Michelle Afkhami

Assistant Professor of Ecology,
Department of Biology,
University of Miami

Scaling down and scaling up from mutualistic effects on fitness

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A fundamental aspect of mutualisms is that they result in net positive fitness effects for the participating species. To gain a more complete understanding of mutualistic interactions across levels of biological organization, research must scale down to understand the mechanistic basis of these fitness effects and scale up from individual fitness to their consequences for higher order biological processes. In this talk, I will discuss studies from my lab both scaling up and scaling down from the fitness effects of microbial mutualists (e.g., mycorrhizal fungi, rhizobia, fungal endophytes) on plants using a combination of manipulative experiments, next-generation sequencing, selection analysis, and demographic modeling. Specifically, I will explore the molecular basis of interactive effects of multiple mutualistic symbionts on host fitness, their consequences for selection on host plant traits and for fitness alignment between plants and mutualists, and whether microbial effects on individual plant performance influence host population persistence. We document pervasive mutualist-driven genome-wide changes in gene expression that can be linked to synergistic fitness effects of multispecies mutualisms. We also find that mutualist diversity leads to surprising non-additive effects on gene expression and non-additive selection on host traits, fitness alignment between partners depends on the presence of a third party-mutualist, and microbial mutualists are required for population persistence of an endangered plant species.

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