiont diversity and specificity in family Gomphillaceae (lichenized Ascomycota) reveals the importance of Heveochlorella (Trebouxiophyceae) in tropical environments

Elise Lebreton ¹, Emmanuël Sérusiaux ¹, Nicolas Magain ¹

¹ Integrative Biological Sciences research (UR InBioS), Biology Ecology Evolution department (BEE), University of Liège, Botanical Institute B22, Chemin de la vallée, 4, 4000 Liège.

Found in all terrestrial ecosystems, lichens are the result of a symbiosis between a fungus and an alga and/or a cyanobacterium. Lichens are known to grow on various substrates such as rocks, tree bark and soil. In tropical and subtropical environments, colonisation on tree leaves, known as "foliicolous lichens", is an atypical and poorly understood lifestyle for these organisms. A large part of foliicolous lichens belong to the family Gomphillaceae and associate with green algae (Trebouxiophyceae). The identity of these algae is only known for a small number of taxa. In the context of a PhD thesis, we aim to understand the phylogenetic affinities of photobionts with fungi in order to better understand their role in the establishment of lichens on various substrates, in particular on leaves but also on rocks and bark in tropical and subtropical environments. Specimens of Gomphillaceae and associated photobiont were collected in Guadeloupe (Lesser Antilles) and sequenced with two fungal marker genes (nuLSU and mtSSU) and an algal marker gene (RBCL). Additional specimens from around the world were added to determine association patterns on a broader geographical scale. Photobionts of Gomphillaceae are diverse, and sequences obtained represent 13 different clades, most of which belong to, or are closely related to Heveochlorella (whose genus delimitation is unclear), regardless of the substrate colonised by the lichen. A majority of fungi from the genus Gyalectidium show very high specificity towards a clade closely related to Heveochlorella. The presence of the same photobiont in lichenized fungi from other territories, notably New Caledonia (Oceania), indicates a potentially worldwide distribution of several algae. We conclude that the genus Heveochlorella in the broad sense is a major clade of photobionts for family Gomphillaceae from tropical and subtropical regions worldwide and that its ecological significance should be reevaluated.

Impacts of land use change on biomass and diversity in the forest landscape of Yangambi Biosphere Reserve, DRC

Lisette Mangaza ^1,2, Jean-Remy Makana ³, Wannes Hubau ^4,5, Denis Sonwa ⁶, Germain Batsi ³, Adeline Fayolle ¹

¹ University of Liege, ² University of Goma, ³ University of Kisangani, ⁴ Royal Museum for Central Africa (MRAC), ⁵ Ghent University, ⁶ Center for International Forestry Research (CIFOR).

The tropical forests of the Democratic Republic of Congo are threatened by deforestation and forest degradation, which affect tree structure and diversity. This study aims to quantify the loss of biomass and diversity due to deforestation and degradation, focusing on the Yangambi Biosphere Reserve. Four 50 m x 50 m plots were inventoried in each of the eight land-use types identified: mixed mature forest, Gilbertiodendron dewevrei mature forest, food crop fields, fallow land (5 to 10 years), secondary forest (20 to 40 years), cocoa plantations, coffee plantations and oil palm plantations. Biomass stocks in mature forests amount to ~ 400 and 380 Mg ha-1 for G. dewevrei forest and mixed forest respectively. The results show that mature forest loses 50, 70 and 90% of its above-ground biomass when converted to cocoa, coffee and palm plantations, respectively, and almost all (99%) when converted to food crop fields; but when the field is abandoned, biomass gradually recovers to 7.5% after 5-10 years and to 38.8% after 20-40 years. Diversity is also impacted by conversion, and although species richness appears to recover faster than biomass, composition is fundamentally altered. These results provide essential information for quantifying the impacts of 'natural' solutions to climate change: protection of mature forests, improved forest management and reforestation, although the approach needs to be scaled up.

A first Dynamic Global Vegetation model to simulate the carbon dynamics of the Congo Basin rainforests

Félicien Meunier ^1,2, Marijn Bauters ^1,2, Pascal Boeckx ², Hans Verbeeck ¹

¹ Computational and applied vegetation ecology, Ghent University, ² Isotope Bioscience Laboratory, Ghent University

