References of "Mahy, Grégory"
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See detailNaturalization and impact of a horticultural species, Cotoneaster horizontalis (Rosaceae) in biodiversity hotspots in Belgium
Piqueray, Julien ULg; Mahy, Grégory ULg; Vanderhoeven, Sonia

in Belgian Journal of Botany (2008), 141

Cultivation of ornamental plant species has been recognized to foster plant naturalization of exotics by counteracting environmental stochasticity and continuously providing propagules. As a preliminary ... [more ▼]

Cultivation of ornamental plant species has been recognized to foster plant naturalization of exotics by counteracting environmental stochasticity and continuously providing propagules. As a preliminary attempt to describe the invasion status of C horizontalis, we gathered information on the occurrence of the species in Belgium by compiling various databases. We assessed the naturalization status of C. horizontalis in Belgian calcareous grasslands, high-value habitats recognized as biodiversity hotspots, by characterizing its occurrence, population status, preferred habitats, invaded communities, growth rate and fruiting capacity. We also assessed the impact of the species on calcareous grasslands communities and on individual species. Cotoneaster occurred in seven of the nine investigated sites, with densities varying from 0.34 to 10 individuals/ha. In the most invaded sites, the high proportion of small individuals suggests an important ongoing colonization process, emphasized by the fact that fruiting capacities were demonstrated for 3-year-old individuals. Invaded habitats were typically Mosan Xerobromion habitats, which are priority Natura 2000 habitats. The presence of C horizontalis was associated with changes in both the structure and composition of the community by decreasing species richness and diversity, and affecting grassland specialist species. These impacts are expected to intensify over time with population age and increasing propagule pressure due to close urbanization. [less ▲]

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See detailContribution Of Delayed Autonomous Selfing To Reproductive Success In Kosteletzkya Virginica
Ruan, Cj.; Zhou, Lj.; Zeng, Fy. et al

in Belgian Journal of Botany (2008), 141(1), 3-13

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See detailLandscape Dynamics And Habitat Selection By The Alien Invasive Fallopia (Polygonaceae) In Belgium
Tiebre, Marie-Solange; Saad, Layla ULg; Mahy, Grégory ULg

in Biodiversity & Conservation (2008), 17(10), 2357-2370

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See detailPlant species extinction debt in a biodiversity hotspot: community and species approaches
Piqueray, Julien ULg; Bisteau, Emmanuelle ULg; Cristofoli, Sara ULg et al

in Belgian Journal of Botany (2008), 141(2), 189

Destruction and fragmentation of natural and semi-natural habitats are considered as major threats for plant species richness. However, the response of plant species richness to habitat alteration is ... [more ▼]

Destruction and fragmentation of natural and semi-natural habitats are considered as major threats for plant species richness. However, the response of plant species richness to habitat alteration is sometimes delayed. This delay induces an extinction debt in plant communities that are thus prone to undergo species extinctions in the following years. Several methodologies were proposed to detect this extinction debt and estimate the mean number of species yet to disappear. In this study, we developed a new methodology for the estimation of the extinction debt extent. Moreover, we proposed a species approach aimed at determining which species are more sensitive to extinction as a consequence of habitat destruction and fragmentation. Finally, we explored the colonization ability of habitat specialist species. This aspect is of fi rst importance to counteract local species extinctions. Our model habitat is calcareous grasslands of Southeast Belgium that have suffered an important fragmentation process since the beginning of the twentieth century. We estimated that the mean extinction debt of the calcareous grassland patches was ca. 24 species, including ca. six specialist species. We showed that 16 of the 46 specialist species did not meet their area requirement anymore and were therefore considered as sensitive to extinction. However, the species composition of the more recent grasslands indicates a non-negligible recolonization potential of specialist species. There is thus a real possibility to reduce extinction risk by restoring suitable habitats. [less ▲]

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See detailEtude de l'écologie des communautés macrophytiques en vue de fournir des indicateurs paléo-environnementaux pour les lacs-cratères d'Afrique de l'Est
Lebrun, Julie ULg; Mahy, Grégory ULg

in Anne Bonis (Ed.) Actualité de la recherche en écologie des communautés végétales. Actes du quatrième Colloque ECOVEG: Rennes, 12-14 mars 2008 (2008)

This research is part of an integrated paleoecological project which aims at coupling reconstructions of past vegetation and water-quality changes with climate variability. Crater-lakes from East Africa ... [more ▼]

This research is part of an integrated paleoecological project which aims at coupling reconstructions of past vegetation and water-quality changes with climate variability. Crater-lakes from East Africa are favourable to the conservation of proxy indicators such as plant macrofossils used to reconstruct the lake ecosystem. The study of modern macrophytic communities in relationship with present environmental parameters was the first step of this research. Eventually, it will allow us to select species with high proxy-indicator value. Phytosociologic and environmental data were collected in 18 crater-lakes in South-western Uganda. In each relevé, species abundance and habitat conditions were described. Environmental parameters were used to develop a lake typology. A cluster analysis identified 6 aquatic and semi-aquatic communities and the indicator species were highlighted. The CA ordination emphasized the importance of geography, physico-chemistry and trophic level in the community structure. Temperature, pH, sediment type, depth and slope were the most correlated parameters to floristic variation in the CCA ordination. These preliminary results give some trends about the ecology of macrophytes communities. A complete dataset and the study of species ecological range will allow us to go further in the ecological significations of macrofossils. [less ▲]

