17 years of grassland management leads to parallel local and regional biodiversity shifts among a wide range of taxonomic groups

Conservation management is expected to increase local biodiversity, but uniform management may lead to biotic homogenization and diversity losses at the regional scale. We evaluated the effects of renewed grazing and cutting management carried out across a whole region, on the diversity of plants and seven arthropod groups. Changes in occurrence over 17 years of intensive calcareous grassland management were analysed at the species level, which gave insight into the exact species contributing to regional homogenization or differentiation. Reponses were compared between species differing in habitat affinity, dispersal ability, food specialisation and trophic level. Local species richness increased over the sampling period for true bugs and millipedes, while carabid beetles and weevils declined in local species richness. Species richness remained unchanged for plants, woodlice, ants and spiders. Regional diversity and compositional variation generally followed local patterns. Diversity shifts were only to a limited extent explained by species’ habitat affinity, dispersal ability, trophic level and food specialisation. We conclude that implementation of relatively uniform conservation management across a region did not lead to uniform changes in local species composition. This is an encouraging result for conservation managers, as it shows that there is not necessarily a conflict of interest between local and regional conservation goals. Our study also demonstrates that shifts in diversity patterns differ markedly between taxonomic groups. Single traits provide only limited understanding of these differences. This highlights the need for a wide taxonomic scope when evaluating conservation management and demonstrates the need to understand the mechanisms underlying occurrence shifts.     

Mesopredator behavioral response to olfactory signals of an apex predator

Olfactory signals constitute an important mechanism in interspecific interactions, but little is known regarding their role in communication between predator species. We analyzed the behavioral responses of a mesopredator, the red fox (Vulpes vulpes), to an olfactory cue (scat) of an apex predator, the lynx (Lynx lynx) in Bia?owie?a Primeval Forest, Poland, using video camera traps. Red fox visited sites with scats more often than expected and the duration of their visits was longer at scat sites than at control sites (no scat added). Vigilant behavior, sniffing and scent marking (including over-marking) occurred more often at scat sites compared to control sites, where foxes mainly passed by. Vigilance was most pronounced during the first days of the recordings. Red fox behavior was also influenced by foxes previously visiting scat sites. They sniffed and scent marked (multiple over-marking) more frequently when the lynx scat had been over-marked previously by red fox. Fox visits to lynx scats may be seen as a trade-off between obtaining information on a potential food source (prey killed by lynx) and the potential risk of predation by an apex predator.     

Effects of pH,Salinity, Biomass Concentration,and Algal Organic Matter on Flocculant Efficiency of Synthetic Versus Natural Polymers for Harvesting Microalgae Biomass

This study investigated the effects of pH, salinity, biomass concentration, and algal organic matter (AOM) on the efficiency of four commercial cationic flocculants. The tannin-based biopolymers Tanfloc SG and SL and the polyacrylamide polymers Flopam FO 4800 SH and FO 4990 SH were tested for flocculation of two microalgae models, the freshwater Chlorella vulgaris and the marine Nannochloropsis oculata. Both biomass concentration and AOM presence affected all polymers evaluated, whereas salinity and pH affected only Flopam and Tanfloc, respectively. A restabilization effect due to overdosing was only observed for Flopam polymers and increasing Tanfloc dose resulted in improved efficiency. Flopam polymers showed a significant decrease in the maximum quantum yield of photosystem II as function of polymer dose for Chlorella, which supported the need for toxicological studies to assess the potential toxicity of Flopam. In overall, Tanfloc was not affected by salinity nor presented potential toxicity therefore being recommended for the flocculation of both freshwater and marine species.     

