Monoculture-based consumer-resource models predict species dominance in mixed batch cultures of dinoflagellates.

Global change will disturb the frequency, scale and distribution of harmful algal blooms (HABs), but we are unable to predict future HABs due to our limited understanding of how physicochemical changes in the environment affect interspecific competition between dinoflagellates. Trait-based mechanistic modelling is an important tool to unravel and quantify various direct and indirect interactions between species. The present study explores whether MacArthur's consumer-resource model can be used as a viable base model to predict dinoflagellate growth in closed multispecies systems. To this end, two batch culture experiments (294 cultures in total) with monocultures and multispecies cultures of Alexandrium minutum, Prorocentrum lima, P. micans, Protoceratium reticulatum and Scrippsiella trochoidea were performed. Despite changes to the relative (different nitrate concentrations) and absolute nutrient availability (dilutions of L1 medium), P. micans outcompeted all other species in mixed cultures. Consumer-resource modelling parameterized using monoculture growth correctly predicted this species dominance (R² between 0.80 and 0.95). Parameter estimates revealed that P. micans had a faster uptake of nitrogen when compared to its competitors, but did not differ in resource efficiency and natural mortality rate. Yet, while the model accurately predicted community dynamics during the growth phase, it was not able to predict their dynamics beyond the point of quiescence. Consumer-resource modelling was shown to differentiate the roles of resource assimilation, resource efficiency, and natural mortality rates in batch culture experiments with minimal data requirements beyond common measurements. The results suggest that consumer-resource models provide a promising basis for trait-based modelling of interspecific competition between (harmful) algae.

Functional connectivity network between terrestrial and aquatic habitats by a generalist waterbird, and implications for biovectoring.

Birds are vectors of dispersal of propagules of plants and other organisms including pathogens, as well as nutrients and contaminants. Thus, through their movements they create functional connectivity between habitat patches. Most studies on connectivity provided by animals to date have focused on movements within similar habitat types. However, some waterbirds regularly switch between terrestrial, coastal and freshwater habitats throughout their daily routines. Lesser black-backed gulls that overwinter in Andalusia use different habitat types for roosting and foraging. In order to reveal their potential role in biovectoring among habitats, we created an inter-habitat connectivity network based on GPS tracking data. We applied connectivity measures by considering frequently visited sites as nodes, and flights as links, to determine the strength of connections in the network between habitats, and identify functional units where connections are more likely to happen. We acquired data for 42 tagged individuals (from five breeding colonies), and identified 5676 direct flights that connected 37 nodes. These 37 sites were classified into seven habitat types: reservoirs, natural lakes, ports, coastal marshes, fish ponds, rubbish dumps and ricefields. The Doñana ricefields acted as the central node in the network based on centrality measures. Furthermore, during the first half of winter when rice was harvested, ricefields were the most important habitat type in terms of total time spent. Overall, 90% of all direct flights between nodes were between rubbish dumps (for foraging) and roosts in other habitats, thereby connecting terrestrial and various wetland habitats. The strength of connections decreased between nodes as the distance between them increased, and was concentrated within ten independent spatial and functional units, especially between December and February. The pivotal role for ricefields and rubbish dumps in the network, and their high connectivity with aquatic habitats in general, have important implications for biovectoring into their surroundings.

Flow cytometry community fingerprinting and amplicon sequencing for the assessment of landfill leachate cellulolytic bioaugmentation.

Flow cytometry (FCM) is a high throughput single cell technology that is actually becoming widely used for studying phenotypic and genotypic diversity among microbial communities. This technology is considered in this work for the assessment of a bioaugmentation treatment in order to enhance cellulolytic potential of landfill leachate. The experimental results reveal the relevant increase of leachate cellulolytic potential due to bioaugmentation. Cytometric monitoring of microbial dynamics along these assays is then realized. The flow FP package is used to establish microbial samples fingerprint from initial 2D cytometry histograms. This procedure allows highlighting microbial communities' variation along the assays. Cytometric and 16S rRNA gene sequencing fingerprinting methods are then compared. The two approaches give same evidence about microbial dynamics throughout digestion assay. There are however a lack of significant correlation between cytometric and amplicon sequencing fingerprint at genus or species level. Same phenotypical profiles of microbiota during assays matched to several 16S rRNA gene sequencing ones. Flow cytometry fingerprinting can thus be considered as a promising routine on-site method suitable for the detection of stability/variation/disturbance of complex microbial communities involved in bioprocesses.

