Evidence against hydrogen-based microbial ecosystems in basalt aquifers

It has been proposed that hydrogen produced from basalt-ground-water interactions may serve as an energy source that supports the existence of microorganisms in the deep subsurface on Earth and possibly on other planets. However, experiments demonstrated that hydrogen is not produced from basalt at an environmentally relevant, alkaline pH. Small amounts of hydrogen were produced at a lower pH in laboratory incubations, but even this hydrogen production was transitory. Furthermore, geochemical considerations suggest that previously reported rates of hydrogen production cannot be sustained over geologically significant time frames. These findings indicate that hydrogen production from basalt-ground-water interactions may not support microbial metabolism in the subsurface.     

A decision-tree to optimise control measures during the early stage of a foot-and-mouth disease epidemic

A decision-tree was developed to support decision making on control measures during the first days after the declaration of an outbreak of foot-and-mouth disease (FMD). The objective of the tree was to minimise direct costs and export losses of FMD epidemics under several scenarios based on livestock and herd density in the outbreak region, the possibility of airborne spread, and the time between first infection and first detection. The starting point of the tree was an epidemiological model based on a deterministic susceptible–infectious–recovered approach. The effect of four control strategies on FMD dynamics was modelled. In addition to the standard control strategy of stamping out and culling of high-risk contact herds, strategies involving ring culling within 1 km of an infected herd, ring-vaccination within 1 km of an infected herd, and ring-vaccination within 3 km of an infected herd were assessed. An economic model converted outbreak and control effects of farming and processing operations into estimates of direct costs and export losses. Ring-vaccination is the economically optimal control strategy for densely populated livestock areas whereas ring culling is the economically optimal control strategy for sparsely populated livestock areas.     

Evaluation of the Rate of Evolution in Natural Populations of Guppies (Poecilia reticulata)

Natural populations of guppies were subjected to an episode of directional selection that mimicked natural processes. The resulting rate of evolution of age and size at maturity was similar to rates typically obtained for traits subjected to artificial selection in laboratory settings and up to seven orders of magnitude greater than rates inferred from the paleontological record. Male traits evolved more rapidly than female traits largely because males had more genetic variation upon which natural selection could act. These results are considered in light of the ongoing debate about the importance of natural selection versus other processes in the paleontological record of evolution.