Herbivory in early Tertiary Arctic forests

Early Tertiary High Arctic forest ecosystems are unique in that they have no equivalent among modern forests. Today, no forest ecosystem exists at such high latitudes. To assess the potential role of herbivory during the early Tertiary warm period at high latitudes, we have surveyed 1567 fossil angiosperm leaves from Svalbard for the presence or absence of 35 insect damage types (DTs). Our investigation for the first time uncovered a wealth of insect trace fossils from the early Tertiary northern high latitudes. These include galls, mines, and feeding traces on fossil leaves. Most of the folivory includes unspecific external foliage feeding that cannot be ascribed to a particular group of insects. Exceptions are the mining damage types that are most similar to those made by leaf-mining moths (Lepidoptera: Gracillaroidea). Nevertheless, the abundance of folivory indicates that herbivorous insects were an important component of the forests thriving in the Arctic realm. The observed change in insect herbivory from the Middle Paleocene to the Late Eocene/Early Oligocene in Spitsbergen may be attributed to climatic variables because they influence insect life-cycle timing, population density, and geographic range.

► First study on insect trace fossils from the Tertiary northern high latitudes.
► Changes in insect herbivory mostly attributed to climatic variables.
► Results are consistent with estimates of ‘simpler’ trophic level structures.