Speaker
Description
The evolution of multicellularity created new ecosystems, fundamentally changing Earth’s ecology (Szathmáry & Smith, 1995). While multicellularity has evolved numerous times in diverse lineages (Knoll et al. 2011), no prior work has directly examined the impact of this major evolutionary transition on multicellular diversity. Using long-term experimental evolution, we show that the evolution of multicellularity drove niche partitioning and the adaptive divergence of two distinct, specialized lineages from a single multicellular ancestor. Over 715 daily transfers, snowflake yeast were subject to selection for rapid growth followed by selection for larger organismal size (Ratcliff et al. 2012). Both small and large-bodied lineages evolved from a monomorphic ancestor, coexisting for over 3,000 generations. These small and large-bodied snowflake yeast lineages have specialized on divergent aspects of a trade-off between growth rate and survival, mirroring classical predictions from ecological theory. Through theoretical modeling and experimentation, we demonstrate that coexistence is maintained by a trade-off between organismal size and competitiveness for dissolved oxygen. Taken together, this work shows how the evolution of a new level of biological complexity can rapidly drive adaptive diversification and the expansion of a novel ecosystem, one of the most historically-impactful emergent properties of this evolutionary transition.
