ALBERT

Description: Students of Earth history have long recognized the correlation between the quantity of preserved sedimentary rock and the diversity of life recorded as fossils. But paleontologists have yet to determine whether this pattern reflects a causal relationship or a unidirectional sampling bias in fossil data imposed by preserved rock quantity. Distinguishing between these two alternatives has been complicated by the fact that many of the basic patterns of paleontologic and lithologic covariation have yet to be quantified rigorously. Here we present the first analyses of the covariation between the macrostratigraphic and macroevolutionary histories of North America based on geographically and temporally explicit co-occurrences of rocks and fossils. The analyses use independent quantitative summaries of the stratigraphic and fossil records by integrating the Paleobiology Database (PaleoDB) and Macrostrat, a macrostratigraphy database for North America, which allows a more direct comparison of the stratigraphic and biological histories of the continent than has heretofore been possible. Within the Macrostrat database, the rock record is divided into discrete packages of sediment that are bound by hiatuses resolvable at the stage-level. Using per interval, per package rates of sediment package initiation and truncation, and genus first and last appearances (herein regional origination and extinction), we find a substantially stronger positive correlation between sediments and biology for extinction-like parameters than we do for origination-like parameters. Four of the largest coincident pulses of regional extinction and sediment truncation occur during the widely recognized end-Ordovician, late Permian, end-Triassic, and end-Cretaceous mass extinction intervals. A further comparison of the global ranges of North American genera to North American macrostratigraphy indicates that the regional and global extinction of genera are more likely to occur in the same stage than are global and regional originations. Together, these results suggest that our general understanding of biodiversity dynamics from the fossil record may not be strongly biased by the preservation of sediments and leaves open the possibility that certain large perturbations to the Earth system are responsible for major changes of state in both the sedimentary and biological systems.

Description: The macroevolutionary effects of extinction derive from both intensity of taxonomic losses and selectivity of losses with respect to ecology, physiology and/or higher taxonomy. Increasingly, palaeontologists are using logistic regression to quantify extinction selectivity because the selectivity metric is independent of extinction intensity and multiple predictor variables can be assessed simultaneously. We illustrate the use of logistic regression with an analysis of physiological buffering capacity and extinction risk in the Phanerozoic marine fossil record. We propose the geometric mean of extinction intensity and selectivity as a metric for the influence of extinction events. The end-Permian mass extinction had the largest influence on the physiological composition of the fauna owing to its combination of high intensity and strong selectivity. In addition to providing a quantitative measure of influence to compare among past events, this approach provides an avenue for quantifying the risk posed by the emerging biodiversity crisis that goes beyond a simple projection of taxonomic losses.