References of "Mahy, Grégory"
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See detailChemical soil factors influencing plant assemblages along copper-cobalt gradients: implications for conservation and restoration
Seleck, Maxime ULg; Bizoux, Jean-Philippe ULg; Colinet, Gilles ULg et al

in Plant and Soil (2013), 373

Aims Define the chemical factors structuring plant communities of three copper-cobalt outcrops (Tenke-Fungurume, Katangan Copperbelt, D. R. Congo) presenting extreme gradients. Methods To discriminate ... [more ▼]

Aims Define the chemical factors structuring plant communities of three copper-cobalt outcrops (Tenke-Fungurume, Katangan Copperbelt, D. R. Congo) presenting extreme gradients. Methods To discriminate plant communities, 172 vegetation records of all species percentage cover were classified based on NMDS and the Calinski criterion. Soil samples were analyzed for 13 chemical factors and means compared among communities with ANOVA. Partial canonical correspondence analysis (pCCA) was used to determine amount of variation explained individually by each factor and site effect. Results Seven communities were identified. Six of the studied communities were related to distinct sites. Site effect (6.0 % of global inertia) was identified as the most important factor related to plant communities’ variation followed by Cu (5.5 %), pH (3.6 %) and Co (3.5 %). Unique contribution of site effect (3.8 %) was higher than that of Cu (1.1 %) and Co (1.0 %). Conclusions In restoration, not only Cu and Co contents will be important to maintain vegetation diversity, attention should also be given to co-varying factors potentially limiting toxicity of metals: pH, organic matter, Ca and Mn. Physical parameters were also identified as important in the creation of adequate conditions for diverse communities. Further studies should focus on the effect of physical parameters and geology. [less ▲]

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See detailCes essences importantes que l’on retrouve en forêt claire (miombo)
Hick, Aurélie ULg; Hallin, Maud; Kizika Wimana, Pacifique et al

Poster (2013, November 29)

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See detailDistribution de 8 espèces végétales endémiques du Katanga (R.D.Congo) le long d'un gradient de cuivre et de cobalt
Boisson, Sylvain ULg; Lebrun, Julie ULg; Mahy, Grégory ULg

Poster (2013, November 06)

Au sud de la province du Katanga (R.D.Congo), se développe une végétation unique sur des sols recouvrant une centaine d’affleurements de cuivre et de cobalt parmi les plus importants au monde (Arc ... [more ▼]

