Over the long-term, most species will have to adapt to new climate conditions as mean global temperatures are expected to rise by at least 1.5-2.0 °C and ocean pH is expected to decline by at least 0.036-0.042 pH units by 2100. The specific goal of Theme II is to extend the results of Theme I’s focus on the immediate impact of climate change on fitness and acclimatization to understand how our model systems will adapt and evolve to new environmental conditions over long-term exposure.

Our proposed approach uses Long Term Evolutionary Experimental Approaches (LTEE) to explicitly test how symbioses will adapt to climate change stress. We field validate the outcomes of LTEEs by investigating the adaptation of species and populations in the environment, treating them as natural experiments. We have identified ecological and climate gradients in Hawaii (leafhoppers) and Australia (squid and Aiptasia) with close relatives adapted to climate extremes. Finally, we further aim to understand the evolutionary constraints and mechanistic impacts of increased temperatures on host-symbiont co-adaptation, particularly as it relates to protein evolution and function (Theme I). Results from this combined approach will form the development of an adaptability index in Theme III that can be used by land managers to evaluate resource investment.