Providing Indirect Evidence Of Other Organisms

There are size and habitat limitations to the types of organism that can be trapped in amber. For example, many plants would not normally leave flowers or leaves in the resin, and when they did, the remains would likely be difficult to identify. Vertebrates might leave hairs, feathers, or scales but these structures would also be difficult to identify. However, arthropods that are specific to certain hosts (e.g., ticks and mammals) can provide clues to other organisms that existed at that time. This use of fossils relies heavily on the principle of behavioral fixity, which asserts that, at least at the generic level, the behavior of a fossil organism would have been similar to that of its present-day descendants.

FIGURE 2 The unique morphological features (smooth, flattened body) of this fossil palm bug (Paleodoris lattini) in Dominican amber not only characterize it systematically but also provide clues to its lifestyle of living in confined spaces between the unopened fronds of pinnately leafed palms.

Many insects form specific associations with plants. Such associations can often be deduced by the morphological features of the insect (functional morphology). One extremely flattened hemipteran in Dominican amber (Fig. 2) that was identified as a palm bug displayed characters similar to those of an existing species in the same subfamily. The extant species lives between the closed leaves of royal palms (Roystonea spp.) in Cuba. This fossil provided indirect evidence that pinnately leafed palms, quite likely an extinct species of Roystonea, existed in the original amber forest. Other plant-specific insects, such as fig wasps and palm bruchids, provide evidence of figs and palms in the original ecosystem.

Insects that require a blood meal to complete their development can also be used as indirect evidence of a vertebrate group. Evidence of birds in the original Dominican amber forest is implied by the presence of a female Anopheles mosquito in amber because extant species of this subgenus normally attack birds. The presence of other vertebrate groups is implied by fleas (Siphonaptera), horseflies (Diptera: Tabanidae), biting midges (Diptera: Ceratopogonidae), and other bloodsucking arthropods such as ticks.

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