CONNECTING THE LATITUDINAL GRADIENT OF DRILLING PREDATION AND SPECIES RICHNESS IN MOLLUSKS ASSEMBLAGES ALONG THE TEMPERATE EAST COAST OF SOUTH AMERICA AND ANTARCTIC PENINSULA

RIVADENEIRA, M. M. ; GORDILLO, S.; CHARÓ. M. P.

Mendoza

Congreso; 4th International Palaeontological Congress; 2014

CONICET- MENDOZA

The analysis of patterns and processes of drilling predation provides a powerful tool to reconstruct the variability of species interactions across geographic and evolutionary time-scales. However, efforts aimed at describe the variation in drilling predation across large latitudinal gradients are still scant. Moreover, its connections with the well-known latitudinal gradient of species richness phenomenon have been little explored. Here we evaluate the existence of latitudinal gradient of drilling predation and its connection with species richness patterns, synthesizing information gathered over a decade of studies carried out on different mollusk assemblages (bivalves and gastropods), in 62 localities of the Southwestern Atlantic, from Buenos Aires to Antarctic Peninsula, spanning over 30 degrees of latitude. The analysis of more than 16,000 shells reveals that the percentage of drilled species decline monotonically towards higher latitudes, from up 50% around Buenos Aires to less than 20% in Antarctica. In contrast, the percentage of drilled individuals showed a non-linear trend, characterized by an abrupt peak of ca. 40% at Tierra del Fuego in the southern tip of the continent. These patterns can be linked to the patterns of latitudinal gradient of species richness of bivalves and gastropods observed along the study region. Whereas the fraction of drilled species is more related to the species richness of bivalves (which follow the canonical decline towards higher latitudes), the percentage of drilled individuals is associated to the species richness of gastropods (particularly muricids, but not naticids) characterized by a non-linear latitudinal trend with a large peak of richness at Tierra del Fuego. This suggests that the intensity of predation is related to the availability of both predator and prey species. Whether predation intensity is a cause or consequence of the latitudinal gradient of species richness remains an open question.