Insect origination and extinction in the Phanerozoic

Abstract

Insects (Superclass Hexapoda) are the most successful group of living terrestrial arthropods and the richness of their fossil record is only just beginning to be realized with the recent publication of two extensive databases. Hexapods first appeared in the Early Devonian, post-dating the Cambrian ‘explosion’ of marine arthropods by some 140 Ma. The earliest Hexapoda belong to primitively wingless taxa; however, these ‘Apterygota’ comprise less than 1% of all hexapod species. The appearance of winged insects (Pterygota) in the mid-Carboniferous was accompanied by a major adaptive radiation of non-holometabolous hexapods at ordinal level This was supplemented in the Permian by the radiation of insects with complete metamorphosis (Holometabola). The number of insect orders present in this period was similar to that at the present day. The family data suggest four major periods of origination in the Phanerozoic, with peaks in the Permo-Carboniferous, Early Jurassic, Early Cretaceous and Eocene. Unlike the Tertiary, the Palaeozoic and Cretaceous peaks are accompanied by considerable turnover of families; they are followed by reduced palaeodiversity in the Early Triassic and Late Cretaceous and Palaeocene. The former decline may be linked with the general extinction at the Permian/Triassic boundary and the latter with the rise of the angiospermous flowering plants. Insect generic data for the Phanerozoic reflect the pattern shown by families but not orders. In general, insect diversity may be explained by an overall trend towards low extinction and steady origination at a subordinal level since the Palaeozoic.

Fossil evidence for key innovations in the evolution of insect diversity

“…These facts, long casually observed, have suggested that key evolutionary changes have been responsible for generating much of the richness in this very diverse group, and four such evolutionary innovations have held centre stage [18,19]: the insect bauplan [35], wings [36], wing folding [21] and complete metamorphosis [23]. Here, we have reported evidence that both fossil family rspb.royalsocietypublishing.org Proc.…”

“…Four progressive evolutionary steps have traditionally been recognized in the evolutionary history of the hexapods, based on the sequence in which they appear in the fossil record [18,19] and phylogenies (e.g. [20]) (figure 1).…”

The Pollination of Mid Mesozoic Seed Plants and the Early History of Long-proboscid Insects1,2,3

“…This continuity indicates a shift from earlier fluid feeding on pollination drops of gymnosperms to subsequent nee taring on angiosperms. These transfers probably represent opportunistic cladogenetic events in the plant and fly lineages, with an effect at higher taxonomic ranks, seen in family-level diversity data (Labandeira & Sepkoski, 1993;Jarzembowski & Ross, 1996). It is unknown why, for pollinators, only the Diptera escaped the extinction blitz.…”

“…Although the family-level analyses of fossil insect diversity by Labandeira and Sepkoski (1993) need to be updated, these and other analyses (Jarzembowski & Ross, 1996;Dmitriev & Ponomarenko, 2002) indicate that the plateau in the earlier semilogarithmic rise of family-level insect diversity may be real, attributable to a biological event that transformed plant species dominance from gymnosperm to angiosperm. An alternative explanation is that this plateau represents a lull in the recovery of insect taxa from earlier deposits with high numbers of insect species.…”

The Permostridulidae fam. n. (Panorthoptera), a new enigmatic insect family from the Upper Permian of France

“…Despite their antiquity and their biodiversity peak during the Permian (Labandeira & Sepkoski, 1993;Jarzembowski & Ross, 1996) the Palaeozoic "polyneopterous" insects are rarely considered in phylogenetic analyses. Nevertheless, the usefulness of inclusion of fossil taxa in phylogenies is widely admitted (Smith, 1994).…”