Perturbation experiments reveal patterns of parasite community assembly with implications for host health
Parasite community composition can influence host health and parasite transmission, yet no consensus has been reached regarding the structure of parasite communities. By perturbing parasite communities, we gained insight into the outcomes of species interactions and the role of biotic interactions in parasite community assembly. We experimentally disturbed parasite communities of African buffalo (Syncerus caffer) and examined how treated communities differed from controls and varied with time since disturbance at two scales: across populations of hosts and within individual hosts. Next, we tested the implications of parasite community structure for host health in terms of horn growth and length-weight residuals. Lastly, we tested the ability of sub-lethal techniques to detect patterns of community composition.
Across host populations, control communities were more species rich than treated communities, but that diversity was spread among hosts, rather than within individuals. At the within-host scale, treated communities were less intense, but more diverse and than those within control hosts. Notably, they increasingly resembled control communities as the time since disturbance passed. Our results suggest that species interactions may play a role in early community succession that diminishes as communities reach equilibrium. This change in interactivity over time may help explain variability among previous studies of parasite community composition and highlights the need for future experimental and longitudinal studies. Secondly, we found that parasite community diversity was positively associated with host health. Hosts with less diverse communities, as observed in control comminutes and as time since disturbance increased, had lower rates of horn growth and lower residual body condition. Finally, we found that lethal and sub-lethal techniques for estimating prevalence, intensity, species-specific abundance, and community composition were largely indistinguishable. This validation of sub-lethal sampling methods will allow monitoring of changes in parasite community composition over time, and provide a way to investigate the factors that shape parasite communities as well as the consequences of parasite community composition for host health and parasite transmission.