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Ecological scaffolding and the origins of multicellularity
Par Paul B Rainey (New Zealand Institute for Advanced Study and ESPCI)
Le 29 Mars 2017 à 11h00 - Salle de séminaires 5ème étage, Tour 32-33


The evolution of multicellular life from unicellular predecessors marks a Major Evolutionary Transition that underpins the emergence of biological complexity.  Cooperation is central to the process, however the means by which the earliest groups of cells maintained integrity in the face of destructive cheating types is unclear.  One idea posits cheats as a primitive germ line in a life cycle that facilitates group reproduction.  Crucially, it depends upon the emergence of Darwinian properties by ecological scaffolding.  I will describe an on-going experiment in which simple cooperating lineages of bacteria were propagated under a selective regime that rewarded collective-level fecundity.  Collectives reproduced via life cycles that either embraced, or purged, cheating types.  When embraced, the life cycle alternated between phenotypic states.  Selection fostered inception of a developmental switch that underpinned the emergence of collectives whose fitness, during the course of evolution, became decoupled from the fitness of constituent cells.  Such development and decoupling did not occur when groups reproduced via a cheat-purging regime.  I will elaborate on findings that capture key events in the evolution of Darwinian individuality.  If time permits, I will discuss new results arising from continuation of the core experiment with a modification to allow exploration of the evolution of cancer and a potential resolution to Peto’s paradox.