Data from: De novo origins of multicellularity in response to predation

The transition from unicellular to multicellular life was one of a few
major events in the history of life that created new opportunities for
more complex biological systems to evolve. Predation is hypothesized as
one selective pressure that may have driven the evolution of
multicellularity. Here we show that de novo origins of simple
multicellularity can evolve in response to predation. We subjected
outcrossed populations of the unicellular green alga Chlamydomonas
reinhardtii to selection by the filter-feeding predator Paramecium
tetraurelia. Two of five experimental populations evolved multicellular
structures not observed in unselected control populations within ~750
asexual generations. Considerable variation exists in the evolved
multicellular life cycles, with both cell number and propagule size
varying among isolates. Survival assays show that evolved multicellular
traits provide effective protection against predation. These results
support the hypothesis that selection imposed by predators may have played
a role in some origins of multicellularity.