Identifying environmental drivers of spatial genetic structure of the European pine marten (<Emphasis Type="Italic">Martes martes</Emphasis>)

Context

In a global context of erosion of biodiversity, the current environmental policy in Europe is oriented towards the creation and the preservation of ecological networks for wildlife. However, most of the management guidelines arose from a structural landscape diagnostic without truly taking into consideration species’ needs.

Objectives

We tested whether and how landscape elements influence the functional connectivity of landscapes for a forest specialist species, the European pine marten (Martes martes), in Northeastern France.

Methods

We collected pine marten scats and tissues from 13 evenly distributed study sites across the whole study area in order to test several types of barriers such as highways, waterways, and open agricultural fields. We crossed the results of several methods: spatial autocorrelation analysis, causal modelling framework, and clustering methods.

Results

The study indicates significant genetic differentiation among the sampling sites. A signal of isolation by distance was detected but disappeared after partialling out landscape or barrier resistance. The only model that was fully supported by causal modelling was the one identifying waterways as the main driver of genetic differentiation. Moreover, clustering analyses indicated the presence of genetic clusters, suggesting that pine marten spatial genetic pattern could be explained by the presence of waterways but also by their reluctance to cross open fields.

Conclusions

The current ecological network could thus be improved by increasing permeability of waterways, in particular navigation canals, and by maintaining and restoring forested corridors in agricultural plains.

     

The feasibility of offshore aquaculture and its potential for multi-use in the North Sea

Following the Blue Growth ambition of the European Commission, the interest in the potential of offshore is growing. This paper aimed to contribute to the discussion on the feasibility of offshore aquaculture development and its potential for multi-use with other maritime activities. A review of national and international projects forms the basis of the paper, where the Dutch North Sea is used as a case-study area. Analysis of technical, economic and ecological boundaries indicated that the potential of fish culture is limited, that seaweed cultivation is likely to gain potential when challenges related to processing will be overcome and that mussel culture has the highest potential in the near future. The North Sea is an area where many stakeholders claim space, which might set boundaries to the number of sites available for mussel culture. Competing claims are a potential source of conflict but may also lead to mutual benefits when smart combinations are sought, e.g. with wind parks, fisheries and nature conservation; especially, the possibility of combining mussel culture in or around wind parks is worthwhile to be further explored. A spatial distribution model adapted for the Dutch North Sea conditions demonstrated that offshore mussel production in wind farms can be profitable. Yet, the commercial interest for offshore development of mussel culture is still limited. Actions required to stimulate further development of the offshore mussel industry are presented for the government, the private sector, research institutes and civil society organizations.     

Optimization of blue mussel (Mytilus edulis) seed culture using recirculation aquaculture systems

By introducing recirculation aquaculture systems (RAS) in the nursery phase of the blue mussel (Mytilus edulis) (17–18 mm), we aimed at a similar growth and survival and a similar water quality compared to the commonly used flow‐through systems (FTS). To calculate water flow and size of the biofilter, a series of experiments were done to determine clearance rate (9.26 mL min^?1), pseudo faeces threshold (60 000 cells Pavlova lutheri mL^?1), nitrogen production (0.00065 mg TAN h^?1 ind^?1 and 1.6 × 10^?5 mg NO₂–N h^?1 ind^?1) and oxygen consumption (0.03 ± 0.01 mg O₂ h^?1 ind^?1). RAS showed no significant differences in water quality (0.06 mg TAN L^?1; 7.7 mg O₂ L^?1) and growth performance of mussel seed specific growth rate (SGR = 5% day^?1) after the experimental period of 4 weeks compared with FTS. The low water refreshment, 10% per day, as well as the constant chlorophyll concentrations (9.76 ± 1.06 μg L^?1), suggests the potential of RAS as culture system for mussel seed.     

Impact of severe forest dieback caused by Phytophthoracinnamomi on macrofungal diversity in the northern jarrah forest of Western Australia

The relative diversity and abundance of different functional groups of macrofungi were investigated in the northern jarrah forest, a mediterranean climate sclerophyllous forest dominated by eucalyptus trees in Western Australia. We sampled paired sites that were either severely affected by dieback, a disease caused by Phytophthora cinnamomi which causes selective plant mortality, or unaffected by this type of forest decline. Macrofungi were sampled 3 times during the growing season along six 100 m × 2 m transects in these sites. Dieback-unaffected sites were found to have significantly different macrofungal floras than unaffected sites. Macrofungal abundance and diversity were approximately 1.5 times and 1.8 times greater respectively in dieback-unaffected sites than in severely affected sites. Dieback-affected sites had a similar diversity of saprotrophic and ectomycorrhizal fungi, whereas more fungal taxa on dieback-unaffected sites were mycorrhizal (>60%). Dung fungi were the most common saprophytes, especially in dieback-affected sites, but abundance data greatly overestimated the importance of these relatively small fungi. We concluded that vegetation changes linked to dieback had a negative effect on fungal community structure and biodiversity in the northern jarrah forest, in a similar manner to other forms of severe disturbance. Conversely, high tree mortality increased the abundance of wood decay fungi, at least in the short term. We expect that reductions in macrofungal species richness were indirectly linked to impacts on mycorrhizal host plants and saprotrophic substrates. Our data show that changes in vegetation composition had the greatest effect on ectomycorrhizal fungi, presumably due to their obligate symbiotic associations.     

