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Urban forests are generally fragmented in small isolated remnants, embedded in an inhospitable human-used matrix, and incur strong anthropogenic pressures (recreational activities, artificialization, pollution and eutrophication). These lead to particularly high constraints even for common forest herbs, whose genetic response may depend on life-history traits and population demographic status. This study investigated genetic variation and structure for 20 allozyme loci in 14 populations of Primula elatior, a self-incompatible long-lived perennial herb, occurring in forest fragments of Brussels urban zone (Belgium), in relation to population size and young plants recruitment rate. Urban populations of P. elatior were not genetically depauperate, but the small populations showed reduced allelic richness. Small populations showing high recruitment rates -and therefore potential rejuvenation- revealed lower genetic diversity (Ho and He) than those with low or no recruitment. No such pattern was observed for the large populations. There was a significant genetic differentiation among populations within forest fragments (FSC = 0.052, P < 0.001), but not between fragments (FCT = 0.002, P > 0.10). These findings suggest restricted gene flow among populations within fragments and local processes (genetic drift, inbreeding) affecting small populations, strengthened when there is recruitment. Urban forest populations of long-lived perennial herbs can be of conservation value. However, restoration of small populations by increasing population size through regeneration by seedling recruitment may lead to negative genetic consequences. Additional management, aiming to restore gene flow among populations, may need to be applied to compensate the loss of genetic diversity and to reduce inbreeding

BR Staff Publications [a] (paper in international, peer reviewed journal)

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Urban and peri-urban forests incur high anthropogenic pressures (e.g. recreational activities, artificialization, and eutrophication). Plant species from early-successional, transient, forest habitats, often characterized by a short life span and a persistent seed bank in the soil may differ from late-successional species in key-factors for population persistence. This study investigated variation in population size and seedling recruitment for different forest succession stages and three consecutive years in Centaurium erythraea, an early-successional biennial herb, occurring in a peri-urban forest of Brussels urban zone (Belgium). Forest succession stage had a significant impact on C. erythraea population size and on its temporal fluctuation. Populations in closing vegetation (evolving to late-succession stages) showed small population sizes and a low number of recruits compared to populations from stable early-succession vegetation and clearcuts. The number of recruits was the highest after clearcutting, which can be related to the expression of the soil seed bank. Populations showed year-to-year variation in size (flowering individuals and recruits), even in stable (over three years) early-succession forest vegetation. In the absence of disturbance changing succession stage, population size is expected to depend on seed set of the previous years and subsequent seedling recruitment, which can be affected by environmental stochasticity. Opening gaps in the herbaceous vegetation may stimulate seedling recruitment, also in unoccupied patches where "cryptic" seed populations are present in the soil. Forest path and road verges, despite their potential negative impact on forests, can constitute refuge habitats for early-successional forest plant species. Their management should involve the preservation of these species

BR Staff Publications [a] (paper in international, peer reviewed journal)

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Ahstract. - Towards a classification of the vascular flora based on molecular phylogeny. Studf of plant DNA using new molecular techniques, in addition to advances in mathematics and computer software, allows highly effiClent data analyses and a new perspective on ( taxonomy and phylogeny. The evolution of plants has been reconstructed based mainly on chloroplastic DNA and genes encoding ribosomial RNA. These phylogenetic hypotheses allow us to revise the classification -and delimitation of the orders- and families of plants. This paper compares these new insights with the classification systern of the vascular plants in the "Nouvelle Flore de la Bdgique, du Grand-Duche du Luxembourg, du Nord de la France et des Regions voisines". The modifications and practical implications for identifying plants are discussed.

BR Staff Publications [b] (paper in not reviewed journal)

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BR Staff Publications [b] (paper in not reviewed journal)

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BR Staff Publications [b] (paper in not reviewed journal)