Rapid Adaptation to Road Salts in a Freshwater Microbial Eukaryote

Abstract

Humans are changing habitat for wildlife in myriad ways and for populations to persist, they must adapt to this change. In parts of the world that experience snow and ice, road salts are often used to make driving safer in the winter. Runoff from these roads increases the salinity in nearby bodies of water, which has been shown to have detrimental physiological and ecological effects in freshwater ecosystems; however, the evolutionary consequences of salinization remain unclear. Tetrahymena are microbial eukaryotes that live in freshwater habitats and serve as an important link in the microbial food loop. In this study, we test how T. thermophila can evolve in response to increasing concentrations of road salts in their environment. Using experimental evolution, we found that T. thermophila adapt quickly to survive and grow better in increasing salinity. However, populations adapted to the highest salt concentrations experience fitness tradeoffs in salt-free environments. These results demonstrate the rapidity with which microbial populations can respond to anthropogenic changes to their environment, yet highlight the potential costs associated with this adaptation.