[Keynote]

Plant evolution - gather around the Tree of Life

Lars Chatrou

Ghent University

Phylogenetics has revolutionized the botanical science for the past 30 years or so. In botany, the application of phylogenetics primarily started with the goal to infer phylogenetic relationships in the interest of classification. Gradually, the focus has shifted from pattern-based research to the use of phylogenetics to learn about the processes of plant evolution. In my presentation, I will illustrate some new approaches to long-standing questions in evolutionary biology of plants, and demonstrate how the use of phylogenetics can help to integrate seemingly divergent fields such as morphology and anatomy, molecular biology and ecology.

[Oral Presentation]

A first look at the effects of whole genome duplication on the phenotype and evolvability of Chlamydomonas reinhardtii

Quinten Bafort ¹, Eylem Aydogdu ¹, Lucas Prost ¹, Olivier De Clerck ² & Yves Van de Peer ¹

¹ VIB-UGhent Center for Plant Systems Biology, Belgium

² Ghent University, Belgium

Whole genome duplication (WGD) is a genomic mutation with far-reaching consequences. The increase in genetic material can alter the phenotype considerably e.g. via the well-established correlation between cell and genome size, altering surface area to volume ratios. Additionally the presence of an extra (redundant) genome copy that is free to evolve is supposed to increase the genomic and epigenetic flexibility and therefore the evolvability. Consequently an increased ploidy level creates the potential to adapt faster to changing environments or outside niche conditions. We study the consequences of whole genome duplication using experimental evolution of the unicellular green algae Chlamydomonas reinhardtii. Two haploid and two diploid strains of Chlamydomonas are evolving in dodecaplicate in both standard benign laboratory conditions and a stressful saline environment. We have followed cell size and growth parameter evolution for over more than 700 generations. After WGD, we observed an increase in cell size (in both environments), an increase in the maximum growth rate (in benign environment) and a reduction in the maximum population size (in both environments). The immediate effect of exposure to a saline environment for both ploidy levels is an increase in cell size, a reduction in maximum growth rate and a reduction in the maximum population size. Over time the size of diploid cells evolving in the saline medium dropped below that of those in a benign environment, the maximum growth rates of both haploid and diploid lines increased in both environments and this increase in growth rate came at least for some lines at the cost of a reduction in the maximum population size.

[Oral Presentation]

Selection on attractive floral traits: are there differences between males and females in a dioecious species?

Estelle Barbot ¹, Mathilde Dufaÿ ² & Isabelle De Cauwer ¹

¹ Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo, France

² CEFE, Université Montpellier, CNRS, Université Paul Valéry Montpellier, France

³ EPHE, IRD, Montpellier, France

Studies of natural selection in flowering plant generally focus on female fitness, because studying male fitness implies molecular tools. However, selection via male fitness must not be neglected because it can differ from selection via female fitness. One evidence for this assumption is that entomogamous species with separate sexes often present sexual dimorphism for attractive floral traits, with males being more attractive. This discrepancy between sexes is thought to result from the fact that males rely more on pollinator attraction for their reproductive success than females. In this study, we investigated this hypothesis in an experimental population of Silene dioica. We measured several floral traits potentially implicated in (i) attractiveness (i.e., visual signals and rewards), and (ii) in fertility (i.e., ovule and pollen production). We assessed female reproductive success and fertility by sampling fruits and counting seeds and non-fertilized ovules. Male reproductive success was estimated using offspring genotyping and a paternity analysis. We explored the link between (i) attractive floral traits and (ii) female and male reproductive success using selection gradients in order to compare both sexes. Finally, we estimated pollen limitation and pollinator-mediated selection on females by comparing selection gradient between open- and hand-pollinated females. This allowed us to identify attractive floral traits under selection in males only, females only, or in both sexes. Differences between open- and hand-pollinated females suggest that at least for some traits, pollinator-mediated selection is operating.

[Oral Presentation]

Growth strategy and phenology of the invasive species Cecropia peltata in Cameroon and comparison with its native equivalent Musanga cecropioides

Claire Baudoux

Université Libre de Bruxelles

Thirty years ago, McKey (1988) highlighted the invasiveness of the pioneering Neotropical tree species Cecropia peltata (Urticaceae) in Cameroon, which was probably introduced to the Limbe Botanical Garden in the early 20th century. The spatial progression of C. peltata, which now extends within a radius of about 85 km around Douala, appears to be at the expense of Musanga cecropioides, a local pioneer tree species belonging to the same family and playing a similar role in forest succession. Studies on the architectural development of Cecropia species in Amazonian forests have shown that their internodes length fluctuations reflect the seasonality with short internodes elongated in the dry season. In addition, flowering and branching processes are expressed with an annual or biennial period. The internodes, inflorescences and branches leaving visible scars throughout the life of the tree, these morphological markers make it possible to determine year’s limits and retrospectively reconstruct the tree development. In this study, we tested if C. peltata and M. cecropioides showed similar phenological patterns and morphological markers related to the seasonality expressed in Cameroon. We applied an architectural analysis to characterize the development trajectory of neighboring trees and tested the hypothesis of an exclusion of M. cecropioides by C. peltata through competition for space. The two species studied show morphological markers similar to the Cecropia species studied in the Amazon. We were able to reconstruct the past development of trees of about 13 meters in a 7 years stand. These two species show comparable growth dynamics in height that do not support the hypothesis of direct competition for space. In contrast, the density of M. cecropioides individuals were much lower than that of C. peltata. It appears possible that if an exclusion phenomenon exists, it occurs at very early stages (e.g. germination process) or on pollination-dispersion processes.

[Oral Presentation]

How old is coffee? Using phylogenomic data to infer the evolutionary history of the allotetraploid species Coffea arabica L.

Yves Bawin ^1,2,3,4, Tom Ruttink ¹, Ariane Staelens ¹, Annelies Haegeman ¹, Lauren Verleysen ^1,2, Piet Stoffelen ³, Isabel Roldán-Ruiz ^1,4, Olivier Honnay ² & Steven B. Janssens ^2,3

¹ Flanders Research Institute for Agriculture, Fisheries, and Food (ILVO), Belgium

² Plant Conservation and Population Biology, KU Leuven, Belgium

³ Crop wild relatives and useful plants, Meise Botanic Garden, Belgium

⁴ Department of Plant Biotechnology and Bioinformatics, Ghent University, Belgium

Hybrid speciation is relatively common in vascular plants, but the evolutionary history of many hybrid plant species is not well understood. Here, we studied the hybrid origin of Coffea arabica L., the only known allotetraploid species in the genus Coffea. It is also the wild progenitor species of Arabica coffee, one of the most valuable beverages in the world. C. arabica is endemic to a relatively small region in southwestern Ethiopia, being the only Coffea species found in that area. Phylogenetic relationships between C. arabica and related Coffea species were inferred based on genetic variation in nuclear DNA sequences that were retrieved using Genotyping-by-Sequencing (GBS), which is a high-throughput sequencing technique. In order to assess the phylogenetic position of C. arabica, we first assigned its GBS alleles to one of the two C. arabica subgenomes by comparing the genetic similarity between each allele and the corresponding alleles in samples of Coffea species belonging to each of the two parental lines. Then, a multilabeled phylogenetic tree was reconstructed wherein the two C. arabica subgenomes were positioned separately as if they were distinct species. This allowed us to reconstruct the phylogenetic origin of C. arabica in relation to other Coffea species. Furthermore, the age of the hybridization event situated at the origin of C. arabica was estimated using a Bayesian molecular dating approach. Compared to earlier studies on the age estimation of C. arabica, our obtained age estimate of approximately 800k years dates the origin of C. arabica further back in time compared to previous estimates.

[Poster]

Green Pioneers: Raising awareness of invasive plants at all ages

Ann Bogaerts, Sofie De Smedt, Sofie Meeus, Jutta Kleber & Quentin Groom

Meise Botanic Garden, Belgium

When asked about the issues that prevent adequate control of invasive species, researchers and managers of invasive species rank public awareness first among all the issues (Dehnen-Schmutz et al., 2018). It is therefore imperative to raise the general public's awareness of the potential risks of introducing alien species into the wild.

