The Effect of Genetic Diversity on Ecosystem Functioning in Vegetated Coastal Ecosystems

In species-poor communities, genetic diversity potentially plays an important role for ecosystem functioning, though this is still largely unexplored in marine and estuarine ecosystems. We studied how genetic diversity (sensu genotypic diversity and/or allelic richness) affects ecosystem functioning in marine habitat-forming plant communities. First, we conducted a 15-month field experiment in the highly seasonal Baltic Sea and established mono- and polycultures of different genotypes and genotype combinations of Zostera marina. Second, we reviewed existing literature and performed a meta-analysis of 12 studies including this study. We found no evidence of positive genetic diversity effects on shoot production in the field experiment, but diversity enhanced community stability over time. The literature review revealed that a majority of the included studies observed positive effects of genetic diversity on ecosystem functions such as primary production and nutrient uptake. The results from the meta-analysis support the hypothesis that genetic diversity effects on productivity are stronger during or after periods of stress. These diversity effects were also more positive in the field compared to mesocosm studies. Our results indicate that genetic diversity has positive effects on ecosystem functioning, particularly during increased environmental stress. Thus, local genetic diversity should be preserved especially in species-poor ecosystems, where it potentially provides insurance against environmental change.     

Size-asymmetric root competition in deep,nutrient-poor soil

Aims There is much evidence that plant competition below ground is size symmetric, i.e. that competing plants share contested resources in proportion to their sizes. Several researchers have hypothesized that a patchy distribution of soil nutrients could result in size-asymmetric root competition. We tested this hypothesis.     

Sexually dimorphic SCAMP1 expression in the forebrain motor pathway for song production of juvenile zebra finches

Mechanisms regulating sexual differentiation of the zebra finch song system are not well understood. The present study was designed to more fully characterize secretory carrier membrane protein 1 (SCAMP1), which was identified in a cDNA microarray screen as showing increased expression in the forebrains of developing male compared with female zebra finches. We completed the sequence of the open reading frame and used in situ hybridization to compare mRNA in song control regions of juvenile (25-day-old) individuals. Expression was significantly greater in the HVC (used as a proper name) and robust nucleus of the arcopallium (RA) in males than in females. Immunohistochemistry revealed that SCAMP1 protein is also expressed in these two brain regions, and qualitatively appears greater in males. Western analysis confirmed that the protein is increased in the telencephalon of males when compared with females at 25 days of age. These results are consistent with the idea that SCAMP1 is involved in masculinization of these brain areas, perhaps facilitating the survival of cells within them.     

Single and combined effects of two trace elements (Cd and Cu) on the asexual reproduction of Aurelia sp. polyps

Aquatic Ecology - Jellyfish blooms are an increasingly common event in our seas. Occurring via polyps’ asexual reproduction induced by human stresses, they represent a hazard for ecosystems...     

Acceptability of Drosophila suzukii as prey for common predators occurring in cherries and berries

The invasive cherry vinegar fly, Drosophila suzukii, has been identified in Europe as a destructive fruit pest since its arrival in 2008. In the present laboratory study, three predatory insects (Orius majusculus, Chrysoperla carnea, and Forficula auricularia) naturally occurring on fruit crops in Europe were investigated for their ability to attack and feed on D. suzukii within and outside fruits. The predators were provided with various D. suzukii life stages (eggs, larvae, pupae or adults) exposed or within infested cherries. The anthocorid bug O. majusculus fed on eggs and larvae, but was not able to attack pupae. Larvae of the lacewing C. carnea preyed upon D. suzukii eggs, larvae and pupae and also captured adult flies. The European earwig F. auricularia was the most voracious predator of these three tested species. Although the earwigs were not able to catch adult flies, they readily preyed upon every other developmental stage. Adult O. majusculus or third instar larvae of C. carnea significantly reduced the offspring of D. suzukii from infested cherries, when these contained the egg stage of the pest. None of the predators were able to attack early larval stages inside the cherries. But pupae that protruded from the fruit epicarp or that had pupated outside the fruit were accessible to lacewing larvae and earwigs and significantly reduced by them. Orius bugs, lacewing larvae and earwigs were able, under laboratory conditions, to capture and prey upon various life stages of the invasive pest, if not completely concealed inside the fruit. Our findings suggest that these generalist predators may have some control capacity on infested fruit in cultivated fruit crops and also in non‐crop habitats.     

Description of Haemonchus placei (Place, 1893) (Nematoda, Trichostrongylidae, Haemonchinae), identification and intra-specific morphologic variability

Haemonchus placei in cattle has never been completely described, possibly due to great morphological similarity with small ruminants Haemonchus contortus. It is newly described on one isolate from Argentina. It has clear distinct morphological features from sheep and goats Haemonchus contortus and presents only two female morphotypes (linguiform and knobbed) instead of three recorded in H. contortus. A key is proposed to identify females. Female as well as male Haemonchus placei from New World (Argentina, Mexico, USA) are morphologically different from those of Old World (Africa: Burkina-Faso, Mauritania and Ivory Coast) or Australia, possibly due to local evolution since their introduction several centuries ago from Africa or India. We propose to differentiate three sub-species, H. placei placei in Australia, H. placei africanus in western Africa and H. placei argentinensis in the New World.     

Mistletoe viscotoxins induce membrane permeabilization and spore death in phytopathogenic fungi

Viscotoxins (Vts) are basic peptides expressed in mistletoe leaves, seeds and stems which have been shown to be cytotoxic to mammalian cells. The aim of this study was to analyse whether Vts were able to control and/or inhibit the growth of phytopathogenic fungi to obtain a clue to their biological function. Incubation of two Vt isoforms, VtA₃ and VtB, at a final concentration of 10 µ M resulted in a complete blockage of the germination of spores from three different pathogenic fungi. It was also shown that lower concentrations than 10 µ M of VtA₃ and VtB inhibit their mycelial growth in a dose-dependent manner. The protein dose required to inhibit the growth of Fusarium solani and Sclerotinia sclerotiorum to a 50% was between 1.5 and 3.75 µ M , which represents a potent activity. No significant differences in the antifungal potency for each Vt isoform, either VtA₃ and VtB, were observed, although they have been shown to exert differential cytotoxicity on mammalian cells. It was also demonstrated that Vts act as fungicidal compounds. To explore the basis of the antifungal activity the ability of VtA₃ to induce changes in membrane permeability and on the oxidative status of F. solani spores was analysed. By using a specific fluorescent probe on intact spores, it was demonstrated that VtA₃ produces rapid changes in fungal membrane permeability. It also induces H₂O₂ production verified by a histochemical staining. The data presented in this study support a direct role of Vts in the plant defence determined by their lethal effect on fungal pathogens.