Dataset: Phosphorus uptake model
Deployment: X0619

As described in Lomas et al. 2014, a model that considers interactions between ecology and evolution is used with the aim of replicating the cruise data contained in this project’s database. The model consists of an ecological model that combines the classic Droop model for cell growth with a mechanistic representation of phytoplankton’s ability to regulate the number of proteins used for nutrient uptake, positively correlated with maximum uptake rate. Size is chosen as adaptive trait, as size is linked to all the key traits in this trait-based representation. 

For each species to be replicated, a specific allometry for half-saturation constant and maximum growth rate is chosen. Thus, each species (or, more generally, ecotype or functional group) is characterized by fixed parameters for these two allometries (see model database). Different chemostat conditions (i.e. dilution rates) are used to simulate different locations.

For each location, an initial ecotype reproduces, and mutations are allowed. As time goes by, more and more mutants co-exist temporarily, with continuous alternation in dominance and extinctions, and ecological responses (plasticity, i.e. changes in the number of uptake proteins) and adaptive responses (i.e. mutations) occurring simultaneously. After a transient, the population finds a strain that dominates over any other possible strain, or in other words, the system reaches the evolutionary stable strategy for size. When that happens, the simulation stops, and the uptake-related observables of that strain are selected as potential representative of that location; a series of replicates per location is necessary, due to the stochastic nature of the adaptive process (see ecolutionary-simulation entries in the model database).  Use uptake rate for each location and phosphate availability in the database to replicate Fig.4 in main text of Lomas et al 2014.

For the kinetic data (and Fig.S5 in the mentioned paper), a representative size is chosen per species that is to be replicated. Then, different dilution rates allow for increases in stationary nutrient concentrations.