Green Pioneers aims to address this issue across age groups. The project’s aims to

1. Create awareness on invasive species, how can invasions be avoided and how can the negative impacts be reduced.

2. Improve communication between citizens and scientist on conservation and invasive plant species. Augment the quality and quantity of data on invasive species in Flanders.

The project is developing three kinds of activity, specifically to attract a broad demographic

· Young Pioneers, by developing tools for teachers in STEM;

· Online Pioneers, through our online citizen science platform DoeDat.be, by helping us with the transcription of label information on herbarium specimens;

· Visiteers, by inviting companies and working age people to help us in the collection and to inform them about invasive species

Finally, we will be organizing a BioBlitz in spring 2020 at Meise Botanic Garden where we will celebrate plants and all our Green Pioneers, while also spreading the message of invasive plant awareness.

Ultimately, Groene Pioniers wants to encourage recording of alien species by amateur botanists and create a generation of responsible gardeners who understand the consequences of releasing problem plants into the wild.

Dehnen‐Schmutz, K., Boivin, T., Essl, F., Groom, Q. J., Harrison, L., Touza, J. M., & Bayliss, H. (2018). Alien futures: What is on the horizon for biological invasions?. Diversity and Distributions, 24(8), 1149-1157.

[Poster]

Do photobionts and endolichenic fungi play a more decisive role than previously assumed in sex and thallus morphology of lichens? Arthoniales as a test-case

Luca Borgato ^1,2, Damien Ertz ^2,3 & Annemieke Verbeken ¹

¹ Ghent University, Biology Department, Research Group Mycology, Belgium

² Meise Botanic Garden, Research Group Lichenology, Belgium

³ Fédération Wallonie-Bruxelles, Service général de l'Enseignement supérieur et de la Recherche scientifique, Belgium

Lichens are mutualistic relations between a fungus, a eukaryotic algae and/or cyanobacteria. Recently, more complex relations with endolichenic basidiomycete yeasts were revealed. The coevolution that led to these associations is only partially known. Recent studies suggested that the photobionts might influence the reproduction strategy of the mycobiont Lecanographa amylacea. Moreover, the role of basidiomycete yeasts in the production of lichenic acids was demonstrated in the Parmeliaceae; these yeasts seem also to have influenced the evolution of the thallus, leading to foliose forms in this family.

The Arthoniales are a large group of mainly lichenized, cosmopolite ascomycetes. The group is thought to be originally lichenized with independent reversions to the non-lichenized forms. The phylogeny of the mycobiont is now well established. This project aims at developing phylogenies of the photobionts and the basidiomycetes yeast, and to analyse gene expression of the three partners within the different Arthoniales families. It aims to (1) test if the lichenization in this order is issued from a single event, (2) explore the impact of the algae in the reproduction of the fungi within selected species known to have sorediate versus fertile thalli, (3) examine if basidiomycetes yeasts have a role in the transition from crustose to fruticose growth forms in Arthoniales, (4) study the coevolution of the three partners.

[Poster]

Standards for describing Russula species

Ruben De Lange ¹, Slavomır Adamcık ², Bart Buyck ³, Annemieke Verbeken ¹

¹ Ghent University, Belgium

² Slovak Academy of Sciences, Slovakia

³ Muséum national d’histoire naturelle, France

Description styles for Russula species are not consistent and have regional or author-specific patterns. Most recent publications still favour descriptions of spores compared to hymenium and pileipellis elements, only the spore size is provided with statistical support and differences between pileus margin and centre are not recognised. Nevertheless, microscopic characters from all parts of the basidiomata can be equally important for species recognition and they deserve the same treatment including number of measurements and statistics. Furthermore the importance to specify the origin of pileipellis observations must be emphasized. Standards for the micromorphological description of Russula species are presented as proposed by Adamčík et al. 2019, The quest for a globally comprehensible Russula language, Fungal Diversity. A description template, the template measurements table, the specific terminology and the essential chemical reagents are suggested. A candidate new species from Thailand is used as an example.

[Poster]

Guyanese Lactarius and Lactifluus species exhibit contrasting diversity patterns

L. Delgat ¹, T. Henkel ², M.C. Aime ³, A. Verbeken ¹ & J. Nuytinck ⁴

¹ Ghent University, Belgium

² Humboldt State University, U.S.A

³ Purdue University, U.S.A

⁴ Naturalis Biodiversity Center, the Netherlands

Diversity of ectomycorrhizal (EM) fungi in the Neotropics is still relatively poorly known. Tropical rainforests, where EM hosts constitute only a fraction of the tree diversity, dominate the region. However, in Guyana some forests are dominated by EM trees of the Fabaceae family, such as the genus Dicymbe. An important group of EM fungi in Dicymbe forests are the milkcap mushrooms of the genera Lactifluus and Lactarius. Molecular and morphological study of these milkcap collections revealed a total of 17 species, of which nine are Lactifluus and eight Lactarius, most of which are undescribed. The Lactifluus species are well distributed infragenerically, occurring in three out of four subgenera, and some exhibit unusual characteristics such as a partial veil or a pleurotoid habit. For Lactarius, eight species have been found in Guyana, a striking fact given that the main center of diversity for the genus is in Northern temperate regions. In contrast to the Guyanese Lactifluus species being well spread throughout the genus, all but one of these newly discovered Lactarius species form a single early diverging clade in Lactarius subg. Plinthogalus. While this subgenus is predominantly known from the Northern hemisphere, it also contains early diverging African lineages and was previously thought to have originated in Africa. The discovery of Neotropical taxa in Lactarius subg. Plinthogalus changes our ideas about the evolution and biogeography of this subgenus and even Lactarius as a whole. In addition, this illustrates the importance of including tropical taxa in the study of fungi.

[Oral Presentation]

Species delimitation and phylogeography of African trees of the genus Parkia (Fabaceae, Mimosoideae)

Oscar Doré Ahossou ¹, Kasso Dainou ², Steven Janssens ³ & Olivier J. Hardy ¹

¹ Laboratory of Evolutionary Biology and Ecology, ULB, Belgium

² Laboratory of Tropical and Subtropical Forestry, ULg, Belgium

³ Meise Botanic Garden, Belgium

Taxonomic classification within African Parkia has been controversial due to phenotypic polymorphisms and clinal variations. Currently, three parapatric species of Parkia are recognized in continental Africa: P. biglobosa in the Sudanian savanna, P. bicolor in the Guineo-congolian rain forest, and P. filicoidea in the Zambezian miombo, with more or less overlaps across the ranges. A fourth species, P. madagascariensis, is restricted to Madagascar. However, more species or varieties of Parkia have been suggested in continental Africa.

The present research aims to assess the main land species diversity by using genetic markers and morphological characters. 889 individual plants (including herbarium specimens) were genotyped using 10 microsatellite markers. All the samples were first analyzed for different macro-morphological characters and assigned to the three continental morphospecies based on the existing taxonomic literature. Then, Bayesian clustering algorithms were implemented in Structure to identify genetic units within the defined morphospecies. Results showed six genetic clusters in P. biglobosa, while P. bicolor and P. filicoidea, each, displayed four genetic clusters. Gene pools in P. biglobosa are congruent with clinal variations in leaflets size and present generally lower differentiation values. Contrarily, genetic clusters in P. bicolor and P. filicoidea showed higher differentiation values and followed habitat gradients. Morphological descriptions in previous taxonomic studies are congruent to partly congruent with the observed genetic clusters.

We concluded that only one species (Parkia biglobosa) should be considered in the Sudanian savanna and other names like P. clappertoniana, P. africana and P. oliveri or P. intermedia should be considered as synonyms. However, P. bicolor and P. filicoidea might each represent a complex of species or include different varieties. Thus, the hypotheses of multiple species or varieties within P. bicolor (P. bicolor, P. agboensis, P. klainei, P. zenkeri) and P. filicoidea (P. filicoidea, P. bussei, P. hildebrandtii) should be further investigated.

