The cobblers stick to their lasts: pollinators prefer native over alien plant species in a multi-species experiment

The majority of plant species rely, at least partly, on animals for pollination. Our knowledge on whether pollinator visitation differs between native and alien plant species, and between invasive and non-invasive alien species is still limited. Additionally, because numerous invasive plant species are escapees from horticulture, the transition from human-assisted occurrence in urbanized habitats to unassisted persistence and spread in (semi-)natural habitats requires study. To address whether pollinator visitation differs between native, invasive alien and non-invasive alien species, we did pollinator observations for a total of 17 plant species representing five plant families. To test whether pollinator visitation to the three groups of species during the initial stage of invasion depends on habitat type, we did the study in three urbanized habitats and three semi-natural grasslands, using single potted plants. Native plants had more but smaller flower units than alien plants, and invasive alien plants had more but smaller flowers than non-invasive alien plants. After accounting for these differences in floral display, pollinator visitation was higher for native than for alien plant species, but did not differ between invasive and non-invasive alien plant species. Pollinator visitation was on average higher in semi-natural than in urbanized habitats, irrespective of origin or status of the plant species. This might suggest that once an alien species has managed to escape from urbanized into more natural habitats, pollinator limitation will not be a major barrier to establishment and invasion.

The more the merrier: Multi-species experiments in ecology

A major objective in ecology is to find general patterns, and to establish the rules and underlying mechanisms that generate those patterns. Nevertheless, most of our current insights in ecology are based on case studies of a single or few species, whereas multi-species experimental studies remain rare. We underline the power of the multi-species experimental approach for addressing general ecological questions, e. g. on species environmental responses or on patterns of among-and within-species variation. We present simulations that show that the accuracy of estimates of between-group differences is increased by maximizing the number of species rather than the number of populations or individuals per species. Thus, the more species a multi-species experiment includes, the more powerful it is. In addition, we discuss some inevitable methodological challenges of multi-species experiments. While we acknowledge the value of single-or few-species experiments, we strongly advocate the use of multi-species experiments for addressing ecological questions at a more general level.

Little evidence for release from herbivores as a driver of plant invasiveness from a multi-species herbivore-removal experiment

Enemy release is frequently posed as a main driver of invasiveness of alien species. However, an experimental multi-species test examining performance and herbivory of invasive alien, non-invasive alien and native plant species in the presence and absence of natural enemies is lacking. In a common garden experiment in Switzerland, we manipulated exposure of seven alien invasive, eight alien non-invasive and fourteen native species from six taxonomic groups to natural enemies (invertebrate herbivores), by applying a pesticide treatment under two different nutrient levels. We assessed biomass production, herbivore damage and the major herbivore taxa on plants. Across all species, plants gained significantly greater biomass under pesticide treatment. However, invasive, non-invasive and native species did not differ in their biomass response to pesticide treatment at either nutrient level. The proportion of leaves damaged on invasive species was significantly lower compared to native species, but not when compared to non-invasive species. However, the difference was lost when plant size was accounted for. There were no differences between invasive, non-invasive and native species in herbivore abundance. Our study offers little support for invertebrate herbivore release as a driver of plant invasiveness, but suggests that future enemy release studies should account for differences in plant size among species.

Genetic diversity and differentiation follow secondary succession in a multi-species study on woody plants from subtropical China

Aims: Species diversity and genetic diversity may be affected in parallel by similar environmental drivers. However, genetic diversity may also be affected independently by habitat characteristics. We aim at disentangling relationships between genetic diversity, species diversity and habitat characteristics of woody species in subtropical forest. Methods: We studied 11 dominant tree and shrub species in 27 plots in Gutianshan, China, and assessed their genetic diversity (Ar) and population differentiation (F’ST) with microsatellite markers. We tested if Ar and population specific F’ST were correlated to local species diversity and plot characteristics. Multi-model inference and model averaging were used to determine the relative importance of each predictor. Additionally we tested for isolation-by-distance and isolation-by-elevation by regressing pairwise F’ST against pairwise spatial and elevational distances. Important findings: Genetic diversity was not related to species diversity for any of the study species. Thus, our results do not support joint effects of habitat characteristics on these two levels of biodiversity. Instead, genetic diversity in two understory shrubs, Rhododendron simsii and Vaccinium carlesii, was affected by plot age with decreasing genetic diversity in successionally older plots. Population differentiation increased with plot age in Rhododendron simsii and Lithocarpus glaber. This shows that succession can reduce genetic diversity within, and increase genetic diversity between populations. Furthermore, we found four cases of isolation-by-distance and two cases of isolation-by-elevation. The former indicates inefficient pollen and seed dispersal by animals whereas the latter might be due to phenological asynchronies. These patterns indicate that succession can affect genetic diversity without parallel effects on species diversity and that gene flow in a continuous subtropical forest can be restricted even at a local scale.