Au sud de la province du Katanga (R.D.Congo), se développe une végétation unique sur des sols recouvrant une centaine d’affleurements de cuivre et de cobalt parmi les plus importants au monde (Arc cuprifère katangais). Le paysage de cette région est composé de collines isolées les unes des autres et présentant des communautés végétales distinctes selon la concentration en éléments traces métalliques du sol. Les savanes steppiques se retrouvent sur des sols faiblement contaminés tandis que les pelouses sont inféodées aux sols pouvant être contaminés à des teneurs avoisinant les 10 000 mg.kg-1 de cuivre et 1000 mg.kg-1 de cobalt. Plus de 600 espèces d’angiospermes métallophytes y sont retrouvées dont 32 vivant exclusivement sur des sols contaminés (endémiques strictes). Ces espèces présentent des adaptations physiologiques et biologiques leur permettant de tolérer les concentrations exceptionnelles dans le sol. Certaines d’entre-elles ont d’ailleurs été identifiées comme des hyperaccumulatrices de cuivre et/ou de cobalt. Le caractère unique de la plupart des espèces endémiques de cette flore est aujourd’hui menacé par les activités minières intenses dans la province. Ces espèces représentent pourtant des ressources génétiques de grands intérêts pour développer des stratégies de restauration et de remédiation des sites pollués par leur rôle potentiel en phytostabilisation des sols. L’objectif de l’étude est de caractériser la niche écologique réalisée de 8 espèces endémiques le long du gradient de cuivre et cobalt en vue d’adapter les stratégies de conservation et de restauration des espèces. Les espèces étudiées sont Triumfetta likasiensis, Lopholaena deltombei, Tinnea coerulea var. obovata, Sopubia neptunii, Basananthe kisimbae, Barleria lobelioides, Commelina zigzag, Euphorbia cupricola. Pour chaque espèce, 3 sites ont été prospectés en faisant un transect de 2 m de large le long des gradients métalliques et en identifiant tous les individus de l’espèce. Ensuite, 5 individus ont été sélectionnés parmi le nombre total d’individus comptés : 2 extrêmes, 1er quartile, 1 médian, 3ème quartile. Pour chacun d’eux, un quadrat d’un mètre carré y a été centré au sol et le nombre d’individus de l’espèce dénombrés. Un échantillon de sol composite a ensuite été prélevé entre 0 et 15 cm de profondeur afin de déterminer les teneurs en cuivre et cobalt par une spectrométrie d’absorption atomique dans la flamme à partir de l’extrait NH4-Acétate-EDTA du sol. Les niches écologiques réalisées ont été modélisées pour chaque métal par la méthode d’estimation des noyaux avec le logiciel R 3.0.1 (package ‘vioplot’). Les résultats montrent que les niches écologiques de ces espèces endémiques se répartissent entre 50 et 11 000 mg.kg-1 de sol pour le cuivre et 4 et 1500 mg.kg-1 de sol pour le cobalt. Six espèces se situent dans des concentrations inférieures à 100 mg.kg-1 le long du gradient de cobalt. Le long du gradient de cuivre, deux espèces ont des optima écologiques supérieurs à 3000 mg.kg-1. La niche écologique de B. kisimbae est la plus étroite avec un optimum environnant les 200 mg Cu.kg-1 et 50 mg Co.kg-1. L’espèce S. neptunii est présente sur l’entièreté du gradient de cobalt et est retrouvée dans les concentrations élevées. La variation des niches écologiques le long des gradients métalliques indique que les stratégies de conservation doivent être adaptées selon les espèces à conserver. Dans cette étude, 4 des 8 espèces pourraient être conservées sur un sol contaminé à 500 mg Cu.kg-1 et 30 mg Co.kg-1. Pour les autres, il est indispensable de mettre en place les stratégies de conservation en considérant, dans un premier temps, les espèces au cas par cas. [less ▲]

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See detailCommunautés floristiques et paramètres édaphiques : comment se répartissent les forêts claires dans la plaine de Lubumbashi ?
Hick, Aurélie ULg; Hoffait, Nicolas; Kizila Wimana, Pacifique et al

Poster (2013, November 06)

Au sud de la République Démocratique du Congo, dans la province du Katanga, le redéveloppement des activités minières a entrainé un développement démographique exponentiel des principales villes minières ... [more ▼]

Au sud de la République Démocratique du Congo, dans la province du Katanga, le redéveloppement des activités minières a entrainé un développement démographique exponentiel des principales villes minières. La population de Lubumbashi, capitale du Katanga, est passée en 50 ans d’environ 100 000 habitants à plus d’1 million et demi (Munyemba Kankumbi, 2010). Cette évolution démographique a accentué la pression sur la forêt claire de type Miombo par l’augmentation des prélèvements, la pression immobilière et l’agriculture de subsistance (Malaisse, 1997). Dans la zone périurbaine de Lubumbashi, les surfaces de forêts claires qui occupaient 85 % du territoire en 1956 ont été réduites à moins de 12 % en 2009 (Munyemba Kankumbi, 2010). Afin de comprendre l’écosystème à restaurer, nous procédons à la caractérisation des communautés de Miombo dans la plaine de Lubumbashi en fonction des conditions édaphiques. Pour ce faire, 116 placettes forestières de 18m de rayon ont été placées aléatoirement dans les derniers massifs forestiers présents dans un rayon de 50km au nord de la ville. L’ensemble des arbres adultes de diamètre supérieur à 2cm de d.b.h ont été inventoriés. De plus, un second cercle de 5 mètres de rayon a été placé au centre de chaque placette de 18m afin de répertorier l’ensemble de la régénération forestière (< à 2cm de d.b.h). Un sondage descriptif de sol à la tarière a été réalisé dans chaque placette et un échantillon de sol composite a été prélevé pour les analyses chimiques de sol (C, N, pH KCl, K, Ca, Na, Mg, Mn). Les données floristiques ont subies une transformation de corde afin de pouvoir les traiter dans une analyse en composante principale (ACP). Une classification k-means a été réalisée sur les scores de l’ACP afin d’obtenir des groupes de communauté floristique. Chaque groupe a été caractérisé par leurs espèces indicatrices et dominantes. Ces analyses ont été menées sur le peuplement adulte et sur la régénération. Une analyse canonique des correspondances a permis de mettre en évidence le lien entre ces communautés et les paramètres édaphiques. Le miombo de la plaine de Lubumbashi est caractérisé par 6 communautés floristiques : une communauté à Uapaca nitida et Uapaca pilosa, une communauté à Brachystegia boehmii, une communauté à Marquesia macroura, une communauté à Julbernardia globiflora, une communauté à Uapaka kirkiana et pour finir une communauté à Diplorhynchus condylocarpon, Pseudolactnostylis maprouenifolia et Julbernardia paniculata. L’analyse nous révèle que ces communautés sont contraintes par les données édaphiques. Les communautés se différencient d’une part par la profondeur du sol, la charge caillouteuse, le carbone, l’azote et le potassium et d’autre part par le magnésium, le manganèse et le sodium. Dans une optique de restauration, il est donc essentiel de tenir compte du type de sol en place et de la communauté à restaurer. [less ▲]

