Ecologie, génétique et biologie des populations de Silene nutans L. une espèce rare en Belgique

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Guidelines for genetic monitoring of translocated plant populations

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Assessing spatial mating patterns in translocated populations of Campanula glomerata

Plant translocations represent a solution for rescuing nonviable populations and recreating population networks. An essential criterion for translocation success is genetic diversity enhancement or maintenance in post-translocation generations. Genetic mixing, i.e. individual relatedness and spatial structure, also needs to be considered. We investigated the processes involved in the spatial patterns of genetic diversity in the first post-translocation generation (recruits and seed progeny) of translocated populations of the insect-pollinated, self-incompatible herb Campanula glomerata. We combined direct and indirect estimates of contemporary mating and gene dispersal using 15 microsatellite loci to estimate clonal extent, and genetic diversity and structure, to reconstruct sibship and parentage and to estimate pollen and seed dispersal distances. Genetic diversity in the first post-translocation generation is representative of the natural seed-source populations. Combining sources enhanced the effective number of breeders (Ne = 102–175). Clonal propagation was only marginal. Pollen and seed dispersal occurred at short distances within populations (up to 18 m), favouring fine-scale spatial genetic structure (SGS). This means that the enhanced genetic diversity, random mating and high admixture levels are ascribed to the mixed spatial arrangement of transplants. Stronger SGS might lead to biparental inbreeding and reduced seed set due to a lack of compatible neighbours, and impact the long-term population genetic sustainability. Increasing seed-dispersal distances within and among sites might be mediated by grazing livestock used for grassland management. Some long-distance pollen flow events (0.68–2.35 km) between populations were also detected, suggesting the potential of creating large translocated populations to restore connectivity by gene flow

Pre-translocation considerations in rare plant reintroductions: implications for designing protocols

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Exudation of low molecular weight organic acids by germinating seeds of two edaphic ecotypes of Silene nutans L.

Two parapatric ecotypes of Silene nutans, exhibiting distinct allozyme patterns, morphology and autecology were investigated for differences in exudation of low molecular weight organic acids from germinating seeds, and for differences in seed phosphorus content. The calcicolous ecotype is restricted to calcareous soils, and the silicicolous one predominantly occurs on acid soils, and sometimes, although less frequently, on neutral to alkaline soils. No clear difference was found between ecotypes. However, within the silicicolous ecotype seed samples showed marked differences in exudation pattern and seed phosphorus content depending on origin along the soil acidity gradient. Seeds of low-pH origin exuded more dicarboxylic acids (malic + succinic acid, oxalic acid) and had a lower phosphorus content than seeds of high pH origin. The exudation of dicarboxylic acids from seeds of low pH origin is probably an adaptation to adverse conditions (aluminium toxicity) on acid soils. The pattern is similar to that found among different cultivars of wheat. It is contrasted to the pattern found on comparison of a suite of calcifugous and calcicolous species, where exudation of di- and tricarboxylic acids is associated with solubilisation of recalcitrantly bound phosphorus and iron in calcareous soils. (C) 2001 Editions scientifiques et medicales Elsevier SAS

Evaluating pollen flow indicators for an insect-pollinated plant species

For insect-pollinated plant species, reproductive success and genetic exchange via the transfer of pollen between flowers depends (i.a.) on the efficiency, abundance and behaviour of floral visitors. These in turn are expected to respond to plant population size and flower density. High floral densities for example usually attract large numbers of pollinators that visit more flowers per plant or patch, which increases pollen deposition at short distances. Thus, population characteristics might serve as indicators for pollen dispersal patterns and help to identify suitable habitat size and quality for conservation measures. To test this hypothesis, we observed floral visitors of a generalist, entomophilous species, Comarum palustre, and compared their abundance and visitation rates in populations of different sizes and flower densities. At the same time, we mimicked pollen flow using fluorescent dye. In the large and dense populations, pollinator abundance and visitation rates were high and dye was dispersed to the edges of the populations (up to 200 m). In the medium-sized population with high flower density, insect abundance and visitation rates were unexpectedly low and dye dispersal declined very quickly. On the contrary, in the smallest population with scattered flowers, especially bumble bee abundance was similar to the large populations and dye dispersal mirrored this high bumble bee activity. Thus, our results indicate that in smaller habitat fragments, the mere size of a population might be insufficient to suggest pollen flow for a plant species. Instead, the abundance of its major pollinators should be considered. © 2012 Gesellschaft für Ökologie

Barriers to hybridization in calcicolous and silicicolous populations of Silene nutans from Belgium

In Belgium, Silene nutans has evolved very distinct populations in relation to the nature of the bedrock, calcareous or siliceous: striking divergences occur in flower, infrutescence, fruit, and seeds features as well as in allozyme markers. This paper shows that barriers to crossing were strong between the two types of populations both at the prezygotic (pollen-stigma incompatibility) and postzygotic (F1 hybrids sterility) stages. Calcicolous (Ca-) and silicicolous (Si-) populations from Belgium have reached an advanced stage in the sympatric differentiation process. Such a level of differentiation is not found in other parts of Europe.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The diversity of lichenized trentepohlioid algal (Ulvophyceae) communities is driven by fungal taxonomy and ecological factors

Trentepohliales are a group of both free-living and lichenized algae, with most diversity occurring in tropical regions. Recent studies showed that the abundance of lichens with a trentepohlioid photobiont has been increasing in temperate habitats, probably because of global warming, which makes them an interesting study case. A detailed molecular study of the diversity of lichenized Trentepohliales, epiphytic as well as epilithic, was performed in three forests of north-western Europe. Additional samples of lichens of the Arthoniales order (associating essentially with a trentepohlioid photobiont) from other European regions and from other continents were also sequenced. A total of 195 algal sequences were obtained. Phylogenetic analyses with rbcL and ITS loci were performed and associations between phylogenetic distances of photobionts and ecological factors (substratum, climate or Wirth indices, mycobiont taxonomy, and geographic location) were tested by variation partitioning and phylogenetic signal analyses. The high number of rbcL algal haplotypes found in some lichens or on different substrata revealed that the Trentepohliales diversity in extratropical regions was underestimated. The phylogenetic patterns showed selectivity of some photobionts in their fungal partner choice and vice-versa, while others were linked with several haplotypes. Photobionts seemed to be less selective than mycobionts. The main factors influencing lichenized algal community were climate and mycobiont species. Coevolution between mycobionts and photobionts as well as switching between free living and lichenized lifestyles appeared to drive the evolution of Trentepohliales and might explain the high cryptic diversity observed, which might be changing in some regions due to climate change