Seed dispersal in a polder after partial tidal restoration: Implications for salt‐marsh restoration

Question: The vegetation in a polder after partial tidal restoration does not resemble the targeted salt‐marsh vegetation. Is this difference in vegetation due to lack of dispersal or unsuitable abiotic conditions? What could be done for a better restoration of the site? Location: Northwestern France. Methods: Seeds were trapped at the single inlet of the polder with a 200‐μ m mesh net to estimate inputs of seeds from the bay. In parallel, seed dispersal was studied in the polder by placing Astroturf® seed traps on the surface of the sediment at three different elevations in three distinct areas. Abiotic conditions such as flooding frequency, water table level and soil salinity were monitored. Results: All but one species from the adjacent salt marshes were trapped at the inlet. Not all of these species were on the seed traps inside the polder. Seed dispersal was not homogeneous in the polder and seed trap content mostly discriminated in function of their elevation. Salinity and water logging at the bottom of the slope were very high compared to tolerance of most halophytes but decreased rapidly higher up the slope. Conclusions: The development of salt marsh target species is highly restricted by limited hydrochory inside the polder but also by unfavourable soil conditions induced by the actual hydrological regime. Halophytes are excluded at the bottom of the slope by abiotic conditions and out‐competed by sub‐halophytes higher up. In order to restore salt marsh vegetation inside the polder, a larger opening should be induced in order to increase the flooded surface, and diminish water logging and flooding frequencies.     

Interplay Between Side Chain Pattern,Polymer Aggregation,and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk‐Heterojunction Solar Cells

Poly(benzo[1,2‐b:4,5‐b′]dithiophene–alt–thieno[3,4‐c]pyrrole‐4,6‐dione) (PBDTTPD) polymer donors with linear side‐chains yield bulk‐heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% with phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as the acceptor, while a PBDTTPD polymer with a combination of branched and linear substituents yields a doubling of the PCE to 8%. Using transient optical spectroscopy it is shown that while the exciton dissociation and ultrafast charge generation steps are not strongly affected by the side chain modifications, the polymer with branched side chains exhibits a decreased rate of nongeminate recombination and a lower fraction of sub‐nanosecond geminate recombination. In turn the yield of long‐lived charge carriers increases, resulting in a 33% increase in short circuit current (J _sc). In parallel, the two polymers show distinct grazing incidence X‐ray scattering spectra indicative of the presence of stacks with different orientation patterns in optimized thin‐film BHJ devices. Independent of the packing pattern the spectroscopic data also reveals the existence of polymer aggregates in the pristine polymer films as well as in both blends which trap excitons and hinder their dissociation.     

Elevation as a barrier: genetic structure for an Atlantic rain forest tree (Bathysa australis) in the Serra do Mar mountain range,SE Brazil

Distance and discrete geographic barriers play a role in isolating populations, as seed and pollen dispersal become limited. Nearby populations without any geographic barrier between them may also suffer from ecological isolation driven by habitat heterogeneity, which may promote divergence by local adaptation and drift. Likewise, elevation gradients may influence the genetic structure and diversity of populations, particularly those marginally distributed. Bathysa australis (Rubiaceae) is a widespread tree along the elevation gradient of the Serra do Mar, SE Brazil. This self‐compatible species is pollinated by bees and wasps and has autochoric seeds, suggesting restricted gene dispersal. We investigated the distribution of genetic diversity in six B. australis populations at two extreme sites along an elevation gradient: a lowland site (80–216 m) and an upland site (1010–1100 m.a.s.l.). Nine microsatellite loci were used to test for genetic structure and to verify differences in genetic diversity between sites. We found a marked genetic structure on a scale as small as 6 km (F_ST = 0.21), and two distinct clusters were identified, each corresponding to a site. Although B. australis is continuously distributed along the elevation gradient, we have not observed a gene flow between the extreme populations. This might be related to B. australis biological features and creates a potential scenario for adaptation to the different conditions imposed by the elevation gradient. We failed to find an isolation‐by‐distance pattern; although on the fine scale, all populations showed spatial autocorrelation until ~10‐20 m. Elevation difference was a relevant factor though, but we need further sampling effort to check its correlation with genetic distance. The lowland populations had a higher allelic richness and showed higher rare allele counts than the upland ones. The upland site may be more selective, eliminating rare alleles, as we did not find any evidence for bottleneck.     

