Parasite prevalence can vary greatly across space, and the drivers of this variability are not always well understood. Spatial patterns in parasite prevalence can be revealed through observational studies, but to understand the mechanisms that underlie these patterns, standardized and controlled comparisons are needed. A serendipitous result from our collaborative, large-scale experiment on oyster reef trophic ecology allowed us to examine spatial variability in infection of the eastern oyster (Crassostrea virginica) by its pea crab parasite (Zaops ostreus) across 700 km of the southeastern U.S. coastline. Oyster pea crabs sit on the gills of oysters and steal food from their hosts.
Juvenile oysters from a homogeneous source stock (minimizing the influence of host genetics on infection patterns) were outplanted and raised in the field for 3 months at multiple sites with similar environmental characteristics. We found that prevalence of pea crab infection varied between 24 and 73% across sites, but not systematically across latitude. Of all measured environmental variables, oyster recruitment correlated most strongly (and positively) with pea crab infection, explaining 92% of the variability in infection across sites. These data suggest that regional processes driving variation in oyster recruitment similarly affect the recruitment of one of its common parasites.
Byers, J. E., T. L. Rogers, J. H. Grabowski, A. R. Hughes, M. F. Piehler, D. L. Kimbro. 2014. Host and parasite recruitment correlated at a regional scale. Oecologia 174:731–738. PDF