Evolutionary History of the Hymenoptera

Abstract

Hymenoptera (sawflies, wasps, ants, and bees) are one of four mega-diverse insect orders, comprising more than 153,000 described and possibly up to one million undescribed extant species [1, 2]. As parasitoids, predators, and pollinators, Hymenoptera play a fundamental role in virtually all terrestrial ecosystems and are of substantial economic importance [1, 3]. To understand the diversification and key evolutionary transitions of Hymenoptera, most notably from phytophagy to parasitoidism and predation (and vice versa) and from solitary to eusocial life, we inferred the phylogeny and divergence times of all major lineages of Hymenoptera by analyzing 3,256 protein-coding genes in 173 insect species. Our analyses suggest that extant Hymenoptera started to diversify around 281 million years ago (mya). The primarily ectophytophagous sawflies are found to be monophyletic. The species-rich lineages of parasitoid wasps constitute a monophyletic group as well. The little-known, species-poor Trigonaloidea are identified as the sister group of the stinging wasps (Aculeata). Finally, we located the evolutionary root of bees within the apoid wasp family "Crabronidae." Our results reveal that the extant sawfly diversity is largely the result of a previously unrecognized major radiation of phytophagous Hymenoptera that did not lead to wood-dwelling and parasitoidism. They also confirm that all primarily parasitoid wasps are descendants of a single endophytic parasitoid ancestor that lived around 247 mya. Our findings provide the basis for a natural classification of Hymenoptera and allow for future comparative analyses of Hymenoptera, including their genomes, morphology, venoms, and parasitoid and eusocial life styles.

Mechanisms of ovipositor insertion and steering of a parasitic wasp

“…The valves can slide along each other (5, 7) and do not get dislocated under natural conditions, because they are longitudinally connected via a tongue-and-groove mechanism (5,(8)(9)(10). The ovipositor and the "wasp waist," a constriction of the body between the first and second abdominal segment (11), are essential in probing behavior and are therefore considered to be instrumental in the evolution of the order (11)(12)(13)(14)(15). The shape, structure, and mechanical properties of the ovipositors are putatively adapted to the substrates into which the animals need to probe (6,(16)(17)(18), and because both substrates and hosts are so diverse, this might have resulted in high species diversification of the hymenopterans (13,14).…”

Sensory and cognitive adaptations to social living in insect societies

“…Perhaps, then, bees did evolve more complex brains as they became more social, and it is only wasps that rely on collective "swarm intelligence." Recently, solid large-scale phylogenies have become available of all of the major social insect groups and their direct solitary ancestors (6,(20)(21)(22)(23)(24) (Fig. 1).…”

Translucent cuticle and setiferous patches in Megaspilidae (Hymenoptera, Ceraphronoidea)

“…Even the relationship of Ceraphronoidea to other Hymenoptera remains unclear, although the superfamily is robustly monophyletic (Mikó et al 2013). Different molecular analyses have grouped Ceraphronoidea with Stephanoidea, Ichneumonoidea, Megalyroidea, or with Ichneumonoidea and Proctotrupomorpha (Klopfstein et al 2013;Mao et al 2014;Peters et al 2017;Sharkey 2007;Sharkey et al 2012). Contrary to the belief that ceraphronoids are too small for morphological characters to be of phylogenetic use (Klopfstein et al 2013), the group contains taxa with morphological structures that may serve as characters to corroborate both the phylogenetic relationships among members within the superfamily.…”

“…As the putative sister to Apocrita, Orussidae represent an important step in the evolution of Hymenoptera and the parasitoid lifestyle (Mao et al 2014;Peters et al 2017;Sharkey 2007). Orussidae also have patches of smooth cuticle similar to the syntergal and synsternal translucent patches found in Ceraphronoidea.…”