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See detailThe Code of conduct on invasive alien plants in Belgium: results after two years of communication with the horticultural sector
Halford, Mathieu ULg; Branquart, Etienne; Vanderhoeven, Sonia et al

Conference (2013, October 10)

In Belgium there are around 60 plant species listed as invasive (http://ias.biodiversity.be). Most of them were introduced as ornamentals. Except a few plants that have become famous invaders throughout ... [more ▼]

In Belgium there are around 60 plant species listed as invasive (http://ias.biodiversity.be). Most of them were introduced as ornamentals. Except a few plants that have become famous invaders throughout the country, the invasiveness of these ornamentals remains unknown outside the scientific audience. Due to this lack of information, the major part is still available in nurseries. In order to reduce the introductions of these plants, a Code of conduct was launched in September 2011 within the frame of the AlterIAS project (ALTERnatives to Invasive Alien Species), an ‘Information & Communication’ Life project dedicated to invasive plants and prevention in the green sector (www.alterias.be). The Code was elaborated in consultation with horticulture professionals, scientists and representatives of administrations. Five measures were approved: (1) know the list of invasive plants in Belgium; (2) stop the trade and the plantation of some invasive plants; (3) disseminate information on invasive plants; (4) promote the use of non invasive alternative plants and (5) participate in early detection of new invaders. Restrictions of use target a list of 28 species negotiated with the sector. An awareness campaign entitled “Plant different” is on progress to promote the Code among professionals and gardeners. Different communication tools are used. Social surveys were realized to assess the tools most efficient and the subsequent change of attitudes. But raising awareness on invasive plants is difficult due to different public perception. Communication should be focused on positive messages. Negative communication with alarming terms or military metaphors re-enforces the feeling of being guilty instead of encouraging concrete solutions. Thanks to constant efforts in communication, this ‘environmentally safe’ charter is attracting new partners over time. But changing people’s attitude is a long term process. The Code of conduct will require more time than two years to be widely adopted by the horticultural sector in Belgium. [less ▲]

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See detailTrees communities and filters to restoration along a periurban gradient of tropical forest degradation
Hick, Aurélie ULg; Tooth, Martin; Tshibungu, Alain et al

Conference (2013, October 09)

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See detailHow to increase species diversity in phytostabilization strategies near Lubumbashi (D.R.C.)
Boisson, Sylvain ULg; Collignon, Julien ULg; Le Stradic, Soizig ULg et al

Conference (2013, October 08)

Copper contamination of soils represents a threat to natural areas and to human health. Phytostabilization, i.e using plants to immobilize contaminants, represents a well-known technology to hemper heavy ... [more ▼]