Systems medicine and integrated care to combat chronic noncommunicable diseases

We propose an innovative, integrated, cost-effective health system to combat major non-communicable diseases (NCDs), including cardiovascular, chronic respiratory, metabolic, rheumatologic and neurologic disorders and cancers, which together are the predominant health problem of the 21st century. This proposed holistic strategy involves comprehensive patient-centered integrated care and multi-scale, multi-modal and multi-level systems approaches to tackle NCDs as a common group of diseases. Rather than studying each disease individually, it will take into account their intertwined gene-environment, socio-economic interactions and co-morbidities that lead to individual-specific complex phenotypes. It will implement a road map for predictive, preventive, personalized and participatory (P4) medicine based on a robust and extensive knowledge management infrastructure that contains individual patient information. It will be supported by strategic partnerships involving all stakeholders, including general practitioners associated with patient-centered care. This systems medicine strategy, which will take a holistic approach to disease, is designed to allow the results to be used globally, taking into account the needs and specificities of local economies and health systems.

Plant-microbe-herbivore interactions in invasive and non-invasive alien plant species

1. Plants interact with many organisms, such as microbes and herbivores, and these interactions are likely to affect the establishment and spread of plants. In the context of plant invasions, mycorrhizal fungi and constitutive and induced resistance of plants against herbivores have received attention independently of each other. However, plants are frequently involved in complex multi-trophic interactions, which might differ between invasive and non-invasive alien plants. 2. In a multi-species comparative experiment, we aimed to improve our understanding of plant traits associated with invasiveness. We tested whether eight invasive alien plant species use the mycorrhizal symbiosis in a more beneficial way, and have higher levels of constitutive or induced resistance against two generalist bioassay herbivores, than nine non-invasive alien species. We further assessed whether the presence of mycorrhizal fungi altered the resistance of the plant species, and whether this differed between invasive and non-invasive alien species. 3. While invasive species produced more biomass, they did not differ in their biomass response to mycorrhizal fungi from non-invasive alien species. Invasive species also did not have higher levels of constitutive or induced resistance against the two generalist herbivores. Mycorrhizal fungi greatly affected the resistance of our plant species, however, this was also unrelated to whether the alien species were invasive or not. 4. Our study confirms the previous findings that invasive species generally grow faster and produce more biomass than non-invasive alien species. We further show that alien plant species used a variety of defence strategies, and also varied in their interactions with mycorrhizal fungi. These multi-trophic interactions were not consistently related to invasiveness of the alien plant species. 5. We suggest that awareness of the fact that alien plant species are involved in multi-trophic interactions might lead to a more complete understanding of the factors contributing to a plant's success.

Effect of photoactivated disinfection with a light-emitting diode on bacterial species and biofilms associated with periodontitis and peri-implantitis

