Acceptable loss: Fitness consequences of salinity-induced cell death in a halotolerant microalga

Environmentally induced reductions in fitness components (survival, fecundity) are generally considered as passive, maladaptive responses to stress. However, there is also mounting evidence for active, programmed forms of environmentally induced cell death in unicellular organisms. While conceptual work has questioned how such programmed cell death (PCD) might be maintained by natural selection, few experimental studies have investigated how PCD influences genetic differences in longer-term fitness across environments. Here, we tracked the population dynamics of two closely related strains of the halotolerant microalga Dunaliella salina, following transfers across salinities. We showed that after a salinity rise, only one of these strains displayed a massive population decline (-69% in one hour), largely attenuated by exposure to a PCD inhibitor. However, this decline was followed by a rapid demographic rebound, characterized by faster growth than the non-declining strain, such that sha..., We tracked the population dynamics of two closely related strains of the halotolerant microalga Dunaliella salina, following transfers across salinities, using a cytometer and/or a spectrometer., Raw data are .fcs files opened in the software Incyte (version 3.2), from where we extracted the population densities. Whole-well fluorescence spectrometer raw data (.RUC files) were opened in the software Mars (version 3.32). All statistical analyses were performed on Rstudio (R version 3.6) using MASS version 7.3.53, tidyverse 1.3.1 and lubridate 1.8.0 packages.