Although connectivity can promote species persistence over a larger metapopulation, dispersal may also act as an agent for disease transmission by bringing hosts and parasites into contact. This problem is further complicated by the fact that parasite distribution can impact dynamics. We investigated the effects of connectivity and initial distribution of parasites throughout the metapopulation on microparasite-host dynamics, using guppies and the monogenean ectoparasite Gyrodactylus turnbulli. We created metapopulations of four tanks of eight fish and introduced either two parasites to all tanks or eight to one tank. Every 10 days, one randomly selected fish from each tank were moved to the next tank in the metapopulation. Additionally, we introduced either two or eight parasites to isolated tanks of eight fish that allowed no dispersal of fish or parasites. Parasite counts were performed on each fish every other day until no parasites were found in the system for two consecutive counting days or for 120 days. We analyzed the effects of connectivity and of initial conditions on parasite persistence, host mortality and peak parasite load/mean abundance using generalized linear mixed effects models.
Results/Conclusions
Parasites persisted longer in metapopulations than isolated tanks. Mortality was lowest in isolated tanks where two parasites were introduced and did not differ among connected tanks. Peak parasite load and mean abundance were influenced by the interaction of connectivity and parasite introduction levels. When parasites were introduced at low levels, being in a metapopulation helped the parasite persist longer but had little effect on host parasite burden or death. However, when parasites were introduced at high levels, being in a metapopulation also benefited the hosts, as parasite burdens were lower. These findings have important implications for disease management and species conservation.