BACKGROUND To determine the effect of photoactivated disinfection (PAD) using toluidine blue and a light-emitting diode (LED) in the red spectrum (wave length at 625-635 nm) on species associated with periodontitis and peri-implantitis and bacteria within a periodontopathic biofilm. METHODS Sixteen single microbial species including 2 Porphyromonas gingivalis and 2 Aggregatibacter actinomycetemcomitans and a multispecies mixture consisting of 12 species suspended in saline without and with 25% human serum were exposed to PAD. Moreover, single-species biofilms consisting of 2 P. gingivalis and 2 A. actinomycetemcomitans strains and a multi-species biofilm on 24-well-plates, grown on titanium discs and in artificial periodontal pockets were exposed to PAD with and without pretreatment with 0.25% hydrogen peroxide. Changes in the viability were determined by counting the colony forming units (cfu). RESULTS PAD reduced the cfu counts in saline by 1.42 log₁₀ after LED application for 30s and by 1.99 log₁₀ after LED application for 60s compared with negative controls (each p<0.001). Serum did not inhibit the efficacy of PAD. PAD reduced statistically significantly (p<0.05) the cfu counts of the P. gingivalis biofilms. The viability of the A. actinomycetemcomitans biofilms and the multi-species biofilms was statistically significantly decreased when PAD was applied after a pretreatment with 0.25% hydrogen peroxide. The biofilm formed in artificial pockets was more sensitive to PAD with and without pretreatment with hydrogen peroxide compared with those formed on titanium discs. CONCLUSIONS PAD using a LED was effective against periodontopathic bacterial species and reduced viability in biofilms but was not able to completely destroy complex biofilms. The use of PAD following pretreatment with hydrogen peroxide resulted in an additional increase in the antimicrobial activity which may represent a new alternative to treat periodontal and peri-implant infections thus warranting further testing in clinical studies.

Tracing the origin of Arctic driftwood

Arctic environments, where surface temperatures increase and sea ice cover and permafrost depth decrease, are very sensitive to even slight climatic variations. Placing recent environmental change of the high-northern latitudes in a long-term context is, however, complicated by too short meteorological observations and too few proxy records. Driftwood may represent a unique cross-disciplinary archive at the interface of marine and terrestrial processes. Here, we introduce 1445 driftwood remains from coastal East Greenland and Svalbard. Macroscopy and microscopy were applied for wood anatomical classification; a multi-species subset was used for detecting fungi; and information on boreal vegetation patterns, circumpolar river systems, and ocean current dynamics was reviewed and evaluated. Four conifer (Pinus, Larix, Picea, and Abies) and three deciduous (Populus, Salix, and Betula) genera were differentiated. Species-specific identification also separated Pinus sylvestris and Pinus sibirica, which account for ~40% of all driftwood and predominantly originate from western and central Siberia. Larch and spruce from Siberia or North America represents ~26% and ~18% of all materials, respectively. Fungal colonization caused different levels of driftwood staining and/or decay. Our results demonstrate the importance of combining wood anatomical knowledge with insight on boreal forest composition for successfully tracing the origin of Arctic driftwood. To ultimately reconstruct spatiotemporal variations in ocean currents, and to better quantify postglacial uplift rates, we recommend consideration of dendrochronologically dated material from many more circumpolar sites.

Invasive plant species do not create more negative soil conditions for other plants than natives

Abstract A major task in ecology is to establish the degree of generality of ecological mechanisms. Here we present results from a multi-species experiment that tested whether a set of invasive species altered the soil conditions to the detriment of other species by releasing allelopathic compounds or inducing shifts in soil biota composition, and whether this effect was more pronounced relative to a set of closely related native species. We pre-cultivated soil with 23 exotic invasive, 19 related native and 6 related exotic garden species and used plain soil as a control. To separate allelopathy from effects on the soil biota, we sterilized half of the soil. Then, we compared the effect of soil pre-cultivation and sterilization on germination and growth of four native test species in two experiments. The general effect of soil sterilization was positive. The effect of soil pre-cultivation on test species performance was neutral to positive, and sterilization reduced this positive effect. This indicates general absence of allelopathic compounds and a shift toward a less antagonistic soil biota by cultivation species. In both experiments, pre-cultivation effects did not differ systematically between exotic invasive, exotic garden or native species. Our results do not support the hypothesis that invasive plants generally inhibit the growth of others by releasing allelopathic compounds or accumulating a detrimental soil biota.

In-vitro activity of taurolidine on single species and a multispecies population associated with periodontitis.

