The Evolution of Integrative Insect Systematics

Background: Traditional morphological taxonomy fails in some cases; even when it succeeds, the use of other disciplines significantly accelerates identification and enhances our understanding of the processes in speciation.

Arthropods: The arthropod tree of life is now divided into FIVE major branches: Pcynogonida, Euchelicerata, Myriapoda, Crustacea and Hexapoda. Crustacea and Hexapoda are in a clade, Tetraconata (Pancrustacea). Blattaria is more closely related to Isoptera; Strepsiptera is closely related to Coleoptera.
History of Entomological Classification: This history is segregated into four periods: Pre-Linnaean era, First century spanning Linnaeus’ “Systema Naturae” to Darwin’s “On the Origin of species”, Darwinian Era up to the Cladistic Revolution, Hennigian Era leading to today. Classification in the pre-Linnaean era was based solely on morphological characteristics. Binomial nomenclature was developed in the first century. Phylogeny of insect orders along the lines of Darwinian evolution was evident in the third period. Hennigian Era utilized only taxa that are monophyletic. Cytogenetics, electron microscopy and DNA sequencing are widely used. Integrative Taxonomy: In addition to morphological and molecular techniques, other disciplines (including Ecology, Behaviour, Reproductive compatibility, Life history, Zoogeography, Chemistry) are utilized. Integrated taxonomy does not replace traditional taxonomy but improves rigour.
Outcomes: Delimiting species by integrative taxonomy has yielded a better biodiversity inventory, by both increasing and decreasing species numbers. Increases have been especially due to the discovery of cryptic species. The arthropod tree of life has been re-evaluated.
Conclusion: The advances in systematics have been fuelled by: new sources of data from nucleic acid sequences, theoretical advances in the nature and analysis of systematic data, development of powerful, affordable computers and new statistical tools for data analysis, integrative taxonomy, etc. The disciplines of Insect Taxonomy and Insect Phylogenetics are complementary; thus programmes on Insect taxonomy should be inclusive.