[Poster]

Moss-inhabiting diatoms from Campbell Island (sub-Antarctic Region)

Charlotte Goeyers ^1,2 & Bart Van de Vijver ^1,2

¹ Meise Botanic Garden, Research Department, Belgium

² University of Antwerp, Department of Biology, ECOBE, Belgium

Diatoms (Bacillariophyta) are one of the most abundant algal groups in polar ecosystems, both in number of specimens as in number of species. Their characteristic silica outer shell and the significant responses on changes in their physical and chemical environment, make them excellent bio-indicators used in both applied environmental, biogeographical and paleo-ecological studies.

Especially in Polar regions, diatoms proved to be very useful indicators of environmental and climatic changes. It is generally accepted that the current climate changes will have their greatest impact in Polar regions. Despite this, our knowledge of diatoms in these areas is unfortunately not profound. Due to outdated species taxonomy, force-fitting and incorrect identifications, a revision of the polar diatom flora is required.

In the present study, the diatom flora found in an historic moss collection, sampled on the sub-Antarctic Campbell Island in 1969-1970 by D. Vitt was analysed. Campbell Island (New Zealand territory) is a small, uninhabited sub-Antarctic island located in the southern Pacific Ocean. The island is the main island of a small volcanic archipelago and has a surface area of 113 km2 in total. A total of 66 moss samples were retrieved from the British Antarctic Survey herbarium in Cambridge, UK. A well-developed and species-rich diatom flora was observed in the samples, mainly belonging to the genera Humidophila, Pinnularia, Planothidium and Psammothidium. During the survey a large number of at present unknown diatoms were observed that could not be identified using the currently available literature. Detailed analysis of light and scanning electron microscopy observations and comparisons with similar taxa worldwide led to the description of several new species. The poster shows some of these new species belonging to the genera Angusticopula, Arcanodiscus and Ferocia. The revision of the diatom flora of Campbell Island will contribute to a better understanding of polar diatom biodiversity.

[Oral Presentation]

Rapid thermophilization of forest understorey plant communities

Sanne Govaert, Pieter Vangansbeke, Kris Verheyen & Pieter De Frenne

Ghent University, Belgium

An ever increasing mixture of anthropogenic stressors is acting on forests worldwide. Among these are eutrophication, climate change and intensified forest management (opening up the canopy), all three impacting ecosystem functions and biodiversity.

In temperate forests, 80% of the biodiversity is represented by the understorey plant community. The understorey plays key roles in several ecosystem functions such as tree generation, nutrient cycling and carbon dynamics. Observational data on the effects of these stressors on the understorey is available and well-studied. However, long term experimental data focusing on the interactive effects of these anthropogenic stressors is lacking. This kind of data is needed to soundly inform forest managers how best to adapt to climate change to conserve forest biodiversity.

Here, we studied the influence of enhanced nitrogen inputs, passive warming and light addition (as a proxy for management-driven understorey light availability) on understorey plant communities of temperate broadleaved forest. We report eight years of post-treatment data. Plant communities shifted in this relative short time scale towards more warm-adapted and less cold-adapted communities. What is interesting is that we find a shift in all treatments as well as control plots.

[Poster]

Differential effects of sulfate and chloride salinities on rice genes expression patterns: a comparative transcriptomic approach

Willy Irakoze ^1,2, Hermann Prodjinoto ¹, Séverin Nijimbere ², Gervais Rufyikiri³, Muriel Quinet ¹ & Stanley Lutts ¹

¹ Groupe de Recherche en Physiologie végétale – Earth and Life Institute – Agronomy (ELI-A), Université catholique de Louvain, Louvain-la-Neuve, Belgium

² Faculté d’Agronomie et de Bio-ingénierie, Université du Burundi, Bujumbura, Burundi

³ Geneva Centre for Security Policy (GCSP), Geneva, Switzerland

Salinity is among the most serious challenges to rice production in the word today. To elucidate genome-level responses to chloride or sulfate salinity stress in rice, I Kong Pâo (salt-sensitive cultivar) seedlings have been exposed to salt stress (EC of c.a 20 dS m-1 NaCl or Na2SO4) for 48 hours. A combined transcriptomic and physiological study have been performed after exposure to saline solutions in order to clear the main metabolic pathways involved in rice response to salt stress. Our results showed that a large number of genes were expressed under sulfate than chloride salinity, this difference being the most remarkable in root. Most of the genes involved in response to salt stress were up-regulated in Na2SO4-treated plants whatever the considered organs while more genes were down-regulated in NaCl-treated plants, organs combined. The comparison of expression profiles among different salinity stresses showed largely stress-specific patterns of regulation. Moreover, both stresses appeared to alter the expression patterns of a significant number of genes involved in response to abiotic stimulus, signal transduction and transport in a largely organ-specific manner. Modification in some genes expression could be followed by modification in corresponding metabolic products and physiological properties, or differed depending on the type of salt stress or organ for some others, underlying the importance of an integrated study. Our study offered the first comprehensive picture of genome expression modulation in response to sulfate salinity stress in two distinct rice organs and could be very useful in improving of rice plant tolerance to Na2SO4 stress.

[Poster]

NaCl and Na2SO4 salinities have different impact on photosynthesis and yield-related parameters in rice (Oryza sativa L.)

Willy Irakoze ^1,2, Hermann Prodjinoto ¹, Séverin Nijimbere ², Gervais Rufyikiri ³ & Stanley Lutts ¹

¹ Groupe de Recherche en Physiologie végétale – Earth and Life Institute – Agronomy (ELI-A), Université catholique de Louvain, Louvain-la-Neuve, Belgium

² Faculté d’Agronomie et de Bio-ingénierie, Université du Burundi, Bujumbura, Burundi

³ Geneva Centre for Security Policy (GCSP), Geneva, Switzerland

To elucidate the comparative effect of chloride and sulfate salinities on photosynthesis and yield components in rice, plants of Oryza sativa (cv. I Kong Pâo (salt-sensitive)) were exposed in nutrient solutions to 20 mM Na2SO4 or 40 mM NaCl (electrical conductivity of c.a. 4.30 dS m-1 for both solutions) from seedlings to maturity stage. Both types of salt induced a strong decrease in net photosynthesis (AN) at the seedling and tillering stages while the intracellular CO2 concentrations (Ci) remained unaffected. Instantaneous transpiration (E) and stomatal conductance (gs) decreased at tillering and seedling stages respectively only in plants exposed to NaCl. Chloride salinity also strongly decreased photosynthetic pigments while no impact was detected in response to Na2SO4. All yield-related parameters were affected by salinities but NaCl was significantly more deleterious than Na2SO4 for the mean number of tillers produced per plant, spikelets sterility and non-viable pollen percentage. In contrast, both types of salinity similarly impacted the percentage of fertile tillers and 1000-grain weight. At the grain level, more than 90% of toxic ions (Na+, excess of Cl- and S2-) accumulated in the hulls, thus preserving the internal part of the caryopses from ion injuries.

[Oral Presentation]

Phylloporia (Basidiomycota, Hymenochaetales) in tropical Africa: an overview

Matthieu Jérusalem

Département de Biologie, Ecologie et Evolution, Université de Liège, Belgium

A synthesis on the taxonomic, ecological, and phylogenetic knowledge of Phylloporia (Hymenochaetaceae, Basidiomycota) in tropical Africa is presented. Sixteen named Phylloporia species are currently reported from tropical Africa, of which 4 species, originating from the lower Guinean forest in Gabon and from medium elevation, montane forest in Kenya, are shown to represent undescribed taxa, on the basis of morphological, ecological, and DNA multilocus phylogenetic data. Nine species are described and, for the time being, only known from the Guineo-Congolian phytogeographic region. Eight of them are only known from its western edge in Gabon, where the wood-decaying basidiomycete communities are continuously surveyed. However, it should be noted also that the reports in Tropical Africa of several species originally described from other continents and biogeographic areas, in South America or the Southern Pacific, such as P. chrysites, P. fruticum, P. parasitica, or still P. weberiana, must be taken as sensu auctores, as already emphasized (Yombiyeni & Decock 2017). Their presence in Tropical Africa still should be confirmed. The distribution range of these species is still poorly known, and largely depend on the distribution rage of their hosts. However, globally, the Guineo-Congolian phytogeographic region, of which the vast Congo basin forest remains still very poorly surveyed. Multilocus phylogenetic inferences of African Phylloporia, also provide some preliminary clues to understand the affinities of the species present in Africa and to resolve the structure of the genus.