Alveolar echinococcosis in a Belgian urban dweller.

Human alveolar echinococcosis is a rare parasitic disease caused by larvae of the tapeworm E. multilocularis that colonizes the intestines of foxes. The disease predominantly affects the liver and mimics slow growing liver cancer. With a mere 13 reports coming mostly from southern rural regions Belgium has so far been spared from the disease. However alveolar echinococcosis appears to be slowly spreading to non-endemic European countries like Belgium and to urban centres. We report the first autochthonous case involving a patient having lived exclusively in downtown Brussels. Heightened awareness by the medical community is necessary to detect this lethal disease at an early curable stage. In patients with an undetermined focal liver lesion--especially if calcified--and no firm evidence of malignancy, serological screening should be performed to exclude alveolar echinococcosis.

Migration and opportunistic feeding increase PCB accumulation in Arctic seabirds.

It is widely accepted that body concentrations of persistent organic pollutants (POPs) tend to increase with trophic level (TL). Yet, little attention has been paid to the causes in the underlying differences in POP body concentrations between species occupying similar TLs. In this paper we use two modeling approaches to quantify the importance of migration and opportunistic feeding, relative to that of trophic level, in explaining interspecific differences in polychlorinated biphenyl (PCB) body concentrations between 6 Arctic seabird species breeding in the Barents Sea: Little Auk (Alle alle), Black Guillemot (Cepphus grylle), Brünnich's Guillemot (Uria lomvia), Common Eider (Somateria mollissima), Black-legged Kittiwake (Rissa tridactyla), and Glaucous Gull (Larus hyperboreus). As a first approach, we use additive models to analyze two independent data sets (n = 470 and n = 726). We demonstrate that migration, opportunistic feeding, and TL significantly (p < 0.001) increase PCB body concentrations by a factor 3.61-4.10, 2.66-20.95, and 2.38-2.41, respectively. Our second approach, using a mechanistic bioaccumulation model, confirmed these positive effects on the body burdens but suggested lower effects of migration, opportunistic feeding, and TL (1.55, 2.39, and 2.38) than did our statistical analysis. These two independent approaches demonstrate that the effects of migration and opportunistic feeding on seabird body burdens can be similar to that of an increase of one TL and should therefore be accounted for in future analyses.

Evaluation of a diverse red clover collection for clover rot resistance (Sclerotinia trifoliorum).

Sclerotinia trifoliorum Erikks. causes clover rot (clover cancer, Sclerotinia crown and root rot), an important disease in European red clover crops (Trifolium pratense L). The fungus infects plants in autumn through ascospores and entire fields can be destroyed by early spring. Although previous studies have evaluated various red clover populations for clover rot resistance, screening was often performed with one local isolate on just a few local varieties, often cultivars. Until today, no large collections of diverse red clover accessions have been screened. In this study, we studied the variation in clover rot susceptibility among 122 red clover accessions, including 85 accessions from the NPGS-USDA core collection. Cultivars (both diploid and tetraploid), landraces and wild accessions were included and different S. trifoliorum isolates were used. In a field experiment, plant yield, branching and susceptibility to mildew, rust and virus disease were scored for 122 red clover accessions. A similar collection of germplasm was screened for clover rot resistance by a bio-test on young plants using a mixture of five aggressive S. trifoliorum isolates. The effects of the variety type, ploidy level, growth habit, resistance to other diseases and levels of isoflavones (available for the NPGS-USDA collection) on clover rot susceptibility were determined. Possible sources of resistance were identified. Our red clover accessions differed significantly in susceptibility but no accession was completely resistant Three accessions (Maro, Tedi and No. 292) were significantly less susceptible than the other accessions. Intensive branching or a prostrate growth habit did not render plants more resistant. Accessions resistant to mildew or viruses were not more resistant to clover rot and accessions with high levels of isoflavones were not better protected against clover rot. On the other hand, tetraploid cultivars were on average 10% less susceptible than diploid cultivars. Cultivars were generally less susceptible than landraces and wild accessions. Allocating sources of resistance for breeding purposes is difficult. The best way to improve clover rot resistance may be to select and intercross resistant plants from cultivars with low susceptibility.

