Acoustic communication has played a key role in the evolution of animals especially vertebrates and insects, ranging from mating to warning calls and even including social learning. On December 13, 2022 PNAS published the novel insight from an international team of paleoentomologists on acoustic evolution of Mesozoic katydids and evolution of the Mesozoic soundscape.
Acoustic communication is commonly used in behaviors such as courtship, mating, predation, and avoidance of natural predators. The result is an amazingly diverse and complex modern soundscape. The reconstruction of ancient acoustic signals is challenging, however, due to the extreme rarity of fossilized organs.
Insects were the first terrestrial animals to use air-borne sound signals for long-distance communication. Among acoustically signaling insects, katydids stand out as an ideal source to investigate the evolution of acoustic organs and behavior.
PhD student XU Chunpeng from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS), under the supervision of Profs. WANG Bo and ZHANG Haichun from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS), carried out a detailed and global investigation of fossil katydids from the Mesozoic Era (commonly referred to as the age of the dinosaurs).
We research team reported the earliest tympanal ears and sound-producing system (stridulatory apparatus) in exceptionally preserved Mesozoic katydids. We also studied the stridulatory apparatus and wing morphology of Mesozoic katydids, calculating their probable singing frequencies and analyzed the evolution of their acoustic communication.
“The newly found tympanal ears in prophalangopsids katydids from the Middle Jurassic Daohugou Konservat-Lagerst？tte represent the earliest-known insect ears, extending the age range of the modern-type auditory tympana by 100 million years to the Middle Jurassic, some 160 million years ago”, says XU Chunpeng.
The reconstruction of singing frequencies of Mesozoic katydids and oldest tympanal ears demonstrate that katydids had evolved complex acoustic communication, including mating signals, inter-male communication, and directional hearing, at least by the Middle Jurassic. Also, katydids had evolved a high diversity of singing frequencies, including high-frequency musical calls, accompanied by acoustic niche partitioning—all at least by the Late Triassic (200 million years ago). WANG Bo says that “we suggest that acoustic communication could have been an important evolutionary driver already in the early radiation of terrestrial insects after the Permo-Triassic mass extinction.”
The Early and Middle Jurassic katydid transition from extinct haglid- to extant prophalangopsid-dominated insect faunas coincided with the diversification of derived mammalian groups (clades) and improvement of hearing in early mammals, supporting the hypothesis of acoustic co-evolution of mammals and katydids. The high-frequency songs of Mesozoic katydids could even have driven the evolution of intricate hearing systems in early mammals, and conversely, mammals with progressive hearing ability could have exerted selective pressure on the evolution of katydids, including faunal turnover.
Our findings demonstrate that insects, especially katydids, dominated the choruses during the Triassic, which is different from the modern soundscape. After the appearance of birds and frogs in the Jurassic, the forest soundscape became almost the same as the modern one in the Cretaceous, except lacking the sound of cicadas (which have less musical calls). And all of these results also highlight the ecological significance of insects in the Mesozoic soundscape, which has hitherto been largely unknown in the palaeontological record.
This research was supported by the National Natural Science Foundation of China, Strategic Priority Research Program of the Chinese Academy of Sciences, and the Deep-time Digital Earth (DDE) Big Science Program.
Reference: Xu Chunpeng, Wang Bo*, Wappler T., Chen Jun, Kopylov D., Fang Yan, Jarzembowski E.A., Zhang Haichun, Michael S.E. (2022) High acoustic diversity and behavioral complexity of katydids in the Mesozoic soundscape. PNAS, https://doi.org/10.1073/pnas.2210601119.
Figure 1 Stridulatory files of Triassic katydids (A–C) and tympanal ears of Jurassic katydids (D–E).
Figure 2 Frequency range of hearing in vertebrates (above) and frequency range of tones used by extant crickets and fossil katydids (below).
Figure 3 The origins of some key acoustic evolutionary events according to the fossil evidence.
Figure 4 Ecological restoration of singing katydids from the Middle Jurassic Daohugou Konservat-Lagerst？tte of China.
LIU Yun, Propagandist
Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences
Nanjing, Jiangsu 210008, China
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