[Poster]

The drivers of sapwood and heartwood development in a light demanding tree species: the case study of Pericopsis elata (Harms) Meeuwen (Fabaceae)

Chadrack Kafuti ^1,2,5, Hans Beeckman ², Jan Van Den Bulcke ¹, Romain Lehnebach ¹, Tom De Mil ^1,2, Joris Van Acker ¹ & Nils Bourland ^2,3,4

¹ Ghent University, Belgium

² Royal Museum for Central Africa, Belgium

³ Center for International Forestry Research, Belgium

⁴ Resources & Synergies Development, Belgium

⁵ University of Kinshasa, RDCongo

Pericopsis elata is one of the most valuable and highly logged timber species in Africa. The species is commonly logged for its heartwood known as having a high natural durability, mechanical strength, and dimensional stability, all this combined with its widely appreciated decorative values. Currently, the sawmill yield of the species is evaluated to almost 49%, suggesting that almost 51% of wood volume extracted are lost. Understanding the conversion of sapwood into heartwood is of crucial importance to select highly valuable trees, reduce sawmill losses and support the sustainability of timber harvest. Information on sapwood-heartwood proportions is also crucial for understanding tree performances in a forest stand. In this study, we measured sapwood and heartwood amounts on trees from different locations in the Congo Basin. Tree-rings measurements were performed to assess the age and the growth rate. Heartwood and sapwood amounts as well as heartwood initiation age are analyzed in light of tree characteristics such as growth rate, age and size.

[Oral Presentation]

Daily stem size fluctuations and growth phenology of a light demanding tree species from the Congo Basin

Chadrack Kafuti ^1,2,5, Tom De Mil ^1,2, Nils Bourland ^2,3,4, Joris Van Acker ¹, Jan Van den Bulcke ¹ & Hans Beeckman ²

¹ Ghent University, Belgium

² Royal Museum for Central Africa, Belgium

³ Center for International Forestry Research, Belgium

⁴ Resources & Synergies Development, Belgium

⁵ University of Kinshasa, RDCongo

Changes in environmental conditions are expected to occur in tropical forests due to global change and human-induced disturbances. Understanding how trees respond to current short-term variations of environmental factors is crucial for the prediction of species performance and forest resilience under future conditions. Continuous monitoring of stem size variations has shown to help predictions of tree responses to the environment.

In this study, we used automatic point dendrometers to highlight the dynamics and drivers of intra-annual tree growth of Pericopsis elata (Harms) Meeuwen, a highly valuable light demanding African tall tree species. A total of 9 trees from different size classes have been selected for an annual 30-minute monitoring of stem size fluctuations in the Biosphere Reserve of Yangambi (Democratic Republic of the Congo). In addition, leaf phenology was daily monitored using time lapse cameras. Daily precipitation of the site was measured by the local weather station of Yangambi, while an on-site weather station allowed to record temperature and relative humidity every 30 minutes. Tree growth starts in February, peaks in May and ends in November. The growing season lasts 175 ± 53 days and growth rate varied between 0.26 and 3.39 mm/year. Trees with higher growth rate tend to begin their growing season at the end of March but did not necessarily growth longer. Foliar and reproductive phenology of the species tended to synchronize with stem growth phenology. The peak of leaf shedding occurred in February when stem growth begins and the peak of leaf renewal and flowering occur in March. Daily stem size fluctuation showed high sensitivity to climate. As one of the first attempts revealing the rhythms of tropical trees in the Congo Basin, results from this study provide useful insights for the prediction of the response of Congo Basin forests to climate change.

[Poster]

Pith-to-bark profiles of xylem vessel traits reveal unique information on tree performance in a tropical moist semi-deciduous forest of the Congo Basin

Emmanuel Kasongo Yakusu ^1,2,3, Victor Deklerck ^1,2, Wannes Hubau ^1,2, Kevin Lievens ¹, Félix Laurent ¹, Nils Bourland ¹, Jan Van den Bulcke ², Joris Van Acker ² & Hans Beeckman ¹

¹ Royal Museum of Central Africa, Belgium

² Ghent University, Belgium

³ Université de Kisangani, RDCongo

Xylem vessel features are the most investigated anatomical traits of Angiosperm wood. They are being analyzed in ecophysiological projects aiming at understanding sap flow and vulnerability to drought stress. Since long, size, grouping and density of vessels are also used as one of the first steps in timber identification, as they can easily be observed even with a hand lens.

Vessels are also known to be related to tree height. The volumetric sap flow rate is inversely related to the length of the path, so that vessels need to widen at lower parts of the tree and taper towards the higher parts to assure optimal transport and a stable hydraulic resistance with progressing growth in height. Vessels are expected to narrow from roots to stem and further to the branches and the petioles. Accordingly it is also predictable that vessel features on pith-to-bark profiles are a proxy for height growth for individual trees. Since the functional groups of species of a tropical rainforest are based on height grow rate (related to light needs), it is expected that pith-to-bark profiles of vessels reveal information on temperament of the species.

A methodology has been developed to establish pith-to-bark profiles of vessel features, based on long microtomic sections, image analysis and machine learning. Entandrophragma was used as a model genus. The differences between the four most common species of this genus have been explored. Wilcoxon signed rank test indicate that the difference in mean vessel size is significant between every species combination except between Entandrophragma candollei and Entandrophragma cylindricum. Interesting to note is the large vessel size range possible for Entandrophragma utile. Currently, pith-to-bark vessel trends are constructed that could help explaining difference in growth strategy. The approach offers appealing perspectives to find a formal way for sub setting tree species into functional groups and develop indexes for growing conditions of forest sites.

[Oral Presentation]

Flower resources for pollinators at an agricultural landscape level. How can we link floral resources to bee health?

Alban Langlois ¹, Thierry Hance ¹, Florence Hecq ¹, Charlotte Descamps ¹, Julien Piqueray ² & Anne-Laure Jacquemart ¹

¹ Earth and Life Institute, UCLouvain, Belgium

² Natagriwal asbl, Belgium

Flowers provide pollen and nectar, essential resources for pollinating insects, which in turn ensure their pollination. Nectar is mainly the source of sugars; pollen is the main source of amino acids, proteins and sterols. The ongoing generalized decline of pollinators depends on several causes often related to the decrease or modification of available floral resources. These changes include the destruction and fragmentation of biotopes, uniformity and impoverishment of flora, invasive alien species, pesticides, or global climate change. Agricultural environments are particularly singled out, following agricultural intensification and the standardization of crops.

In three Belgian biogeographical regions (Condroz, Famenne, Calestienne), we studied agricultural landscapes that differ in their agricultural intensification. Two sites per region (intensive vs. extensive) were monitored throughout a flowering, and therefore foraging, season to estimate the influence of landscape structure and floral resource availability on pollinator health. We estimated flower densities per plant species, biotope and month. In particular, we estimated and extrapolated the nectar floral resources. We also placed and monitored Bombus terrestris hives in the center of each of the six sites and estimated plant-pollinator interactions in the different biotopes.

Our results showed that in early spring (March-April), flowers and their abundant resources in hedges and stubble-free maize fields were essential. Floral resources decreased in April-May, at the time of the increasing establishment and development of bee colonies, except in landscapes dominated by oilseed rape (Brassica napus) fields. In June, diversified grasslands (mainly wet hay meadows) and roadsides represented diversified resources for maintaining colonies. Nevertheless, links with bumblebee health are still under study.