Copper contamination of soils represents a threat to natural areas and to human health. Phytostabilization, i.e using plants to immobilize contaminants, represents a well-known technology to hemper heavy metals spread across landscapes. In Katanga (Congo D.R.), Microchloa altera was recently identified as a candidate species to stabilize copper in soil. This grass naturally tolerates and accumulates high copper concentrations and belongs to the typical copper flora of Katanga. However more than 600 species compose this flora and other grasses may be used in phytostabilisation strategies. But little is known about the phenology reproductive strategy and demography of these species, which makes their use in current phytostabilization strategies difficult. The present study aims to characterize the reproduction capacity of seven other dominant grass species for future phytostabilisation tests. A total of 67 quadrats (1m²) were randomly placed across three sites. At two periods over the fruiting season, three inflorescences per species per quadrat were collected in order to estimate the number of spikes, spikelets and viable seeds. All species have sexual reproductive strategy and spikelets number presents little variation between populations. Three species are very common (Andropogon shirensis, Loudetia simplex and Eragrostis racemosa) and represent potential candidates to increase species diversity in phytostabilization strategies in Katanga. Further research, including germination tests and phytostabilization tests in situ, is planned in a near future. [less ▲]

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See detailCity pattern as a factor influencing the impact of urbanization on ecosystems - A diachronic analysis of the dynamic of two cities: Kisangani and Lubumbashi (Democratic Republic of Congo)
Andre, Marie ULg; Mahy, Grégory ULg; Lejeune, Philippe ULg et al

Conference (2013, September 06)

The patterns and dynamics of two cities between two years (2002 and 2010 for Kisangani; 2002 and 2008 for Lubumbashi, both part of the Democratic Republic of Congo) have been examined in order to estimate ... [more ▼]

The patterns and dynamics of two cities between two years (2002 and 2010 for Kisangani; 2002 and 2008 for Lubumbashi, both part of the Democratic Republic of Congo) have been examined in order to estimate how they influence the impact of extension and/or of densification on urban internal and peripheral ecosystems. For each city two SPOT 5 images were classified with a oriented-object supervised approach; then composition landscape metrics (built area proportion index, anthropized surface proportion index, equitability index of area proportion of classes, dominant class index, dominant class proportion index) have been evaluated in order to 1) identify the extend of each area (urban, suburban, rural) within the urban-rural gradient, 2) quantify the most commonly cited morphological characteristics to describe these different areas and 3) quantify the dynamic of the different areas during this decade. Landscape ecology assumes that the landscape pattern description is important because, according to the central hypothesis called “pattern-process paradigm”, the ecological processes influence landscape structure and vice versa. Composition metrics, which are commonly used in landscape ecology, describe the pattern among other things in quantifying the presence and the number of patches from the various classes within the landscape. This study singularizes itself from the subjective ones by its quantified and objective approach. The similarities and differences between these cities, relevance and gaps in the method have then been identified and discussed. The results of this study are aimed to be used by urban planners for the evaluation of the potential resistance of internal and peripheral natural ecosystems to the extension and/or the densification of a given city, taking into account its pattern and dynamic. It might help them in their choice between different planning alternatives. [less ▲]

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See detailCity pattern as a factor influencing the impact of urbanization on ecosystems - A diachronic analysis of the dynamic of two cities: Kisangani and Lubumbashi (Democratic Republic of Congo)
Andre, Marie ULg; Mahy, Grégory ULg; Lejeune, Philippe ULg et al

in Nunes Silva, Carlos (Ed.) Colonial and postcolonial urban planning in Africa (2013, September 06)

The patterns and dynamics of two cities between two years (2002 and 2010 for Kisangani; 2002 and 2008 for Lubumbashi, both part of the Democratic Republic of Congo) have been examined in order to estimate ... [more ▼]

