Assessing the Fossil Record of Plant-Insect Associations - Ichnodata Versus Body-Fossil Data

Two basic approaches are used to assess the paleobiology of continental associations between insect herbivores and their host plants. First is a biological approach that emphasizes phylogeny of extant representatives of lineages with fossil records. Second is a paleobiological approach that provides intrinsic evaluation of fossil associational evidence, of which there are several types of studies. One type of study is intensive examination of single insect-herbivore associations that involve a continuum from generalists to specialists requiring detailed autecological deductions about life habits. Another tack is assessment of herbivore damage patterns from selected plant hosts through slices of time for understanding the ecological evolution of a component community. Alternatively, comprehensive analyses can be made of the feeding patterns within a single or a series of regional floras.

The record of plant-insect associations has five advantages. Associational data (1) are typically present in deposits that lack insect body fossils; (2) often surpass in abundance and usefulness insect body fossils in the same deposit; (3) frequently antedate their respective insect body fossils; (4) provide invaluable behavioral data that are unavailable from body fossils; and (5) supply crucial data for testing hypotheses in paleobiology and evolutionary biology that otherwise are unachievable. Disadvantages involve difficulties in circumscribing insect culprits, absence of extant ecological data to which fossil data can be compared, and lack of attention by paleobotanists and botanists in collecting damaged specimens. An associational view of fossil land plants and insects provides a dynamic, process-oriented view of ecosystem evolution that is needed in paleobiology