Understanding the impact of flooding on trait-displacements and shifts in assemblage structure of predatory arthropods on river banks

1. Species assemblages of naturally disturbed habitats are governed by the prevailing disturbance regime. Consequently, stochastic flood events affect river banks and the inhabiting biota. Predatory arthropods occupy predominantly river banks in relation to specific habitat conditions. Therefore, species sorting and stochastic processes as induced by flooding are supposed to play important roles in structuring riparian arthropod assemblages in relation to their habitat preference and dispersal ability. 2. To ascertain whether assemblages of spiders and carabid beetles from disturbed river banks are structured by stochastic or sorting mechanisms, diversity patterns and assemblage-wide trait-displacements were assessed based on pitfall sampling data. We tested if flooding disturbance within a lowland river reach affects diversity patterns and trait distribution in both groups. 3. Whereas the number of riparian spider species decreased considerably with increased flooding, carabid beetle diversity benefited from intermediate degrees of flooding. Moreover, regression analyses revealed trait-displacements, reflecting sorting mechanisms particularly for spiders. Increased flooding disturbance was associated with assemblage-wide increases of niche breadth, shading and hygrophilic preference and ballooning propensity for spider (sub)families. Trait patterns were comparable for Bembidiini carabids, but were less univocal for Pterostichini species. Body size decreased for lycosid spiders and Bembidiini carabids with increased flooding, but increased in linyphiid spiders and Pterostichini carabids. 4. Our results indicate that mainly riparian species are disfavoured by either too high or too low degrees of disturbance, whereas eurytopic species benefit from increased flooding. Anthropogenic alterations of flooding disturbance constrain the distribution of common hygrophilous species and/or species with high dispersal ability, inducing shifts towards less specialized arthropod assemblages. River banks with divergent degrees of flooding impact should be maintained throughout dynamic lowland river reaches in order to preserve typical riparian arthropod assemblages.     

Analysis of the specificity of three root-feeders towards grasses in coastal dunes

Among the root-feeding nematodes that accumulate in the rhizosphere of grasses in European dunes, the genus Pratylenchus is of special relevance given its diversity and distribution. Although different species of Pratylenchus have been reported in dune grasses, the specificity towards dune plants, a fundamental aspect of the biology of the species, has hitherto not been studied. Two inoculation experiments using different combinations of grasses and nematodes were performed. The multiplication and the effect on plant growth of P. dunensis and P. brzeskii, two species which only occur in dune areas was compared with that of P. penetrans, a broad host-range species. The three Pratylenchus spp. could multiply under all hosts; however, there was a clear host-dependent response. The species-specific response observed might account for the shift of Pratylenchus spp. detected in the field. Although, a negative effect on the growth of A. arenaria was demonstrated for the three nematode species, different densities were needed to observe the same effects in plant biomass which point at nematode-specific tolerance. While the typical dune species needed very high densities to produce damage, P. penetrans needed very few specimens. The results obtained indicate that species with similar feeding adaptations show very different multiplication abilities on co-occurring hosts, an aspect that is usually overlooked for belowground herbivores in natural systems. The obtained results might suggest a coevolutionary relationship between specific nematode species and Ammophila arenaria.     

Conservation units based on mitochondrial and nuclear DNA variation among European bullhead populations (Cottus gobio L., 1758) from Flanders, Belgium

In this study, we aimed to delineateevolutionarily significant units (ESUs) andmanagement units (MUs) for the Europeanbullhead in Flanders (Belgium). Therefore, wedetermined the genetic interrelationshipsbetween 11 bullhead populations, using lengthvariation at 7 polymorphic microsatellite lociand sequence variation in the d-loop of themitochondrial DNA (mtDNA). Despite therelatively small geographical scale of ourstudy, the analysis of the d-loop sequencesshows that the Flemish bullhead populationscontain 3 haplotype groups, which can beassigned to 3 previously described EuropeanmtDNA clades. Because of the importantdifferences between these clades, they may bedefined as evolutionarily significant units,which should be managed separately. Analysis ofmicrosatellite data reveals very high degreesof isolation between populations, with theexception of 3 pairwise comparisons whichinvolved adjacent populations. Our data suggestthat the 3 haplotype groups probably qualify asESUs, as they show phylogeographicdifferentiation for mtDNA variants as well assignificant divergence of allele frequencies atnuclear loci. However, one of these units,limited to a single population, may be ofCentral European origin. All populations of theScheldt basin meet the criteria for MUrecognition, since significantly differentmicrosatellite allele frequencies as well asprivate alleles are found. In contrast, geneticdifferentiation among the 3 populations of theMeuse basin is very low.     