Short communication: Associations between teat dimensions and milking-induced changes in teat dimensions and quarter milk somatic cell counts in dairy cows.

Although many studies have examined the relation between a wide range of factors and quarter milk somatic cell count (qSCC), including physical characteristics of the teat and changes in teat tissue due to milking, the effect of short-term, milking-induced changes in teat dimensions on somatic cell count has not yet been investigated. To identify teat dimensions and milking-induced changes in teat dimensions associated with qSCC, we conducted a longitudinal study (n(herds)=6, n(cows)=72, n(measurements)=12). Parity, stage of lactation, teat barrel diameter, and changes in teat barrel diameter during milking were identified as factors associated with qSCC. Teats with wider barrels had higher qSCC. Negative changes in the diameter of the teat barrel during milking (i.e., thinner teats postmilking compared with premilking) were associated with lower qSCC, whereas positive changes (i.e., thicker teats postmilking compared with premilking) were associated with higher qSCC. Selection toward more optimal teat characteristics may therefore result in improved milk quality and udder health. However, a threshold might exist for the maximum reduction in teat barrel diameter below which udder health is negatively influenced. If so, changes in teat barrel diameter might serve as an indicator for suboptimal milking and incorrect choice of teatcup liner or milking machine settings and thus help improve management of the herd.

Short communication: Intraoperator repeatability and interoperator reproducibility of devices measuring teat dimensions in dairy cows.

Various methods have been applied to measure teat dimensions. However, the accuracy and precision needed to obtain reliable results are often poor or have not yet been investigated. To determine the precision of the ruler, the caliper, and a recently developed 2-dimensional (2D) vision-based measuring device under field conditions, for respectively teat length, teat diameter, and both teat length and diameter, 2 experiments were conducted in which the consistency of measurements within operators (repeatability) and between operators (reproducibility) was tested. In addition, the agreement of the 2D device with the ruler and the caliper was studied. Although the ruler and the 2D device poorly agreed, both methods were precise in measuring teat length when the operators had experience in working with cows. The caliper was repeatable in measuring teat diameter, but was not reproducible. The 2D device was also repeatable in measuring teat diameter, and reproducible when the operators had experience with the device. The methods had poor agreement, most likely due to the operator-dependent pressure applied by the caliper. Because the 2D device has the advantage of measuring both teat length and teat diameters in a single measurement and is accurate and practical, this method allows efficient and fast collection of data on a large scale for various applications.

Variance components of teat dimensions in dairy cows and associated factors.

Traditionally, all cows within a herd are milked with the same teat cup liner, although it is hypothesized that considerable variation in teat dimensions exists between cows and quarters within cows. To study at which level (herd, cow, or quarter) most variation in teat dimensions resides, and to identify factors explaining (part of) this variation, both a cross-sectional (n=2,715) and a longitudinal study (n=8,678) were conducted. Using an objective and easy-to-use measuring device, teat length and teat diameters were determined. In both studies, most variation in teat dimensions was present at the cow or within-cow level, and not at the herd level, indicating that choosing a teat cup liner that is identical for all cows in a herd is far from optimal. Quarter position (front versus hind), parity and lactation stage were identified as factors associated with teat length and teat diameters. Generally, front teats were longer and broader than hind teats. Teat length and diameters increased with parity, although the increase in teat length was not significant from second parity onwards in front teats, based on observations from the longitudinal study. After the first 30 d in milk, teat length substantially and significantly increased, whereas teat diameters decreased. We conclude that better results in teat condition, and eventually in udder health, might be yielded when different teat cup liners are chosen for front versus hind teats or for cows of different parity or lactation stage, with special attention to the first 30 d in milk. However, the biological relevance of these differences should be examined first.

The influence of stocking density on broiler chicken bone quality and fluctuating asymmetry.

