Fish trophic level and the similarity of unspecific larval parasite assemblages

TIMI, J.T.; ROSSIN, M.A.; ALARCOS, A.J.; BRAICOVICH, P.E.; CANTATORE, D.M.P.; LANFRANCHI, A.L.

Melbourne

Congreso; XIIth International Congress of Parasitology (ICOPA); 2010

Whereas the effect of parasites on food webs is increasingly recognized and has beenextensively measured and modelled, the effect of food web on parasites has been not quantifiedin a similar way. Here, we apply the concept of decay in community similarity with increasingdistance, 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 tomeasure rates of community change as a function of host feeding habits and it is applied for thefirst time across host species in marine waters. We focused on a suit of 15 species oftrophically-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 assumedthat 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 thedifferences in their ecological characteristics. We used differences in TL and body length (areliable surrogate of TL) as measurements of size and trophic distances. It was found thatsimilarity at both infracommunity and component community levels showed a very clear decaypattern 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 amongparasite communities. Multivariate analyses also discriminated fish species according their TLand habitat. Furthermore, the relationships between host TL and community similarity allowedto identify those fishes for which the TL was apparently under- or overestimated and also topredict the TL of host species based only parasite data.