Parasite communities in three sympatric flounder species (Pleuronectiformes: Paralichthyidae): similar ecological filters driving toward repeatable assemblages.

The relative role of host phylogeny and ecology on parasite community structure is analyzed in three sympatric paralichthyids from Argentine waters: the carcinophagous Xystreurys rasile and the piscivorous Paralichthys isosceles and P. patagonicus. Their relatedness, inherited ecological and physiological traits and shared past histories should result in certain similarities in their parasite assemblages. With this as our null hypothesis, we focused on the effects of measurable traits (size, age and diet) across fish species, with departures from a general pattern being interpreted as a consequence of ecological filters preventing homogeneous infections. The percentage of individuals/species that host-specific parasites contributed to each component community, as well as their effect on similarity of assemblages within/across host species, showed that they were not important contributors to abundance, richness and similarity, being irrelevant for the repeatability within component communities and across fish species as a phylogenetically related group. To minimize the effect of variables other than diet or trophic level only trophically transmitted nonspecific parasites were included in further analyses. After controlling for fish size, the congeneric host species harboured assemblages significantly different from those found in X. rasile, but were similar to each other because of their shared high trophic levels. Assemblages of equivalent structure harboured by fish with different age-size relationships showed that these variables seem to act at dissimilar rates on different features of the parasites assemblages. Indeed, age affected mainly the parasite abundance, whereas body size influenced mostly species richness. In conclusion, similar ecological filters produce analogous infections across host species driving towards homogeneous parasite communities.