Because broiler chickens are juvenile animals undergoing physical development, stocking density during rearing may influence this development. Some of these physical changes may cause welfare problems, for example, decreased bone quality, which may lead to fracture during catching and transport. Others do not influence welfare directly but can be used as indicators of the animal's ability to cope with its environment (e.g., fluctuating asymmetry). The present study evaluates the effect of stocking density on bone quality and fluctuating asymmetry. Birds were stocked at densities of 2.4, 5.8, 8.8, 12.1, 13.6, 15.5, 18.5, and 21.8 birds/m(2) from 1 until 39 d of age. Increased stocking density had a negative effect on some aspects of bone quality (tibia curvature and shear strength). Tibias were shorter at high density, possibly due to increased curvature. Several other bone quality aspects (tibia weight, torsion, and dyschondroplasia, and femur curvature and epiphysis shape) remained unaffected. Middle-toe length was the only character that showed a significant increase with increasing density when each character was analyzed separately. Nevertheless, a composite index of fluctuating asymmetry, which combined data on all 11 measured characters, tended to increase with stocking density. Such increased fluctuating asymmetry may indicate decreased welfare. However, one of the assumptions of fluctuating asymmetry is that the animal is subjected to the same environmental influences on both sides. This assumption may not be fulfilled when leg deformations occur, as these may lead to asymmetric changes in bone growth by altering the division of force over the 2 legs. In addition, leg deformations decrease the accuracy of bone length measurements made in a straight line. This raises some concerns on the applicability of fluctuating asymmetry measurements on broiler chicken legs, especially because stocking density did not effect the asymmetry of the head.

Aggressiveness study on Sclerotinia isolates from red clover crops.

Sclerotinia trifoliorum Erikks. causes clover rot (clover cancer, Sclerotinia crown and root rot) in red clover crops (Trifolium pratense L.), an important disease in Europe. Little is known about the aggressiveness of Scierotinia isolates and aggressiveness studies were never conducted on a European scale. In this study we compared the aggressiveness of 30 Sclerotinia isolates isolated from red clover crops in 25 locations in 12 European countries using a plant-based bio-test. Plants from 6 red clover cultivars with different resistance levels were spray inoculated at the age of 12 weeks with 1 to 1.5 ml mycelium fragment suspension per plant. After 10 days incubation, plants were scored on a scale from 1 (healthy plant) to 5 (dead plant) and the disease index was calculated. The experiment was repeated 3 times and all repetitions were highly correlated. Average disease indices ranged from 52.6% to 82.7%. Significant differences were detected between isolates and between cultivars, but there was no isolate--cultivar interaction. Based on these results, the most aggressive isolates can be selected for resistance breeding. Future work should investigate whether the differences in aggressiveness are due to a higher growth speed or due to a higher secretion of cell-wall degrading components and pathogenicity factors.

Construction of a bio-test for infecting red clover plants with Sclerotinia trifoliorum.

Sclerotinia trifoliorum causes clover cancer in red clover crops. Clover cancer is difficult to control and completely resistant red clover varieties are not available. Breeding for resistant red clover varieties is being slowed down because little is known about the diversity of European S. trifoliorum populations and because of the lack of bio-tests that are useable in breeding programs. The first objective of this research was to develop a reliable high-throughput bio-test, useable in breeding programs. The second objective was to optimise another bio-test, based on isolated leaves, for more precise studies. First, we optimised a method for ascospore production of S. trifoliorum. Once produced, the ascospores were used to evaluate the effects of climate conditions, ascospore concentration and plant age on the high-throughput bio-test. For the bio-test on isolated leaves, the effects of infection method, incubation conditions, incubation period, ascospore concentration, leaf growth stage and mechanical damage were evaluated. In the high-throughput bio-test, disease levels rose with increasing ascospore concentration up to 20,000 spores/ml. The plant age had a small, yet significant effect on the disease level. For the isolated leaf bio-test, the most effective and most repeatable infection method was spraying of an ascospore suspension. Disease levels continued to increase with rising concentrations and incubation time did not interact with plant susceptibility levels. The youngest completely opened leaf yielded the most repeatable results. Both bio-tests were shown to be correlated and could be valuable instruments for breeding programs and for studying plant-pathogen interactions.

