Department of Biology

Invasion of the body snatchers: the role of parasite introduction on host distribution and salinity response

Dr. April Blakeslee
East Carolina University

February 9, 2024
3-4 pm

Hosted By Dr. Tim Lee

In dynamic systems, organisms are faced with variable forces that may impose selective trade-offs. Salinity is a major physical driver of estuarine diversity, while parasites are key biotic forces shaping host distribution and demography. To test for trade-offs between low-salinity stress and parasitism, my collaborators and I performed field surveys every 6-8wks over a 3 year time period along salinity gradients in North Carolina estuaries to determine factors influencing parasite prevalence of an invasive castrating parasite, host abundance of a native mud crab, infection probability, and taxa diversity. We examined demographic data from ~12,000 crabs across 20 seasonal sampling events. We also set up a lab experiment to investigate signatures of low-salinity stress on host response (time-to-right and gene expression). Our results found salinity and temperature to significantly affect parasite prevalence, with sites <10 PSU lacking infection, and populations in moderate salinities at warmer temperatures attaining prevalence as high as 60%. An individual’s infection probability was driven by salinity, host size, and season, while host abundance was negatively associated with parasite prevalence. Gene expression was plastic to acclimation salinity, but several osmoregulatory and immune-related genes demonstrated source-dependent salinity response. We identified a salinity-associated genetic marker, suggesting possible selection on standing variation. Altogether, our study found evidence of selective tradeoffs in an ecologically-important host species, and by examining the parasite’s invaded range, we can observe ‘evolution in action’ as the parasite shapes host response in a dynamic system underpinned by multiple abiotic and biotic forces.