[Poster]

Methodology for the treatment of increment cores to assess the vessel size distribution of a tree along a pith-to-bark transect

Félix Laurent ¹, Victor Deklerck ¹, Emmanuel Kasongo Yakusu ¹, Kévin Lievens¹, Tom De mil ², Wannes Hubau ¹ & Hans Beeckman ¹

¹ Royal Museum for Central Africa (RMCA), Belgium

² Laboratory of three-ring research University of Arizona, U.S.A.

The sampling of increment cores constitutes a non-destructive approach to study the wood anatomy of a tree along a radial transect. The distribution and variability of anatomical features along such a transect can serve as a proxy of a tree’s growth dynamics. It is therefore valuable to develop methods of accessing and analyzing these data, such as the distribution of vessel sizes along a pith-to-bark transect.

The processing of the increment cores begins with the production of long cross sections, 10 to 20 µm thick, using a microtome. The cross sections are then stained to highlight the anatomical features. Next, the cross sections are digitized using the Stream Motion software (Olympus Optical Co. Japan) on a scanning stage (SCAN 100 x 100, Märzhäuser Wetzlar, Germany) to create high resolution images. A pre-treatment of the images, with an image manipulation program such as GIMP 2 (www.gimp.org), is then required to enable their use for data analyses. This includes associating fragments to reconstruct a linear and continuous cross section, since it is difficult to consistently prevent the formation of tearing when cutting the cores.

The data contained in the cross section images is finally accessed using the ImageJ software (www.imagej.net). Data such as the position, size, and vessels density along a pith-to-bark transect are then acquired and can therefore be used to study the physiology and growth dynamics of the trees. ImageJ features such as the Trainable Weka Segmentation plugin offer the opportunity to automatize the analyses, therefore allowing for a larger sampling size and faster processing.

[Oral Presentation]

Impact of dominance hierarchy on deleterious mutations linked to the S locus in Arabidopsis

Audrey Le Veve, Vincent Castric, Xavier Vekemans & Eleonore Durand

University of Lille, France

Self-incompatibility (SI) is a genetic system preventing inbreeding and promoting outcrossing in hermaphrodite plant species. In Brassicaceae, the sporophytic SI system is controlled by a genomic region, the S-locus, composed of two linked genes encoding pollen and pistil proteins. Pollination between partners with the same S-haplotype leads to the formation of a ligand-receptor complex that permits pollen recognition and rejection.

SI is a classic case of negative frequency-dependent selection (one form of balancing selection), which is expected to promote heterozygosity and allelic diversity at the S-locus and also in the linked genomic regions around the S-locus, resulting in the accumulation of a sheltered load of recessive deleterious mutations. In numerous SI species, a dominance hierarchy among S-haplotypes exists: only the protein encoded by the most dominant S-allele in a diploid genotype is deposited on pollen. The dominance hierarchy between S-haplotypes is expected to impact the magnitude of the sheltered load of deleterious mutations, with a more important load associated with more dominant S-alleles. While the theoretical predictions are clear, few empirical studies have attempted to estimate the sheltered load linked to the S-locus, and none of them focused on the molecular genetic basis of the load.

Here, we tested these predictions by focusing on natural populations of two self-incompatible species A. halleri and A. lyrata. We resequenced the genomic regions linked to the S-locus to identify segregating mutations in 47 individuals and evaluated their potential deleterious effect based on conservation and functional annotation. This approach allows us to test the effect of S-allele dominance on the magnitude of the load of deleterious mutations they carry. We are also planning to estimate experimentally inbreeding depression linked to the S-locus in S-haplotypes with three different dominance levels.

[Oral Presentation]

Three-dimensional soil heterogeneity modulates the responses of plant community to drought in experimental mesocosms

Yongjie Liu

University of Antwerp, Belgium

Heterogeneous distribution of soil resources is an intrinsic characteristic of soils. And such distribution significantly affected terrestrial ecosystems. Ongoing climate change influences both heterogeneous soils and plant ecosystems. However, the joint effects of climate change and soil heterogeneity on plant communities are poorly studied. It is complicated to explore soil heterogeneity in natural conditions since many co-occurring factors (e.g. biotic or abiotic factors) make it difficult to precisely ascribe causes and consequences.

To investigate the joint effects of soil heterogeneity and drought on plant communities, we conducted a semi-natural experiment, where factors other than soil heterogeneity were kept constant with a recently developed technique. Soil heterogeneity was created in mesocosms layer by layer with resource-rich and resource-poor substrate in all dimensions, resulting in four levels of soil heterogeneity (cell size 0, 12, 24 to 48 cm). A seed mixture of 24 species that naturally occur in grasslands in Western Europe was evenly sowed on each mesocosm in May 2016. Temporary rainout shelters were added on mesocosms to simulate drought tress, which lasted three weeks in August 2016. Then recovery started and ended in November 2016. We measured soil water content, canopy temperature, plant mortality and green cover of each mesocosm during drought and soil water content and green cover during recovery. Moreover, shoot and root biomass was harvested once after drought and shoot biomass was harvest again after recovery.

Results demonstrated that shoot and root biomass was not affected by drought × soil heterogeneity interaction, but root biomass was affected by soil heterogeneity, and more root biomass was found in mesocosms with higher soil heterogeneity. Furthermore, drought × soil heterogeneity × measured date interaction affected soil water content and green cover. Green cover of mesocosms with higher soil heterogeneity and higher biomass decreased mostly faster than other mesocosms. In general, during drought soil water content in mesocosms decreased firstly, and then it increased the canopy temperature, which caused more water loss. As a result increased plant mortality, and decreased green cover. Overall, our results indicate that soil heterogeneity interacting with plant productivity modulates the effect of drought on plant communities.

[Poster]

Morphological characterization of Fusarium oxysporum f.sp cubense (Foc) in North and Central Vietnam

Loan L.T.¹, Huy N.D.2, Anh Tuấn P.L.², Janssens S.³, Tuong V. D.¹ & Vu D.T.¹

¹ Plant Resources Center, Ha Noi, Viet Nam

² Viet Nam National University of Agriculture, Ha Noi, Viet Nam

³ Meise Botanic Garden, Belgium

Bananas are amongst the most important fruit crops in tropical and subtropical regions. The past decades, bananas are increasingly suffering various viral, bacterial and fungal diseases.

One of the most destructive diseases of bananas is the panama wilt disease caused by Fusarium oxysporum f. sp cubense. Also in Viet Nam Fusarium oxysporum f. sp cubense is readily present among different banana cultivars and wild species, as we isolated and grew the fungus on PDA media in the range 25 - 30°C and pH 6 – 8. Conidia formed on PDA are not as consistent in both size and shape as those formed on CLA or SNA media yet the isolated fungi that were grown on CLA produced macroconidia which were uniform in size and shape. In addition, also the morphology of macroconidia grown on SNA was not uniform. On rice media, the mycelium obtained was dark red without any aroma. Current result showed that the isolates collected from the field could be identified as Tropical Race 1.

[Oral Presentation]

Building on a solid foundation: a case study of how careful systematics can enhance ecology and genomics

Nicolas Magain ¹, Jolanta Miadlikowska ², Emmanuël Sérusiaux ¹ & François Lutzoni ²

¹ Université de Liège , Belgium

² Duke University, U.S.A.

For almost a decade, we have conducted a thorough phylogenetic revision of the Peltigera-Nostoc lichen symbiosis (Lecanoromycetes, Fungi; and Nostocales, cyanobacteria, respectively). It has resulted in recognising more than twice as many species as previously detected, for both partners. We will present a few examples of how careful systematics, paired with meaningful collaborations, has largely expanded the outcomes of this work. Indeed, OTUs representing meaningful evolutionary lineages are crucial for many aspects of biology. First, correctly understanding the identity and diversity of partners allowed the discovery of a large range of specificity patterns between symbionts. The symbiosis was then studied through ecological network analyses at a global scale. It further allowed us to gain insights into patterns of nitrogen fixation by lichen-associated cyanobacteria in the boreal realm. Finally, it also led us to adequately design our sampling for comparative and functional metagenomics, with the goal to better understand the mechanisms of the association.

