Olivier J Hardy

Olivier J Hardy
Université Libre de Bruxelles | ULB · Evolutionary Biology and Ecology Unit

Doctor of Philosophy

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423
Publications
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Publications

Publications (423)
Article
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Background and aims – Brachystegia is a species-rich tree genus found in tropical Africa and a typical element of Miombo woodlands, a widely distributed subtype of the Zambezian savanna. Plastid DNA was shown to be largely uninformative to assess species phylogenetic relationships due to widespread chloroplast capture among species. Here, we aim to...
Article
Khaya (Meliaceae) is a widespread genus of trees distributed from the tropical forests of Africa to Madagascar and the Comoros. Khaya species are very close morphologically and some contain considerable phenotypic and ecological diversity, raising the question of their delimitation: this is the case of Khaya anthotheca s.l. (sensu lato, including K...
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Significance Our full-scale comparison of Africa and South America’s lowland tropical tree floras shows that both Africa and South America’s moist and dry tree floras are organized similarly: plant families that are rich in tree species on one continent are also rich in tree species on the other continent, and these patterns hold across moist and d...
Preprint
Full-text available
Epiphytic communities live in a unique, three-dimensional micro-habitat space that offers an original framework to disentangle the contribution of environmental filters, biotic interactions and dispersal limitation to community structure at small spatial scales. We took advantage of a tropical canopy crane facility to record and model spatio-tempor...
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Climatic niche evolution during the diversification of tropical plants has received little attention in Africa. To address this, we characterised the climatic niche of >4000 tropical African woody species, distinguishing two broad bioclimatic groups (forest vs. savanna) and six subgroups. We quantified niche conservatism versus lability at the genu...
Article
Plant translocation is a useful tool for implementing assisted gene flow in recovery plans of critically endangered plant species. Although it helps to restore genetically viable populations, it is not devoid of genetic risks, such as poor adaptation of transplants and outbreeding depression in the hybrid progeny, which may have negative consequenc...
Article
Oceanic islands have played an important role in our understanding of the diversification of organisms, and phylogenetic estimates have been used in this context to investigate the origin of island diversity and its relationship to the continent. Using a typical orchid genus rich in island endemics and with widespread continental relatives, we aim...
Article
Endemism is one of the most important concepts in biogeography and is often used to guide biodiversity conservation, yet our understanding of the determinants of endemism in many biodiverse tropical regions is limited. This is true for western Central Africa, a region with one of the highest levels of plant diversity in tropical Africa, where endem...
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Background and objectives—Podocarpus latifolius (synonym of P. milanjianus) is a key tree representative of Afromontane forests where it is highly threatened by climate and land-use changes. While large populations occur in East Africa, only a few isolated and usually small populations remain in western Central Africa (Cameroon to Angola). Studying...
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Most Central African rainforests are characterized by a remarkable abundance of light-demanding canopy species: long-lived pioneers (LLP) and non-pioneer light demanders (NPLD). A popular explanation is that these forests are still recovering from intense slash-and-burn farming activities, which abruptly ended in the 19th century. This “human distu...
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Background Comparative phylogeographic studies on rainforest species that are widespread in Central Africa often reveal genetic discontinuities within and between biogeographic regions, indicating (historical) barriers to gene flow, possibly due to repeated and/or long-lasting population fragmentation during glacial periods according to the forest...
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Reproductive strategies are diverse and a whole continuum of mixed systems lies between strict sexuality and strict clonality (apomixis), including automixis, a parthenogenetic mode of reproduction involving a meiosis and increasing homozygosity over generations. These various systems impact the genetic structure of populations, which can therefore...
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Because of the quality of their wood and their many traditional uses, species of the Entandrophragma genus are being intensively logged, and this is likely to compromise their survival unless sustainable management is introduced. This study reviews the current status of the five main commercial Entandrophragma species: Entandrophragma angolense, E....
Article
The cold-tolerant leaf beetle Gonioctena quinquepunctata displays a large but fragmented European distribution and is restricted to mountain regions in the southern part of its range. Using a RAD-seq-generated large single nucleotide polymorphism (SNP) data set (> 10,000 loci), we investigated the geographic distribution of genetic variation within...
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Phylogenetic turnover has emerged as a powerful tool to identify the mechanisms by which biological communities assemble. When significantly structured along environmental gradients, phylogenetic turnover evidences phylogenetic niche conservatism, a critical principle explaining patterns of species distributions at different spatio-temporal scales....