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See detailFitness And Genetic Variation Of Viola Calaminaria, An Endemic Metallophyte: Implications Of Population Structure And History
Bizoux, Jean-Philippe ULg; Daïnou, Kasso ULg; Raspe, O. et al

in Plant Biology (2008), 10(6), 684-693

We investigated variations in genetic diversity and plant fitness in a rare endemic metallophyte of calamine soils, Viola calaminaria, in relation to population size, population connectivity and ... [more ▼]

We investigated variations in genetic diversity and plant fitness in a rare endemic metallophyte of calamine soils, Viola calaminaria, in relation to population size, population connectivity and population history in order to evaluate and discuss potential conservation strategies for the species. Mean population genetic diversity (Hs = 0.25) of V. calaminaria was similar to endemic non-metallophyte taxa. Twenty-one per cent of the genetic variation was partitioned among populations and a low (9%) but significant differentiation was found among geographical regions. Our results did not support the hypothesis that the acquisition of metal tolerance may result in reduced genetic diversity, and suggested that strict metallophytes do not exhibit higher inter-population differentiation resulting from scattered habitats. There were no relationships between population genetic diversity and population size. Significant correlations were found between plant fitness and (i) population size and (ii) connectivity index. Recently-founded populations exhibited the same level of genetic diversity as ancient populations and also possessed higher plant fitness. There was no indication of strong founder effects in recently-established populations. The results suggest that the creation of habitats through human activities could provide new opportunities for conservation of this species. [less ▲]

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See detailClinal differentiation during invasion: Senecio inaequidens (Asteraceae) along altitudinal gradients in Europe.
Monty, Arnaud ULg; Mahy, Grégory ULg

Poster (2008)

Plant population differentiation may play a role in decreasing the ability to predict whether, where, and when an introduced species will invade. However, few studies have addressed the level of genetic ... [more ▼]

Plant population differentiation may play a role in decreasing the ability to predict whether, where, and when an introduced species will invade. However, few studies have addressed the level of genetic change an alien species may undergo during range expansion, e.g. in response to climatic variation with altitude. In the present study, we tested the hypothesis that invasive populations of Senecio inaequidens (Asteraceae) differentiated during migration from two independent introduction sites into divergent altitudinal and climatic zones. We carried out two years of common garden experiments with eight populations from a Belgian altitudinal transect and ten populations from similar French transect. Climatic analysis revealed that the Belgian transect followed a temperature and precipitation gradient. A temperature and summer drought gradient characterized the French study site. We evaluated differentiation and clinal variation in the following characters: days to germination, days to flowering, height at maturity, final plant height and aboveground biomass. Results showed that S. inaequidens populations differentiated in growth traits during invasion. First year of experiment, regressing population growth trait means against source population altitude indicated the presence of clinal variation along both transects. Second year, similar results were found along the French transect, i.e. a reduction in height at maturity, plant height and aboveground biomass with increasing altitude. Including seed mass as a covariate did not change the outcome of the analysis. The possible evolutionary causes for the differentiation observed are discussed. [less ▲]

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See detailLes messicoles, fleurs des moissons
Legast, Marie ULg; Mahy, Grégory ULg; Bodson, Bernard ULg

Book published by Claude Delbeuck/Direction générale de l'Agriculture (2008)

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See detailSeed rain pattern of the invasive weed Senecio inaequidens (Asteraceae)
Monty, Arnaud ULg; Stainier, Charles; Lebeau, Frédéric ULg et al

in Belgian Journal of Botany (2008), 141(1), 51-63

Dispersion capacity of alien invasive plants is a key feature for understanding invasion processes and risks. Here, we present an experimental study focussing on the seed rain pattern of Senecio ... [more ▼]

Dispersion capacity of alien invasive plants is a key feature for understanding invasion processes and risks. Here, we present an experimental study focussing on the seed rain pattern of Senecio inaequidens, an African plant widespread throughout Europe, under common favourable dispersal conditions. One hundred achenes from two Belgian populations underwent a drop time in still air experiment in order to assess linear correlation between several morphological traits and terminal velocity. Variation in morphological traits was measured for 250 additional achenes per population. The trait best correlated to terminal velocity was the square root of the plume loading. We then used this trait to model terminal velocity using a linear regression (r(2) of 79.7%). With this regression and imposing ecological parameters such as wind speed, turbulences and height of release to be representative of favourable dispersal conditions, we established a Gaussian tilted plume model to predict the seed rain pattern of the species. A wind tunnel experiment consequently permitted to validate the model. Under a wind speed of 5 m s(-1) with 2% turbulences along the vertical axis, and height of release of 0.40 m, 99.8% of achenes were dispersed within 100 meters, with a maximum deposition rate at 5.2 m from the parent plant. Uplifted achenes, not forecasted by the model, represent 6.25% of all achenes. [less ▲]

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See detailRestoration assessment of calcareous grasslands in Belgium : soil conditions and floristic diversity
Piqueray, Julien ULg; Bottin, Gaëtan; Bisteau, Emmanuelle et al

Conference (2008)

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See detailHybridisation efficiency in generating Hybridisation efficiency in generating invasive progeny in the alien Fallopia (Polygonaceae) complex
Saad, Layla ULg; Tiébré, Marie-Solange; Hardy, Olivier et al

Poster (2007, November 16)

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