Grant: Discovery Grants Program - Individual

Global climate change due to human activities is driving extreme temperatures and biodiversity loss, as well as leading to more outbreaks of infection in new host species. There is a need for investigation of the fundamental principles underlying host-parasite evolution in an increasingly human-altered world, as well as demand for HQP to tackle these issues. Here, I outline the experimental research my group will accomplish through NSERC funding: Objective 1. Host-parasite evolution in a warming world The severity of heating events will threaten the persistence of many species. The extent to which both thermal stress and infection will impair host health over time is unclear. My group has been developing a tractable host-parasite system (Caenorhabditis-Leucobacter) found in decaying fruit to directly test related hypotheses using experimental evolution approaches. We will test for feedback between a host's thermal performance and their coevolution with parasites. We will also track changes in parasite virulence to provide insight as to whether host populations experiencing heating amidst climate change might be hotbeds for more debilitating infections. Objective 2. Parasite evolution across levels of host genetic diversity With increasing losses of genetic diversity, there is a clear need to determine whether such populations are more vulnerable to infection. My group has documented evidence in favour of the `monoculture effect' in wild populations whereby high diversity increases the chance parasites will encounter resistant hosts. By experimentally evolving the Caenorhabditis-Leucobacter system, we will test the role of host genetic diversity (incl. its loss and augmentation) on the evolution of parasite virulence, transmission, and specialization. We will further examine whether host ecology (e.g., density, nutrition) interacts with diversity to shape parasite transmission and infection dynamics. These experiments will develop the framework for better understanding how biodiversity loss may shape parasite transmission and virulence in protected areas. Objective 3. Parasite evolution following host shifts Parasite performance upon infection of a novel host species is commonly suboptimal - either failing to thrive or showing maladaptive virulence. Novel hosts represent a fundamentally new environment to which parasites are not adapted and cannot initially optimally exploit. We will apply experimental evolution to interactions between Leucobacter spp. and Caenorhabditis spp. in which host shifts may occur naturally within communities. These experiments will explore the extent to which a host shift spurs an intense bout of selection, whether evolutionary rate is greater than in the original host species, and whether adaptation to a new host alters host range. Managing future outbreaks can be helped by an understanding of parasite evolutionary potential and paths in host communities.