Coevolution of Insects and vertebrates in the Mesozoic: examples from katydids and giant cicadas

Insects are the most diverse groups on earth and preserved with plenty of fossils. Disentangling their ecological roles are crucial for understanding the evolution of terrestrial ecosystems, however, reconstructing the adaptive evolution of extinct insects has been proven to be highly challenging. Here, we conduct integrated approaches to reveal the macroevolution of two insect clades, katydids (Hagloidea) and giant cicadas (Palaeontinidae), on the basis of newly compiled morphological datasets. Our results provide novel information for coevolution of insects and vertebrates in the Mesozoic, and highlight the significance of fossil morphologies. 1) Acoustic evolution of katydids. We present a database of the stridulatory apparatus and wing morphology of Mesozoic katydids and analyze the evolution of their acoustic communication. Our results demonstrate that katydids evolved complex acoustic communication including mating signals, intermale communication, and directional hearing, by the Middle Jurassic; evolved high-frequency musical calls by the Late Triassic. The Early—Middle Jurassic katydid transition coincided with the diversification of mammalian clades, supporting the hypothesis of the acoustic coevolution of mammals and katydids. 2) Flight evolution of giant cicadas. We reveal the flight evolution of the Mesozoic arboreal insect clade Palaeontinidae. Our analyses unveil a faunal turnover from early to late Palaeontinidae during the Jurassic–Cretaceous, accompanied by a morphological adaptive shift and improvement in flight abilities including increased speed and enhanced maneuverability. The adaptive aerodynamic evolution of Palaeontinidae may have been stimulated by the rise of early birds, supporting the hypothesis of an aerial evolutionary arms race between Palaeontinidae and birds.