The Congo Basin hosts the second largest expanse of tropical rainforests in the World. As such, it plays a critical role in our changing Earth System among others by being a more efficient Carbon sink than any other tropical forest. Yet, despite the functional, structural, and taxonomic uniqueness of the African biome, most of its process understanding of the Central African forests originates from the Amazon. Because of the striking discrepancy between the paramount importance of the Congo Basin forests on the one hand and the poor scientific and public attention given to these forests on the other, the current generation of land surface models fails at capturing the carbon dynamics in tropical African forests. As of today, these models cannot reliably project the impact of climate and land use changes on the ecosystem services that those forests provide. Here, we present the first attempt to fill this gap by combining a state-of-the-art Land Surface Model with some of the most up-to-date observations of the Carbon cycle in the Congo Basin. More specifically, we developed and calibrated a dynamic vegetation model (the Ecosystem Demography model, version 2) to reproduce the land fluxes from the first ever fluxtower established in the Congo Basin, as well as regrowth trajectories of multiple local chronosequences. We show that the model default version significantly underestimates the ecosystem net productivity and equilibrium biomass while it overestimates the forest regrowth rate after disturbance. When upscaled to the regional scale, the model-data discrepancies led to an overall overestimation of the forest recovery and resilience, which could indicate a higher risk of large-scale diebacks by the end of this century.

Where do macaronesian bryophytes come from?

Sébastien Mirolo

University of Liège

Bryophytes exhibit efficient long-distance dispersal capacities, ‘all-purpose’ genotypes, low levels of endemism and limited biotic interactions. Their community structure and composition are therefore expected to display little differences with continental sources. However, endemic species show different patterns compared to non-endemic: the former have affinities with neotropical clades while the latter are almost the same as in Europe. To test this hypothesis, we identify, based on analyses of floristic similarities, coalescence phylogeographic analyses of non-endemic species, and phylogenies of endemic species, which continental floras are and have been the most likely sources for the Macaronesian flora.

Patterns and drivers of beta diversity across geographic scales and lineages in the Macaronesian flora

Lea Mouton ¹, Jairo Patiño ^2,3, Mark Carine ⁴, Fred Rumsey ⁴, Miguel Menezes de Sequeira ^5,6, Juana María González-Mancebo ², Rosalina Maria de Almeida Gabriel ⁷, Olivier. J. Hardy ⁸, Manuela Sim-Sim ^9,10, J. Alfredo Reyes-Betancort ¹², Flavien Collart ¹¹, Alain Vanderpoorten ¹

¹ University of Liège, Institute of Botany, B22 Sart Tilman, 4000 Liège, Belgium, ² Plant Conservation and Biogeography Group, Department of Botany, Ecology and Plant Physiology, Biology Section, Science Faculty. MailBox 456, University of La Laguna, Tenerife (Canary Islands), 38200, Spain, ³ Island Ecology and Evolution Research Group, Institute of Natural Products and Agrobiology (IPNA-CSIC), C/ Astrofísico Francisco Sánchez 3, La Laguna, Tenerife (Canary Islands), 38206, Spain, ⁴ Algae, Fungi & Plants division, Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom, ⁵ Madeira Botanical Group (GBM), Faculty of Life Sciences, University of Madeira, Campus da Penteada, 9000-390, Funchal, Portugal, ⁶ InBio, Research Network in Biodiversity and Evolutionary Biology, CIBIO-Azores, Pólo dos Açores, 9501-801, Ponta Delgada, Azores, Portugal, ⁷ Azorean Biodiversity Group, CE3C–Centre for Ecology, Evolution and Environmental Changes, Universidade dos Açores, Angra do Heroísmo, 9700-042 Açores, Portugal, ⁸ Evolutionary Biology and Ecology, CP 160/12, Université Libre de Bruxelles, 50 Av. F. Roosevelt 1050 Brussels, Belgium, ⁹ Universidade de Lisboa, Faculdade de Ciências de Lisboa, DBV- Departamento de Biologia Vegetal, 3cE3c - Centre for Ecology, Evolution and Environmental Changes, C2, Campo Grande, 1749-016 Lisboa, Portugal, ¹⁰ Museu Nacional de História Natural e da Ciência, Universidade de Lisboa, Rua da Escola Politécnica, 58, 1250-102 Lisboa, Portugal, ¹¹ Department of Ecology and Evolution (DEE), University of Lausanne, CH-1015 Lausanne, Switzerland, ¹² Unidad de Botánica Aplicada, Instituto Canario de Investigaciones Agrarias, Jardín de Aclimatación de La Orotava, Puerto de La Cruz, Santa Cruz de Tenerife, Spain