The patterns and dynamics of two cities between two years (2002 and 2010 for Kisangani; 2002 and 2008 for Lubumbashi, both part of the Democratic Republic of Congo) have been examined in order to estimate how they influence the impact of extension and/or of densification on urban internal and peripheral ecosystems. For each city two SPOT 5 images were classified with a oriented-object supervised approach; then composition landscape metrics (built area proportion index, anthropized surface proportion index, equitability index of area proportion of classes, dominant class index, dominant class proportion index) have been evaluated in order to 1) identify the extend of each area (urban, suburban, rural) within the urban-rural gradient, 2) quantify the most commonly cited morphological characteristics to describe these different areas and 3) quantify the dynamic of the different areas during this decade. Landscape ecology assumes that the landscape pattern description is important because, according to the central hypothesis called “pattern-process paradigm”, the ecological processes influence landscape structure and vice versa. Composition metrics, which are commonly used in landscape ecology, describe the pattern among other things in quantifying the presence and the number of patches from the various classes within the landscape. This study singularizes itself from the subjective ones by its quantified and objective approach. The similarities and differences between these cities, relevance and gaps in the method have then been identified and discussed. The results of this study are aimed to be used by urban planners for the evaluation of the potential resistance of internal and peripheral natural ecosystems to the extension and/or the densification of a given city, taking into account its pattern and dynamic. It might help them in their choice between different planning alternatives. [less ▲]

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See detailExtent of intra-population functional variability along a local environmental gradient for four calcareous grasslands species
Harzé, Mélanie ULg; Monty, Arnaud ULg; Mahy, Grégory ULg

Conference (2013, August 19)

In the last few years, an increasing body of evidence has highlighted the role of functional traits as reliable predictors of species resistance to disturbance and response to environmental gradients ... [more ▼]

In the last few years, an increasing body of evidence has highlighted the role of functional traits as reliable predictors of species resistance to disturbance and response to environmental gradients. However, most studies focused on functional comparisons at the interspecific level while intraspecific functional trait variation has received remarkably little attention. As intraspecific traits variability is a necessary condition for species to adapt to environmental changes, studying intraspecific functional traits variation along environmental gradients is a major issue in a context of global change. The aim of our study was to evaluate the extent of intraspecific functional variability of four species along an environmental gradient of water stress at a local scale and to compare species response to the gradient. Calcareous grasslands species are present along a xeric gradient from mesophilous to xerophilous grasslands. Changes of exposure, slope and soil depth lead to differences of water availability for plants along the gradient. We measured the maximum vegetative height (MVH), the specific leaf area (SLA, one side area of a fresh leaf divided by its oven-dry mass) and the leaf dry matter content (LDMC, leaf oven-dry mass divided by its water-saturated fresh mass) on randomly selected individuals along a gradient of xericity on three study sites located in south Belgium. Functional traits were measured on about 60 individuals per site and per species. The soil depth was measured around each individual. The exposure and the slope were measured in order to calculate a heat load index for each individual. The extent of local intraspecific functional variability of our data was compared to data covering the species European range. Results are species dependent but for some study species intraspecific functional variability at local scale is not negligible compared to European data. Species functional responses to the gradient (soil depth and heat load index) showed a decrease in SLA and MVH and an increase in LDMC with increasing xericity for all study species. Response extent was species dependent. Main implications for species resistance to disturbance and climate change adaptation will be discussed. [less ▲]

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See detailPerformance Indicators Framework for Biodiversity Management in Gypsum Quarries Throughout Europe
Pitz, Carline ULg; Mahy, Grégory ULg; Marlet, Christine et al

Report (2013)

This study aims to establish a common Key Performance Indicators (KPIs) framework to report biodiversity for the Gypsum Industry at the European level. An original approach of participatory process has ... [more ▼]

This study aims to establish a common Key Performance Indicators (KPIs) framework to report biodiversity for the Gypsum Industry at the European level. An original approach of participatory process has been developed in order to integrate the different opinions and to reach a consensus framework between different stakeholders’ groups: - Eurogypsum stakeholders - European and local authorities - Scientific panel : universities and consulting offices - European and local associations for the conservation of nature - Stakeholders from the mining sector The strategy is based on five main steps: (i) To Build a stakeholders’ network; (ii) To build a framework proposal to be submitted to stakeholders by selecting a maximum set of indicators based on the literature and reaching an agreement on indicators with Eurogypsum (Focus Group); (iii) Reaching a consensus framework with all the stakeholders and evaluating feasibility by a Delphi Policy survey, by the analysis of the EIAs of the Gypsum Industry and by visiting three European quarries; (iv) Final validation with Eurogypsum (meeting); (v) Creating indicators’ Factsheets and a Eurogyspum report to the destination of the public. The resulting framework contains eleven indicators which are the most acceptable set of indicators for all the stakeholders. It answers to European legislation and strategies for biodiversity. It is intended to improve sustainability in the quarries and to help managing biodiversity, to allow setting up of appropriate reporting systems. The aim is to maintain the biodiversity status of the gypsum quarries. It is a flexible framework adaptable given the local context of each gypsum quarry in order to prove if a No Net Loss has been reached at a quarry’s scale. [less ▲]

