Host-associated bacteria (both pathogens and mutualists) are found across the tree of life and can have crucial influences on the performance of their hosts. Despite the clear importance of such intimate host-microbe associations for individual hosts, it remains a mystery how and when these associations establish, and how these may impact host evolution and adaptation. As an evolutionary ecologist with broad interests in life history evolution and population ecology, Marjolein Bruijning blends theory and empirical research to study the evolutionary dynamics of host-microbe systems. She uses Daphnia (water fleas) as an experimental study system, for instance investigating how Daphnia interactions with a common parasite shape host-parasite coevolutionary trajectories. Her research highlights how building links between individual- to population-level processes offers a mechanistic understanding into the drivers of coevolutionary responses, paving the way to unravel the origin, function and evolution of the vast ubiquity of the host-microbe associations surrounding us.