Crocin Prevents Patulin‐Induced Acute Toxicity in Cardiac Tissues via the Regulation of Oxidative Damage and Apoptosis

Patulin (PAT) is a mycotoxin produced by several species of the genera of Penicillium, Aspergillus, and Byssochlamys principally by Penicillium expansum. This mycotoxin is suspected to affect several organs including kidney and liver. However, its toxic effect on heart remains unknown. The present study investigated for the first time the cardiotoxic effect of PAT in mice. We demonstrated that PAT increased creatinin phosphokinase (CPK) level, induced lipoperoxydation and protein oxidation, and triggered the antioxidant enzymes such as superoxide dismutase and catalase activities. We also demonstrated that acute administration of PAT triggers apoptosis via P53 overexpression and caspase 3 activation. We further investigated the antioxidant efficiency of crocin (CRO), a carotenoid pigment, against PAT‐induced cardiotoxicity. We found that pretreatment with CRO prevents cardiac impairment by reducing CPK levels, restoring the redox statute and suppressing apoptosis. Collectively, our data provide new preventive effect of CRO toward PAT‐induced cardiotoxicity in mice.     

Shedding light on host niches: label‐free in situ detection of Mycobacterium gordonae via carotenoids in macrophages by Raman microspectroscopy

Macrophages are the primary habitat of pathogenic mycobacteria during infections. Current research about the host–pathogen interaction on the cellular level is still going on. The present study proves the potential of Raman microspectroscopy as a label‐free and non‐invasive method to investigate intracellular mycobacteria in situ. Therefore, macrophages were infected with Mycobacterium gordonae, a mycobacterium known to cause inflammation linked to intracellular survival in macrophages. Here, we show that Raman maps provided spatial and spectral information about the position of bacteria within determined cell margins of macrophages in two‐dimensional scans and in three‐dimensional image stacks. Simultaneously, the relative intracellular concentration and distributions of cellular constituents such as DNA, proteins and lipids provided phenotypic information about the infected macrophages. Locations of bacteria outside or close to the outer membrane of the macrophages were notably different in their spectral pattern compared with intracellular once. Furthermore, accumulations of bacteria inside of macrophages exhibit distinct spectral/molecular information because of the chemical composition of the intracellular microenvironment. The data show that the connection of microscopically and chemically gained information provided by Raman microspectroscopy offers a new analytical way to detect and to characterize the mycobacterial infection of macrophages.     

Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream

1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%). 3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment. 4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.     

Minimizing the biodiversity impact of Neotropical oil palm development

Oil palm agriculture is rapidly expanding in the Neotropics, at the expense of a range of natural and seminatural habitats. A key question is how this expansion should be managed to reduce negative impacts on biodiversity. Focusing on the Llanos of Colombia, a mixed grassland–forest system identified as a priority zone for future oil palm development, we survey communities of ants, dung beetles, birds and herpetofauna occurring in oil palm plantations and the other principal form of agriculture in the region – improved cattle pasture – together with those of surrounding natural forests. We show that oil palm plantations have similar or higher species richness across all four taxonomic groups than improved pasture. For dung beetles, species richness in oil palm was equal to that of forest, whereas the other three taxa had highest species richness in forests. Hierarchical modelling of species occupancy probabilities indicated that oil palm plantations supported a higher proportion of species characteristic of forests than did cattle pastures. Across the bird community, occupancy probabilities within oil palm were positively influenced by increasing forest cover in a surrounding 250 m radius, whereas surrounding forest cover did not strongly influence the occurrence of other taxonomic groups in oil palm. Overall, our results suggest that the conversion of existing improved pastures to oil palm has limited negative impacts on biodiversity. As such, existing cattle pastures of the Colombian Llanos could offer a key opportunity to meet governmental targets for oil palm development without incurring significant biodiversity costs. Our results also highlight the value of preserving remnant forests within these agricultural landscapes, protecting high biodiversity and exporting avian ‘spill‐over’ effects into oil palm plantations.