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See detailSynthesis and new definition of the areas included in the urban-rural gradient
Andre, Marie ULg; Mahy, Grégory ULg; Lejeune, Philippe ULg et al

Conference (2013, July 26)

Every scientific studies should begin with the delimitation of the studied system. Ours aims at evaluating and quantifying the resistence of landscape classes and ecosystems to the urbanization process ... [more ▼]

Every scientific studies should begin with the delimitation of the studied system. Ours aims at evaluating and quantifying the resistence of landscape classes and ecosystems to the urbanization process. This is done by studying a dozen cities in sub-Saharan Africa, conducting a diachronic (2000 - 2010) landscape evolution analysis from SPOT satellite imagery. Paradoxaly, when tackling this subject, one must recognize that no consensus exists about the definition and localization of the areas included in the urban-rural gradient. This prevents from comparing the results of different cities. A bibliography analysis has been conducted in order to 1) identify the different areas in the urban-rural gradient, the characteristics and types of characteristics used to define the most cited ones (i.e. urban, suburbs, sprawl, exurban, rurban, periurban and rural) ; 2) Through citation frequency indexes, evaluate the relative importance of characteristics and types of characteristics for every area and then for the whole gradient; 3) Evaluate the principal characteristics according to a series of criteria (the best characteristic is supposed to be quantitative, integrative, marking a consensus, discriminative and easy to apply on the field); 4) On the basis of retained characteristics, propose single and simple definitions to the most cited areas. These new definitions aim at enable areas identification on the field and on satellite images. These new definitions have been applied to the field study of the city of Lubumbashi (D.R.C) and seem to be convenient. Retained characteristics have then been translated into landscape composition indexes for the future study of the following cities on basis of satellite imagery, without field research. Indeed, such indexes are commonly used in landscape ecology because they allow the description of the urban landscape pattern or structure which, according to the central hypothesis of landscape ecology, i.e. “pattern-process paradigm”, influence landscape ecological processes. [less ▲]

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See detailPlant ecological niche distribution along heavy metal gradients
Boisson, Sylvain ULg; Monty, Arnaud ULg; Seleck, Maxime ULg et al

Conference (2013, June 26)

Why species do not occur everywhere? The concept of ecological niche is central to understand relationships among biotic/abiotic factors and species distribution. Gradients of environmental stress ... [more ▼]

Why species do not occur everywhere? The concept of ecological niche is central to understand relationships among biotic/abiotic factors and species distribution. Gradients of environmental stress associated to interspecific interactions generate testable patterns of specie’s response curves. Distribution of response curves have been seldom tested along toxicity gradient, in contrast to resource gradients. On Katangan copper hills (south R.D.C.), natural copper and cobalt concentrations span a large range: 2 - 1000 mg kg-1 for cobalt and 30 - 10 000 mg kg-1 for copper. In this study, we evaluate three hypotheses related to niche distributions and shapes along metal toxic gradients: (1) Species optima are uniformly distributed over copper-cobalt gradient. (2) Realized niche width varies in relation to the niche optimum along copper and cobalt gradient. (3) Absolute values of skewness coefficient are higher when plant species optima are in the extremes of cobalt gradient with a niche tails toward mesic conditions. Realized niches of 80 taxa were modeled with general additive models (GAM) using presence/absence data in 172 1m² plots. Niche optima, niche widths and skewness coefficients were estimated from species response curves. The three hypotheses were globally validated. Three groups of species were distinguished according to their optima position along metal gradient with packed optima on intermediate concentrations suggesting higher interspecific competition in low metal concentrations. Niche width increased with metal concentrations. Highest metal tolerant plant species had broader niches. Skewness coefficient was inversely related to niche optima positions. Our study demonstrates that species distribution pattern on toxicity gradient presents similarities with resource gradient. Broad realized amplitude of species adapted to high levels of copper cobalt concentrations suggests that fundamental niche of specialist metallophytes may be larger than expected. This should be further tested in controlled conditions in association to competition tests. [less ▲]

