Recalibration of the insect evolutionary time scale using Monte San Giorgio fossils suggests survival of key lineages through the End-Permian Extinction

Abstract

Insects are a highly diverse group of organisms and constitute more than half of all known animal species. They have evolved an extraordinary range of traits, from flight and complete metamorphosis to complex polyphenisms and advanced eusociality. Although the rich insect fossil record has helped to chart the appearance of many phenotypic innovations, data are scarce for a number of key periods. One such period is that following the End-Permian Extinction, recognized as the most catastrophic of all extinction events. We recently discovered several 240-million-year-old insect fossils in the Mount San Giorgio Lagerstätte (Switzerland–Italy) that are remarkable for their state of preservation (including internal organs and soft tissues), and because they extend the records of their respective taxa by up to 200 million years. By using these fossils as calibrations in a phylogenomic dating analysis, we present a revised time scale for insect evolution. Our date estimates for several major lineages, including the hyperdiverse crown groups of Lepidoptera, Hemiptera: Heteroptera and Diptera, are substantially older than their currently accepted post-Permian origins. We found that major evolutionary innovations, including flight and metamorphosis, appeared considerably earlier than previously thought. These results have numerous implications for understanding the evolution of insects and their resilience in the face of extreme events such as the End-Permian Extinction.

Molecular Phylogeny and Infraordinal Classification of Zoraptera (Insecta)

“…Within Spiralizoridae, the distribution of Latinozorinae is restricted to the Panamanian and north Neotropical regions, and Spiralizorinae are known from the tropics and subtropics of America, Asia, and Oceania, but not from Africa ( Figure 1C). The current distribution of the main evolutionary lineages across all continents (except Australia) points to the Paleozoic origin of Zoraptera, which was confirmed by recent studies [3][4][5].…”

“…Zoraptera, whose members are commonly known as angel insects, is one of the smallest and least-known insect orders [1][2][3]. This order represents an old evolutionary lineage with a Paleozoic origin [3][4][5]. The systematic placement of this group has always been controversial (see "the Zoraptera problem" introduced by Beutel and Weide [6]), and different insect lineages, such as Psocoptera, Isoptera, and Embioptera, have been proposed as the closest relatives of Zoraptera (see Mashimo et al [1] for a review).…”

“… Kirstová et al [29];2 Yoshizawa and Johnson[23];3 Ma et al[24];4 Terry and Whiting[10];5 Terry and Whiting (unpublished);6 Wang et al[49]; * chimaeric taxon (isolate 002 for 18S rRNA, isolate 016 for 16S rRNA and COI mtDNA).…”

The age of insects and the revival of the minimum age tree

“…An instructive example of the impact of different calibration densities comes from three studies on the insect tree of life (Misof et al 2014; Tong et al 2014; Montagna et al 2019). In the first study, Misof et al (2014) compiled an unprecedented molecular dataset that included 1478 single‐copy nuclear genes obtained from the transcriptomes of 144 taxa, covering all major insect lineages.…”

“…Later on, new fossil discoveries from Middle Triassic deposits (~240 Ma) on Monte San Giorgio in Switzerland yielded six additional and two older calibrations within the insect tree; these were added to the Tong et al . calibration scheme and provided an updated timeline of insect diversification (Montagna et al 2019).…”