[Oral Presentation]

The use of high-throughput sequencing for the identification of illegally logged African trees

Maurizio Mascarello ^1,2, Hans Beeckman ³, Erik Smets ^2,4 & Steven Janssens ^1,2

¹ Meise Botanic Garden, Belgium

² KU Leuven, Plant Conservation and Population Biology, Belgium

³ Royal Museum of Central Africa, Belgium

⁴ Naturalis Biodiversity Center, The Netherlands

Illegal logging represents a serious threat for the survival of tree species in tropical regions. It has been estimated that up to 90% of the total timber production may be obtained from illegal logging activities in tropical countries such as the Democratic Republic of Congo. The utilization of forensic techniques such as wood anatomy and standard plant DNA barcodes often fail to differentiate closely-related timber species. In this study, we perform the recently developed genomic technique “Genome skimming by shotgun sequencing” as a complement to standard forensic methods to discover novel plant genetic markers for a fast and reliable identification of major commercial timber species in tropical Africa. Our results will be essential to promote the conservation of endangered African timber species within the framework of CITES and EU Timber Regulation. DNA libraries have been obtained for selected timber species, which were analyzed with Illumina HiSeq. With the data obtained, we performed a de novo reconstruction of the whole chloroplast genomes. Our results confirm that the standard plant barcodes matK and rbcL do not provide sufficient genetic variability for the discrimination of closed-related species in some genus. In addition, multiple alignments of the chloroplast genomes showed further genetic sequences which could be used as candidate genetic markers for species identification. These would be essential for the detection of wood and timber products under the illegal trade of protected tree species.

[Poster]

The value of Species Distribution Modelling to assess the conservation status of wild banana species (Musa spp.)

Arne Mertens ^1,2, Rony Swennen ^1,3,4, Nina Rønsted ^5,6; Filip Vandelook ², Bart Panis ⁴, Gabriel Sachter-Smith ⁷, Dang Toan Vu ⁸ & Steven Janssens ²

¹ Laboratory of Tropical Crop Improvement, Department of Biosystems, KU Leuven, Belgium

² Crop wild relatives and useful plants, Meise Botanic Garden, Belgium

³ International Institute of Tropical Agriculture, Arusha, Tanzania

⁴ Bioversity International, Heverlee, Belgium

⁵ Natural History Museum, Copenhagen, Denmark

⁶ National Tropical Botanical Garden, Koloa, Hawaii

⁷ University of Hawaii, Mānoa, Hawaii

⁸ Research Planning and International Department, Plant Resources Centre, Vietnam

Crop wild relatives (CWR), wild plants closely related to domesticated crops, are valuable for the improvement of crop yield and quality and the improvement of biotic and abiotic stress resistance. Though they receive much public and political support, there is a large gap in the number of CWR taxa that are conserved ex- and in-situ. Conservation biologists deal with the questions (1) which areas should be protected for additional in-situ conservation of CWR taxa and (2) where should additional CWR germplasm be collected.

In this study, we focus on wild relatives of one of the most important fruit crops in the world, the banana (Musa spp.). IUCN conservation status of Musa species is assessed and based on a species distribution modelling approach, their potential climate envelope is inferred as well as their current in- and ex-situ conservation status. Highest species richness is found in northeastern India and the south China-northern Vietnam border, regions also marked with the highest number of threatened banana species. Out of 59 assessed wild Musa species, 12 are classified as vulnerable and 10 as endangered. Distribution models reveal that the northern Indo-Burmese region has high climatic suitability for most banana species and that lowland rainforests generally are highly suitable while dry, swampy and more alpine areas are not. Conservation assessments indicate that only four species are sufficiently conserved in germplasm collections and that 48 are of high priority for additional ex-situ conservation efforts. Evaluation of in-situ conservation status suggests that 11 wild species are of low priority for further in-situ conservation and at least 46 species require additional in-situ conservation efforts. To date, very little of the CWRs of wild banana is sufficiently conserved both ex- and in-situ. By providing potential distribution maps for each species, we provide guidance where additional material could be sampled or protected.

[Poster]

Reproductive isolation among lineages of Silene nutans: a potential involvement of nucleo-plastidic incompatibilities

Zoé Postel¹, Céline Poux¹, Sophie Gallina¹, Jean-Stéphane Varré², Fabienne Van Rossum³ & Pascal Touzet¹

¹ Univ. Lille, EEP- Ecologie, Evolution, Paléontologie, , France

² Univ. Lille, Inria, - CRIStAL Centre de Recherche en Informatique Signal et Automatique de Lille, France

³ Meise Botanic Garden, Belgium

How species arise and maintain is one of the main questions in evolutionary biology. Speciation often occurs through the emergence of pre- and post-zygotic barriers to reproduction, leading to reproductive isolation. The emergence of post-zygotic barriers can be the result of genetics incompatibilities and notably cytonuclear incompatibilities leading to hybrid breakdown, through the combination of mismatched nuclear and cytoplasmic gene products in hybrids. Many plastid protein complexes include subunits encoded by plastid and nuclear genomes leading to coevolution between the plastid and nuclear genes encoding these complexes. This coevolution will be disrupted among individuals combining plastid and nuclear genome coming from different species or divergent populations, leading to incompatibilities between plastid and nuclear genes and ultimately to reduced hybrid fitness.

In Silene nutans (Angiosperm), four lineages genetically differentiated have been identified and show strong and asymmetric reproductive isolation (high proportion of seedling mortality and chlorotic hybrids), suggesting the presence of nucleo-plastidic incompatibilities between these four lineages. We tried to identify plastid and nuclear genes encoding subunits of plastid proteins complexes, using gene-capture methodology, by searching over most of the plastid genes and their potential nuclear interactors, the non-synonymous substitutions fixed differently between lineages. The search for signatures of positive selection on these variants revealed a potential involvement of genes encoding the plastid genes expression but also the photosynthetic machineries. Given the great diversity of its plastid genome, S. nutans, seems to exhibit an accelerated rate of plastid genome evolution, which could promote the occurrence of nucleo-plastid incompatibilities between fast evolving plastid genes and their co-adapted nuclear interactors.

[Oral Presentation]

Effects of slash-and-burn practice and woody charcoal production on xerophytic thickets of southwestern Madagascar

Heriniaina Olivier Radosy ¹, Josoa R. Randriamalala ¹, Stephanie M. Carrière ², Hans Beeckman ³ & Dominique Hervé ²

¹ Université d’Antananarivo, École Supérieure des Sciences Agronomiques, Département Eaux et Forêts, Madagascar

² Institut de Recherche pour le Développement (UMR 220 GRED: IRD-UPV), Université Paul Valéry, Montpellier, France

³ Royal Museum for Central Africa (RMCA), Wood Biology Service, Belgium

Little is known about the functioning of the xerophytic thickets of southwestern Madagascar. Even though their low regeneration rates due to extreme climatic condition, bush were intensively exploited by the local population. Focusing on the effects of human disturbance, this study investigates: the effects of slash and burn practice for crop cultivation and charcoal production on the xerophytic bush on calcareous limestone soil.

Thirty square plots of 100 m² were randomly sampled according to the type of disturbance: slash-and-burn agriculture or woody charcoal production areas vs. less disturbed area (selective logging) in two communes. Diversity, stem density, total height of all plants were recorded in charcoal production and fallow area aged from 10 to 30 years (to studying the effect of slash and burn crop cultivation). Fifty-one square plots of 16 m² were randomly sampled too to estimate the above ground biomass by harvesting method.

Results show that charcoal production and slash and burn practice (regarding the fallow vegetation) reduced species richness and modified floristic composition. These disturbances also decreased mean height, stem density and the above-ground biomass. Finally, shrub regeneration rate was low even in less disturbed area, however, slash-and-burn agriculture and charcoal production slow down their recovery.

