Climatic drivers of hemispheric asymmetry in global patterns of ant species richness

Although many taxa show a latitudinal gradient in richness, the relationship between latitude and species richness is often asymmetrical between the northern and southern hemispheres. Here we examine the latitudinal pattern of species richness across 1003 local ant assemblages. We find latitudinal asymmetry, with southern hemisphere sites being more diverse than northern hemisphere sites. Most of this asymmetry could be explained statistically by differences in contemporary climate. Local ant species richness was positively associated with temperature, but negatively (although weakly) associated with temperature range and precipitation. After contemporary climate was accounted for, a modest difference in diversity between hemispheres persisted, suggesting that factors other than contemporary climate contributed to the hemispherical asymmetry. The most parsimonious explanation for this remaining asymmetry is that greater climate change since the Eocene in the northern than in the southern hemisphere has led to more extinctions in the northern hemisphere with consequent effects on local ant species richness. © 2009 Blackwell Publishing Ltd/CNRS.Peer Reviewe

Negative spill-over effects of agricultural practices on plant species conservation in nature reserves

Nature reserves are one of the most important instruments for biodiversity protection and to limit regional species extinctions. However, these functions can only be fulfilled if environmental influences from the surroundings, such as agrochemical inputs do not negatively affect the protected habitats.Here, we compare the effectiveness of conservation measures under the influence of yield-optimized cultivation in Germany using vegetation analyses of transects from the edge to the core of protected areas at 21 sites. By analysing nitrogen and phosphate deposition, herbicide number and concentration in soil and vegetation as well as Ellenberg indicator values of plant communities as a function of the distance from the field margin at each site, we aimed at assessing the impact of these stressors in different environmental settings.The results indicate strong chemical edge effects and negative influences for plant communities resulting from increased nutrient input and amounts of herbicide residues closer to the edge of the agricultural fields. Concordantly, the number of endangered plants species decreased with increasing proximity to the field edge. The strong influence of yield-optimized cultivation on the edges of nature reserves which decrease with distance show that nature protection needs effective buffer zones surrounding conservation areas, especially if nature reserves are only small and narrow. To prevent spill-over effects the application of fertilizer and herbicides on croplands adjacent to conservation areas has to be reduced. This could be achieved most effectively through organic farming and targeted agricultural subsidies