title: A model for the origin of group reproduction during the evolutionary transition to multicellularity.
abstract: During the evolution of multicellular organisms, the unit of selection and adaptation, the individual, changes from the single cell to the multicellular group. To become individuals, groups must evolve a group life cycle in which groups reproduce other groups. Investigations into the origin of group reproduction have faced a chicken-and-egg problem: traits related to reproduction at the group level often appear both to be a result of and a prerequisite for natural selection at the group level. With a focus on volvocine algae, we model the basic elements of the cell cycle and show how group reproduction can emerge through the coevolution of a life-history trait with a trait underpinning cell cycle change. Our model explains how events in the cell cycle become reordered to create a group life cycle through continuous change in the cell cycle trait, but only if the cell cycle trait can coevolve with the life-history trait. Explaining the origin of group reproduction helps us understand one of life's most familiar, yet fundamental, aspects-its hierarchical structure.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, 85721 AZ, USA.
authors.forename: Odile
authors.initials: O
authors.lastname: Maliet
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, 85721 AZ, USA.
authors.forename: Deborah E
authors.initials: DE
authors.lastname: Shelton
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, 85721 AZ, USA michod@u.arizona.edu.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Michod
mesh_terms: D005075:Biological Evolution; D008954:Models, Biological; D012098:Reproduction; D012641:Selection, Genetic; D016823:Volvocida / Q000502:physiology*
keywords: cell cycle; coevolution; group reproduction; individuality; multicellularity; volvocine algae