196 Paleontology: Macroevolution & Macroecology

Tuesday, 20 October 2009
1:30 PM - 5:30 PM
Portland Ballroom 256

A 600 MILLION YEAR RECORD OF ECOLOGICAL DIVERSIFICATION

Paper number: 196-16
Program: Technical Sessions
Time: 5:15 PM – 5:30 PM

Authors

Abstract

The ecological diversity of marine landscapes may be defined as the number of unique ways in which organisms interact with the environment and with one another (feeding, locomotion, and tiering), herein referred to as ecospace. Previous studies have shown that realized ecospace has increased markedly since the earliest known marine animal ecosystems. These studies are, however, limited to snapshots through evolutionary history. The Paleobiology Database (www.paleodb.org) provides a unique resource for analyzing a continuous time-series of ecospace occupancy from the fossil record. The present analysis incorporates nearly half a million fossil occurrences, and represents close to 20,000 genera of marine animals.

We show that globally sampled ecospace indeed rose sharply between the Ediacaran and the Cambrian, although this is partly biased by the exceptional preservation of non-skeletonized organisms in Cambrian konservat-lagerstätten. Sampled ecospace reaches a plateau during the Late Ordovician, only increasing further during the mid-Jurassic. Even though the number of ecospace units occupied remained relatively stable following the early Paleozoic increase, ecological composition shifted dramatically. Most notable is a shift from Paleozoic epifaunal to post-Paleozoic infaunal life-habits, and an increase in carnivory through the Phanerozoic. These data can also be used to test the severity of extinction events in the context of ecological complexity. The end-Permian is the only major extinction event to result in a long-term shift in the occupation of ecospace, with epifaunal stationary suspension-feeders declining and nektonic actively mobile carnivores increasing in their frequency of occurrence. Analysis of community-scale occupation of ecospace (the typical number of modes of life observed in individual assemblages) reveals a slightly different pattern; remaining low throughout the Paleozoic before rising sharply in the early Mesozoic. These results point to the need to investigate evolutionary processes and the consequences of abiotic perturbations with new data, analytical approaches, and at a range of spatial scales