Specialist plant species harbour higher reproductive performances in recently restored calcareous grasslands than in reference habitats

peer reviewedBackground and aims_Calcareous grasslands are local biodiversity hotspots in temperate regions that suffered intensive fragmentation. Ecological restoration projects took place all over Europe. Their success has traditionally been assessed using a plant community approach. However, population ecology can also be useful to assess restoration success and to understand underlying mechanisms. Methods_We took advantage of three calcareous grassland sites in Southern Belgium, where reference parcels coexist with parcels restored in the late twentieth century and with more recently restored parcels. We evaluated the colonization stage of three specialist species (Sanguisorba minor, Potentilla neumanniana and Hippocrepis comosa) using occurrence data. We also measured the reproductive traits of 120 individuals per species and compared components of fitness between recent restorations, old restorations and reference habitats. Key results_We found that the occurrence of H. comosa was similar in the different restoration classes, whereas both P. neumanniana and S. minor occurrences decreased from reference grasslands to recent restorations. In contrast, these two latter species exhibited a much higher reproductive output in recent restorations, thanks to an increased production of flowers and seeds. Conclusions_Our results suggest that, during colonization of recently restored calcareous grasslands, favourable environmental conditions, low competition and sufficient genetic mixing may lead to an increased fitness of individuals and a faster population growth than in the reference habitat. These results demonstrate how population processes can increase ecological resilience and highlight the interest of a population-based approach to assess the success of ecological restoration

Within-Population Genetic Structure And Clonal Diversity Of A Threatened Endemic Metallophyte, Viola Calaminaria (Violaceae)

We studied the within-population genetic structure and the clonality extent of Viola calaminaria, a rare endemic species of calamine soils, by means of RAPD markers in two populations (one recent and one ancient) with expected harsh and heterogeneous heavy-metal stress. At a very local scale (0.2 3 m), clonal propagation was detected in both populations, but the levels of clonal diversity were high (number of genets/number of ramets sampled ¼ 0.9 [recent] and 0.76 [ancient]) and the maximal observed extension of the clones was 0.4 m. This indicated that clonality is not, for the species, an important mode of propagation and that clonal growth cannot be interpreted as a strategy for propagating or perpetuating adapted genotypes under harsh ecological constraints. Spatial autocorrelations revealed a significant (P , 0.001) negative value of correlogram slope in the two populations even when a single individual per clone was considered (i.e., analysis at the genet level). We conclude that spatial genetic structure at a very local scale reflects limited gene flow due to restricted seed dispersal rather than variation in clonal pattern in response to environmental heterogeneity. At a larger scale (2–30 m), spatial autocorrelations revealed a positive (P , < 0.001) correlation at , 3 m and a random pattern at larger distances for the two populations. This suggested a patchy distribution of the genetically linked individuals associated with a disrupted pattern at a longer distance probably due to gene flow by pollen dispersal and a seed bank effect. The implications for the conservation of V. calaminaria are discussed

Impact of population history on Viola calaminaria conservation, an endemic species of calamine sites

The zinc violet, Viola calaminaria is a threatened species, endemic to calamine sites in Belgium and West Germany. Since the end of 19th century, the V. calaminaria habitat network have exhibited a huge dynamics, with creation of new habitats resulting from industrial pollution and destruction of habitats by urbanisation and site remediation. In the present study, we analysed the effect of population history (recent/ancient population) on genetic diversity, fitness and reproductive success in order to discuss conservation strategies for the species. Recently founded populations exhibited similar level of genetic diversity (Hs) as ancient populations but showed a lower genetic differentiation among population (Fst). No indication of strong founder effects in recently established populations was detected. Plant fitness (seed set and germination percentage) was higher in recent populations while other reproductive traits (vegetative density, flower density, fructification percentage) did not differ according to population history. Results suggest that the creation of habitats through human activities can provide new opportunities for conservation of this species. In increasingly disturbed environments, this indicates that, at least for some species, conservation strategies should not focus solely on traditional and natural habitats but also consider the potential benefits offered by modified landscapes