To assess whether beta diversity varies across taxa and archipelagos, identify the mechanisms behind beta diversity variation across taxa and archipelagos at different spatial scales, and determine how these variations affect the biogeographic relationships among island land plant lineages. Species turnover and nestedness were compared within and among archipelagos across the four taxonomic groups. The relationship between species turnover and nestedness, climatic, geological and geographic factors was analysed using generalised dissimilarity models. Species turnover, but not nestedness, increased with geographic scale. This increment sequentially decreased from spermatophytes, pteridophytes, and then mosses and liverworts. Species turnover was significantly higher in the Canary Islands than in Azores in pteridophytes and spermatophytes, but similar among archipelagos in bryophytes. Mosses and liverworts exhibited a significantly higher nestedness than spermatophytes, and the reverse trend was observed for species turnover. Precipitation contributed more to the explained deviance of turnover in bryophytes and pteridophytes than in spermatophytes while Island age exhibited the reverse trend. Archipelago adscription significantly contributed to explain turnover in spermatophytes, but not in bryophytes and pteridophytes. Spermatophyte floras clustered by archipelago, whereas the clustering patterns in pteridophyte and bryophyte floras reflect macroclimatic conditions. The lower increment of species turnover with spatial scale and the higher nestedness in bryophytes and pteridophytes than in spermatophytes reflect the variation in dispersal capacities and distributions ranges among land plant lineages. Accordingly, extant climatic conditions contributed more to explain turnover in bryophytes and pteridophytes than in spermatophytes, whereas factors associated with dispersal limitations, including island age, geographic distance, and archipelago adscription, exhibited the reverse trend. The differences in beta diversity patterns, caused by different responses of Macaronesian land plant lineages to the main factors shaping their community composition, explain their different biogeographic affinities, spermatophyte floras clustering by archipelago, whereas pteridophyte and bryophyte floras tend to cluster as a function of macroclimatic factors. These differences reflect distinct mechanisms of origin and diversification among Macaronesian land plant lineages and archipelagos.

Mushrooms of the African Great Lakes Region. Ethnomycology, sensory analysis and nutritional composition

Assumpta Mukandera ¹, Eric Dulière ², Jérôme Degreef ³, Claire Beaufay ⁴, Cony Decock ⁵, Stéphanie Fraselle ⁶, Jean Claude Rizinde ⁷, Charles Karangwa ⁸, Caroline Stévigny ⁹

¹ Université libre de Bruxelles, ² Haute Ecole Léonard de Vinci, ³ Meise Botanic Garden, ⁴ Haute Ecole Léonard de Vinci, ⁵ Université Catholique de Louvain, ⁶ Université libre de Bruxelles, ⁷ Université Catholique de Louvain, ⁸ University of Rwanda-College of Medicine and Health Sciences, ⁹ Université libre de Bruxelles.

The Great Lakes Region is well known for its astonishing biodiversity, but also for its economic and food shortage. The protein sources are extremely low for local populations [1]. The fungal resources found in the mountain forests play important ecological and economic roles. Studies on mushroom diversity and nutritional values have been carried out in various African countries, including the Miombo woodlands of the D.R. Congo [2] but, until now, knowledge about edible mushrooms of the mountain forests is still fragmentary. The overall objective of the present study is to describe the ecology, the use and to assess the nutritional quality of mushrooms consumed in the Great Lakes Region. Their quality as food is also evaluated through food surveys carried out locally for assessing the interest of their consumption in the local diet. Ethnomycological surveys were conducted with local people to determine which species were most valued. For sensory analysis, the fresh sporophores were cooked, and a nine-point hedonic scale method was used to establish food preferences. The sporophores of six wild edible mushrooms (Termitomyces microcarpus (Berk. & Broome) R. Heim, Termitomyces schimperi (Pat.) R. Heim, Termitomyces robustus (Beeli) R. Heim, Auricularia delicata (Mont. ex Fr.) Henn., Schizophyllum commune Fr., and Hypholoma subviride (Berk. & M.A. Curtis) Dennis) and two cultivated species (Pleurotus ostreatus (Jacq.) P. Kumm. And Agaricus bisporus (J.E. Lange) Imbach), were dried, powdered, and analysed for macronutrients and mineral elements compositions. Data were calculated as % on dry matter basis. The results show that all mushroom samples contained interesting amounts of essential nutrients. The ash, crude protein, total lipids and crude fiber were in the ranges of 3.40-10.85%, 9.38-28.77%, 1.13-2.62% and 10.29-44.99% respectively. Among the eight studied mushrooms, Termitomyces genus contains the highest protein amounts. This specific property coincides with their use to treat children suffering from kwashiorkor as reported by the interviewed local populations. Other mushroom species reported for traditional medicine are S. commune used for enhancing sexual potency in men, and A. delicata used for relieving joint pain. Further analyses on the responsible active compounds are needed for scientific confirmation. The analysed samples also contained appreciable amounts of K, Mg, Fe and Cu. The results of sensory analysis revealed a high appreciation for T. microcarpus, T. schimperi, T. robustus, H. subviride, P. ostreatus and A. bisporus, and a moderate appreciation for A. delicata and S. commune as they scored 8 and 6.98 respectively. [1] M. Bertomeu Pardo & G. Durán-Romero, 2022 Food security: Agricultural innovation to increase resilience and adaptation to climate change in developing countries, 40 (1), [2] A. De Kesel, & F. Malaisse, 2010, Edible wild food: Fungi. In: F. Malaisse. How to live and survive in Zambezian open forest (Miombo Ecoregion): 41-56. Gembloux, Presses agronomiques.

