The use of citizen science data to determine spatio-temporal patterns in monarch butterfly (Danaus plexippus) parasite infection in the Southeastern US

Climate change and urbanization are driving animals to change migratory patterns, with some species forming new non-migratory populations. These shifts in migratory behavior may indirectly impact host-parasite interactions through changes in species geographic ranges, densities, and interspecific interactions. Parasites can shape host population dynamics and even contribute to the decline of host species, particularly when host populations are threatened by exogenous stressors. The eastern migratory monarch butterfly population (Danaus plexippus) are believed to be forming  non-migratory populations across the southeastern US.  We used citizen science data from Project Monarch Health to determine the spatiotemporal patterns from 2011-2018 of  infection prevalence of a debilitating obligate parasite, Ophryocystis elektroscirrha (OE) in five regions across the southeastern US.  We found that infection prevalence was correlated with latitude and plant hardiness zone.  In the northern regions, where winter breeding was not found to routinely occur, overall OE prevalence was low (4.5 - 12.3%). Prevalence was highest regions where winter-breeding occurred more frequently, with the highest values in south (83.6%), followed by north Florida (71.5%) and the Western Gulf Coast (63.9%). In Florida, variation in infection prevalence was best explained by maximum daily temperatures experienced during the larval stage and infection prevalence showed almost no seasonal variation within a year. In the Western Gulf Coast where winter breeding is common but less consistent than Florida, strong seasonal patterns were observed and prevalence was best explained by an interaction between daily minimum temperature and urbanization.