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See detailGradient urbain-rural de la ville de Lubumbashi: dynamique entre 2002 et 2009
Andre, Marie ULg; Bogaert, Jan ULg; Mahy, Grégory ULg et al

in Ernoult, Aude (Ed.) Dynamiques écologiques des paysages: de l'agricole à l'urbain (2013, June 12)

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See detailSpecies delimitation and diversification in the widespread tree genus Milicia (Moraceae)
Daïnou, Kasso ULg; Mahy, Grégory ULg; Duminil, Jérôme et al

Conference (2013, June)

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed ... [more ▼]

The long generation time and large effective size of widespread forest tree species can result in slow evolutionary rate and incomplete lineage sorting, complicating species delimitation. We addressed this issue with the African timber tree genus Milicia that comprises two morphologically similar and often confounded species: M. excelsa, widespread from West to East Africa, and M. regia, endemic to West Africa. We combined information from nuclear microsatellites (nSSRs), nuclear and plastid DNA sequences, and morphological systematics to identify significant evolutionary units and infer their evolutionary and biogeographical history. We detected five geographically coherent genetic clusters using nSSRs and three levels of genetic differentiation. First, one West African cluster matched perfectly with the morphospecies M. regia, which formed a monophyletic clade at both DNA sequences. Second, a West African M. excelsa cluster formed a monophyletic group at plastid DNA and was more related to M. regia than to Central African M. excelsa, but shared many haplotypes with the latter at nuclear DNA. Third, three Central African clusters appeared little differentiated and shared most of their haplotypes. Although gene tree paraphyly could suggest a single species in Milicia following the Phylogenetic Species Concept, the existence of mutual haplotypic exclusivity and non-admixed genetic clusters in the contact area of the two taxa indicate strong reproductive isolation, and thus, two species following the Biological Species Concept. Molecular dating of the first divergence events showed that speciation in Milicia is ancient (Tertiary), indicating that long-living tree taxa exhibiting genetic speciation may remain similar morphologically. [less ▲]

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See detailTrees communities and filters to restoration along a periurban gradient of tropical forest degradation
Hick, Aurélie ULg; Tooth, Martin; Tshibungu, Alain et al

Conference (2013, June)

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See detailIntegrated management of wild chamomile populations by tillage
Jaunard, Delphine ULg; Monty, Arnaud ULg; Mahy, Grégory ULg et al

in Agricultural and Apllied Biological Sciences (2013, May 21)

Gembloux, Belgium Chemical weeding in agriculture increasingly raises environmental, health and economic preoccupations. European authorities has set up legislations (directive 91/414, settlement 1107 ... [more ▼]

Gembloux, Belgium Chemical weeding in agriculture increasingly raises environmental, health and economic preoccupations. European authorities has set up legislations (directive 91/414, settlement 1107/2009, directive 2009/128) aiming to reduce risks related to the use of pesticides and encouraging integrated pest management. This situation leads professionals and scientists to take interest in the biology and population dynamics of weeds and to study the impacts of integrated pest management on weeds and crops. Tillage can potentially be an efficient weed control method in winter wheat (Triticum aestivum L.). We studied wild chamomile (Matricaria chamomilla L.) population dynamics and crop yields in an experimental winter wheat crop, in relation to tillage methods. Five modalities (i.e. different combinations of a stubble cultivator and/or a moldboard plow, including a no-tillage control) were applied during three years (2009-2012), with four replications, in Gembloux (Belgium). In each plot, M. chamomilla density was recorded throughout the seasons. In summer 2012, wild chamomile density was significantly lower in plots tilled with a moldboard plow. The use of a stubble cultivator did not significantly affect M. chamomilla density. In addition, we found higher wheat yields in ploughed plots, indicating that the decrease in M. chamomilla density reduced competition for wheat. To confirm these results, experiments are still under investigation in similar conditions. [less ▲]

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