Zooplankton community structure and environmental conditions in a set of interconnected ponds

We studied the zooplankton community structure in a set of 33 interconnected shallow ponds that are restricted to a relatively small area (`De Maten', Genk, Belgium, 200 ha). As the ponds share the same water source, geology and history, and as the ponds are interconnected (reducing chance effects of dispersal with colonisation), differences in zooplankton community structure can be attributed to local biotic and abiotic interactions. We studied zooplankton community, biotic (phytoplankton, macrophyte cover, fish densities, macroinvertebrate densities), abiotic (turbidity, nutrient concentrations, pH, conductivity, iron concentration) and morphometric (depth, area, perimeter) characteristics of the different ponds. Our results indicate that the ponds differ substantially in their zooplankton community structure, and that these differences are strongly related to differences in trophic structure and biotic interactions, in concordance with the theory of alternative equilibria. Ponds in the clear-water state are characterised by large Daphnia species and species associated with the littoral zone, low chlorophyll-a concentrations, low fish densities and high macroinvertebrate densities. Ponds in the turbid-water state are characterised by high abundances of rotifers, cyclopoid copepods and the opposite environmental conditions. Some ponds show an intermediate pattern, with a dominance of small Daphnia species. Our results show that interconnected ponds may differ strongly in zooplankton community composition, and that these differences are related to differences in predation intensity (top-down) and habitat diversity (macrophyte cover).     

An environmental gradient dominates ecological and genetic differentiation of marine invertebrates between the North and Baltic Sea

Environmental gradients have emerged as important barriers to structuring populations and species distributions. We set out to test whether the strong salinity gradient from the marine North Sea to the brackish Baltic Sea in northern Europe represents an ecological and genetic break, and to identify life history traits that correlate with the strength of this break. We accumulated mitochondrial cytochrome oxidase subunit 1 sequence data, and data on the distribution, salinity tolerance, and life history for 28 species belonging to the Cnidaria, Crustacea, Echinodermata, Mollusca, Polychaeta, and Gastrotricha. We included seven non‐native species covering a broad range of times since introduction, in order to gain insight into the pace of adaptation and differentiation. We calculated measures of genetic diversity and differentiation across the environmental gradient, coalescent times, and migration rates between North and Baltic Sea populations, and analyzed correlations between genetic and life history data. The majority of investigated species is either genetically differentiated and/or adapted to the lower salinity conditions of the Baltic Sea. Species exhibiting population structure have a range of patterns of genetic diversity in comparison with the North Sea, from lower in the Baltic Sea to higher in the Baltic Sea, or equally diverse in North and Baltic Sea. Two of the non‐native species showed signs of genetic differentiation, their times since introduction to the Baltic Sea being about 80 and >700 years, respectively. Our results indicate that the transition from North Sea to Baltic Sea represents a genetic and ecological break: The diversity of genetic patterns points toward independent trajectories in the Baltic compared with the North Sea, and ecological differences with regard to salinity tolerance are common. The North Sea–Baltic Sea region provides a unique setting to study evolutionary adaptation during colonization processes at different stages by jointly considering native and non‐native species.     

Acetohydroxyacid synthase mutations conferring resistance to imidazolinone or sulfonylurea herbicides in sunflower

Wild biotypes of cultivated sunflower (Helianthus annuus L.) are weeds in corn (Zea mays L.), soybean (Glycine max L.), and other crops in North America, and are commonly controlled by applying acetohydroxyacid synthase (AHAS)-inhibiting herbicides. Biotypes resistant to two classes of AHAS-inhibiting herbicides—imidazolinones (IMIs) or sulfonylureas (SUs)—have been discovered in wild sunflower populations (ANN-PUR and ANN-KAN) treated with imazethapyr or chlorsulfuron, respectively. The goals of the present study were to isolate AHAS genes from sunflower, identify mutations in AHAS genes conferring herbicide resistance in ANN-PUR and ANN-KAN, and develop tools for marker-assisted selection (MAS) of herbicide resistance genes in sunflower. Three AHAS genes (AHAS1, AHAS2, and AHAS3) were identified, cloned, and sequenced from herbicide-resistant (mutant) and -susceptible (wild type) genotypes. We identified 48 single-nucleotide polymorphisms (SNPs) in AHAS1, a single six-base pair insertion-deletion in AHAS2, and a single SNP in AHAS3. No DNA polymorphisms were found in AHAS2 among elite inbred lines. AHAS1 from imazethapyr-resistant inbreds harbored a C-to-T mutation in codon 205 (Arabidopsis thaliana codon nomenclature), conferring resistance to IMI herbicides, whereas AHAS1 from chlorsulfuron-resistant inbreds harbored a C-to-T mutation in codon 197, conferring resistance to SU herbicides. SNP and single-strand conformational polymorphism markers for AHAS1, AHAS2, and AHAS3 were developed and genetically mapped. AHAS1, AHAS2, and AHAS3 mapped to linkage groups 2 (AHAS3), 6 (AHAS2), and 9 (AHAS1). The C/T SNP in codon 205 of AHAS1 cosegregated with a partially dominant gene for resistance to IMI herbicides in two mutant × wild-type populations. The molecular breeding tools described herein create the basis for rapidly identifying new mutations in AHAS and performing MAS for herbicide resistance genes in sunflower.     

