- UW Department of Geology and Geophysics
Well-preserved, middle Eocene floras from the Pacific Northwest, particularly the graben-fill deposit at Republic, Washington, offer an unique window for examination of some of the earliest documented, modern-aspect, plant-insect associations in the fossil record. Of special interest is fossil plant damage attributable to leaf mining and galling taxa that is very similar or identical to modern damage on the same host genera, indicating the geologically long-term persistence of some associations. Other types of middle Eocene, insect-mediated damage appear generalized and are not assignable to known types of modern associations, owing in part to imperfect taxonomic resolution of plant host, insect herbivore, or more likely, extinction. This preliminary report records the taxonomically diverse and morphologically detailed wealth of preserved foliar material in a Lagerstätte, which is important for addressing the macroevolutionary tempo of plant-insect associations. This relevance includes the prevalence of long-term associations, extinction of plant host and interacting insect herbivores, and the occurrence of host-switching at Cenozoic time scales for taxa presently confined to eastern Asia and North America.