The study looked at how different factors affect the structure of parasite communities in freshwater mussels. They found that the diversity of parasites between different sites and host species was higher than expected. Parasite communities within individual hosts were less nested than expected, suggesting a modular organization. The researchers used a model to show possible competition among parasites within hosts, which could explain the observed patterns. Overall, understanding parasite communities requires looking at factors at multiple scales to get a complete picture of how they are put together.