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Numerous studies have shown reduced performance in plants that are surrounded by neighbours of the same species1,2, a phenomenon known as conspecific negative density dependence (CNDD)3. A long-held ecological hypothesis posits that CNDD is more pronounced in tropical than in temperate forests4,5, which increases community stabilization, species coexistence and the diversity of local tree species6,7. Previous analyses supporting such a latitudinal gradient in CNDD8,9have suffered from methodological limitations related to the use of static data10–12. Here we present a comprehensive assessment of latitudinal CNDD patterns using dynamic mortality data to estimate species-site-specific CNDD across 23 sites. Averaged across species, we found that stabilizing CNDD was present at all except one site, but that average stabilizing CNDD was not stronger toward the tropics. However, in tropical tree communities, rare and intermediate abundant species experienced stronger stabilizing CNDD than did common species. This pattern was absent in temperate forests, which suggests that CNDD influences species abundances more strongly in tropical forests than it does in temperate ones13. We also found that interspecific variation in CNDD, which might attenuate its stabilizing effect on species diversity14,15, was high but not significantly different across latitudes. Although the consequences of these patterns for latitudinal diversity gradients are difficult to evaluate, we speculate that a more effective regulation of population abundances could translate into greater stabilization of tropical tree communities and thus contribute to the high local diversity of tropical forests.

Food and clean water are provided for free in refugee camps, so why are refugees expected to provide public sanitation facilities themselves? Refugees often have to contribute labour and materials in constructing these facilities just at a time when they are most exhausted or traumatized. Marco Visser argues that sanitation should be provided free in these situations.

The ability of medical organizations to respond quickly and effectively to outbreaks of Ebola has evolved significantly in recent years. Medecins Sans Frontieres (MSF) has responded to several epidemics of Ebola across Africa, and was called to stem an outbreak in 2003 in heavily forested Cuvette Ouest in the Republic of Congo (ROC). The isolation measures taken and an overview of the latest developments are presented.