Adaptation to complex environments reveals pervasive trade-offs and genomic targets with large pleiotropic effects

Abstract

AbstractPopulations in nature rarely adapt to a single stress at a time. Various biotic and abiotic factors come together to produce a complex environment to which populations must adapt. How populations adapt to multiple stressors simultaneously, and how trade-offs evolve between these stressors has been of interest to evolutionary biologists for decades. But natural populations often present logistical challenges to understanding the dynamics of evolution and isolating the genetic basis of adaptation. Here we use methods in experimental evolution to test how adaptation proceeds in the presence of co-occurring stressors, and to quantify the evolution of trade-offs between stressors in a complex environment. We adapted populations of the yeast Saccharomyces cerevisiae to a full-factorial combination of four stressors over the course of 15 serial transfers. We observed rapid increases in fitness paired with the accumulation of mutations related to specific stressors. Trade-offs evolved rapidly and dynamics of trade-off evolution varied between stressors, likely due to the inherent physiological and genetic basis of resistance to each stressor. The degree of parallelism at the phenotypic level showed evidence of being modified by the degree of environmental complexity, while parallelism at the genic level was apparent between populations which shared stressors.