Maureen O’Malley (UMR 5164, Université de Bordeaux)
From endosymbiosis to holobionts: implications for evolutionary theory

Contemporary discoveries of large-organism dependence on microorganisms are often accompanied by a tendency to see these findings as problematizing standard evolutionary theory. Although such thoughts have much older historical antecedents, a common inspiration comes from Lynn Margulis’s ideas in the 1970s about endosymbiosis (one cell living inside another cell) and symbiosis (intimate interactions between organisms). As part of her broader project on the evolutionary implications of symbiosis, Margulis coined the term ‘holobiont’ to refer to a unified entity of symbiont and host. This concept is now applied in controversial ways in microbiome research, which is the molecular study of large organisms (particularly animals) and the microbial communities that inhabit them. When these collectives are called holobionts, the term implies not just a physiological unit but also various senses of an evolving unit. After outlining the issues and problems of such conceptualizations, I will discuss Margulis’s legacy for the study of microbial-host systems and evolutionary research.