Much is still to be learned about the molecular basis of mental disorders. The identification of a signalling pathway that is affected in schizophrenia, and which thus provides potential therapeutic targets, is a welcome advance

Nested, or hierarchically arranged, mutualisms allow ecosystems to support more species than they otherwise would. But in this and other contexts, the growth of such networks could carry a heavy price

John Maddox, who died on 12 April, was editor of Nature during 1966–73 and 1980–95. He transformed the journal from a collegially amateurish publication into one that was challenging and professional in its assessment of science and in its journalistic reportage