ECOLOGICAL DISPARITY INCREASES THROUGHOUT THE PHANEROZOIC

Phanerozoic trends in ecology are well known, but most are based on piecemeal studies of individual geologic intervals, individual aspects of ecology (tiering, predation), or anecdotal evidence. Needed are synoptic analyses that treat the entire Phanerozoic in a standardized and comprehensive manner amenable to statistical analysis. Here I present a new database of Phanerozoic marine life habits that embarks on this goal. The database currently includes approximately 3000 species, with coverage spanning the gamut of marine taxa: nearly all fossiliferous orders and most major superfamilies are represented. Life habits are coded using the ecospace framework of Novack-Gottshall (2008, 2016a,b), which includes 18 dimensions (38 states) of mobility, diet and foraging habits, and substrate relationships, among others. For taxa whose states are not informed by existing literature on functional morphology, environmental distributions, ichnology, in situ preservation, and body size, functional inferences are determined algorithmically based on the states of their closest studied relatives. Although the database includes a small portion of Phanerozoic genus diversity, it adequately captures many established ecological patterns, including generally increasing body size and proportional increases in hunting predation, infaunality, and reliance on biotic substrates through time.

Ecological disparity is measured using eight metrics adopted from morphological disparity and functional ecology studies. Ecological diversity (number of unique life habits) tracks species richness throughout time. In contrast, most metrics of ecological disparity tend to increase consistently throughout the Phanerozoic, reaching greatest values in the Cenozoic (or sometimes Cretaceous). The disparity trends are largely independent of species richness, suggesting they are not simple artifacts of heterogeneous or incomplete data. The trends are also unchanged when using different algorithms to estimate life habits and body sizes of those taxa not previously studied in the literature. These analyses suggest marine animals have continued to expand ecospace throughout their evolutionary history.