Central African Floras

Marc S.M. Sosef

Meise Botanic Garden, Nieuwelaan 38, 1860 Meise, Belgium

A Flora is a tool primarily serving the need for plant identification. It also provides basic information on each species and often acts as a crucial entry to additional data. As such, Flora’s are essential not only to a wide variety of biological research fields, but also in conservation and management. In tropical Africa, the western and eastern regions are covered by several major Flora’s that are complete (Fl. W. trop. Afr., Fl. Trop. E. Africa, Fl. Ethiop., Fl. Somalia, Fl. Tchad) or almost so (Fl. Zamb.). Halfway the previous century, three major Flora series related to C. Africa, Flore du Cameroun, Flore du Gabon, Flore d’Afrique centrale, were started up. All have shown rapid progress at the start, with a notable decline in speed after several decades, leading to an asymptotic production curve. An exception is the Flora of Rwanda, completed in 4 vols, published in 1978-1987 and treating 2383 native species. Flore du Gabon is now well ahead of the other two, with c. 84% treated. The Central African Republic and the Republic of the Congo still remain without any Flora initiative to date. Despite major efforts, and even specific funding, progress of the C. African Flora’s remains slow. Although producing a Flora account is no longer a priority for many taxonomic specialists, the need to reliably identify plant material remains high. The development of e-Flora’s and standards like World Flora Online may support, but probably not speed up the production. Having in mind the huge importance of correctly identified plant material, along with the dwindling taxonomic capacities worldwide, the potential role of identification by image recognition is briefly discussed.

POSTER PRESENTATIONS

A guided tour into genomic contamination detection

Luc Cornet ¹ & Denis Baurain ²

¹ BCCM/IHEM, Mycology and Aerobiology, Sciensano, Bruxelles, Belgium, ² InBioS–PhytoSYSTEMS, Eukaryotic Phylogenomics, University of Liège, Liège, Belgium

Nowadays, genomes constitute the basis of many research endeavors. This is especially true since the decrease of sequencing cost has led to an explosion of the number of genomes in public repositories, prokaryotic or eukaryotic. Estimating the amount of contamination, i.e. the inclusion of unwanted DNA in genomic materials, of this deluge of data has become a field in itself, with numerous algorithms now available and an increasing rate of publication over the years. As newly released tools do not simply replace older ones, but have their own scope, it becomes difficult for scientists to efficiently determine which tool to use in their study. Recently, we have published an overview of the main characteristics and applicability of 18 algorithms dedicated to the estimation of genomic contamination. For instance, the conceptual differences between database-free tools and those associated with a reference database have an effect on detection sensitivity, as do the difference between genome-wide and marker-based methods. Beyond this typology of tools, we present here a new analysis designed to compare algorithms on a large simulated dataset derived from empirical data. This protocol, dubbed CRACOT for CRitical Assessment of Contamination detection at multiple Taxonomic levels, reveals both under- and over-detection by even the most commonly used algorithms, with simulated contamination events ranging from inter-phylum to inter-species.

Monitoring carbon storage potential on spontaneous regrowing forests: a result of the fire exclusion on anthropogenic savannas in the Democratic Republic of Congo

Brice Y. Djiofack ^1,2, Hans Beeckman ¹, Nils Bourland ¹, Basile Luse ^1,3, Félix Laurent ^1,2, Bhely Angoboy Ilondea ⁴, Wannes Hubau ^1,2

¹ Royal Museum for Central Africa, Wood Biology Service, Leuvensesteenweg 13, B-3080 Tervuren, Belgium, ² UGent-Woodlab, Laboratory of Wood Technology, Department of Environment, Ghent University, Coupure Links 653, B-9000 Gent, Belgium, ³ Gembloux Agro-Bio Tech, University of Liege, Passage des Déportés, 2, 5030 Gembloux, Belgium, ⁴ Institut National pour l’Études et la Recherche Agronomiques, Avenue des Cliniques 13, Kinshasa, D.R. Congo.

