Meeting Abstract
Infection rates often vary substantially among host populations, both on local and global scales. Here, we take advantage of the freshwater adaptive radiation of the threespine stickleback (Gasterosteus aculeatus) in southcentral Alaska following the last glacial maximum. Oceanic stickleback independently colonized freshwater habitats where they encountered Schistocephalus solidus, a trophically transmitted cestode that has a long evolutionary history of parasitizing freshwater stickleback but that is not viable in marine environments. Initial work in British Columbia suggests, as expected, that oceanic stickleback exhibit little resistance to infection, whereas freshwater populations exhibit lower infection rates under experimental conditions, suggesting evolved resistance. Population differentiation of S. solidus is unlikely due to a highly mobile definitive host (piscivorous birds). Some stickleback populations have persistently low parasite loads, some have consistently high loads, and some exhibit extreme fluctuations in parasite loads and stickleback population sizes across years. In a first step toward understanding the interaction of such systems, we looked at the timing of infections by S. solidus in four Alaskan stickleback populations with different S. soldius frequencies. Our goal was to pinpoint the timing of the first exposure of the stickleback to S. solidus and to determine the course of infection over the winter.
