Implications of Time-Averaged Death Assemblages for Ecology and Conservation Biology

Abstract

Biologists increasingly appreciate the importance of community-level attributes in the functioning and temporal turnover of ecosystems, but data other than species richness are difficult to acquire over the habitat-to-regional and decadal-to-millennial scales needed to recognize biodiversity change, discriminate between natural and anthropogenic drivers, and inform theoretical and applied ecology. Death assemblages (DAs)—the actively accumulating organic remains encountered in present-day seabeds and landscapes, as distinct from permanently buried fossil assemblages—are an underexploited source of historical information at precisely these scales. Meta-analyses, dynamic modeling, and individual case studies, particularly of mollusks and mammals, reveal that DAs differ from censused living assemblages (LAs) primarily because they are temporally coarse, time-averaged samples, contrary to concerns that postmortem bias dominates. Temporal pooling predictably damps the ability of DAs to detect small-scale variation, but promotes their ability to inventory rare species; estimate the abundance structure of the metacommunity; document range changes; evaluate historic habitat use; and identify now-absent species, community states, and anthropogenically shifted baselines.