Threats of land use to the global diversity of vascular plants

Aim

Land use is a main driver of biodiversity loss worldwide. However, quantifying its effects on global plant diversity remains a challenge due to the limited availability of data on the distributions of vascular plant species and their responses to land use. Here, we estimated the global extinction threat of land use to vascular plant species based on a novel integration of an ecoregion-level species-area model and the relative endemism richness of the ecoregions.

Location

Global.

Methods

First, we assessed ecoregion-level extinction threats using a countryside species–area relationship model based on responses of local plant richness to land use types and intensities and a high-resolution global land use map. Next, we estimated global species extinction threat by multiplying the relative endemism richness of each ecoregion with the ecoregion-level extinction threats.

Results

Our results indicate that 11% of vascular plant species are threatened with global extinction. We found the largest extinction threats in the Neotropic and Palearctic realms, mainly due to cropland of minimal and high intensity, respectively.

Main Conclusions

Our novel integration of the countryside species–area relationship and the relative endemism richness allows for the identification of hotspots of global extinction threat, as well as the contribution of specific land use types and intensities to this threat. Our findings inform where the development of measures to protect or restore plant diversity globally are most needed.     

Interaction matters: Bottom-up driver interdependencies alter the projected response of phytoplankton communities to climate change

Phytoplankton growth is controlled by multiple environmental drivers, which are all modified by climate change. While numerous experimental studies identify interactive effects between drivers, large-scale ocean biogeochemistry models mostly account for growth responses to each driver separately and leave the results of these experimental multiple-driver studies largely unused. Here, we amend phytoplankton growth functions in a biogeochemical model by dual-driver interactions (CO₂ and temperature, CO₂ and light), based on data of a published meta-analysis on multiple-driver laboratory experiments. The effect of this parametrization on phytoplankton biomass and community composition is tested using present-day and future high-emission (SSP5-8.5) climate forcing. While the projected decrease in future total global phytoplankton biomass in simulations with driver interactions is similar to that in control simulations without driver interactions (5%–6%), interactive driver effects are group-specific. Globally, diatom biomass decreases more with interactive effects compared with the control simulation (−8.1% with interactions vs. no change without interactions). Small-phytoplankton biomass, by contrast, decreases less with on-going climate change when the model accounts for driver interactions (−5.0% vs. −9.0%). The response of global coccolithophore biomass to future climate conditions is even reversed when interactions are considered (+33.2% instead of −10.8%). Regionally, the largest difference in the future phytoplankton community composition between the simulations with and without driver interactions is detected in the Southern Ocean, where diatom biomass decreases (−7.5%) instead of increases (+14.5%), raising the share of small phytoplankton and coccolithophores of total phytoplankton biomass. Hence, interactive effects impact the phytoplankton community structure and related biogeochemical fluxes in a future ocean. Our approach is a first step to integrate the mechanistic understanding of interacting driver effects on phytoplankton growth gained by numerous laboratory experiments into a global ocean biogeochemistry model, aiming toward more realistic future projections of phytoplankton biomass and community composition.     

Development of a monoclonal antibody for ELISA of CYP1A in primary cultures of rainbow trout Oncorhynchus mykiss hepatocytes

Induction of cytochrome P4501A CYP1A in cultured cells can be used to determine the induction potencies of xenobiotics or complex environmental samples. This report describes the development of an enzyme linked immunosorbent assay ELISA for measurement of CYP1A expression in primary cultures of rainbow trout Oncorhynchus mykiss hepatocytes. Juvenile rainbow trout were injected with naphthoflavone BNF 25 mg kg-1 body weight to induce the synthesis of CYP1A. The CYP1A isoenzyme was purified, characterized by immunological cross reactivity and N terminal sequencing and used to prepare a monoclonal antibody in Balb C mice. The specificity of the antibody for CYP1A was proved by Western blotting of samples from control and BNF injected fish. Two ELISA methods, a direct and a competitive one, were evaluated, with both methods being of comparable sensitivity. Rainbow trout hepatocytes, maintained as monolayers in serum free, chemically defined medium, were exposed to naphthoflavone, and the induction response was measured both by 7 ethoxyresorufin O deethylase EROD activity and the direct ELISA method. Comparison between EROD activity and immunodetectable CYP1A protein can provide information on the catalytic efficiency of CYP1A.     

Recent evolutionary history of American Onchocerca volvulus, based on analysis of a tandemly repeated DNA sequence family

Polymerase chain reaction (PCR) products were characterized for a repeated sequence family (designated "O-150") of the human filarial parasite Onchocerca volvulus. In phylogenetic inferences, the O-150 sequences clustered into closely related groups, suggesting that concerted evolution maintains sequence homology in this family. Using a novel mathematical model based on a nested application of an analysis of variance, we demonstrated that African rainforest and savannah strain parasite populations are significantly different. In contrast, parasites collected in the New World are indistinguishable from African savannah strains of O. volvulus. This finding supports the hypothesis that onchocerciasis was recently introduced into the New World, possibly as a result of the slave trade.      

