Final Report Summary - EVOCHANGE (Complex adaptation in photosynthetic microbes evolving in response to global change.) The ERC project “Evochange” focussed on how photosynthetic microbes, specifically unicellular algae, evolve in complex environments. Much of our understanding of the way evolution works is based on experiments and theory where one environmental driver is overwhelmingly important, which is the case with, for example, the evolution of antibiotic resistance, where bacteria must evolve to survive in an environment that is made toxic to them by a single substance. However, in many cases, for example in aquatic systems, many aspects of the environment change at once – freshwater and marine systems will heat, experience changes in nutrients, change in pH, for example, all at once. We evolved populations of a single species of microalgae in 96 different multidriver environments with between 1 and 8 drivers to learn how evolution to one driver differs from evolution to many drivers. We learned that populations in multidriver environments have a higher chance of going extinct, but if they survive, they adapt more than populations in single driver environments, and that most of the evolutionary response was explained by the presence or absence of a few dominant drivers. This shows that studies using simplified environments and focussed on dominant drivers are extremely useful for understanding evolutionary responses to environmental change, and is relevant to understanding how the base of aquatic food webs responds to global change. We are now investigating the genomic basis for adaptation in the simple vs. complex environments to understand how the phenotypic (organismal) and genetic changes are related. Interestingly, we found that many of the drastic changes in traits (changes in cell size or pigmentation) that the organisms underwent when they were first exposed to the multidriver environments reversed over a few hundred generations (months). This is important, as it means that short-term studies may overestimate the amount of change in organisms over longer periods of time. My group is currently investigating ways of understanding which traits evolve to change and which traits evolve to revert in new environments. This will be a key part of predicting how microbes act in future environments. A second project focused on how being able to produce and transmit epigenetic information between generations affects the ability to evolve in the same photosynthetic alga. Epigenetic changes can affect gene expression, and thus the characters of an organism, but do not change the underlying genetic sequence. Previous work by my group, and continued work during my ERC grant used computer simulations to show that this epigenetic information could affect evolution over hundreds or thousands of generations, but there was no test of this in real organisms. During the ERC grant, we evolved microalgae in the laboratory for hundreds of generations and manipulated the extent to which they could use epigenetic changes. We found that being able to produce and transmit epigenetic information allowed populations to adapt more, demonstrating that epigenetic changes affect evolutionary processes even over timescales where genetic mutations can occur.
