Spatial structure of the helminth parasite communities of the tonguefish, Symphurus plagiusa, from the Campeche coast, southern Mexico.

The goals of this paper were to determine whether the helminth communities of the blackcheek tonguefish, Symphurus plagiusa, exhibit a spatial structure and, if so, to determine the relative influence of selected environmental and spatial variables. The parasite communities of tonguefish and environmental data (e.g., temperature, salinity, oxygen) were sampled monthly over a network of 37 stations over 1 year (February 2006 to January 2007). Analysis of similarities (ANOSIM), non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) were used. Spatial variables were generated using the analysis of principal coordinates of neighbour matrices (PCNM) method. A total of 1,010 flatfishes and nine helminth taxa were collected. For the environmental variables, hierarchical cluster analyses produced groups of stations associated with the Yucatan dry, rainy and winter seasons. At the infracommunity level, there was no group formation as indicated by ANOSIM and NMDS nor association with environmental or spatial variables. At the component community level, there was significant group formation, and RDA analyses of core, satellite and all species produced significant associations with environmental variables. However, model fit improved substantially (from 17-52% to 49-83% of explained variance) when the spatial variables (variables generated with PCNM method) were added. Thus, the helminth component communities of S. plagiusa were affected by associated environmental variables and unknown ecological processes captured by the spatial variables acting at different spatial scales over time. In contrast, at the infracommunity level there was apparently a very fine spatial grain, where the numerical dominance of core species resulted in biased group formation.