Meeting Abstract
Biodiversity levels can be correlated with widespread, geologic shifts in environmental parameters similar to those occurring in the Anthropocene. Sand dollars (Clypeasteroida, Echinoidea) have a superb fossil record throughout the Cenozoic northern Pacific, in an arc from Japan, along the Aleutians, and south to California and Mexico. With a robust skeleton and high fossilization potential in ambient sediments, clypeasteroids record the influence of environmental change on faunal histories. A database incorporating 160+ northern Pacific sand dollars since their Eocene origin was developed through museum collections and published resources, integrating stratigraphic occurrences, biogeographic data, and morphology. Taking into account sampling bias, we correlated biodiversity fluctuations in clades over geologic time with factors including temperature, current regimes, oceanic pH, and geologic events such as the opening of the Bering Strait and the closure of the Central American seaway. Among several correlations, we noted radiations in certain clades as the Bering Strait opened near the end of Miocene. These taxa exhibit eccentric placement of various features instrumental to their life history. Eccentricity evolved independently in three clades, and is correlated with upright, suspension-feeding behavior. Suspension-feeding likely provided advantages for these taxa during cold periods characterized by strengthened upwelling. Global change today suggests that the tropics will become larger, just as they have in the past. Other changes in the distribution of many sand dollar groups suggest future alterations linked to ongoing, anthropogenic change.