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Tropical forests store 40-50% of terrestrial vegetation carbon. Spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests. Because of climatic and soil changes with increasing elevation, AGC stocks are lower in tropical montane compared to lowland forests. Here we ass...
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Tropical forests store 40–50 per cent of terrestrial vegetation carbon1. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests2. Owing to climatic and soil changes with increasing elevation3, AGC stocks are lower in tropical montane forests compared with...
Article
Although today the forest cover is continuous in Central Africa, this may have not always been the case, as the scarce fossil record in this region suggests that arid conditions might have significantly reduced tree density during the ice ages. Our aim was to investigate whether the dry ice age periods left a genetic signature on tree species that...
Article
Tropical forests are the most diverse and productive ecosystems on Earth. While better understanding of these forests is critical for our collective future, until quite recently efforts to measure and monitor them have been largely disconnected. Networking is essential to discover the answers to questions that transcend borders and the horizons of...
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Tropical forests represent vast carbon stocks and continue to be key carbon sinks and buffer climate changes. The international policy constructed several mechanisms aiming at conservation and sustainable use of these forests. Illegal logging is an important threat of forests, especially in the tropics. Several laws and regulations have been set up...
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Seed and pollen dispersal are important for defining sustainable forest management practices. By reducing population density, selective logging could affect not only the seed production of timber species but also the selfing rate and the patterns of seed and pollen rains. To assess these risks, we characterized seed and pollen dispersal patterns an...
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O objetivo foi abordar um mosaico de vegetação de savana (áreas marginais-MS e disjuntas-DS) no Cerrado Setentrional Brasileiro para investigar o papel desempenhado por fatores ambientais como determinantes da organização comunitária em escala espacial, a fim de compreender os padrões divergentes ao longo de uma gradiente ambiental. Analisamos pred...
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The responses of tropical forests to environmental change are critical uncertainties in predicting the future impacts of climate change. The positive phase of the 2015–2016 El Niño Southern Oscillation resulted in unprecedented heat and low precipitation in the tropics with substantial impacts on the global carbon cycle. The role of African tropica...
Article
Tropical forests are the most diverse and productive ecosystems on Earth. While better understanding of these forests is critical for our collective future, until quite recently efforts to measure and monitor them have been largely disconnected. Networking is essential to discover the answers to questions that transcend borders and the horizons of...
Article
Tropical forests are the most diverse and productive ecosystems on Earth. While better understanding of these forests is critical for our collective future, until quite recently efforts to measure and monitor them have been largely disconnected. Networking is essential to discover the answers to questions that transcend borders and the horizons of...
Article
Aim: Miombo woodlands form a characteristic vegetation type covering 2.7 million km² in southern and eastern Africa. Despite their wide geographical extent, their origin, floristic and spatial evolution through time remain understudied. To fill this gap, we studied the evolution of Brachystegia trees, one of the most representative genera of these...
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Secondary metabolites are essential for plant survival and reproduction. Wild undomes-ticated and tropical plants are expected to harbor highly diverse metabolomes. We investigated the metabolomic diversity of two morphologically similar trees of tropical Africa, Erythrophleum suave-olens and E. ivorense, known for particular secondary metabolites...
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Description of the subject. Pericopsis elata (Fabaceae) is a long-lived light-demanding tree from African rain forests that produces timber of high economic value. Natural populations suffer from overexploitation and a deficit of natural regeneration. Plantations could increase its production and limit the pressure on natural forests. However, we l...
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In the pantropical mimosoid legume genus Parkia, taxonomic classification has remained controversial in Africa due to clinal phenotypic variations. Three species (P. biglobosa, P. bicolor, and P. filicoidea) are currently recognized, ranging from West to East Africa, with partially overlapping ranges across different floristic regions. However, add...
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Aim The Guineo‐Congolian region in Africa constitutes the second largest area of tropical rainforest (TRF) in the world. It covered an estimated 15–22 million km² during the late Miocene (55–11 Ma) and it has experienced since a declining trend, currently reaching 3.4 million km², associated with increasing aridification and the replacement of TRF...
Article
Temporal and spatial patterns in flowering phenology were assessed for eight tropical African tree species. Specifically, the frequency and seasonality of flowering at seven sites in central Africa were determined using field data, graphical analysis and circular statistics. Additionally, spatial variation in the timing of flowering across species...
