Beta‐diversity of central European forests decreases along an elevational gradient due to the variation in local community assembly processes

Beta‐diversity has been repeatedly shown to decline with increasing elevation, but the causes of this pattern remain unclear, partly because they are confounded by coincident variation in alpha‐ and gamma‐diversity. We used 8795 forest vegetation‐plot records from the Czech National Phytosociological Database to compare the observed patterns of beta diversity to null‐model expectations (beta‐deviation) controlling for the effects of alpha‐ and gamma‐diversity. We tested whether β‐diversity patterns along a 1200 m elevation gradient exclusively depend on the effect of varying species pool size, or also on the variation of the magnitude of community assembly mechanisms determining the distribution of species across communities (e.g. environmental filtering, dispersal limitation). The null model we used is a novel extension of an existing null‐model designed for presence/absence data and was specifically designed to disrupt the effect of community assembly mechanisms, while retaining some key features of observed communities such as average species richness and species abundance distribution. Analyses were replicated in ten subregions with comparable elevation ranges. Beta‐diversity declined along the elevation gradient due to a decrease in gamma‐diversity, which was steeper than the decrease in alpha‐diversity. This pattern persisted after controlling for alpha‐ and gamma‐diversity variation, and the results were robust when different resampling schemes and diversity metrics were used. We conclude that in temperate forests the pattern of decreasing beta‐diversity with elevation does not exclusively depend on variation in species pool size, as has been hypothesized, but also on variation in community assembly mechanisms. The results were consistent across resampling schemes and diversity measures, thus supporting the use of vegetation‐plot databases for understanding patterns of beta‐diversity at the regional scale.     

Diversity of European habitat types is correlated with geography more than climate and human pressure

Habitat richness, that is, the diversity of ecosystem types, is a complex, spatially explicit aspect of biodiversity, which is affected by bioclimatic, geographic, and anthropogenic variables. The distribution of habitat types is a key component for understanding broad‐scale biodiversity and for developing conservation strategies. We used data on the distribution of European Union (EU) habitats to answer the following questions: (i) how do bioclimatic, geographic, and anthropogenic variables affect habitat richness? (ii) Which of those factors is the most important? (iii) How do interactions among these variables influence habitat richness and which combinations produce the strongest interactions? The distribution maps of 222 terrestrial habitat types as defined by the Natura 2000 network were used to calculate habitat richness for the 10 km × 10 km EU grid map. We then investigated how environmental variables affect habitat richness, using generalized linear models, generalized additive models, and boosted regression trees. The main factors associated with habitat richness were geographic variables, with negative relationships observed for both latitude and longitude, and a positive relationship for terrain ruggedness. Bioclimatic variables played a secondary role, with habitat richness increasing slightly with annual mean temperature and overall annual precipitation. We also found an interaction between anthropogenic variables, with the combination of increased landscape fragmentation and increased population density strongly decreasing habitat richness. This is the first attempt to disentangle spatial patterns of habitat richness at the continental scale, as a key tool for protecting biodiversity. The number of European habitats is related to geography more than climate and human pressure, reflecting a major component of biogeographical patterns similar to the drivers observed at the species level. The interaction between anthropogenic variables highlights the need for coordinated, continental‐scale management plans for biodiversity conservation.     

Detection of Southern tomato virus by molecular hybridisation

Southern tomato virus (STV) is a double‐stranded RNA (dsRNA) virus belonging to the genus Amalgavirus from the family Amalgamaviridae. STV has been detected in tomato plants showing symptoms of stunting, fruit discoloration and size reduction, although its role on symptom development is unclear. Also, little is known about the incidence and epidemiology of this virus and how it spreads in tomato crops. In this work, we developed a molecular hybridisation method by using a digoxigenin‐labelled RNA probe based on the nucleotide sequence of the STV putative coat protein which was tested with different procedures for preparation of plant material. This technique was sensitive enough to detect STV from sap extracts (obtained just by grinding in buffer) from different plant tissues such as leaves, fruits, roots and seeds. This procedure is suitable for field surveys since it allows a cheap and quick processing of a high number of samples. Surveys performed in three important tomato production areas (Peninsular Spain, the Canary Islands and Sicily) showed that STV is widely spread, with incidences ranging from 18% to 74% in different local and commercial tomato varieties.     