The E3 ubiquitin ligase complex component COP1 regulates PEA3 group member stability and transcriptional activity.

In this study, we report that the PEA3 group members interact with the mammalian really interesting new gene (RING) E3 ubiquitin ligase constitutive photomorphogenetic 1 (COP1), which mediates ubiquitylation and subsequent proteasome degradation of the p53 and c-Jun transcription factors. This interaction is mediated by the central region of COP1 including the coiled-coil domain and two COP1-interacting consensus motifs localized in the well-conserved N-terminal transactivation domain of the PEA3 group members. At the transcriptional level, COP1 reduces the transcriptional activity of ERM and the two other PEA3 group proteins on Ets-responsive reporter genes; this effect being dependent on the RING domain of COP1 and the two COP1-interacting motifs of ERM. Reduced transcriptional activity was, however, not related to COP1-induced changes in ERM stability. In fact, increased ubiquitylation and subsequent proteasome-mediated degradation of ERM is achieved only when COP1 is expressed with DET1, a key COP1 partner within the ubiquitylation complex. Conversely, we show that the depletion of COP1 or DET1 by small interference RNA (siRNA) in U2OS cells stabilizes endogenous ERM whereas only COP1 knockdown enhances expression of ICAM-1, a gene regulated by this transcription factor. These results indicate that COP1 is a complex regulator of ERM and the two other PEA3 group members.

Consistency of crown rust evaluation in ryegrass cultivars.

Crown rust (Puccinia coronata) is the most important leaf disease in forage ryegrasses (Lolium spp.). In order to evaluate the stability in space and time of crown rust resistance a multisite rust evaluation trial was established by the European breeders association Eucarpia ( Fodder Crops Section). The same seed lots of 33 perennial ryegrass (Lolium perenne) and 18 Italian ryegrass (Lolium multiflorum) varieties were sown in April 2001, 2004 and 2007 at 27 European sites. This paper reports the temporal ranking of the ryegrass varieties for their crown rust susceptibility at the Belgian site and compares this ranking with the mean ranking over the European sites. The crown rust susceptibility was scored in September of each sowing year and of the year after. The rankings of both the perennial and the Italian ryegrass varieties were well correlated between the successive yearly observations at each sowing period. Also the rankings of the varieties of both species were similar over the 3 sowing periods. The rankings at the Belgian site corresponded very well with the mean ranking over the European sites. The crown rust resistance in ryegrass seems to be durable and consistent over a great part of Europe.

Diversity study on Sclerotinia trifoliorum Erikks., the causal agent of clover rot in red clover crops (Trifolium pratense L.).

Since the 16th century, red clover has been an important crop in Europe. Since the 1940s, the European areal of red clover has been severely reduced, due to the availability of chemical fertilizers and the growing interest in maize. Nowadays there is a growing interest in red clover again, although some setbacks still remain. An important setback is the low persistence of red clover crops. Clover rot, caused by the ascomycete fungus Sclerotinia trifoliorum Erikss., is a major disease in Europe and reduces the persistence of red clover crops severely. The fungus infects clover plants through ascospores in the autumn, the disease develops during the winter and early spring and can kill many plants in this period. In early spring, black sclerotia, serving as surviving bodies, are formed on infected plants. Sclerotia can survive up to 7 years in the soil (Ohberg, 2006). The development of clover rot is highly dependent on the weather conditions: a humid fall, necessary for the germination of the ascospores and an overall warm winter with short periods of frost are favourable for the disease. Cold and dry winters slow the mycelial growth down too much and prevent the disease from spreading. Clover rot is difficult to control and completely resistant red clover varieties have yet to be developed. Because of the great annual variation in disease severity, plant breeders cannot use natural infection as an effective means to screen for resistant material. Breeding for resistant cultivars is being slowed down by the lack of a bio-test usable in breeding programs. When applying artificial infections, it is necessary to have an idea of the diversity of the pathogen. A diverse population will require resistance screening with multiple isolates. The objective of this research is to investigate the genetic diversity among isolates from the pathogen S. trifoliorum from various European countries. We assessed diversity using a species identification test based on the sequence of the beta-tubulin gene, vegetative compatibility grouping and AFLP.