title: Fossil evidence for key innovations in the evolution of insect diversity.
abstract: Explaining the taxonomic richness of the insects, comprising over half of all described species, is a major challenge in evolutionary biology. Previously, several evolutionary novelties (key innovations) have been posited to contribute to that richness, including the insect bauplan, wings, wing folding and complete metamorphosis, but evidence over their relative importance and modes of action is sparse and equivocal. Here, a new dataset on the first and last occurrences of fossil hexapod (insects and close relatives) families is used to show that basal families of winged insects (Palaeoptera, e.g. dragonflies) show higher origination and extinction rates in the fossil record than basal wingless groups (Apterygota, e.g. silverfish). Origination and extinction rates were maintained at levels similar to Palaeoptera in the more derived Polyneoptera (e.g. cockroaches) and Paraneoptera (e.g. true bugs), but extinction rates subsequently reduced in the very rich group of insects with complete metamorphosis (Holometabola, e.g. beetles). Holometabola show evidence of a recent slow-down in their high net diversification rate, whereas other winged taxa continue to diversify at constant but low rates. These data suggest that wings and complete metamorphosis have had the most effect on family-level insect macroevolution, and point to specific mechanisms by which they have influenced insect diversity through time.
authors.affiliation: Department of Biology, University of York, York YO10 5YW, UK Department of Natural Sciences, National Museum of Scotland, Chambers Street, Edinburgh, Midlothian EH1 1JF, UK Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK david.nicholson@nhm.ac.uk.
authors.forename: David B
authors.initials: DB
authors.lastname: Nicholson
authors.affiliation: Department of Natural Sciences, National Museum of Scotland, Chambers Street, Edinburgh, Midlothian EH1 1JF, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Ross
authors.affiliation: Department of Biology, University of York, York YO10 5YW, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Mayhew
mesh_terms: D000818:Animals; D044822:Biodiversity; D005075:Biological Evolution; D005580:Fossils / Q000033:anatomy & histology*; D007313:Insecta / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology*; D008675:Metamorphosis, Biological; D010802:Phylogeny
keywords: Hexapoda; adaptive radiation; complete metamorphosis; extinction; flight; macroevolution