How much of the diversity in marine plankton communities is ecologically meaningful? Modern techniques have revealed a spectacular amount of genetic diversity at the base of marine ecosystems, but it remains unclear how much of this translates to measurable differences in ecological function. As a first exploratory step towards addressing this question, I will present results from a novel matrix-based 3D ocean-ecosystem model that is unique in accounting for the evolution of both functional phenotypic traits and ecologically neutral bioinformatic diversity (i.e. genetic drift).
The model accounts for the simultaneous evolution of plankton in 2 trait dimensions. We take the modern ocean and its large-scale circulation as a starting point, and seed the ocean surface with a small phytoplankton at a single location. We then let the co-evolution of global nutrient cycling together with evolution in size and degree of mixotrophy, proceed for several millennia, until a new stable global community emerges. Our results show that while the ecosystem is broadly structured by functional traits, in line with established theory and observational constraints, the ocean circulation additionally gives rise to regional “islands” of functionally identical, yet genetically diverse, lineages. I will relate these findings back to bioinformatic assessments of planktonic diversity, on order to discuss their relationship with functional traits and ecosystem function.