The antimicrobial activity of taurolidine was compared with minocycline against microbial species associated with periodontitis (four single strains and a 12-species mixture). Minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs), killing as well as activities on established and forming single-species biofilms and a 12-species biofilm were determined. The MICs of taurolidine against single species were always 0.31 mg/ml, the MBCs were 0.64 mg/ml. The used mixed microbiota was less sensitive to taurolidine, MIC and the MBC was 2.5 mg/ml. The strains and the mixture were completely killed by 2.5 mg/ml taurolidine, whereas 256 μg/ml minocycline reduced the bacterial counts of the mixture by 5 log10 colony forming units (cfu). Coating the surface with 10 mg/ml taurolidine or 256 μg/ml minocycline prevented completely biofilm formation of Porphyromonas gingivalis ATCC 33277 but not of Aggregatibacter actinomycetemcomitans Y4 and the mixture. On 4.5 d old biofilms, taurolidine acted concentration dependent with a reduction by 5 log10 cfu (P. gingivalis ATCC 33277) and 7 log10 cfu (A. actinomycetemcomitans Y4) when applying 10 mg/ml. Minocycline decreased the cfu counts by 1-2 log10 cfu independent of the used concentration. The reduction of the cfu counts in the 4.5 d old multi-species biofilms was about 3 log10 cfu after application of any minocycline concentration and after using 10 mg/ml taurolidine. Taurolidine is active against species associated with periodontitis, even within biofilms. Nevertheless a complete elimination of complex biofilms by taurolidine seems to be impossible and underlines the importance of a mechanical removal of biofilms prior to application of taurolidine.

Methodical study of nitrous oxide eddy covariance measurements using quantum cascade laser spectrometery over a Swiss forest

Nitrous oxide fluxes were measured at the Lägeren CarboEurope IP flux site over the multi-species mixed forest dominated by European beech and Norway spruce. Measurements were carried out during a four-week period in October–November 2005 during leaf senescence. Fluxes were measured with a standard ultrasonic anemometer in combination with a quantum cascade laser absorption spectrometer that measured N2O, CO2, and H2O mixing ratios simultaneously at 5 Hz time resolution. To distinguish insignificant fluxes from significant ones it is proposed to use a new approach based on the significance of the correlation coefficient between vertical wind speed and mixing ratio fluctuations. This procedure eliminated roughly 56% of our half-hourly fluxes. Based on the remaining, quality checked N2O fluxes we quantified the mean efflux at 0.8±0.4 μmol m−2 h−1 (mean ± standard error). Most of the contribution to the N2O flux occurred during a 6.5-h period starting 4.5 h before each precipitation event. No relation with precipitation amount could be found. Visibility data representing fog density and duration at the site indicate that wetting of the canopy may have as strong an effect on N2O effluxes as does below-ground microbial activity. It is speculated that above-ground N2O production from the senescing leaves at high moisture (fog, drizzle, onset of precipitation event) may be responsible for part of the measured flux.

Gastropod Seed Dispersal: An Invasive Slug Destroys Far More Seeds in Its Gut than Native Gastropods

Seed dispersal is one of the most important mechanisms shaping biodiversity, and animals are one of the key dispersal vectors. Animal seed dispersal can directly or indirectly be altered by invasive organisms through the establishment of new or the disruption of existing seed dispersal interactions. So far it is known for a few gastropod species that they ingest and defecate viable plant seeds and consequently act as seed dispersers, referred to as gastropodochory. In a multi-species experiment, consisting of five different plant species and four different gastropod species, we tested with a fully crossed design whether gastropodochory is a general mechanism across native gastropod species, and whether it is altered by the invasive alien slug species Arion lusitanicus. Specifically, we hypothesized that a) native gastropod species consume the seeds from all tested plant species in equal numbers (have no preference), b) the voracious invasive alien slug A. lusitanicus – similarly to its herbivore behaviour – consumes a higher amount of seeds than native gastropods, and that c) seed viability is equal among different gastropod species after gut passage. As expected all tested gastropod species consumed all tested plant species. Against our expectation there was a difference in the amount of consumed seeds, with the largest and native mollusk Helix pomatia consuming most seeds, followed by the invasive slug and the other gastropods. Seed damage and germination rates did not differ after gut passage through different native species, but seed damage was significantly higher after gut passage through the invasive slug A. lusitanicus, and their germination rates were significantly reduced.