Fish trophic level and similarity of unspecific larval parasite assemblages

TIMI, JUAN T.; ROSSIN, MARÍA A.; ALARCOS, ANA J.; BRAICOVICH, PAOLA E.; CANTATORE, DELFINA; LANFRANCHI, ANA L.

Melbourne, Australia

Conferencia; ICOPA XII; 2010

Whereas the effect of parasites on food webs is increasingly recognized and has been extensively measured and modelled, the effect of food web on parasites has been not quantified in a similar way. Here, we apply the concept of decay in community similarity with increasing distance, previously used for parasites in geographical, phylogenetic and ontogenetic contexts, to differences in the trophic level (TL) of fishes. We propose an accurate quantitative method to measure rates of community change as a function of host feeding habits and it is applied for the first time across host species in marine waters. We focused on a suit of 15 species of trophically-transmitted and unspecific larval helminths across 16 fish species (1783 specimens, 6 orders, 14 families) with different size and TL, gathered from the same region. It was assumed that the presence of these parasites in a given fish species means that this is a suitable host. However not all host species harboured the same number and type of parasites, reflecting the differences in their ecological characteristics. We used differences in TL and body length (a reliable surrogate of TL) as measurements of size and trophic distances. It was found that similarity at both infracommunity and component community levels showed a very clear decay pattern based on values of abundance and relative abundance, with increasing distance in TL, but not in fish size, leading TL to arise as the main explanatory factor for similarity among parasite communities. Multivariate analyses also discriminated fish species according their TL and habitat. Furthermore, the relationships between host TL and community similarity allowed to identify those fishes for which the TL was apparently under- or overestimated and also to predict the TL of host species based only parasite data.