The next 25 years: invertebrate systematics

Abstract

A distinction is made between classification, taxonomy, and systematics. Taxonomic studies in most invertebrate groups will not progress beyond the descriptive stages because of the large number of species to be described, the low profile of taxonomy, and the lack of support for museums. Taxonomy and classification must be seen as immediate economic components of modern biology: systematics should be revived in the universities. The limitations of the morphospecies concept make studies on living forms, freshly killed animals, or specially preserved specimens imperative, but these cannot be completed except in very few instances. Hence we are likely to learn more and more about less and less. Nevertheless, more sibling species complexes will undoubtedly be discovered. When these complexes are understood systematically, and population genetics becomes integrated with the study of speciation, more emphasis will likely be given to the multiplicity of speciation models. A pleuralistic definition of species should follow. Cladistic systematics will continue to expand in the invertebrates. More emphasis should be placed on early Metazoan fossils, and attempts made to fit them into classifications. Fossils can be useful in checking various phylogenetic models, even if they are considered useless for determining evolutionary relationships by some cladists. With the current acceptance that the Protista and Protozoa are both polyphyletic, there will be a major revolution in invertebrate systematics. Ultrastructural and biochemical data are needed to clarify the systematics of both the unicellular eukaryotes and multicellular Metazoa. Only after systematic analyses of wider data sets are complete will it be time to consider a new classification for the "invertebrates." However, the resulting scheme will be very different from that which we accept, follow, and teach today.