Among the multiple factors that limit tree success and the uptake of atmospheric CO2 in savanna, fire appears to be the most widespread. Therefore, discontinuing burning regimes may allow forests to recolonize savannas and C stocks to recover. This method of managing savanna has been tested in the Manzonzi area (Kongo Central Province, Democratic Republic of Congo) since 2005, where the local community has preserved a 200 ha block of savanna with the support of WWF. To better quantify (i) the forest recolonization success over savanna as well as (ii) the efficiency of C storage in this area, 101 permanent plots (40.4 ha in total) were installed in 2010, remeasured in 2014 and 2022. The inventories (at the threshold of 6.5 cm DBH) carried out in 2010 and 2014 allowed to classify tree species into three categories sensu Deklerck et al. 2019: savanna, transition, and forest specialists. Between 2010 and 2022, stem density switched from 221.5 to 52.6 tree/ha, from 19.6 to 64.1 tree/ha and from 30.8 to 232.2 tree/ha for savanna, transition and forest specialists respectively. High mortality of savanna specialists was compensated by the recruitment of forest specialists. The number of tree species found in the experiment thus increased from 58 to 180 between 2010 and 2022. Aboveground C stocks switched from 6.5 to 1.9 Mg/ha, and from 1.3 to 4.1 Mg/ha, for savanna and transition specialists, respectively, while they significantly increased from 1.8 to 8.8 Mg/ha for forest specialists. The total amount of Aboveground C stocks increased from 9.68 to 14.95 Mg/ha. This experiment is potentially a reference in Central Africa firstly in terms of savanna fire management, and secondly in terms of the recolonization of savannas by forest and the related increase of C stocks. Further analysis of our dataset will allow to better characterize the regrowing forests success and the long-term C recovery trajectories in DRC.

Moss diatoms from Greenland

Charlotte Goeyers ^1,2

¹ Meise Botanic Garden, ² Ghent University

There is growing consensus that we have entered the Anthropocene, a new geological epoch during which human activity has altered the global environment and climate system profoundly. The Arctic is particularly sensitive to climate change and warms up 2-3 times faster compared to the global mean, mostly due to positive feedback mechanisms between oceans, the cryosphere, and the atmosphere. The most striking example of rapid climate change is Greenland. Recent studies suggest that climate models still underestimate the magnitude and effects of ongoing warming, and there is uncertainty around how ecosystems will respond to disruptive climate shifts. Diatoms (Bacillariophyta) form an important part of the microbial communities associated with different moss vegetations ranging from the low to the high Arctic. Due to their siliceous cell walls, short generation times, and finely tuned environmental preferences, diatoms are sensitive indicators that allow us to monitor past, present and future responses to climate change. However, the monitoring potential of terrestrial diatoms remains largely underexplored. To apply diatoms as reliable indicators for climate change, we need to expand our knowledge about their taxonomy, habitat, ecological preferences, and biogeographic distributions. Since taxonomic revisions are a laborious process, large-scale diatom datasets are still lacking or waiting for an update. In this study, we explored the diversity and biogeography of moss diatoms in Greenland and produce the first taxonomically fine-grained and internally consistent inventory of Greenland diatoms.

Unravelling evolutionary relationships in the Andean plant genus Polylepis

Ewout Gommers ¹, Maria Claudia Segovia-Salcedo ², Diego Rico Sanjinez ³, Yves Bawin ^1,4,5, Steven B. Janssens ^1,4,6, Edgar Gareca ³, Olivier Honnay ^1,6

¹ Department of Biology, KU Leuven, Leuven, Belgium, ² Departamento de Ciencias de la Vida y Agricultura, Universidad de las Fuerzas Armadas ESPE, Sangolquí, Ecuador, ³ Centro de Biodiversidad y Genética, Universidad Mayor de San Simón, Cochabamba, Bolivia, ⁴ Crop Wild Relatives and Useful Plants, Meise Botanic Garden, Meise, Belgium, ⁵ Plant Sciences Unit, Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Melle, Belgium, ⁶ Leuven Plant Institute, Leuven, Belgium.

