Aim: Viviparity has evolved more times in squamates than in any other vertebrate group. Therefore, squamates offer an excellent model system to study the patterns, drivers, and implications of reproductive mode evolution. Based on current species distributions we examined three selective forces hypothesized to drive squamate viviparity evolution: (1) cold climate, (2) variable climate, and (3) hypoxic conditions, and tested whether viviparity is associated with larger body size. Location: Global. Time period: present day. Taxon:...