Analysis of the <Emphasis Type="Italic">MAT1-2-1</Emphasis> gene of <Emphasis Type="Italic">Colletotrichum lindemuthianum</Emphasis>

A single MAT1-2-1 gene was identified from a mating pair of the filamentous ascomycete Colletotrichum lindemuthianum. The MAT1-2-1 genes from both mating partners carried an open reading frame (ORF) of 870 bp encoding a putative protein of 290 amino acids that includes the highly conserved high mobility group (HMG) domain typical of the fungal MAT1-2-1 genes. Three introns were confirmed within the C. lindemuthianum ORF, two of which were found to be conserved relative to a previously reported MAT1-2-1 gene from C. gloeosporioides. The amino acid sequence of the HMG domain from C. lindemuthianum MAT1-2-1 was also compared with those from other ascomycetes. These results suggest that although the MAT1-2-1 genes are highly conserved among ascomycetes, the mechanism which defines mating partners in the genus Colletotrichum is distinct to the idiomorph system described for other members of this phylum.     

Yeast oxysterol-binding proteins: sterol transporters or regulators of cell polarization?

Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) are a conserved family of soluble cytoplasmic proteins that can bind sterols, translocate between membrane compartments, and affect sterol trafficking. These properties make ORPs attractive candidates for lipid transfer proteins (LTPs) that directly mediate nonvesicular sterol transfer to the plasma membrane. To test whether yeast ORPs (the Osh proteins) are sterol LTPs, we studied endoplasmic reticulum (ER)-to-plasma membrane (PM) sterol transport in OSH deletion mutants lacking one, several, or all Osh proteins. In conditional OSH mutants, ER-PM ergosterol transport slowed ~20-fold compared with cells expressing a full complement of Osh proteins. Although this initial finding suggested that Osh proteins act as sterol LTPs, the situation is far more complex. Osh proteins have established roles in Rho small GTPase signaling. Osh proteins reinforce cell polarization and they specifically affect the localization of proteins involved in polarized cell growth such as septins, and the GTPases Cdc42p, Rho1p, and Sec4p. In addition, Osh proteins are required for a specific pathway of polarized secretion to sites of membrane growth, suggesting that this is how Osh proteins affect Cdc42p- and Rho1p-dependent polarization. Our findings suggest that Osh proteins integrate sterol trafficking and sterol-dependent cell signaling with the control of cell polarization.     

Integral valorization of two legumes by autohydrolysis and organosolv delignification

Two woody legumes species (Chamaecytisus proliferus L.F. ssp. palmensis and Leucaena diversifolia) were evaluated for integrally exploitation. The raw material was subjected to autohydrolysis under variable operating conditions which provided a liquid phase rich in hemicellulose oligomers and a solid phase that was used to obtain cellulose pulp and paper sheets by using organosolv procedures. The chemical properties of both C. proliferus and L. diversifolia allow their integral exploitation by using a hydrothermal treatment prior to their organosolv pulping with ethanol. The pulp yields obtained are quite high (40.3% for L. diversifolia and 58.2% for C. proliferus), and so are the sugar concentrations in the liquors from the thermal pretreatment (viz. 16.1 and 20.0 g oligomers/l in C. proliferus and L. diversifolia, respectively, and 1.5 and 1.1g xylose/l, respectively, in the two raw materials). The strength-related properties of the paper sheets obtained are acceptable (tensile index 7.76 and 10.77 kN m/kg for C. proliferus and L. diversifolia, respectively and kappa index 31 and 12.5 for C. proliferus and L. diversifolia, respectively), but somewhat worse than those provided by other raw materials such as eucalyptus; however, they can be improved by mechanical refining of the pulp.     

Did genome duplication drive the origin of teleosts? A comparative study of diversification in ray-finned fishes

Background  

One of the main explanations for the stunning diversity of teleost fishes (~29,000 species, nearly half of all vertebrates) is that a fish-specific whole-genome duplication event (FSGD) in the ancestor to teleosts triggered their subsequent radiation. However, one critical assumption of this hypothesis, that diversification rates in teleosts increased soon after the acquisition of a duplicated genome, has never been tested.