The rapid evolution of flowering plants can partially be attributed to polyploidy and hybridization events. Also at low taxonomic level, these processes occurred frequently, as is clearly seen in the evolutionary history of the Andean plant genus Polylepis. Polyploidy and hybridization likely facilitated the remarkable occurrence of Polylepis species in unique woodland ecosystems at altitudes up to 5,200m above sea level in the tropical Andes. Nevertheless, the evolution of Polylepis taxa and the role of hybridization and polyploidization in their evolution is not well understood. The current study aims to infer evolutionary patterns in the Polylepis genus based on phylogenetic trees that were reconstructed using high-throughput sequencing (Hyb-Seq) data of 25 Polylepis taxa. The Hyb-Seq data consisted of 100 base pairs Illumina reads from 256 low copy nuclear genes and near-complete assemblies of the chloroplast genome. Based on differences in single nucleotide polymorphisms (SNPs), we created a Jaccard similarity matrix of the nuclear data and a separate phylogenetic tree for the nuclear and chloroplast data. Whereas patterns based on the nuclear data were often unclear due to the confounding effects of polyploidy, the reconstructed phylogenetic tree based on the chloroplast genome data was well supported. Remarkably, both phylogenies did not coincide with taxon groupings in earlier phylogenetic studies, which were mostly based on morphology and a few molecular markers with relatively low discriminatory power. In addition, we determined four chloroplast genome regions with a high density of informative SNPs in Polylepis that could be used as barcode markers in future studies. This study provides new insights into the evolution of Polylepis taxa. Knowledge on the molecular identification and the evolution of Polylepis can contribute to the conservation of these species.

Deciphering salinity resistance in Amaranthus cruentus in relation to its nutritional value: a bright future for an old plant

Adrien Luyckx ¹, Christophe Bernard Gandonou ², Gea Guerriero ³, Stanley Lutts ¹ and Muriel Quinet ¹

¹ Groupe de Recherche en Physiologie Végétale, Earth and Life Institute – Agronomy (ELIA), Université Catholique de Louvain, Louvain-la-Neuve, Belgium, ² Laboratoire de Physiologie végétale et d'Etude des Stress Environnementaux, Faculté des Sciences et Techniques (FAST/UAC), Université Abomey-Calavi, Cotonou, Benin, ³ Research and Innovation Department, Luxembourg Institute of Science and Technology, Esch/Alzette, Luxembourg.

Several amaranths (Amaranthus spp.) are orphan crops. These plants with a C4-type photosynthesis are cultivated either for their nutritive leaves or for their seeds rich in proteins with a balanced amino acid profile. Despite the lack of breeding effort, they are promising crops. Among them, Amaranthus cruentus is cultivated for both uses, with distinct varieties. A good tolerance to several biotic and abiotic stresses is recognized. Meanwhile, soil salinity is becoming a major constraint for crop productivity worldwide, especially in arid and semi-arid areas. Four A. cruentus varieties – two bred for grain production and two for leaves production, contrasted regarding their tolerance to salt – were exposed to a moderate salt stress (75 mM NaCl in irrigation water) in greenhouses. The response of the plants was analyzed along the entire life cycle. Growth rate, photosynthesis, transpiration rate and stomatal response were measured during growth. Biomass production was also evaluated. The content of minerals and various metabolites (pigments, antioxidant markers and osmolytes) were investigated, mainly in leaves. The salt stress caused a moderate, or even no, decrease in growth at the vegetative stage (almost no impact on leaves production), but the effect was much stronger at the reproductive stage, with a seed yield loss ranging from -70% to -90 %. Sodium mainly accumulated in the roots and the stem, suggesting that A. cruentus is able to sequestrate sodium outside the leaves, protecting the photosynthetic machinery. The content in several minerals, some of them with a nutritional interest, decreased in leaves (K, Cu, Fe, Zn), whereas it increased for others (Na, Mg). Polyphenols, carbohydrates and pigments content decreased with the salt treatment. These results show that A. cruentus is a good candidate for leaves production on salt-affected soils but with a slight decrease in nutritional quality, whereas grain production is compromised.

Assessing the need for wild edible mushrooms’ conservation actions in the Republic of Congo

Sydney T. Ndolo Ebika ^1,2, Nelly J. Awah-Lekaka ², Isis G. Mienandi ¹, Gallion B. Atikani ¹

¹ Initiative des Champignons et des Plantes du Congo (ICPC), ² Université Marien Ngouabi

