cretaceous Beetles in amber
Study of fossil resin
What is amber?
Amber is the result of the fossilization of plant resins. Amber has the property to preserve organisms or their remains caught inside (bioinclusions) with a high level of detail. There are several hundred of outcrops providing amber worldwide but only a restricted number of them preserve bioinclusions.
Amber deposits with bioinclusions are especially abundant in the Cretaceous. This might be explained by factors that increased resin production at that time, both environmental (volcanic eruptions, storms or hurricanes, wildfires, sustained high temperatures) and biological (such us increased herbivory/pest pressure). Some research teams are currently interested in testing some of these hypotheses in recent tropical forests, but conclusive results are still lacking at this moment.
Resin lump from a Taxodiaceae tree. By David Peris.
Amber piece surrounded by sediment from Cretaceous deposit of San Just (Spain). By Xavier Delclòs.
Resin is a viscous liquid exuded by certain plants that contains volatile compounds. Resin remains sticky for some time, trapping “life portions” from the environment where it was exuded. Once resin reaches the ground, a relatively short transport and fast deposition and burial times are factors that increase the likelihood of resin preservation. If conditions are appropriate, resin polymerizes and loses volatile compounds, becoming copal after a few thousand years and turning into amber after several million years (amberization).
Scheme for the resin fossilization process . From Martínez-Delclòs et al., 2004. Palaeogeography, Palaeoclimatology, Palaeoecology.
What can we study from the amber record?
Amber preserves not only the anatomy of the organisms trapped within, but also in some cases their biotic interactions and ethology. This fact enables very interesting paleontological research. In fact, studies of amber inclusions are now considered as a fundamental source of information to properly understand the evolution, paleoecology, paleobiogeography and classification of present-day forms. In addition, the study of amber and its bioinclusions allows us to gain insight into the climatic and ecological characteristics in which these organisms lived.
Invertebrates encompass 80% of all living species described on Earth. Beetles, with ca. 380,000 described species, comprise about a quarter of the total of described invertebrates, making these insects the primary contributor to Earth’s biodiversity! Studying fossil beetles, particularly those preserved in amber, provides paramount data to elucidate their evolution and to understand the ecological interactions that the group has experienced through time.
Estimated number of described species worldwide . Based on Scheffers et al., 2012. Trends in Ecology and Evolution.
Phylogenetic proposal for the order Coleoptera. From Bocak et al., 2014. Systematic Entomology.
