The Kinetics of Aragonite Formation from Solution via Amorphous Calcium Carbonate.

Magnesium doped Amorphous Calcium Carbonate was synthesised from precursor solutions containing varying amounts of calcium, magnesium, H2O and D2O. The Mg/Ca ratio in the resultant Amorphous Calcium Carbonate was found to vary linearly with the Mg/Ca ratio in the precursor solution. All samples crystallised as aragonite. No Mg was found in the final aragonite crystals. Changes in the Mg to Ca ratio were found to only marginally effect nucleation rates but strongly effect crystal growth rates. These results are consistent with a dissolution-reprecipitation model for aragonite formation via an Amorphous Calcium Carbonate intermediate.

The nano- and meso-scale structure of amorphous calcium carbonate.

Understanding the underlying processes of biomineralization is crucial to a range of disciplines allowing us to quantify the effects of climate change on marine organisms, decipher the details of paleoclimate records and advance the development of biomimetic materials. Many biological minerals form via intermediate amorphous phases, which are hard to characterize due to their transient nature and a lack of long-range order. Here, using Monte Carlo simulations constrained by X-ray and neutron scattering data together with model building, we demonstrate a method for determining the structure of these intermediates with a study of amorphous calcium carbonate (ACC) which is a precursor in the bio-formation of crystalline calcium carbonates. We find that ACC consists of highly ordered anhydrous nano-domains of approx. 2 nm that can be described as nanocrystalline. These nano-domains are held together by an interstitial net-like matrix of water molecules which generate, on the mesoscale, a heterogeneous and gel-like structure of ACC. We probed the structural stability and dynamics of our model on the nanosecond timescale by molecular dynamics simulations. These simulations revealed a gel-like and glassy nature of ACC due to the water molecules and carbonate ions in the interstitial matrix featuring pronounced orientational and translational flexibility. This allows for viscous mobility with diffusion constants four to five orders of magnitude lower than those observed in solutions. Small and ultra-small angle neutron scattering indicates a hierarchically-ordered organization of ACC across length scales that allow us, based on our nano-domain model, to build a comprehensive picture of ACC formation by cluster assembly from solution. This contribution provides a new atomic-scale understanding of ACC and provides a framework for the general exploration of biomineralization and biomimetic processes.

Dataset of costs of the mitigation hierarchy and plant translocations in France.

These data are coming from the derogation requests for the destruction of protected species in the context of construction or development work in France. These derogation requests include, among other things, the contents of an environmental impact assessment and the costs of the measures suggested to reduce the impact on the environment. In the article connected to this dataset, we studied the quality of the plant translocation protocols proposed in 95 derogation files (see Julien et al., 2022). We additionally collected during the reading of the files data that we make available here about the costs of (i) the total project, (ii) the mitigation hierarchy and (iii) the plant translocation operations and monitoring. These data complement our aforementioned paper by documenting how much translocations cost and in what proportion of the other costs reported in the projects we evaluated for quality. These data can be helpful for environmental stakeholders but also to further studies to determine the extent to which the environment is considered in land planning.

Quality assessment of mitigation translocation protocols for protected plants in France.

Mitigation translocations are increasingly used worldwide in response to land planning pressures. The quality of translocation protocols and their adjustment to the ecological traits of the translocated populations are crucial to optimise translocation success. We studied the quality of translocation protocols presented in derogation requests, a mandatory step in France to translocate a protected plant species. We analysed 103 translocation proposals for 93 different species in 92 files examined between 2018 and 2020. After tracing the history of the place of translocations in legal procedures in France, we assessed each translocation proposal according to an evaluation grid, which involved the quantity and quality of information on plant species and translocation sites in the files and the quality of translocation protocols. We have shown that the translocation protocols are of low quality, with a lot of missing information. The biology and ecology of the species suggested for translocation are not sufficiently known, nor are the ecological characteristics of the host sites. Derogation requests that received a favourable opinion from the assessment body are more likely to propose a protected host site and post-translocation monitoring. We believe that, to optimise their outcome, mitigation translocations need to be improved upstream, with more detailed protocols and better species knowledge. We highly recommend following the same guidelines for mitigation translocations as for conservation translocations.

How does urbanization affect the reproductive characteristics and ecological affinities of street plant communities?

Anthropogenic activities in urban ecosystems induce a myriad of environmental changes compared with adjacent rural areas. These environmental changes can be seen as series of abiotic and biotic selection filters affecting the distribution of plant species. What are the attributes of plant species that compose urban communities, compared with rural communities, as related to their ecological affinities (e.g., to temperature, humidity), and reproductive traits (e.g., entomophily, autogamy, floral morphology)? Using a floristic dataset from a citizen science project recording plant species growing spontaneously in the streets, we analyzed the distribution of species according to their ecological requirements and reproductive traits along an urbanization gradient in the Parisian region. We developed an original floral and pollinator typology composed of five floral and four pollinator morphotypes. The proportion of impervious areas, used as a proxy of urbanization, was measured at different spatial scales, to reveal at which spatial scales urbanization is selecting plant traits. We found significant differences in plant communities along the urbanization gradient. As expected with the warmer and drier conditions of urban areas, species with higher affinities to higher temperature, light and nutrient soil content, and lower atmospheric moisture were over-represented in urban plant communities. Interestingly, all of the significant changes in plant abiotical affinities were the most pronounced at the largest scale of analysis (1,000 m buffer radius), probably because the specific urban conditions are more pronounced when they occur on a large surface. The proportion of autogamous, self-compatible, and nonentomophilous species was significantly higher in urban plant communities, strongly suggesting a lower abundance or efficiency of the pollinating fauna in urban environments. Last, among insect-pollinated species, those with relatively long and narrow tubular corollas were disadvantaged in urban areas, possibly resulting from a reduction in pollinator abundance particularly affecting specialized plant-pollinator interactions.