A report published by FAO (Boa 2006) classified the Republic of Congo among countries where little is known about wild edible mushrooms (WEM). Ngoliele (2014) mentioned the word fungi only once in the 4th national report on Biodiversity. This motivated us to study and document fungi in the country (e.g. Buyck et al. 2020; Ndolo Ebika et al. 2013, 2018). According to Bishop (1998), monitoring and evaluating benefits of Non-Timber Forest Products on a national and local scale should be a priority as resulting information can be used in forestry regulations, pricing policy, etc. Thus, this study aimed at (i) generating data on the circuit of WEM; (ii) inventorying species sold in the markets and (iii) identifying potential threats on WEM and their habitats. The study was conducted from January to November 2021 in three localities: Brazzaville, Sibiti and Ouesso to: (1) monitor markets for interviewing retailers of WEM (Zent & Zent 2011; Pfoze et al. 2012, Koné et al. 2013) and buying mushrooms sold there; (2) weigh and identify WEM bought and (3) conduct fieldwork with harvesters to assess harvesting techniques and potential threats on WEM habitats. Five mains markets in Brazzaville and four sites (2 in Sibiti and 2 in Ouesso) were monitored. While most WEM sold are carpophores, rhizomorphs (white filamentous and thickened hyphae) were also sold and only harvested in on department of the country. Forty harvesting zones are recorded but Sibiti and Île Mbamou being the main ones. Clearing of Gilbertiodendron dewevrei forest for agricultural and urbanization purposes constitutes the main threat to ectomycorrhizal fungi. We envisage to continue gathering solid evidence in order to propose recommendations to authorities in charge of forest, biodiversity and policy makers in the Republic of Congo for conservation of wild fungi in the country.

Étude de la relation entre la diversité du sous-bois et celle des arbres dominants dans la Réserve de Biosphère de Yangambi, RDC

Benjamin Ntumba Katshela ¹, Filip Vandelook ² , Jonas Depecker ², Nshimba Seya Wa Malale ³

¹ Centre de surveillance de la Biodiversité, ² Université de Kisangani, ³ Meise Botanic Garden

En ce qui concerne la gestion des écosystèmes de forêts tropicales, on pense surtout à l'extraction du bois des espèces d'arbres dominants qui conduit à une perte de diversité chez les arbres dominants et/ou utiles, et à celle du sous-bois alors que beaucoup de ces espèces ligneuses du sous-bois ont une valeur économique ou médicinale pour les communautés riveraines. Les connaissances sur la biodiversité du sous-bois de forêts tropicales sont quasi-inexistantes. C’est ainsi que cette étude se propose d’analyser la démarcation, du point de vue de la composition floristique et diversité spécifique, entre le sous-bois et les arbres dominants dans la Réserve de Biosphère de Yangambi (RBY), RDC. Sur ce, les données floristiques, des arbres dominants, issues de travaux du projet COBIMFO couplées aux données d’inventaire du sous-bois, issues des campagnes des années 2018 et 2022, ont étés utilisées. Les indices de la biodiversité étaient calculés, l’analyse de la correspondance entre les parcelles mais également entre le sous-bois et les dominants étaient faites. Ces analyses nous ont permis de comparer deux peuplements, la forêt mature mixte (FM) et la forêt monodominante à Gilbertiodendron dewevrei (FMG), par leurs compositions floristiques et leurs biodiversités. A l’issue de ces analyses, il ressort que, les densités sont différentes en fonction de peuplement pour les deux strates, mais concernant la surface terrière, pas une différence significative entre les deux types forestiers selon les strates. La similarité entre le sous-bois et les arbres dominants est faible dans les deux types forestiers. Cette réalité est appuyée par la proportion d’espèces communes entre les deux strates par peuplement mais aussi, par la statistique de Mantel qui démontre que les parcelles les plus proches ont une correspondance significative mais négative, les cas pour chaque parcelle entre les arbres dominants et les sous-bois dont la distance géographique est nulle.

New and interesting Actinella and Eunotia (Bacillariophyta) from the Democratic Republic of the Congo

Jonathan C. Taylor ¹, Christine Cocquyt ²

¹ North-West University/South African Institute for Aquatic Biodiversity, ² Meise Botanic Garden

The Congo basin and Africa in general is largely underexplored in terms of freshwater biodiversity, this is especially the case for the algae although the diatoms have been studied in some depth at various times through the previous century. Despite these studies there remains considerable biodiversity to be discovered in the region. Diatoms in the genus Actinella F.W.Lewis grow on mucilage stalks and are usually attached to a solid substratum (plant material, other algae etc.). The genus occurs almost exclusively in acidic biotopes with low nutrient concentrations and thus the presence of Actinella species is indicative of good water quality conditions with limited impact. The most closely related genus to Actinella is Eunotia Ehrenberg which is also commonly found in acidic waters. Unlike Actinella, Eunotia has a very high diversity in the African tropics with many species as yest undescribed. Actinella differs from Eunotia by the presence of marginal spines as well as being heteropolar in shape with distinctive terminal spines in some cases. There is only a single rimoportula found at one apex in Actinella, Eunotia usually has two, once at each apex. The raphe is rather short and carried on the valve face while that of Eunotia is found mostly on the valve margin and longer. Further elucidation and description of tropical diatom species is important for the eventual implementation and use of diatom-based water monitoring techniques in central Africa.