Ectomycorrhizal fungi enhance nitrogen and phosphorus nutrition of Nothofagus dombeyi under drought conditions by regulating assimilative enzyme activities

Drought stress conditions (DC) reduce plant growth and nutrition, restraining the sustainable reestablishment of Nothofagus dombeyi in temperate south Chilean forest ecosystems. Ectomycorrhizal symbioses have been documented to enhance plant nitrogen (N) and phosphorus (P) uptake under drought, but the regulation of involved assimilative enzymes remains unclear. We studied 1-year-old N. dombeyi (Mirb.) Oerst. plants in association with the ectomycorrhizal fungi Pisolithus tinctorius (Pers.) Coker & Couch. and Descolea antartica Sing. In greenhouse experiments, shoot and root dry weights, mycorrhizal colonization, foliar N and P concentrations, and root enzyme activities [glutamate synthase (glutamine oxoglutarate aminotransferase (GOGAT), EC 1.4.1.13-14), glutamine synthetase (GS, EC 6.3.1.2), glutamate dehydrogenase (GDH, EC 1.4.1.2-4), nitrate reductase (NR, EC 1.6.6.1), and acid phosphomonoesterase (PME, EC 3.1.3.1-2)] were determined as a function of soil-water content. Inoculation of N. dombeyi with P. tinctorius and D. antartica significantly stimulated plant growth and increased plant foliar N and P concentrations, especially under DC. Ectomycorrhizal inoculation increased the activity of all studied enzymes relative to non-mycorrhizal plants under drought. We speculate that GDH is a key enzyme involved in the enhancement of ectomycorrhizal carbon (C) availability by fuelling the tricarboxylic acid (TCA) cycle under conditions of drought-induced carbon deficit. All studied assimilative enzymes of the ectomycorrhizal associations, involved in C, N, and P transfers, are closely interlinked and interdependent. The up-regulation of assimilative enzyme activities by ectomycorrhizal fungal root colonizers acts as a functional mechanism to increase seedling endurance to drought. We insist upon incorporating ectomycorrhizal inoculation in existing Chilean afforestation programs.     

Selective backbone labelling of ILV methyl labelled proteins

Adding the ¹³C labelled 2-keto-isovalerate and 2-oxobutanoate precursors to a minimal medium composed of ¹²C labelled glucose instead of the commonly used (²D, ¹³C) glucose leads not only to the ¹³C labelling of (I, L, V) methyls but also to the selective ¹³C labelling of the backbone C_α and CO carbons of the Ile and Val residues. As a result, the backbone (¹H, ¹⁵N) correlations of the Ile and Val residues and their next neighbours in the (i + 1) position can be selectively identified in HN(CA) and HN(CO) planes. The availability of a selective HSQC spectrum corresponding to the sole amide resonances of the Ile and Val residues allows connecting them to their corresponding methyls by the intra-residue NOE effect, and should therefore be applicable to larger systems.     

Conservation of remnant populations of Colchicum autumnale – The relative importance of local habitat quality and habitat fragmentation

Semi-natural habitat is extremely vulnerable to habitat fragmentation and degradation since its socio-economic value has decreased substantially during the last century in most parts of Europe. We evaluated the relative effects of habitat fragmentation and local environmental conditions on population structure and reproductive performance of the long-lived corm geophyte Colchicum autumnale in 17 highly fragmented populations. Habitat isolation did not affect patch occupancy, population structure or plant performance. In contrast, population size and local environment strongly affected population structure and reproductive performance. Densities of all life stages increased with increasing population size. Large populations also showed a higher reproductive performance and a larger proportion of new recruits. Relationships with local growth conditions pointed towards the importance of an open grassland sward for flower and fruit set and the presence of microsites for successful sexual recruitment. These results suggest that the distribution of C. autumnale consists of an assemblage of basically unconnected populations that are remnants of formerly larger populations. This is in accordance with the species' ability to grow clonally, allowing long-term persistence under deteriorating conditions that occurred during a long period of habitat fragmentation. In conclusion, our results indicate that local habitat and population size are more important than habitat fragmentation (i.e. calcareous grassland isolation and surface area) and argue in favour of a management that is primarily focused on local habitat restoration. This is preferentially accomplished by reintroducing grazing practices, complemented by regular setback of spontaneous succession towards forest.