Buzz in Paris: flower production and plant-pollinator interactions in plants from contrasted urban and rural origins.

Urbanisation, associated with habitat fragmentation, affects pollinator communities and insect foraging behaviour. These biotic changes are likely to select for modified traits in insect-pollinated plants from urban populations compared to rural populations. To test this hypothesis, we conducted an experiment involving four plant species commonly found in both urban and rural landscapes of the Île-de-France region (France): Cymbalaria muralis, Geranium robertianum, Geum urbanum and Prunella vulgaris. The four species were grown in four urban and four rural experimental sites in 2015. For each species and each experimental site, plants were grown from seeds collected in five urban and five rural locations. During flowering, we observed flower production and insect-flower interactions during 14 weeks and tested for the effects of experimental site location and plant origin on flower production and on the number of floral visits. The study species had various flower morphology and hence were visited by different floral visitors. The effect of experimental sites and seed origin also varied among study species. We found that (1) insect visits on P. vulgaris were more frequent in rural than in urban sites; (2) for C. muralis, the slope relating the number of pollinator visits to the number of flowers per individual was steeper in urban versus rural sites, suggesting a greater benefit in allocating resources to flower production in urban conditions; (3) as a likely consequence, C. muralis tended to produce more flowers in plants from urban versus rural origin.

Hydrogen bonding induced distortion of CO3 units and kinetic stabilization of amorphous calcium carbonate: results from 2D (13)C NMR spectroscopy.

Systematic correlation in alkaline-earth carbonate compounds between the deviation of the CO3 units from the perfect D3h symmetry and their (13)C nuclear magnetic resonance (NMR) chemical shift anisotropy (CSA) parameters is established. The (13)C NMR CSA parameters of amorphous calcium carbonate (ACC) are measured using two-dimensional (13)C phase adjusted spinning sidebands (PASS) NMR spectroscopy and are analyzed on the basis of this correlation. The results indicate a distortion of the CO3 units in ACC in the form of an in-plane displacement of the C atom away from the centroid of the O3 triangle, resulting from hydrogen bonding with the surrounding H2O molecules, without significant out-of-plane displacement. Similar distortion for all C atoms in the structure of ACC suggests a uniform spatial disposition of H2O molecules around the CO3 units forming a hydrogen-bonded amorphous network. This amorphous network is stabilized against crystallization by steric frustration, while additives such as Mg presumably provide further stabilization by increasing the energy of dehydration.

Fine-scale genetic structure and gene dispersal in Centaurea corymbosa (Asteraceae). II. Correlated paternity within and among sibships.

The fine-scale pattern of correlated paternity was characterized within a population of the narrow-endemic model plant species, Centaurea corymbosa, using microsatellites and natural progeny arrays. We used classical approaches to assess correlated mating within sibships and developed a new method based on pairwise kinship coefficients to assess correlated paternity within and among sibships in a spatio-temporal perspective. We also performed numerical simulations to assess the relative significance of different mechanisms promoting correlated paternity and to compare the statistical properties of different estimators of correlated paternity. Our new approach proved very informative to assess which factors contributed most to correlated paternity and presented good statistical properties. Within progeny arrays, we found that about one-fifth of offspring pairs were full-sibs. This level of correlated mating did not result from correlated pollen dispersal events (i.e., pollen codispersion) but rather from limited mate availability, the latter being due to limited pollen dispersal distances, the heterogeneity of pollen production among plants, phenological heterogeneity and, according to simulations, the self-incompatibility system. We point out the close connection between correlated paternity and the "TwoGener" approach recently developed to infer pollen dispersal and discuss the conditions to be met when applying the latter.

Population structure of an endangered species living in contrasted habitats: Parnassia palustris (Saxifragaceae).

In endangered species, it is critical to analyse the level at which populations interact (i.e. dispersal) as well as the levels of inbreeding and local adaptation to set up conservation policies. These parameters were investigated in the endangered species Parnassia palustris living in contrasted habitats. We analysed population structure in 14 populations of northern France for isozymes, cpDNA markers and phenotypic traits related to fitness. Within population genetic diversity and inbreeding coefficients were not correlated to population size. Populations seem not to have undergone severe recent bottleneck. Conversely to pollen migration, seed migration seems limited at a regional scale, which could prevent colonization of new sites even if suitable habitats appear. Finally, the habitat type affects neither within-population genetic diversity nor genetic and phenotypic differentiation among populations. Thus, even if unnoticed local adaptation to habitats exists, it does not influence gene flow between populations.

Multilocus genetic structure at contrasted spatial scales of the endangered water fern Marsilea strigosa Willd. (Marsileaceae, Pteridophyta).

Marsilea strigosa (Marsileaceae, Pterydophyta) is a rare water fern found in the Mediterranean basin, in temporary flooded habitats only. We analyzed the level and the distribution of genetic variation at seven microsatellite loci, both at the Mediterranean scale and at a narrower scale within a highly fragmented French metapopulation. Genetic diversity among individuals within each pond suggests that M. strigosa reproduces predominantly through selfing. The very high population differentiation at the Mediterranean scale indicates that gene flow (if any) is highly restricted. Similar differentiation is also found at the scale of a single metapopulation. The distribution of multilocus genotypes suggests that the genetic variation in this species is maintained mainly through the interplay of mutation and low recombination.