Trees in Decline: The IUCN Red List of Endemic and Subendemic Trees of Central Africa

Wesley Tack, Marc SM Sosef

Meise Botanic Garden

With the ongoing ecological degradation and human pressure on biodiversity across the planet comes the need to assess the risk of species extinction and identify and address the root causes of their decline. To identify species threatened with extinction and help guide conservation priorities, we coordinated a project to assess the conservation status of all Endemic (and subendemic) Central African Trees (ECAT). Central Africa, as defined here, includes the Democratic Republic of the Congo, Rwanda and Burundi. Here, we present the main results of the extinction risk assessments carried out during the ECAT project. These assessments were published on the IUCN Red List website and compiled in the book ""Red List of the endemic and subendemic trees of Central Africa"", which can be downloaded free of charge. The data on the 347 Central African tree taxa presented here shows that 221 (64%) are threatened with extinction. Of these, 34 (10%) are Critically Endangered (of which 25 may already be extinct), 106 (31%) are Endangered, and 81 (23%) are Vulnerable. Agriculture, livestock farming and logging are the main threats. Charcoal production and mining also pose significant threats, and the effects of climate change are beginning to emerge. Focused action is needed to ensure the survival of threatened trees and all organisms (including humans) that depend on them.

Large-celled diatoms from the genus Gogorevia in the Zambezi basin

Jonathan C. Taylor ¹, Christine Cocquyt ²

¹ North-West University/South African Institute for Aquatic Biodiversity, ² Meise Botanic Garden

A three-year survey of the freshwaters of Zambia was carried out between 2011 and 2013 as part of the Southern African Rivers Assessment (SAFRASS) project funded by the European ACP. The study was to establish a baseline for aquatic biodiversity. The diatoms were considered an important group for this study as very little work had previously been carried out on this group and the country remained almost entirely unexplored in this respect. Since the conclusion of the project several new taxa have been documented and described and this work continues. The newly described genus Gogorevia Kulikovskiy, Glushchenko, Maltsev & Kociolek contains species previously considered to belong to Achnanthidium Kützing. Based on both morphological and molecular evidence it was decided to split off a group of species from the larger Achnanthidium group. Achnanthidium cells are usually rather small (around 8-15 µm in length) and generally not very robust while representatives of the newly established Gogorevia are in general rather more robust, broader and with well distinguished apices and other morphological features such as a thickened sternum in the center of the cell which is not present in Achnanthidium. The genus Gogorevia is represented in tropical South America by some rather unusually robust forms (e.g. G. parexigua (Metzeltin & Lange-Bertalot) Kulikovskiy & Kociolek). Similar robust forms have been found in samples collected in Zambia. Although similar to those from the neotropics, these species are clearly new to science.

Phylogenetic diversity: a metrics comparison

Kasprzyk Thibault

University of Liege

The broadening of the common diversity metrics by the addition of phylogenies has enabled new developments in ecology. With already more than 70 metrics described, it could be hard to determine which one is the most suitable for each of the possible questions research wants to address. Furthermore, and despite previous efforts, the characteristics of all these metrics are still to be addressed. Using a community simulation model, metrics performance and reliability were assessed under various conditions. This include the ability of a metric to recover an ecological pattern, to be truly neutral as well as the redundancy between the discussed metrics.

DiSSCo Flanders - Towards a Collection Management Infrastructure for Flanders

Maarten Trekels

Meise Botanic Garden

DiSSCo Flanders aims at developing a standardized scientific collections management infrastructure, ensuring proper long-term conservation, and future re-usage of the collections. This four-year project, funded by the FWO (Research Foundation – Flanders), started in January 2021. The project includes 10 Flemish partners and 4 associated federal collections. Flanders aims to become a center of excellence for collection-based data science. Natural science collections, such as the dried plants in the herbarium of Meise Botanic Garden, are an archive from centuries of global exploration. These collections are very diverse, ranging from soil samples and preserved animal, plant, and fungal samples to living accessions and molecular collections. They enable many forms of biological research, from species identification to specialisms as diverse as ecology, food security, health, and the bio-economy. Knowledge derived from collections has made important contributions to life and earth sciences, but collections are still underused. Millions of specimens, in hundreds of institutions worldwide, are inaccessible as they have not been inventoried, or data are stored in isolated databases. The European Research Infrastructure DiSSCo (Distributed System of Scientific Collections) aims to digitally unify all European natural history assets, to ensure that collection data are easily findable, accessible, interoperable, and reusable (FAIR). This will transform a fragmented landscape of collections into an integrated knowledge base, enabling researchers to use and interconnect different collections.