Temperature and Symbiodinium physiology affect the establishment and development of symbiosis in corals

Symbiotic associations are ubiquitous in nature. In fact, all eukaryotic species harbour microbial symbionts that are essential for their health. Often overlooked, symbiosis is an important factor when predicting how organisms might respond to climate change. Some associations are so tight-knit that rapid changes in the environment can lead to extinction of one or both partners. Alternatively, the ability to switch to more stress-tolerant partners can allow for rapid adjustment to environmental change, such as increases in host range size. Here, we outline a mechanism by which symbiotic species that acquire their symbionts anew each generation might adapt to global warming via transgenerational, environmentally mediated changes in host-symbiont partnerships. At temperatures approximating climate change conditions at the end of the century, the larvae of 2 common scleractinian corals established symbiosis with a novel and more thermo-tolerant symbiont. Conversely, the establishment of symbiosis with heat-sensitive symbionts was greatly reduced. Transgenerational change in symbionts is a mechanism by which organisms that engage in flexible mutualistic relationships can rapidly adjust to a changing climate.