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The dating of diversification events, including transitions between biomes, is key to elucidate the processes that underlie the assembly and evolution of tropical biodiversity. Afzelia is a widespread genus of tropical trees, threatened by exploitation for its valuable timber, that presents an interesting system to investigate diversification event...
Article
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Species delimitation remains a crucial issue for widespread plants occurring across forest-savanna ecotone such as Lophira (Ochnaceae). Most taxonomists recognize two parapatric African tree species, widely distributed and morphologically similar but occurring in contrasted habitats: L. lanceolata in the Sudanian dry forests and savannahs and L. al...
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The consequences of the Cretaceous-Paleogene (K-Pg) boundary (KPB) mass extinction for the evolution of plant diversity remain poorly understood, even though evolutionary turnover of plant lineages at the KPB is central to understanding assembly of the Cenozoic biota. The apparent concentration of whole genome duplication (WGD) events around the KP...
Article
Paleo-environmental data show that the distribution of African rain forests was affected by Quaternary climate changes. In particular, the Dahomey Gap (DG) – a 200 km wide savanna corridor currently separating the West African and Central African rain forest blocks and containing relict rain forest fragments – was forested during the mid-Holocene a...
Article
Background and aims: Afromontane forests host a unique biodiversity distributed in isolated high elevation habitats within a matrix of rain forests or savannahs, yet they share a remarkable flora that raises questions about past connectivity between currently isolated forests. Here, we focused on the Podocarpus latifolius - P. milanjianus complex...
Article
Premise: Few studies have addressed the evolutionary history of tree species from African savannahs. Afzelia contains economically important timber species, including two species widely distributed in African savannahs: A. africana in the Sudanian region and A. quanzensis in the Zambezian region. We aimed to infer whether these species underwent r...
Article
In vast areas of central African forests, the upper canopy is presently dominated by light‐demanding tree species. Here, we confront three hypotheses to explain this dominance: (1) these species have expanded their distribution because of widespread past slash‐and‐burn activities, as suggested by important charcoal amounts recorded in the soils of...
Article
Full-text available
Phylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including near...
Article
Full-text available
How the Central African rain forests have been affected by climatic fluctuations of the Quaternary remains debated. Phylogeographical studies have shown that tree species from western Central Africa often display spatially congruent genetic discontinuities, supporting the hypothesis that the forest was previously fragmented. Extensive seed dispersa...
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Background and aims - Most tree species with aril-covered seeds are assumed to be dispersed by frugivores. However, the number of studied African rainforest plant species remains low. This study focused on Afzelia bipindensis, an important timber species, which produces seeds partly covered by an aril. Specifically, this study aimed to: (1) identif...
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Research Highlights: Two novel sets of polymorphic microsatellite markers were developed for Prioria balsamifera and Prioria oxyphylla through high-throughput sequencing. Validation in two populations of each species proved the utility of the developed primers to estimate genetic diversity at population level. Background and Objectives: Prioria ba...
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Phylogenomics is increasingly used to infer deep‐branching relationships while revealing the complexity of evolutionary processes such as incomplete lineage sorting, hybridization/introgression and polyploidization. We investigate the deep‐branching relationships among subfamilies of the Leguminosae (or Fabaceae), the third largest angiosperm famil...
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Determining where species diversify (cradles) and persist (museums) over evolutionary time is fundamental to understanding the distribution of biodiversity and for conservation prioritization. Here, we identify cradles and museums of angiosperm generic diversity across tropical Africa, one of the most biodiverse regions on Earth. Regions containing...
Preprint
Full-text available
Phylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including near...
Preprint
The rainforests of Tropical Africa have fluctuated over time. Although today the forest cover is continuous in Central Africa this may have not always been the case, as the scarce fossil record in this region suggests that more arid conditions might have significantly reduced the density of trees during the Ice Ages. Our aim was to investigate whet...
Article
Do functional and phylogenetic diversity vary along a natural metal gradient? Do resources acquisition and metal tolerance related traits show the same patterns of variation? Is the ability to grow on metal enriched soil phylogenetically conserved or the result of functional convergence? Fungurume V hill (S10°37'03" E 26°17'22"), Upper‐Katanga, Dem...