Global gradients in moss and vascular plant diversity

Knowledge on the distribution and hotspots of different taxon groups is indispensable for improving the state of biodiversity protection. Our aim was to determine if the relations between major environmental factors and species richness of two plant groups, mosses and vascular plants differ on a global scale. The dependence of species richness on environmental factors in 50 regions, covering 17 % of the global terrestrial territory, was analysed with SAS statistical software. Species richness of vascular plants increases significantly towards the equator, but for mosses the increase is not significant. Species richness of mosses and vascular plants are significantly positively correlated only in the near equator zone. Although there were similarities in the trends of mosses and vascular plant diversities at a global scale, their relations with some factors differ with distance from the equator. The effect of precipitation on species richness is similar for both plant groups, but coastline length has a significant positive influence only on moss richness, whereas species richness of vascular plants was related strongly to area and energy input. Therefore, effective conservation policy at both local and global scale demands consideration of all diversity drivers of different taxon groups.     

AIFM1 is a component of the mitochondrial disulfide relay that drives complex I assembly through efficient import of NDUFS5

The mitochondrial intermembrane space protein AIFM1 has been reported to mediate the import of MIA40/CHCHD4, which forms the import receptor in the mitochondrial disulfide relay. Here, we demonstrate that AIFM1 and MIA40/CHCHD4 cooperate beyond this MIA40/CHCHD4 import. We show that AIFM1 and MIA40/CHCHD4 form a stable long‐lived complex in vitro, in different cell lines, and in tissues. In HEK293 cells lacking AIFM1, levels of MIA40 are unchanged, but the protein is present in the monomeric form. Monomeric MIA40 neither efficiently interacts with nor mediates the import of specific substrates. The import defect is especially severe for NDUFS5, a subunit of complex I of the respiratory chain. As a consequence, NDUFS5 accumulates in the cytosol and undergoes rapid proteasomal degradation. Lack of mitochondrial NDUFS5 in turn results in stalling of complex I assembly. Collectively, we demonstrate that AIFM1 serves two overlapping functions: importing MIA40/CHCHD4 and constituting an integral part of the disulfide relay that ensures efficient interaction of MIA40/CHCHD4 with specific substrates.     

Smooth muscle cell transplantation improves bladder contractile function in streptozocin-induced diabetic rats

Background aimsDamage to smooth muscle has been the primary cause of dysfunction in diabetic bladders. Major changes in the filling phase of the bladder result in the loss of compliance and incomplete emptying in patients.MethodsCell-based therapies in the lower urinary tract have shown promising results. We argue that because diabetic bladder dysfunction is primarily a problem arising out of altered smooth muscle cells (SMCs), it would be an interesting approach to introduce healthy SMCs into the bladder wall.ResultsFurthering this hypothesis, in this experiment, we were successful in introducing syngeneic, healthy SMCs into diabetic bladders. We attempted a method wherein bladder function can be improved in streptozocin-induced diabetes mellitus. Ex vivo–cultured healthy SMCs were introduced into the diabetic bladders of syngeneic Sprague-Dawley rats during the hypercontractile phase after induction of diabetes. Cystometry, metabolic cage evaluation, organ bath studies and histological analyses were performed on the healthy control, the diabetic and the diabetic group transplanted with SMCs.ConclusionsDuring the 2-week follow-up period after transplantation, we noticed an increase in contractile response of the bladder correlating to a decrease in residual urine. Cell survival studies revealed a cell survival rate close to 1.5%.     

Bryophyte vegetation in a wooded meadow: relationships with phanerogam diversity and responses to fertilisation

In the Laelatu wooded meadow in Estonia, famous for its phanerogam diversity, the bryophyte community has been investigated in order to compare its flora and diversity relationships with those of the vascular plant community. Ninety-six bryophyte species were found, 13 of them are hepatics; the majority of the bryophytes are epigeic species common to meadows and forests, including many calciphilous species. Vascular plants and bryophytes display opposite responses to fertilisation. For vascular plants, fertilisation increases the coverage and diminishes the number of species, while for bryophytes it diminishes coverage and increases the number of species. The relationship between the number of species in small plots and the total number of species in the area is similar for vascular plants and bryophytes. No significant changes in the bryophyte community in Laelatu wooded meadow has been detected during the last 30 years.     

Vascular Plants Facilitated Bryophytes in a Grassland Experiment

In grassland communities vascular plants and bryophytes form two distinct layers. In order to understand the factors responsible for plant community structure, more information about interactions between these plant groups is needed. Often negative correlations between vascular plant and bryophyte covers have been reported, suggesting competition. Here we tested experimentally whether different grassland vascular plant species (Trifolium pratense, Festuca pratensis, Prunella vulgaris) had different influences on the cover of two bryophyte species (Rhytidiadelphus squarrosus, Brachythecium rutabulum). In a two-year garden pot experiment one bryophyte species and one vascular plant species were planted per pot. Bryophytes were planted at a constant density, vascular plants in four densities. The cover of both bryophyte species increased with increasing vascular plant cover, showing the facilitative effect of vascular plants through creating better microclimate, e.g., optimising temperature. Bryophyte responses to vascular plant species were species-specific. Festuca had significantly positive effects on both bryophyte species in the second year, and Trifolium on Brachythecium in both years, whereas Prunella had no significant effect on bryophytes. The facilitative effect of vascular plants was stronger at the second experimental year. In summary, the biotic effects between bryophytes and grassland vascular plants are species-specific and positive interactions are prevailing at low vascular plant densities.