Jenavier Tejada, a student at Denison University, worked in the lab of Dr. Alex Strauss

Abstract The dilution effect seeks to explain disease transmission in environments with multiple species. Essentially, the dilution effect predicts an increase in diversity will lead to a decrease in disease transmission. In zooplankton communities, the resistant diluter, Ceriodaphnia dubia can lessen disease in the host Daphnia dentifera caused by the parasite Metschnikowia bicuspidata. However, dilution is only effective when diluters and hosts co-exist; because when they compete, competitive exclusion can occur. Fitness of both D. dentifera, and C. dubia depend on temperature. Specifically, C.dubia benefits in warmer temperatures and D. denifera in cooler temperatures. Therefore, in environments where temperatures fluctuate,  this may lead to co-existence, greater abundances of the diluter, and less disease transmission. We are testing whether the dilution effect reduces infection prevalence when a diluter is present, and how dilution effects differ at a constant 20˚C versus a fluctuating temperature around the same mean. We designed a multi-generational mesocosm experiment with communities that contained the host and parasite, and communities that contained the hosts, parasites, and diluters at both constant and fluctuating temperatures. We hypothesize that the changing environmental conditions caused by fluctuating temperature will lead to more diluters, causing a greater dilution effect via co-existence of the host and diluter. This project will help us learn more about the possible effects of climate change – especially variable temperature – on disease dynamics in communities with multiple species.