Meeting Abstract
Monarch butterflies inhabit islands and continents worldwide and undergo a long-distance, seasonal migration in temperate regions. Past work showed that migratory populations experience lower infection prevalence by a specialist protozoan compared to non-migratory populations, and that within migratory populations, infection risk declines after migratory movements. In this talk, we synthesize previous work with new data from wild monarchs to identify mechanisms by which migration limits pathogen spread and to examine how the loss of migration due to human activities alters pathogen dynamics. The results of field monitoring and small scale experiments within the eastern North American monarch population, which undergoes the longest distance migration, show that parasites pose significant costs for monarch migratory success (leading to ‘migratory culling’), and that parasites accumulate in host breeding habitats during the summer months (setting the stage for ‘migratory escape’). More recent observations show that sedentary monarchs in the southern U.S. that forego migration to breed year-round on exotic milkweeds face a high risk of infection that could increase pathogen spillover risk to the larger migratory population. New findings show that a small proportion of monarchs overwintering in Mexico originate from exotic tropical milkweeds and that these monarchs have a slightly higher probability of infection. The body of work from this system underscores the importance of conserving animal migrations and motivates future studies of infection risk and transmission between residents and migrants in monarchs and other species.
