Cover image: Spain's Cantabrian Mountains host two small, isolated populations of European brown bears (Ursus arctos), thought to be the last remnants of the original stock that populated Europe during the Pleistocene. However, analysis of ancient DNA from a sequence of bear remains shows that the Iberian population has historically been a “fluid evolutionary unit,” subject to gene flow from other regions. See the article by Valdiosera et al. on pages 5123–5128. Image courtesy of José María Díaz Formenti (freelance photographer).