[Poster]

Factors affecting success of pollination in an olive orchard: evaluating the effect of spatial distance, self-incompatibility phenotype and wild versus cultivated gene pool

Adèle Ragot-Richard ¹, Pierre Saumitou-Laprade ¹, Julien Balajas ², Cécile Godé ¹, Xavier Vekemans ¹, Philippe Vernet ¹ & Isabelle De Cauwer ¹

¹ Univ. Lille, CNRS, UMR 8198 - Evo-Eco-Paleo, France

² France Olive, CTO, Aix-en-Provence, France

The olive is a typical Mediterranean andromonoecious species in which a diallelic sporophytic self-incompatibility system was recently discovered. In this system, individuals are split in two inter-compatible reproductive groups and fertilization is allowed only between individuals belonging to different groups. This particular system has important consequences in agronomy. Indeed, olive trees are usually vegetatively propagated, thus a cultivar corresponds to a set of individual who share the same genotype and the same compatibility group. Therefore, monovarietal orchards should typically have low proportions of compatible pollen in their pollen cloud and experience low fruit production. In this context, in order to improve the organisation and production of orchards it is important to study factors affecting success of pollination in an orchard, and assess which genotypes contribute to the pollen cloud of cultivars of economic interest. Our study was carried out in a Corsican olive orchard composed of a mixture of two domesticated varieties and wild olives. Using genotypic information on seeds and trees, we investigated how the self-incompatibility system is functioning in situ. The influence of the distance between maternal and paternal trees, as well as the effect of the source of pollen in terms of cultivated vs. wild pollen donors were also assessed. Paternity analyses confirmed the compatibility between the two typical varieties selected by olive growers in former times as fruit producer and pollen donor, and revealed a substantial participation of wild trees in pollination. Except a low proportion of seeds produced by selfing on a single cultivar, self-incompatibility was the rule. Pollen dispersal was spatially restricted in the orchard and inter-tree distances played an important role in the efficacy of pollination. Finally, cultivated trees showed a better fertilization success of cultivated mothers than wild genotypes.

[Oral Presentation]

Diatoms on loggerhead sea turtles: ecology & biogeography

Käthe Robert ^1,2, Sunčica Bosak ³, Roksana Majewska ^4,5 & Bart Van de Vijver^1,2

¹ Meise Botanic Garden, Research Department, Belgium

² University of Antwerp, Department of Biology - ECOBE, Belgium

³ Department of Biology, Faculty of Science, University of Zagreb, Croatia

⁴ Unit for Environmental Sciences and Management, School of Biological Sciences, North-West University, South Africa

⁵ South African Institute for Aquatic Biodiversity (SAIAB), South Africa

In recent years, there is a growing scientific interest in epibiotic communities on sea turtles. A broad array of animals such as crustaceans, annelids, mollusks and macroalgae are known to thrive successfully as macro-epibionts on the sea turtle body surfaces. Together with these macroscopic organisms, sea turtles also host unique and diverse micro-epibiotic diatom communities composed of a large number of genera, several of which been described as new to science in the past five years. Typical examples of epizoic genera include Chelonicola, Medlinella and Poulinea, known exclusively from the carapaces and skin of different sea turtle species (Majewska et al. 2015, Frankovich et al. 2016).

The current study analysed the epibiotic diatom communities associated with the carapace and skin of loggerhead sea turtles (Caretta caretta) from four geographically different populations: Amvrakikos Bay (Greece), Florida Bay (USA), Adriatic Sea (Croatia) and Kosi Bay (South Africa). The aim was to compare the diatom communities between the skin and carapace of loggerheads, between different individuals within one loggerhead population and between geographical different loggerhead populations.

The results of this study show that loggerheads harbour several undescribed taxa and a very divers diatom flora, of which some are presumably exclusively epizoic taxa, but the majority are likely opportunistic taxa able to thrive on both biotic and abiotic substrata. Loggerheads from different populations are dominated by different diatom taxa and there appears to be a difference between the epizoic communities living on the skin and carapace of these sea turtles. Future research provide new insights into co-evolution and biogeography of microbial epibionts and their hosts as well as their capacity to function as ecological indicators of sea turtle behaviour and health.

Frankovich, T. et al. (2016) Phytotaxa 272(2): 101–114.

Majewska, R. et al. (2015) Phytotaxa 233(3): 236–250.

[Oral Presentation]

Unveiling the hidden: mycoparasitism and the evolution of Basidiomycota

Nathan Schoutteten ¹, Mieke Verbeken ¹, Roeland Enzlin ² & Dominik Begerow ³

¹ Onderzoeksgroep Mycologie, Universiteit Gent, Belgium

² Nederlandse Mycologische Vereniging, The Netherlands

³ AG Geobotanik, Ruhr Universität Bochum, Germany

Basidiomycota are best known for their typical mushroom forming fungi, of which the majority are plant symbionts or decayers of diverse organic material. These species all belong to the Agaricomycotina, one of three basidiomycete subpyla. The rusts (Pucciniomycotina) and the smuts (Ustilaginomycotina) constitute the other two subphyla, of which the former one is most likely the oldest. Both groups are dominated by important plant pathogens, but new taxa are being discovered in diverse habitats, unveiling a variety of curious ecological interactions.

The last decades, many fungi paraziting on other fungi (mycoparasites) have been described and found to belong to Basidiomycota. However, almost all of them were only studied morphologically, and molecular and ultrastructural data is lacking for most of them. The sparse molecular data today proves that these species constitute distantly related lineages the Pucciniomycotina. Some of these mycoparasites were even raised to order or class level, highlighting the long evolutionary distances between them.

Most of the basidiomycetous mycoparasites only form minute basidiocarps, making them easily overlooked and challenges their discovery. Others do not produce basidiocarps at all, but rather live entirely in the tissues of their host fungus. This not only hinders their discovery even more, but also obtaining molecular data.

Our current project aims to reveal the diversity mycoparasites and the evolutionary history of this trophic strategy, along with its associated characters like haustoria and a dimorphic life cycle. Thanks to efforts to tackle the forecalled challenges and the involvement of an international network of dedicated mycologists, it is now possible to gain better insights in this enigmatic group of fungi. During the last two years, all scattered literature has been compiled, and up to date identification keys and descriptions have been prepared to serve as a starting point.

[Poster]

Variation in vegetative desiccation tolerance behavior of independently-evolved desert species of Tetradesmus

Elizaveta Terlova ¹, Andreas Holzinger ² & Louise A. Lewis ¹

¹ University of Connecticut, U.S.A

² Innsbruck University, Austria

Vegetative desiccation tolerance (VDT) — the ability of vegetative cells to recover from 80 90% loss of protoplasmic water — is a rare but phylogenetically widespread set of traits. Some VDT species can survive rapid and long-lasting desiccation and restore their physiological activity once water becomes available. Unlike embryophytes, green algae show multiple origins of terrestriality, with algae of desert soil crusts being one example. In Chlorophyta desert species are embedded in aquatic taxa, such as common freshwater genus Tetradesmus (Sphaeropleales, Chlorophyceae). More importantly, the desert Tetradesmus species have independent origins from aquatic ancestors, and we expect them to show variation in VDT traits.

We demonstrated dramatic differences in response to desiccation of aquatic and desert Tetradesmus using PSII chlorophyll fluorescence as a proxy for the physiological state of cells. When hydrated the quantum yield of photosynthesis was the same for all strains. Likewise, desiccation resulted in a complete loss of photosynthetic capacity. Upon rehydration a clear distinction between aquatic and desert species was apparent: only desert species restored their photosynthetic activity, the aquatic species remained inactive even after 15 h. The behavior upon rehydration varied among species depending on mode of desiccation. Rapid desiccation reaching low relative humidity (RH) values (RH ~5% reached in 2 3 h) appears to cause the most damage. Upon rehydration desert species initially had photosynthetic activity but lost it later. Less severe modes of desiccation (RH ~65% reached in 8 h and RH~85% reached in 12 h) resulted in differences among the independently-evolved desert species.

This complex of closely related species of Tetradesmus from different habitats is an ideal system for future investigations of the underlying mechanisms and evolution of desiccation tolerance in chlorophycean algae.

