The Fossil Record of Insect Extinction: New Approaches and Future Directions

Abstract

The fossil record of insect extinction at the family level is characterized by two basic modes: background extinction, which represents an ambient level of taxa extirpation, and mass extinctions, which are occasional severe events in which taxa are eliminated significantly above background levels. The most significant mass extinction, at the end-Permian (Permian–Triassic; P-T), divides the history of insects into two major evolutionary faunas: an earlier Paleozoic Evolutionary Fauna of apterygotes, paleopterans, and basal clades of orthopteroids and hemipteroids; and a subsequent Modern Evolutionary Fauna of more derived clades of orthopteroids and hemipteroids and especially holometabolous insects. In addition to the P-T event, four other extinctions are documented by multiple types of data: Late Pennsylvanian, Late Jurassic, later Early Cretaceous; and the end-Cretaceous (Cretaceous–Paleocene; K-P). There also is an analogous record of insect origination that is characterized by major, above-background events.

Four methods are used to detect insect extinction in the fossil record. The taxic approach is widely used, whereby the temporal durations of fossil taxa are tallied for each geologic unit of interest and analyzed in a manner analogous to demography used in ecology. By contrast, the phylogenetic approach uses clades as the basic units of interest. A recent approach uses proxy data such as quantification of plant–insect associations across major boundaries in lieu of an insect body–fossil record. Last, the clustering of times of origin from modern coevolved plant–insect associations provides data for likely interruptions from major paleoenvironmental perturbations. Pluralism, emphasizing multiple approaches to determine the ecological dynamics of insects during an extinction, is the best strategy to evaluate insect demise or survival in the fossil record.