Sampling the insects of the amber forest

Abstract

Amber, which is fossilized tree resin, is full of surprises. The tail of a feathered dinosaur was recently recovered from mid-Cretaceous (∼99 Ma) amber from Myanmar (1), and anole lizards in Miocene Dominican amber (2) showed that lizard communities have persisted for at least 16 My. Carnivorous plants of the family Roridulaceae, presently confined to South Africa, have been discovered in Eocene amber from the Baltic (3). The great majority of creatures in amber, however, are insects, and they often preserve the finest 3D details. A fly and a mite were discovered trapped in a spider web in Early Cretaceous amber from Spain (4), and a scale insect in mid-Cretaceous Burmese amber is associated with eggs and freshly hatched nymphs, showing that brood care in insects dates back at least 100 My (5). Some amber insects even retain the cellular structure of internal soft tissues, such as muscle (6, 7). However, amber does not trap all of the animals in the forest, and even the insects are subject to sampling bias. This is an important consideration when we use the evidence of fossils entombed in amber to interpret terrestrial environments and ecosystems of the past. A study in PNAS by Solorzano Kraemer et al. (8) compares the range of insects trapped in modern tree resin in a Madagascar forest with the diversity of insects that live there, which represents a major step in determining the extent to which inclusions in amber represent the diversity and ecology of ancient forest communities. Many different plants exude resin. Some of them are extinct, and some living resin producers are not found in the fossil record. Resins harden and darken over time through a process that usually involves polymerization. The rate of this transformation varies with resin chemistry and environmental conditions. Hardened resin … [↵][1]1Email: derek.briggs{at}yale.edu. [1]: #xref-corresp-1-1