Exceptionally preserved fossil deposits record insect response to environmental change in Colorado

Exceptionally preserved fossil insect assemblages from the middle Eocene through late Oligocene of Colorado are currently being studied to determine the ecological and evolutionary responses of insects to dramatic climate change.  Fossil insects in this study include those from the middle Eocene Green River Formation (~49Ma), the late Eocene Florissant Formation (~34Ma), the early Oligocene Pitch Pinnacle Formation (~33Ma) and the late Oligocene Creede Formation (~26Ma).  During the approximately 23 million year time interval examined in this study, regional temperatures are estimated to have decreased by approximately 15.5^oC, while marine temperatures are estimated to have declined by approximately 10^oC.

Occurrence and relative abundance data are being compiled from both historical collections and newly collected materials. Insects are well represented, abundant, and diverse (species richness and ecological breadth) in all of the study localities. We present preliminary data for Coleoptera and Diptera and begin to document how taxonomic composition, richness and abundance distributions have changed during this dramatic cooling event.   Already apparent is the important role of life history characteristics in determining which groups had the strongest response to environmental change.  Future efforts will require greater assistance from the entomological community to understand the systematic and ecologic affinities of previously undescribed fossil insect specimens.