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Contributed Talk

Session: : Species Interactions 1

COS 248-3 - Extreme heat alters the performance of pathogen and host

Thursday, August 10, 2023
8:30 AM – 8:45 AM PDT
Location: E143
Abstract: The frequency and intensity of extreme heat in the environment have increased in the last decade Extreme heat events have wide-ranging impacts on biological systems from the molecular to the community level. However, the effects of extreme heat have been poorly studied in pathogen-host systems. Here, we explore how extreme temperatures affect the interaction among the protozoan pathogen Crithidia mellificae, and its insect hosts Osmia cornifrons and O. lignaria. We hypothesized that extreme heat reduces host heat tolerance as measured by upper limit for locomotion (CTmax) and alters voluntary exploration behavior to extreme temperature zones (ETZ) in the hosts, as well as reduces pathogen growth rate. We predict that extreme heat reduces CTmax, voluntary exposure to warm ET zones, and pathogen growth rate. We do not expect extreme heat to influence each species in a similar way, but to induce a mismatch in the host-pathogen interaction. To answer this question and test this hypothesis, we assessed the effects of heat stress, pathogen infection, and the combination of both factors on the hosts’ heat tolerance and voluntary exploration of cold and warm ETZ. Next, we explored how the changes induced by extreme heat on host thermal tolerance altered the pathogen growth rate. Our results showed that exposures to extreme heat significantly reduced host critical thermal maximum by an average of 4 °C in healthy and 7 °C in infected hosts. Prior extreme heat exposure also reduced the hosts’ voluntary exposure (or transit across) to zones with extreme temperatures (cold and warm ETZ) as well as protozoan pathogen growth rate. Our results provide insight into how short-term exposure to extreme heat may alter ecological interactions between pathogen and host thermal performance.