Facultative mutualisms: A double‐edged sword for foundation species in the face of anthropogenic global change

Ecosystems worldwide depend on habitat‐forming foundation species that often facilitate themselves with increasing density and patch size, while also engaging in facultative mutualisms. Anthropogenic global change (e.g., climate change, eutrophication, overharvest, land‐use change), however, is causing rapid declines of foundation species‐structured ecosystems, often typified by sudden collapse. Although disruption of obligate mutualisms involving foundation species is known to precipitate collapse (e.g., coral bleaching), how facultative mutualisms (i.e., context‐dependent, nonbinding reciprocal interactions) affect ecosystem resilience is uncertain. Here, we synthesize recent advancements and combine these with model analyses supported by real‐world examples, to propose that facultative mutualisms may pose a double‐edged sword for foundation species. We suggest that by amplifying self‐facilitative feedbacks by foundation species, facultative mutualisms can increase foundation species’ resistance to stress from anthropogenic impact. Simultaneously, however, mutualism dependency can generate or exacerbate bistability, implying a potential for sudden collapse when the mutualism's buffering capacity is exceeded, while recovery requires conditions to improve beyond the initial collapse point (hysteresis). Thus, our work emphasizes the importance of acknowledging facultative mutualisms for conservation and restoration of foundation species‐structured ecosystems, but highlights the potential risk of relying on mutualisms in the face of global change. We argue that significant caveats remain regarding the determination of these feedbacks, and suggest empirical manipulation across stress gradients as a way forward to identify related nonlinear responses.     

Spontaneous Return of Biodiversity in Restored Subtropical Thicket: Portulacaria afra as an Ecosystem Engineer

An accepted criterion for measuring the success of ecosystem restoration is the return of biodiversity relative to intact reference ecosystems. The emerging global carbon economy has made landscape‐scale restoration of severely degraded Portulacaria afra (spekboom)‐dominated subtropical thicket, by planting multiple rows of spekboom truncheons, a viable land‐use option. Although large amounts of carbon are sequestered when planting a monoculture of spekboom, it is unknown whether this is associated with the return of other thicket biodiversity components. We used available carbon stock data from degraded, restored, and intact stands at one site, and sampled carbon stocks at restored stands at another site in the same plant community. We also sampled plant community composition at both sites. The total carbon stock of the oldest (50 years) post‐restoration stand (250.8 ± 14 t C ha^?1) approximated that of intact stands (245 t C ha^?1) and we observed a general increase in carbon content with restoration age (71.4 ± 24 t C ha^?1 after 35 and 167.9 ± 20 t C ha^?1 after 50 years). A multiple correspondence analysis separated degraded stands from stands under restoration based on ground cover, floristic composition, and total carbon stock. Older post‐restoration and intact stands were clustered according to woody canopy recruit abundance. Our results suggest that spekboom is an ecosystem engineer that promotes spontaneous return of canopy species and other components of thicket biodiversity. The spekboom canopy creates a cooler micro‐climate and a dense litter layer, both likely to favor the recruitment of other canopy species.     

Development of a multivariate statistical model to predict peroxisome proliferation in the rat,based on urinary 1H-NMR spectral patterns

A previous report of this work (Ringeissen et al. 2003) described the use of nuclear magnetic resonance (NMR) spectroscopy coupled with multivariate statistical data analysis (MVDA) to identify novel biomarkers of peroxisome proliferation (PP) in Wistar Han rats. Two potential biomarkers of peroxisome proliferation in the rat were described, N-methylnicotinamide (NMN) and N-methyl-4-pyridone-3-carboxamide (4PY). The inference from these results was that the tryptophan-nicotinamide adenine dinucleotide (NAD⁺) pathway was altered in correlation with peroxisome proliferation, a hypothesis subsequently confirmed by TaqMan® analysis of the relevant genes encoding two key enzymes in the pathway, aminocarboxymuconate-semialdehyde decarboxylase (EC 4.1.1.45) and quinolinate phosphoribosyltransferase (EC 2.4.2.19). The objective of the present study was to investigate these data further and identify other metabolites in the NMR spectrum correlating equally with PP. MVDA Partial Least Squares (PLS) models were constructed that provided a better prediction of PP in Wistar Han rats than levels of 4PY and NMN alone. The resulting Wistar Han rat predictive models were then used to predict PP in a test group of Sprague Dawley rats following administration of fenofibrate. The models predicted the presence or absence of PP (above on arbitrary threshold of >2-fold mean control) in all Sprague Dawley rats in the test group.     