[Oral Presentation]

Herbarium specimens on your desktop from anywhere: hosting IIIF compliant images at Meise Botanic Garden

Maarten Trekels, Pieter Huybrechts, Mathias Dillen & Quentin Groom

Meise Botanic Garden, Belgium

With increasing numbers of herbarium specimens being imaged all over the world, a massive amount of information is produced. However, in many cases these data are locked up in silos and not readily available. The IIIF (International Image Interoperability Framework) data standard aims to open up access to the many different image sources [1]. By providing an interoperable interface between image repositories, sharing of images becomes easy. IIIF is supported by a large and growing community of research institutes, museums and libraries, which is highly beneficial for long term sustainability and simple integration of desirable features. At Meise Botanic Garden, an IIIF service is implemented that provides the images of herbarium specimens together with their metadata. Initial comparison with specimens from other institutes can be performed in a single image viewer. This can potentially decrease the number of physical loans of fragile herbarium sheets. However, many other use-cases can be envisioned. The framework can contribute to higher visibility of specimens and collectors. Moreover, IIIF enables the possibility of manipulating and annotating the images remotely while keeping the source image unchanged.

[1] IIIF website, https://iiif.io/, consulted 07 Nov 2019.

[Poster]

Megatree: Towards a Comprehensive Phylogeny for Brown Seaweeds (Phaeophyceae, Ochrophyta)

Pierrot Van der Aa ¹, Christophe Vieira ¹, Michael Guiry ², Heroen Verbruggen³ & Olivier De Clerck ¹

¹ Phycology Research Group and Center for Molecular Phylogenetics and Evolution, Ghent University, Belgium

² AlgaeBase, Room 301, Ryan Institute, National University of Ireland, Ireland

³ School of Botany, University of Melbourne, Australia

Large and comprehensive phylogenetic trees are desirable for studying macroevolutionary processes. The brown seaweeds or Phaeophyceae comprise of over 2000 species (Guiry and Guiry, 2018). Over the past few years, molecular-assisted taxonomic studies have significantly contributed to our knowledge of the biodiversity within several phaeophycean groups. Phylogenetic efforts have nonetheless been directed towards lower taxonomic ranks, notable genera or family at best. Silberfeld et al. (2011, 2014) and Kawai et al. (2015, 2016) provided the last phylogenetic trees for the Phaeophyceae including representatives of most orders, refining our understanding of ordinal-level phylogenetic relationships. A comprehensive phylogeny of the Phaeophyceae, encompassing all presently known species, is nevertheless still lacking.

This thesis provides the first tree of life of the brown seaweeds including all species for which molecular data are available, by applying a megatree approach. This was done by compiling sequences of all species of brown seaweeds for 12 well-represented nuclear, mitochondrial and chloroplast markers from online nucleotide databases. Phylogenies at the ordinal level were first constructed using a Bayesian approach, and grafted to an updated backbone phylogeny. The resulting tree includes 32% of the presently described species of brown seaweeds and highlights the gaps in the knowledge of those species.

[Poster]

Assessment of biological quality along a metal pollution gradient applying macroinvertebrates and diatoms

Stijn Van de Vondel ^1,2, Lieven Bervoets ³ & Bart Van de Vijver ^1,2

¹ Meise Botanic Garden, Research Department, Belgium

² University of Antwerp, Department of Biology, ECOBE, Belgium

³ University of Antwerp, Department of Biology, SPHERE, Belgium

Water is an invaluable resource for both nature and man. Several years ago, the European Water Framework Directive (2000/60/EC) was created to monitor and establish the quality of all waterbodies within the European Union urging all EU member states to perform water quality assessment based on biological, physical–chemical and hydro-morphological elements. The biological monitoring includes fish fauna, macrophytes, macroinvertebrates and diatoms. The latter two groups have been shown to form very reliable bio-indicators for general water quality monitoring. Most assessment methods implemented in the WFD have been applicable for effects of oxygen, eutrophication and acidification but fewer seem to be useful to indicate effects of microcontaminants such as metals and herbicides/pesticides despite their generally accepted negative effect on aquatic life.

The present study evaluates the impact of a metal pollution gradient caused by historical contamination in a Flemish lowland river. Following previously performed research in 2006-2007 in which the water quality of the Dommel River was evaluated using both diatoms and macro-invertebrates, and given our current new understandings of diatom taxonomy, it was opted to reiterate the ecological evaluation of the Dommel river, a small (120 km long) stream of which 35 km is located within Belgian borders. Several biotic indices based on both diatoms and macroinvertebrates, are applied to monitor the water quality on six sampling localities of the Dommel river. Using the latest insights in diatom taxonomy, it offers an interesting opportunity to revaluate several samples taken in 2006, along with the appraisal of measures taken in the past decade to improve the water quality of Flemish rivers.

[Oral Presentation]

The search for common origin: Homology revisited

Alexander Vrijdaghs

KU Leuven, Belgium

based on: Ochoterena Helga, Vrijdaghs Alexander, Smets Erik & Classen-Bockhoff Regine (2019) The search for common origin: homology revisited. Systematic Biology 68: 767-780

Understanding the evolution of biodiversity on Earth is a central aim in biology. Currently, various disciplines of science contribute to unravel evolution at all levels of life, from individual organisms to species and higher ranks, using different approaches and specific terminologies. The search for common origin, traditionally called homology, is a connecting paradigm of all studies related to evolution. However, it is not always sufficiently taken into account that defining homology depends on the hierarchical level studied (organism, population, species), which often cause confusion and misunderstanding among scientists. Therefore, we elaborated a conceptual framework which unifies all approaches of homology. We propose to use the overarching term 'homology' only when ‘morphological homology’ (organism level), ‘vertical gene transfer’ (population level) and ‘phylogenetic homology’(species level) are confirmed. Our conceptual framework makes the relation between morphological homology, phylogenetic homology and homoplasy more clear, following Willi Hennig's (1966) idea (founder of cladistic analysis and phylogenetic systematics) of reciprocal illumination: morphological homologues should be distributed in a clade (have a common ancestor) and phylogenetic homologues should have the same morphological origin. If not, homoplasy occurs and homology should be re-examined at the organism, species and population level. The latter is often neglected, assuming that no horizontal gene transfer occurred. In addition, we propose to simplify and logically sort out the existing terminological jungle. We invite all researchers of evolution to consider the proposed framework, offering them a new perspective for their own research.

[Poster]

The wild banana species of the Northern Viet Nam

Tuong Dang Vu ¹, Duc The Ngo ¹, Loan Le Thi ¹, Janssens Steven ² & Vu Dang Toan ¹

¹ Research Planning and International Cooperation, PRC, Ha Noi, Viet Nam

² Meise Botanic Garden, Belgium

Bananas is one of the most popular fruits and is situated in the top 10 most important crops worldwide. Especially in the rural communities of the tropics and subtropics bananas is a staple crop that is important part of their daily livelihood. From 2016 to 2018, multiple banana species over several populations have been collected in the Northern provinces of Viet Nam. In this study, we describe the morphology, ecology and phytogeography of the six Musa species collected between 85 and 1331m. Interestingly, the banana species collected during these missions have diverse ecological and phytogeographical preferences and are also morphologically rather distinct. Among these six species, M. balbisiana and M. acuminata – which are the ancestors of the majority of cultivated bananas were only occasionally found between 100m - 1000m, whereas M. itinerans occurred mainly in large mats of several square meters ranging from 136m to 1331m. In addition, M. lutea, M. paracoccinea, M. haekkinenii were more rare than M. itinerans yet when present, also several individuals per population could be found. All latter three species have a straight upright inflorescence that are easy to identify and can be considered potentially valuable as ornamental plants. Interestingly M. lutea, M. paracoccinea, M. haekkinenii are all occurring in areas that are not competing for light by other species and also have elevation ranges between 80m - 800m. This study demonstrates the wide distribution range and the high morphological diversity of wild Musa species in Northern Viet Nam, which form an important basis for future breeding programs.