Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

The effect of simulated gastric environments on the anti-Helicobacter activity of garlic oil.

AIMS: To investigate the effects of simulated gastric conditions upon the anti-Helicobacter pylori effects of garlic oil (GO). METHODS AND RESULTS: Time course viability experiments assessed the anti-H. pylori activity of GO (16 and 32 microg ml(-1)) in simulated gastric environments. Rapid anti-H. pylori action of GO was observed in artificial gastric juice. Mucus (1-5%) was strongly protective of H. pylori both alone and in the presence of GO, but its protective effect was antagonized by GO. Peptone (5-15 g l(-1)) caused a dose-dependent reduction in the anti-H. pylori activity of GO. Rapeseed oil (5.7-17 g l(-1)) greatly diminished the anti-H. pylori activity of GO. Dextrin (44 and 133 g l(-1)) exhibited direct anti-H. pylori effects and added to those of GO. Simulated meal mixtures decreased but did not eliminate the anti-H. pylori activity of 32 mug ml(-1) GO. CONCLUSIONS: The anti-H. pylori activity of GO was noticeably affected by food materials and mucin. However, substantial activity remained under simulated gastric conditions. Further investigation of the therapeutic potential of GO against H. pylori is therefore warranted. SIGNIFICANCE AND IMPACT OF THE STUDY: Garlic oil may be useful as an alternative treatment against H. pylori, a major cause of gastrointestinal infections in humans