Predicting the success of an invader: Niche shift versus niche conservatism

Invasive species can encounter environments different from their source populations, which may trigger rapid adaptive changes after introduction (niche shift hypothesis). To test this hypothesis, we investigated whether postintroduction evolution is correlated with contrasting environmental conditions between the European invasive and source ranges in the Asian tiger mosquito Aedes albopictus. The comparison of environmental niches occupied in European and source population ranges revealed more than 96% overlap between invasive and source niches, supporting niche conservatism. However, we found evidence for postintroduction genetic evolution by reanalyzing a published ddRADseq genomic dataset from 90 European invasive populations using genotype–environment association (GEA) methods and generalized dissimilarity modeling (GDM). Three loci, among which a putative heat‐shock protein, exhibited significant allelic turnover along the gradient of winter precipitation that could be associated with ongoing range expansion. Wing morphometric traits weakly correlated with environmental gradients within Europe, but wing size differed between invasive and source populations located in different climatic areas. Niche similarities between source and invasive ranges might have facilitated the establishment of populations. Nonetheless, we found evidence for environmental‐induced adaptive changes after introduction. The ability to rapidly evolve observed in invasive populations (genetic shift) together with a large proportion of unfilled potential suitable areas (80%) pave the way to further spread of Ae. albopictus in Europe.     

Pathogenicity of Epicoccum sorghinum towards dragon fruits (Hylocereus species) and in vitro evaluation of chemicals with antifungal activity

Recent reports of plant diseases that result in yield reduction and increasing demand for dragon fruits raise concerns of fruit supply shortage. Emerging plant diseases may play an important role in increasing yield losses and reducing the availability of stem cuttings (source of planting materials). Understanding the aetiology of current and new diseases of dragon fruit is important to address production issues and to formulate effective disease control measures. This study reports Epicoccum sorghinum as a potential emerging pathogen of dragon fruit. Epicoccum sorghinum MBDF0024a was isolated from dragon fruit stems (Hylocereus monacanthus) showing brown spot symptoms. DNA sequence of the internal transcribed spacer (ITS-rDNA), beta tubulin and actin gene regions of fungal isolate MBDF0024a had high similarities to E. sorghinum stains. Epicoccum sorghinum MBDF0024a was pathogenic to three cultivated dragon fruit species (Hylocereus undatus, H. monacanthus and H. megalanthus) in repeated laboratory and glasshouse trials. Large brown lesions developed on 3-week-old inoculated rooted stem cuttings 3 days postinoculation (dpi). Yellowing of the lesion (advance part) started at five dpi, and at seven dpi, yellowing was observed in the stem. As there are no reported control measures for diseases caused by E. sorghinum, this study screened chemicals with antifungal properties. A biopesticide containing B. subtilis (2 ml/400 ml), and chemicals isoprothiolane (2.25 ml/400 ml), mancozeb (2 g/400 ml) and pyraclostrobin (1 ml/400 ml) (chemical control) completely inhibited the in vitro growth of E. sorghinum MBDF0024a. The results establish E. sorghinum as a new and emerging pathogen of dragon fruit that could be a major yield-limiting disease if left uncontrolled. The biopesticide can be considered a fairly safe option for disease management, but glasshouse and field studies are needed for validation.     

Kefir micro-organisms: their role in grain assembly and health properties of fermented milk

Kefir is a homemade viscous and slightly effervescent beverage obtained by milk fermentation with kefir grains, which are built up by a complex community of lactic acid and acetic acid bacteria and yeasts confined in a matrix of proteins and polysaccharides. The present review summarizes the role of kefir micro-organisms in grain assembly and in the beneficial properties attributed to kefir. The use of both culture-dependent and independent methods has made possible to determine the micro-organisms that constitute this ecosystem. Kefir consumption has been associated with a wide range of functional and probiotic properties that could be attributed to the micro-organisms present in kefir and/or to the metabolites synthetized by them during milk fermentation. In this context, the role of micro-organisms in kefir health promoting properties is discussed with particular attention to the contribution of yeast as well as bioactive metabolites such as lactic and acetic acid, exopolysaccharides and bioactive peptides. Even though many advances on the knowledge of this ancient fermented milk have been made, further studies are necessary to elucidate the complex nature of the kefir ecosystem.     

Foot internal stress distribution during impact in barefoot running as function of the strike pattern

The aim of the present study is to examine the impact absorption mechanism of the foot for different strike patterns (rearfoot, midfoot and forefoot) using a continuum mechanics approach. A three-dimensional finite element model of the foot was employed to estimate the stress distribution in the foot at the moment of impact during barefoot running. The effects of stress attenuating factors such as the landing angle and the surface stiffness were also analyzed. We characterized rear and forefoot plantar sole behavior in an experimental test, which allowed for refined modeling of plantar pressures for the different strike patterns. Modeling results on the internal stress distributions allow predictions of the susceptibility to injury for particular anatomical structures in the foot.     

Rate-limiting steps for protein synthesis in isolated rat liver cells. Role of aspartate availability.

Amino-oxyacetate (carboxymethoxylamine) was found to inhibit protein labelling in isolated liver cells. A similar degree of inhibition (about 70%) was observed of basal and substrate-stimulated rates of protein labelling, ruling out an action on the cellular energy state. Its effect does not seem to be related either to a perturbation of the reduction state of the NAD system or to rate changes in the gluconeogenic pathway. The following observations indicate that amino-oxyacetate inhibits protein labelling by limiting aspartate supply. Amino-oxyacetate was ineffective in a postmitochondrial supernatant under non-limiting amino acid supply conditions. The aspartate cellular content decreases in the presence of amino-oxyacetate, although most other amino acids tend to accumulate. L-Cycloserine was unable to decrease aspartate content and was ineffective in decreasing protein labelling. The inhibitory action of amino-oxyacetate was specifically reversed by incubating cells with amino acids that increase the cellular content of aspartate.