Equatorward increase in naticid gastropod drilling predation on infaunal bivalves from Brazil with paleontological implications

Abstract

Abstract Understanding the influence of spatial variation on temporal trends is important for interpreting evolutionary patterns of predation in the fossil record. Geographic data on naticid gastropod drilling predation are contradictory and mostly limited to the Northern Hemisphere. This study examines latitudinal variation in drilling on ~ 24,000 beach-collected Recent bivalves from 6°S to 34°S in Brazil. Twenty-eight localities representing 16 latitudes were sampled in the Brazilian and Argentinean provinces, further subdivided into four smaller ecoregions (Northeastern Brazil, Eastern Brazil, Southeastern Brazil, Rio Grande). Analyses focused on bivalves exhibiting infaunal life habits. Increased drilling equatorward was observed at the assemblage-level across several spatial scales (localities, latitudes, ecoregions, provinces). Taxon-level analyses for eight genera drilled across multiple ecoregions generally indicated greater drilling among lower latitudes; size standardization did not affect patterns at the genus level. An equatorward increase in drilling was documented also upon restricting the data to localities characterized primarily by softer substrates, fine- to medium-grained sediments, and in limiting data to samples obtained by a single collecting strategy, minimizing concerns regarding the influence of local environmental variation and different methodologies on latitudinal patterns in drilling. Latitudinal patterns in drilling may be related to temperature and seasonality in influencing metabolic rates, as well as diversity and predator–prey size distributions. The results of this study do not correspond to existing patterns previously described for Western Atlantic molluscan assemblages of the Northern Hemisphere. However, they may help explain temporal patterns in the fossil record of naticid predation.