Temperature as a driver of phage community ecology and evolution

Thesis

Thermal change has a profound impact on species fitness, ecological interactions, and evolutionary dynamics. Parasite communities are particularly sensitive to thermal change due to their complex life cycles, strong competition for host resources, and dependence on host thermal responses. Previous literature assessing the effects of thermal change on parasites has primarily focused on the relationship between parasites and their hosts. However, hosts in natural populations are frequently co-infected by a diversity of parasites which interact to reduce host fitness and increase host mortality rates. Despite the importance of parasite communities in animal and plant health, the extent to which thermal change alters parasite community dynamics, composition, and diversity remains unclear. In this thesis, I assessed the impact of temperature on parasite community ecology and evolution using a microbial host-parasite system consisting of the bacterium Pseudomonas aeruginosa (host) and three lytic bacteriophages (parasite). Firstly, I conducted an experimental study looking at the impact of temperature on growth rates, life-history traits, and competition in a phage community. Phages were found to vary in their responses to temperature and so thermal change altered competition outcomes and drove phage community composition shifts. I then used experimental evolution and follow-on genomic and phenotypic analyses to assess the interaction between thermal adaptation and phage community dynamics. I discovered that phages can avoid thermal extinction through evolutionary rescue. Rescue, however, results in changes to competition outcomes and promotes the exclusion and evolutionary constraint of phage competitors. This body of work demonstrates that thermal change is a major driver of parasite community ecology and evolution. The findings have implications for understanding the role of temperature in the structure and dynamics of phage communities associated with eukaryotic hosts, as well as the efficacy of phage therapies. More broadly, they show that thermal change can alter community dynamics and drive eco-evolutionary feedbacks, with consequences for species coexistence amidst global climate change.

Authors: Greenrod, STE

• DOI: 10.5287/ora-pmdxjak0j
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English