TESTING THE RELATIONSHIP BETWEEN NUTRIENTS AND FUNCTIONAL DIVERSIFICATION

It has been suggested that throughout the Phanerozoic there has been a positive correlation between origination rates and availability of marine nutrients. This correlation would imply that nutrient pulses are not only responsible for increases in taxic richness, but also the expansion of the ecological space (ecospace). Here we test the correlatives between selected abiotic factors, which may have influenced marine nutrient levels, and ecospace changes through geologic time. We analyzed the pattern of ecospace occupation of 25,000 genera over 540my and their co-variation with abiotic factors. Each genus was classified according to autecological information from the PBDB and literature. Rarefaction was used to standardize the number of genera analyzed using 5my bin resolution. Patterns of functional diversity were assessed using functional richness (FR) and specialization (FS) indices. In addition, paleo-environmental proxy data of temperature (δ¹⁸O), organic matter (δ¹³C), nutrients input from organic matter (δ³⁴S) and continental weathering (Sr/⁸⁶Sr) were obtained from literature and compared with FR and FS estimates. Beta Whittaker’s diversity index was calculated by pairwise comparison of consecutive bins to evaluate temporal changes in the ecospace composition. In addition multivariate statistical approaches were employed to estimate the relative importance of each abiotic factor in influencing the ecological ecospace structure. The results indicate that detrended temporal trends of functional diversity indices are unrelated to environmental proxies. However, a canonical multivariate ordination (CCA) constrained by abiotic factors suggests three major faunal turnover events: Middle-Ordovician, End-Permian and Early-Mesozoic and indicates that these events may have been linked to temperature (δ¹⁸O) and nutrients input (δ¹³C and δ³⁴S). Finally, specialization index is correlated with depleted beta diversity which coincides with strong changes in the abundance of modes of life. Consistent with some previous studies, these preliminary analyses suggest that secular changes in ecospace characteristics may have been influenced by temperature and nutrients input.