Odor Qualities and Thresholds of Physiological Metabolites of 1,8‐Cineole as an Example for Structure?Activity Relationships Considering Chirality Aspects

The present study aimed at analyzing the odor properties of a group of physiological human metabolites of the odorant 1,8‐cineole: 2,3‐dehydro‐, α2,3‐epoxy‐, α/β2‐hydroxy‐, α3‐hydroxy‐, 4‐hydroxy‐, 7‐hydroxy‐, 9‐hydroxy‐, 2‐oxo‐, and 3‐oxo‐1,8‐cineole. These metabolites constitute a group of structurally closely related molecules, which differ mainly in nature and position of O‐containing functional groups. They thus offer the possibility to correlate odor properties with molecular structure, i.e., to establish structure? odor relationships of compounds that are biologically generated from a potent odorant as parent substance. Generally, the metabolites preserved the eucalyptus‐like odor quality of 1,8‐cineole but showed additional odor notes such as sweet, citrus‐like, plastic‐like, earthy, musty, and faecal, which made them distinguishable. The individual enantiomers of chiral molecules also exhibited different odors. With the exception of 2,3‐dehydro‐1,8‐cineole, all metabolites showed a highly decreased odor threshold in comparison to 1,8‐cineole. The determination of odor qualities and odor thresholds was accomplished by gas chromatography/olfactometry (GC/O) on achiral and chiral GC capillaries. The results were correlated with common theories on structure? odor relationships.     

Outlier detection methods are still effective even using virtual species created with the probabilistic approach

Liu et al. (Journal of Biogeography, 2018, 45 :164–176) presented an approach to detect outliers in species distribution data by developing virtual species created using the threshold approach. Meynard et al. (Journal of biogeography, 2019, 46 :2141–2144) raised concerns about this approach stating that ‘using a probabilistic approach … may significantly change results’. Here we provide a new series of simulations using the two approaches and demonstrate that the outlier detection approach based on pseudo species distribution models was still effective when using the probabilistic approach, although the detection rate was lower than when using the threshold approach.     

Disturbance does not have a significant impact on waders in an estuary close to conurbations: importance of overlap between birds and people in time and space

Disturbance of wildlife is a potential cause of conservation concern, not least to overwintering waders Charadrii inhabiting estuaries close to conurbations where human recreational and economic activities are often concentrated. Disturbance from people on and alongside intertidal foraging areas could make it more difficult for birds to survive until spring in good condition by reducing the time available for foraging, increasing energy requirements and displacing birds to poorer foraging areas. We adopted a two-part approach to testing whether such significant impacts occurred in a Special Protection Area where disturbance risk was high because of its small size and close proximity to conurbations. In part one, we recorded over the whole estuary during stages of the tidal cycle when part or all of the intertidal zone was exposed and so accessible to waders (i.e. on receding, low and advancing tides): (1) the numbers and activities of people on the intertidal flats and on the adjacent land in those places where people were visible to waders in the intertidal zone and (2) the numbers of waders present and disturbed into flight, the flight distance and flight duration in the ‘overlap’ areas where people did disturb waders. People occurred on < 25% of the 938 ha of intertidal flats, but most waders foraged on mudflats, whereas most people were on sandflats. People on land were visible to foraging waders along < 35% of the 16.5 km of shoreline. Waders and people were therefore substantially separated in space. Within overlap areas, people and waders were often frequently separated in time: for example, people on land mostly disturbed waders when only the upper shore levels were exposed. The average overwintering wader spent < 0.1% of its foraging time during daylight flying away from people and the additional energy expenditure was equivalent to < 0.02% of its daily requirements. The comparison made in part two between our study area and two comparable estuaries showed that the number of visits each day to the overlap areas would need to be 29 or 43 times greater for disturbance to have lowered the birds’ body condition and winter survival. Both parts of the study therefore suggested strongly that the amount of disturbance was too trivial to have a significant impact on waders. It is concluded that: (1) to properly assess disturbance risk to waders, both extensive and intensive observations must be made on the behaviour of people and birds to quantify the extent to which they overlap in space and time, and (2) it should not be assumed that an estuary's close proximity to conurbations, and the presence of large numbers of people in the vicinity of the SPA, necessarily implies a significant disturbance risk to waders.     

Stability of ultramer as copy number standards in real-time PCR

Since commercial copy number standards are not always available for real-time PCR, alternative sources of DNA are used. Unfortunately, stored genomic DNA or PCR amplicon has been shown to be unstable, resulting in variable copy number. More recently, the use of ultramer as copy number standard has been reported. However, there is little information on the stability of ultramer under different storage conditions. Thus the aim of this study was to determine the stability of ultramer as copy number standard under different storage conditions using different mixing methods. We found that ultramer copy number was not affected by storage at either 4 °C or − 20 °C over a period of 30 days. Furthermore, the method of mixing the ultramer did not appear to contribute to variability in results. Irrespective of storage temperature or mixing method, there was less than 5% variance in Ct value over a period of 30 days. A duplicate set of standards costs approximately $0.01. Therefore, the use of ultramer as copy number standards in real-time PCR, is cost effective and convenient.     

Contribution of genetic and epigenetic mechanisms to Wnt pathway activity in prevalent skeletal disorders

We reported previously that the expression of Wnt-related genes is lower in osteoporotic hip fractures than in osteoarthritis. We aimed to confirm those results by analyzing β-catenin levels and explored potential genetic and epigenetic mechanisms involved.