Macroevolution and the selective advantages of multicellularity

CRISTIAN A. SOLARI

Durham, North Carolina

Workshop; NESCent Catalysis Meeting: The Evolutionary Origins of Multicellularity; 2013

Nescent Institute, Duke University

Multicellularity originated multiple times independently, from quite different prokaryotic and eukaryotic unicellular ancestors. Attaining more complex stages of multicellularity requires not only adhesion but cell-to-cell communication and a developmental program which would only be present in eukaryotic cells. Recent findings have challenged this definition and requirements for multicellularity as an array of prokaryotes are capable of such behaviors. It remains unclear why eukaryotes have commonly evolved more complex stages of multicellularity whereas prokaryotes have not. The evolution of organisms that form cell clusters or multicellularity seems to be a continuous ongoing process; for example, groups such as the brown algae and the volvocine green algae have appeared recently in geological time. The frequency of the emergence of simple multicellular organisms with no cellular differentiation, or with only a few cell types, suggest that selection pressures that favor cell clustering are continuously present and that genetic and developmental constraints that could hinder this transition are not difficult to overcome. Recent experimental and theoretical evidence supports this hypothesis. The transition to simple small multicellular organisms was accessible to many types of prokaryote and eukaryote unicells, but the transition to higher complexity was only reached by a very few, what we might call “singularity events” in evolutionary history: Fungi, Brown Algae, Embryophytes, Metazoans