Diversification of insects since the Devonian: a new approach based on morphological disparity of mouthparts

Abstract

The majority of the analyses of the evolutionary history of the megadiverse class Insecta are based on the documented taxonomic palaeobiodiversity. A different approach, poorly investigated, is to focus on morphological disparity, linked to changes in the organisms’ functioning. Here we establish a hierarchy of the great geological epochs based on a new method using Wagner parsimony and a ‘presence/absence of a morphological type of mouthpart of Hexapoda’ dataset. We showed the absence of major rupture in the evolution of the mouthparts, but six epochs during which numerous innovations and few extinctions happened, i.e., Late Carboniferous, Middle and Late Triassic, ‘Callovian-Oxfordian’, ‘Early’ Cretaceous, and ‘Albian-Cenomanian’. The three crises Permian-Triassic, Triassic-Jurassic, and Cretaceous-Cenozoic had no strong, visible impact on mouthparts types. We particularly emphasize the origination of mouthparts linked to nectarivory during the Cretaceous Terrestrial Revolution. We also underline the origination of mouthparts linked to phytophagy during the Middle and the Late Triassic, correlated to the diversification of the gymnosperms, especially in relation to the complex ‘flowers’ producing nectar of the Bennettitales and Gnetales.

Beetle borings in wood with host response in early Permian conifers from Germany

“…Tunneling wood represents a complex life strategy of insects, which effectively avoid predation and fungal parasites for their offspring (Raffa et al 2015). Contrary to Nel et al (2018), who claim that significant changes in mouthpart morphologies of insects cannot been recognised during the Late Carboniferous to middle Permian, the wood borings reported here imply a series of functional innovation, especially regarding mouthparts and cellulose digestion. Compared with other vegetative organs, wood is a relatively nutrition-poor food source.…”

Molecular phylogeny of the Paleogene fungus gnat tribe Exechiini (Diptera: Mycetophilidae) revisited: Monophyly of genera established and rapid radiation confirmed

“…The remarkable morphological similarity of most the genera of Exechiini is a further indication of a young age of this evolutionary lineage. But on the other hand, the many long terminal (species) branches combined with a rich fossil record where many seemingly apomorphic genera existed at least 36 million years ago, suggest several relatively old species and genera that have survived rather unchanged for millions of years (see further discussion in Nel, Bertrand, & Nel, on diversification of insects).…”

Insect Mouthpart Transcriptome Unveils Extension of Cuticular Protein Repertoire and Complex Organization

“…A single recent publication involving mouthpart transcriptomics did not address the time and organs strictly responsible for cuticular biogenesis stricto sensu (tsetse fly proboscis organ) and was not focused on biomaterial characterization (Awuoche et al, 2017). As part of the feeding specialization process, mouthparts are crucial players with sensory and morphological structures that shape the front line of insect/host coevolutionary processes (Futuyma and Agrawal, 2009;Nel et al, 2018). In Hemiptera, a primarily plant-feeding order, the evolution of one of the 6-9 piercing-sucking type mouthparts of insects (Garrouste et al, 2012;Nel et al, 2018;Huang et al, 2016) has profoundly shaped the ecology of almost the entire order toward a dominant parasitic/predatory lifestyle (Weirauch and Schuh, 2011).…”