Climate change is now considered to be the greatest threat to biodiversity and ecological networks, but its impacts on the bacterial communities associated with plants and animals remain largely unknown. Here, we studied the consequences of climate warming on the gut bacterial communities of an ectotherm, the common lizard (Zootoca vivipara), using a semi-natural experimental approach. We found that 2-3 °C warmer climates cause a 34% loss of populations' microbiota diversity, with possible negative consequences for host survival.

Ecology and evolution unfold in spatially structured communities, where dispersal links dynamics across scales. Because dispersal is multicausal, identifying general drivers remains challenging. In a coordinated distributed experiment spanning organisms from protozoa to vertebrates, we tested whether two fundamental determinants of local dynamics, top-down and bottom-up control, generally explain active dispersal. We show that both factors consistently increased emigration rates and use metacommunity modelling to highlight consequences on local and regional dynamics.