Assessing horizontal transfer of nifHDK genes in eubacteria: nucleotide sequence of nifK from Frankia strain HFPCcI3

The structural genes for nitrogenase, nifK, nifD, and nifH, are crucial for nitrogen fixation. Previous phylogenetic analysis of the amino acid sequence of nifH suggested that this gene had been horizontally transferred from a proteobacterium to the gram-positive/cyanobacterial clade, although the confounding effects of paralogous comparisons made interpretation of the data difficult. An additional test of nif gene horizontal transfer using nifD was made, but the NifD phylogeny lacked resolution. Here nif gene phylogeny is addressed with a phylogenetic analysis of a third and longer nif gene, nifK. As part of the study, the nifK gene of the key taxon Frankia was sequenced. Parsimony and some distance analyses of the nifK amino acid sequences provide support for vertical descent of nifK, but other distance trees provide support for the lateral transfer of the gene. Bootstrap support was found for both hypotheses in all trees; the nifK data do not definitively favor one or the other hypothesis. A parsimony analysis of NifH provides support for horizontal transfer in accord with previous reports, although bootstrap analysis also shows some support for vertical descent of the orthologous nifH genes. A wider sampling of taxa and more sophisticated methods of phylogenetic inference are needed to understand the evolution of nif genes. The nif genes may also be powerful phylogenetic tools. If nifK evolved by vertical descent, it provides strong evidence that the cyanobacteria and proteobacteria are sister groups to the exclusion of the firmicutes, whereas 16S rRNA sequences are unable to resolve the relationships of these three major eubacterial lineages.      

Verzeichniss der im Golfe von Triest gesammelten Meeralgen

Ohne Zusammenfassung     

Iron and phosphate uptake in epiphytic and saxicolous lichens differing in their pH requirements

The hypothesis is tested that pH-dependent Fe and P uptake influence the preference of epiphytic and saxicolous lichens for certain ranges of ambient pH. Five species from acidic substrata (Hypogymnia physodes, Parmeliopsis ambigua, and Platismatia glauca) or covering the range from weakly acidic to alkaline substrata (Lecanora muralis and Phaeophyscia orbicularis) were exposed to solutions of FeCl₂, FeCl₃, or KH₂PO₄ at pH 3 and 8 in the laboratory. Avoidance of alkaline substrata is explainable by low Fe³⁺ uptake at pH 8 in the case of H. physodes and the inability for net P uptake and membrane damage in P. ambigua at this pH. Preference for acidic substrata in Pl. glauca, however, is neither related to Fe nor P uptake. Efficient Fe³⁺ and P uptake at pH 8 explains the tolerance of L. muralis and Ph. orbicularis to alkaline conditions. Intracellular accumulation of Fe²⁺ in probably toxic amounts at pH 3 in Ph. orbicularis is correlated with the absence of this lichen from strongly acidic substrata. Avoidance of acidic sites by L. muralis is not attributable to Fe or P uptake. In summary, the results suggest that pH-dependent Fe and P uptake characteristics are involved in the determination of pH preferences of epiphytic and saxicolous lichens, but are not the only relevant factor.     

Surface hydrophobicity causes SO2 tolerance in lichens

BACKGROUND AND AIMS: The superhydrophobicity of the thallus surface in one of the most SO(2)-tolerant lichen species, Lecanora conizaeoides, suggests that surface hydrophobicity could be a general feature of lichen symbioses controlling their tolerance to SO(2). The study described here tests this hypothesis. METHODS: Water droplets of the size of a raindrop were placed on the surface of air-dry thalli in 50 lichen species of known SO(2) tolerance and contact angles were measured to quantify hydrophobicity. KEY RESULTS: The wettability of lichen thalli ranges from strongly hydrophobic to strongly hydrophilic. SO(2) tolerance of the studied lichen species increased with increasing hydrophobicity of the thallus surface. Extraction of extracellular lichen secondary metabolites with acetone reduced, but did not abolish the hydrophobicity of lichen thalli. CONCLUSIONS: Surface hydrophobicity is the main factor controlling SO(2) tolerance in lichens. It presumably originally evolved as an adaptation to wet habitats preventing the depression of net photosynthesis due to supersaturation of the thallus with water. Hydrophilicity of lichen thalli is an adaptation to dry or humid, but not directly rain-exposed habitats. The crucial role of surface hydrophobicity in SO(2) also explains why many markedly SO(2)-tolerant species are additionally tolerant to other (chemically unrelated) toxic substances including heavy metals.     

[3-cis-3,5-Dimethyl-(1-piperazinyl)alkyl]-bis-(4′-fluorophenyl)amine analogues as novel probes for the dopamine transporter

In a continuing effort to identify novel probes with which to study the dopamine transporter (DAT), we discovered that the σ receptor antagonist, rimcazole, binds with moderate affinity (K_i=224 nM) to the DAT. The results from previous SAR studies suggested that substitution of the carbazole ring system of rimcazole with bis-(4′-fluorophenyl)amine might improve binding affinity and selectivity for the DAT. Thus, a novel series of [3-cis-3,5-dimethyl-(1-piperazinyl)alkyl]bis-(4′-fluorophenyl)amines were synthesized. The most potent compound in this series (9b) displaced [³H]WIN 35,428 binding in rat caudate-putamen (K_i=17.6 nM) with comparable affinity to GBR 12909. Despite high-affinity binding at DAT, and structural similarity to GBR 12909, preliminary studies suggest 9b behaves more like rimcazole than GBR 12909 and does not demonstrate cocaine-like psychostimulant behavior in mice.     

CEACAMs: their role in physiology and pathophysiology

Carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) belong to a group of mammalian immunoglobulin-related glycoproteins. They are involved in cell-cell recognition and modulate cellular processes that range from the shaping of tissue architecture and neovascularization to the regulation of insulin homeostasis and T-cell proliferation. CEACAMs have also been identified as receptors for host-specific viruses and bacteria in mice and humans, respectively, making these proteins an interesting example of pathogen-host co-evolution. Forward and reverse genetics in the mouse now provide powerful novel models to elucidate the action of CEACAM family members in vivo.