Life cycles, fitness decoupling and the evolution of multicellularity.
Cooperation is central to the emergence of multicellular life; however, the means by which the earliest collectives (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 collective reproduction. Here we describe an experiment in which simple cooperating lineages of bacteria were propagated under a selective regime that rewarded collective-level persistence. 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. Our findings capture key events in the evolution of Darwinian individuality during the transition from single cells to multicellularity.
New Zealand Institute for Advanced Study and Allan Wilson Centre for Molecular Ecology &Evolution, Massey University, Auckland 0745, New Zealand.
Katrin
K
Hammerschmidt
New Zealand Institute for Advanced Study and Allan Wilson Centre for Molecular Ecology &Evolution, Massey University, Auckland 0745, New Zealand.
Caroline J
CJ
Rose
Department of Biology and BEACON Center for the Study of Evolution in Action, University of Washington, Seattle, Washington 98195, USA.
Benjamin
B
Kerr
1] New Zealand Institute for Advanced Study and Allan Wilson Centre for Molecular Ecology &Evolution, Massey University, Auckland 0745, New Zealand [2] Max Planck Institute for Evolutionary Biology, Plön 24306, Germany.
Paul B
PB
Rainey
D005075:Biological Evolution; D002468:Cell Physiological Phenomena; D056084:Genetic Fitness; D008018:Life Cycle Stages; D008954:Models, Biological; D010641:Phenotype; D011551:Pseudomonas fluorescens / Q000166:cytology* / Q000254:growth & development / Q000502:physiology*