Contrasting the ecological and taxonomic consequences of extinction

Extinction in the fossil record is most often measured by the percentage of taxa (species, genera, families, etc.) that go extinct in a certain time interval. This is a measure of taxonomic loss, but previous work has indicated that taxonomic loss may be decoupled from the ecological effects of an extinction. To understand the role extinction plays in ecological change, extinction should also be measured in terms of loss of functional diversity. This study tests whether ecological changes increase correspondingly with taxonomic changes during the Late Ordovician M4/M5 extinction, the Ordovician/Silurian mass extinction, and the Late Devonian mass extinction. All three extinctions are evaluated with regional data sets from the eastern United States. Ecological effects are measured by classifying organisms into ecological lifestyles, which are groups based on ecological function rather than evolutionary history. The taxonomic and ecological effects of each extinction are evaluated with additive diversity partitioning, detrended correspondence analysis, and relative abundance distributions. Although the largest taxonomic changes occur in the Ordovician/Silurian extinction, the largest ecological changes occur in the Late Devonian extinction. These results suggest that the ecological consequences of extinction need to be considered in addition to the taxonomic effects of extinction.