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Full-text available
Adaptive evolution is a major driver of organism diversification, but the links between phenotypic traits and environmental niche remain little documented in tropical trees. Moreover, trait-niche relationships are complex because a correlation between the traits and environmental niches displayed by a sample of species may result from (a) convergen...
Article
Bryophytes are typically seen as extremely efficient dispersers. Experimental evidence suggests that efficient short‐distance dispersal coupled with random long‐distance dispersal (LDD) leads to an inverse isolation effect. Under the latter, a higher genetic diversity of colonizing propagules is expected with increasing isolation, counteracting dif...
Article
Ikabanga, D.U., K.G. Koffi, J.M. Onana, B. M'Batchi, O.J. Hardy & T. Stévart (2019). Taxonomic revision of Santiria (Burseraceae) in Tropical Africa. Candollea 74: 115–130. In French, English and French abstracts. DOI: http://dx.doi.org/10.15553/c2019v742a1In Tropical Africa, the genus Santiria Blume (Burseraceae) was considered as having one speci...
Preprint
Full-text available
Few studies have addressed the evolutionary history of tree species from African savannahs at large geographic scales, particularly in the southern hemisphere (Zambezian region). Afzelia (Fabaceae: Caesalpinioideae) contains economically important timber species, including two species widely distributed in African savannahs: A. africana in the Suda...
Article
Full-text available
Combining genetic and morphological markers is a powerful approach for species delimitation, much needed in tropical species complexes. Greenwayodendron (Annonaceae) is a widespread genus of trees distributed from West to East African rainforests. Two species and four infra‐specific taxa are currently recognized. However, preliminary genetic studie...
Article
The natural regeneration of tree species depends on seed and pollen dispersal. To assess if limited dispersal could be critical for the sustainability of selective logging practices, we performed parentage analyses in two Central African legume canopy species displaying contrasted floral and fruit traits: Distemonanthus benthamianus and Erythrophle...
Article
Full-text available
Detarioideae is well known for its high diversity of floral traits, including flower symmetry, number of organs, and petal size and morphology. This diversity has been characterized and studied at higher taxonomic levels, but limited analyses have been performed among closely related genera with contrasting floral traits due to the lack of fully re...
Article
Full-text available
Because of the quality of their wood and their many traditional uses, species of the Entandrophragma genus are being intensively logged, and this is likely to compromise their survival unless sustainable management is introduced. This study reviews the current status of the five main commercial Entandrophragma species: Entandrophragma angolense, E....
Article
Full-text available
Par la qualité de leur bois et leurs nombreux usages traditionnels, les espèces du genre Entandrophragma font l’objet d’une intense exploitation, susceptible de compromettre leur pérennité en l’absence de gestion durable. La présente étude dresse un état de la situation de cinq espèces commerciales principales de ce genre : Entandrophragma angolens...
Preprint
Full-text available
The consequences of the Cretaceous-Paleogene (K-Pg) boundary (KPB) mass extinction for the evolution of plant diversity are poorly understood, even although evolutionary turnover of plant lineages at the KPB is central to understanding the assembly of the Cenozoic biota. One aspect that has received considerable attention is the apparent concentrat...
Article
Full-text available
Quantifying carbon dynamics in forests is critical for understanding their role in long-term climate regulation1–4. Yet little is known about tree longevity in tropical forests3,5–8, a factor that is vital for estimating carbon persistence3,4. Here we calculate mean carbon age (the period that carbon is fixed in trees7) in different strata of Afric...
Article
With the ongoing climate change, African rainforests are expected to experience severe drought events in the future. In Africa, the tropical genus Erythrophleum (Fabaceae) includes two forest sister timber tree species displaying contrasting geographical distributions. Erythrophleum ivorense is adapted to wet evergreen Guineo-Congolian forests, whe...
Preprint
Full-text available
Detarioideae is well known for its high diversity of floral traits, including flower symmetry, number of organs, and petal size and morphology. This diversity has been characterized and studied at higher taxonomic levels, but limited analyses have been performed among closely related genera with contrasting floral traits due to the lack of fully re...
Article
Full-text available
Detarioideae is well known for its high diversity of floral traits, including flower symmetry, number of organs, and petal size and morphology. This diversity has been characterized and studied at higher taxonomic levels, but limited analyses have been performed among closely related genera with contrasting floral traits due to the lack of fully re...