The Rise of Complexity: Pavilion Lake Microbialites Suggest a Pathway toward Macroorganismic Communities

We propose that freshwater calcite microbialites may represent an alternative trajectory toward a community ecology aggregate that achieves some of the biological functions perfected by macroorganismic communities. A distinctive assemblage of microbialites studied at Pavilion Lake, British Columbia, Canada, could be a prototypical example of this transitional stage of biological organization. The community composition, and, significantly, the identification of quorum sensing molecules in these microbialites, is consistent with the view that they represent an independent and incomplete trajectory toward colonial functionality. This, in turn, supports the general view that biological complexity has evolved independently, under a variety of conditions and on a number of occasions in the history of life. Because these microbialites have formed at temperatures between 0 and 10 o C, they provide an example of incipient macroorganismic communities emerging in cold, freshwater environments, analogous to most of the other planetary bodies of our Solar System.