Lobaria pulmonaria, or tree lungwort, showed surprising genetic diversity in boreal rainforest fragments in Norway. The word rainforest usually conjures up visions of brightly coloured birds and hyperactive monkeys swooping through a thick green canopy of leaves, vines and flowers. But rainforests are also found closer to the poles, in the northern or boreal region where temperatures are far cooler. And while there are no monkeys swinging through the trees here, these forests are every bit as endangered as their southern cousins, and highly diverse – if you know where to look.

Researchers from UC San Diego, the University of California Los Angeles and Indiana University report having found, for the first time, that atrial fibrillation or irregular heart rhythms is caused by small electrical sources within the heart, in the form of electrical spinning tops ("rotors") or focal beats. Importantly, they found a way of detecting these key sources, then precisely targeting them for therapy that can shut them down in minutes with long lasting results.