Xylella fastidiosa subspecies and sequence types detected in Philaenus spumarius and in infected plants in France share the same locations

In Europe, the meadow spittlebug Philaenus spumarius is the main known vector of the quarantine bacterium Xylella fastidiosa. So far detection and identification of X. fastidiosa has more often been performed from plant matrices than insects, mainly using a real-time PCR and multilocus sequence typing (MLST) approach. Detection of X. fastidiosa in its insect vectors would enhance knowledge of the epidemiologic situation in France, specifically in the already infected Corsica and Provence-Alpes-Côte d’Azur (PACA) regions. The aim of this study was to validate a methodological approach to detect X. fastidiosa in P. spumarius, analysed individually or in groups of 10, using real-time PCR and MLST, and to apply the approach to more than 4,000 individuals collected between 2015 and 2019 from infected areas. The corresponding results expanded our knowledge of the epidemiology of X. fastidiosa in France: (a) X. fastidiosa subsp. multiplex including the sequence types ST6 and ST7 were identified in the insect vector; (b) the rate of positive insects per infected area was as high as 33.3% in Corsica or 50% in the PACA region; (c) positive adults were found during winter; and (d) the bacterial load in P. spumarius (droplet digital PCR) usually ranged from 10³ to 10⁴ cells per insect, but could be as high as 10⁵ or 10⁶ cells per insect for some individuals (13%). The subspecies and sequence types detected in P. spumarius corresponded to the situation officially reported for plants in the same areas.     

Subtle changes in rhizosphere microbial community structure in response to increased boron and sodium chloride concentrations

Two of the major constraints to grain production in large areas of South-East Australia and cropping soils worldwide are high levels of subsoil boron (B) and excessive salinity (NaCl). Although the effect of these constraints is often studied in plants, the effect on microbially mediated plant-beneficial processes is unclear. To that end, we investigated the impact of B and NaCl on soil microbial community structure (MCS) in the wheat rhizosphere using BIOLOG ecoplates and terminal restriction fragment length polymorphism (T-RFLP). In addition, the effects of B and NaCl on the nitrogen (N) cycle processes of N fixation and ammonia oxidation were assessed by the construction of clone libraries of diazotrophic (nifH) and ammonia oxidising (amoA) rhizobacteria. Analysis of BIOLOG plates using non-metric multidimensional scaling (MDS) revealed addition of both B and NaCl significantly changed MCS, the latter of which was also significant through the analysis of T-RFLP data. Utilisation of several chemical groups of BIOLOG substrates significantly changed in NaCl-amended soil; both B and NaCl affected utilisation of several individual substrates indicative of plant stress including serine and malic acid. A significant decrease in diversity and species richness was observed in high B rhizosphere soil. The community structure of ammonia-oxidising bacteria (AOB), all of which clustered with Nitrosospira-like sequences, did not significantly change in response to addition of B or NaCl, but addition of the latter resulted in a significant increase of diazotroph clones within the α-proteobacteria similar to Azospirillum sp. It appeared that the addition of B and NaCl to soil changed rhizosphere MCS indirectly through increased soil moisture and subtle changes in root exudate patterns, the addition of the latter producing a more distinct change through increased osmotic pressure, leading to a greater increase in rhizodeposition of nutrients, especially carbohydrates. The implications for the current study are that B and NaCl are more likely to affect rhizosphere MCS indirectly through root exudate quantity and/or quality than directly through microbial toxicity, and that plant health is a major determinant in rhizosphere MCS and normal N cycling.     

Assessing potential bioavailability of raspberry anthocyanins using an in vitro digestion system

The bioavailability of anthocyanins from raspberry extracts was assessed using an in vitro digestion procedure that mimics the physiochemical and biochemical changes that occur in the upper gastrointestinal tract (GIT). Effectively all of the total phenol content of the raspberry extract survived gastric digestion and partitioned between the IN sample, which represents the serum available material, and the OUT sample, which represents the material that remains in the GIT and passes through to the colon. All of the anthocyanins also survived gastric digestion, but only approximately 5% entered the IN sample and approximately 70% of total anthocyanins were recovered in the IN and OUT samples. Codigestion of the raspberry extract with commonly combined foodstuffs such as bread, breakfast cereal, ice cream, and cooked minced beef gave a different pattern. The total phenol content of the IN samples was slightly reduced by codigestion with ice cream or breakfast cereal but unaffected by codigestion with bread or minced beef. In most cases, the phenol contents of the postgastric and OUT samples were reduced as compared with the expected values. However, the anthocyanin content of the IN samples was unaffected or increased by coincubation with the foodstuffs. This suggests that polyphenols transiently bind to food matrices during digestion, which protects the more labile anthocyanins from degradation, and they are free to diffuse into the IN sample. The anthocyanin composition of the bioavailability samples was monitored by liquid chromatography-mass spectrometry. All eight anthocyanins previously identified in raspberry were detected in the extract and the postgastric samples at similar yields. All eight anthocyanins could be discerned in the IN and OUT samples, but some such as cyanidin-3-O-glucoside were greatly reduced and others such as pelargonidin-3-O-glucoside were apparently increased in abundance. These differences in stability and their importance for the bioavailability of anthocyanins are discussed.     

Epizootic effect and aftermath in a pilot whale population

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