SFB-TRR 212

Niche construction consequences of parasite virulence in eco-evolutionary dynamics

During infection, parasites construct their niches by altering their hosts’ physiology, morphology, and behaviour. By doing so, parasites can have far-reaching ecological and evolutionary effects. Individuals often differ in their responses to the effects of parasites’ niche construction. Nonetheless, it remains unclear how those individual differences can alter the structure of natural communities, the energy flow of ecosystems, and even drive eco-evolutionary feedbacks? To address this question, we will integrate computational models and large-scale mesocosm experiments to test to what extent parasite effects on niche individualisation of their hosts mediate the widespread ecological and evolutionary effects of parasites. Using computational models, we will investigate under which conditions the individual-level effects of parasites alter individual trophic niche specialisation and eco-evo feedbacks. In mesocosm experiments, we will manipulate the density of three-spined sticklebacks (Gasterosteus aculeatus) and the presence/absence of two strains of the trophically transmitted tapeworm Schistocephalus solidus that vary in their virulence (and thus the strength of their niche construction effects). Using stable isotopes and stomach content data together with transcriptomic data, we will investigate the interactive effects of fish density and parasite virulence on stickleback niche individualisation. Furthermore, we will examine the ecological and evolutionary consequences of these effects by comparing the strength of trophic cascades and the selection regimes that a future fish and parasite generation will experience, thereby testing for eco-evo feedbacks driven by niche individualisation.

We aim to investigate whether the niche construction effects of parasites on hosts’ niche individualisation underlie the widespread ecological and evolutionary effects of parasites by testing the following three hypotheses:

1.  Individualised niches of hosts co-vary with metabolism and immunity upon parasite infection
2. Parasite effects on individual trophic niche specialisation (ITNS) of stickleback hosts are mediated by changes in metabolism and immune responses
3. The direct and indirect ecological effects of parasite virulence are strong enough to lead to eco-evo feedbacks and this depends on niche individualisation of sticklebacks

This work will push the research boundaries in host-parasite interactions by illustrating how parasite traits drive host niche individualisation and shape eco-evolutionary dynamics.