This project has been completed.
We have developed a general theory for ETIs and propose testing this theory using the volvocine green algae as an experimental model. Due to the morphological diversity in these algae, we can investigate the genetic basis for the evolution of key phenotypes spanning the unicellular to multicellular ETI. In no other experimental model is such an undertaking feasible. Germ and somatic cells correspond to the two major fitness components (reproduction and viability); their evolution is a critical part of explaining how and why a cell group sometimes evolves into a new evolutionary individual. We aim to understand the evolution of the regA gene family, which plays a central role in germ soma division of labor (G-S DOL) in the volvocine algae. We will determine the functions of these genes and test whether unicellular-level life history trade-offs drove G-S DOL at the multicellular level, as predicted by our theory. We will use a phenotypic screen for soma-less mutants to uncover other genes involved in G-S DOL. Genomic approaches to the evolution of multicellularity allow investigation into the origin and complexity of gene families in terms of their role in phenotypes associated with the ETI. With this understanding of genotype and multicellularity, we will address the evolution of allocation to germ and soma in a range of environments (i.e., the genotype-phenotype map for GS-DOL) using measurements of cell type allocation in diverse species, artificial selection experiments, and a study of the suppression of reproduction in response to stress. We will subsequently explore the evolution of the genotype-phenotype map for germ-soma allocation using mathematical modeling.