Nongenetic inheritance, evolution, and marine microbes

Abstract: I am broadly interested in predicting trait evolution in large microbial populations on seasonal to decadal timescales. In short, I aim to uncover the rules that evolution is playing by for marine microbes under global change well enough that we can use these rules to make informed projections about changes in functional traits. To do this, I use experimental evolution in model systems ranging from computer simulations, to laboratory model organisms (which I think of as “green simulations”), to freshly isolated or mesocosm-enclosed marine microbes. I build general evolutionary theory to use predictors that can be measured for contemporary or historical populations and environments (individual plasticity, transgenerational effects, genetic diversity, historical and projected environments) to understand what determines the extent and direction of trait evolution. I apply this theory through collaborations with oceanographers. Here, I will focus on work in my group that uses two different aspects of nongenetic inheritance to understand and predict trait evolution in aquatic primary producers. 

First, what makes a winner?While projections of future microbial communities assume that taxa that experience environmental change as being positive, there is a paucity of theory and experiments on evolution in improved environments. Here, I discuss how selection shifts over time for populations in high CO₂environments in cases where increases in CO₂are initially beneficial. Based on this, I discuss the idea that, over evolutionary timescales, population growth rates in rich environments are driven by quantity-quality tradeoffs in daughter cell production, and possible implications for predicting primary production in a higher CO₂world. Second, which currents in the ocean are most likely to produce heat-adapted microbes, and where will those microbes accumulate? We addressed this through a series of studies that looked at how heritable epigenetic changes affect adaptation, how different patterns of environmental variation play into this, and what happens when you use these insights to model marine microbes trapped in currents in a warming ocean.