LARGE-SCALE TRENDS IN ECOLOGICAL DIVERSIFICATION AND INTERACTIONS ACROSS THE PHANEROZOIC

The ecological diversity of marine landscapes may be simply defined as the number of unique ways (modes of life) in which organisms interact with the environment and with one another (feeding, locomotion, and tiering), herein referred to as ecospace. Previous studies of Phanerozoic-scale trends in ecospace utilization have been limited to either snapshots of the fossil record, or have used synoptic databases where data are insufficient to describe the relative complexity of ecospace occupation. The Paleobiology Database (www.paleobiodb.org) provides a unique resource for analyzing a continuous time-series of ecospace utilization through time. The present analysis incorporates over half a million fossil occurrences, and represents more than 25,000 genera of marine animals. We analyze these data using simple descriptive statistics such as the number of modes of life sampled, and their relative richness and extinction characteristics. We also quantify functional diversity using three metrics: functional richness, functional evenness, and functional specialization. Sampling standardization techniques are used throughout to mitigate for uneven reporting of the fossil record.

We show that globally sampled ecospace utilization indeed rose sharply between the Ediacaran and the Cambrian, although this is partly biased by the exceptional preservation of non-skeletonized organisms in Cambrian lagerstätten. Sampled ecospace reaches a plateau during the late Ordovician through Permian. The Permian-Triassic extinction not only had a significant effect on taxonomic structure, its recovery was an important episode of ecological change. Ecospace utilization, functional richness, and functional evenness all increased following the Permian to reach their highest values during the early Mesozoic. These data capture major features of Phanerozoic-scale ecological change, including the abrupt decline in surficial epifaunal suspension feeders and rapid increases in nektonic and benthic predators, surficial grazers, and infaunal suspension feeders follow the Permian-Triassic extinction. Sampling standardization of raw data and disassembly of taphonomic biases are critical to valid interpretation of these data.