Fossil record of stem groups employed in evaluating the chronogram of insects (Arthropoda: Hexapoda).

Yan-Hui Wang,Michael S Engel,Hao-Yang Wu,Qiang Xie,Dávid Rédei,Gang Wang,Xiao-Guang Liu,Wen-Jun Bu,José A Rafael

doi:10.1038/srep38939

Abstract

Insecta s. str. (=Ectognatha), comprise the largest and most diversified group of living organisms, accounting for roughly half of the biodiversity on Earth. Understanding insect relationships and the specific time intervals for their episodes of radiation and extinction are critical to any comprehensive perspective on evolutionary events. Although some deeper nodes have been resolved congruently, the complete evolution of insects has remained obscure due to the lack of direct fossil evidence. Besides, various evolutionary phases of insects and the corresponding driving forces of diversification remain to be recognized. In this study, a comprehensive sample of all insect orders was used to reconstruct their phylogenetic relationships and estimate deep divergences. The phylogenetic relationships of insect orders were congruently recovered by Bayesian inference and maximum likelihood analyses. A complete timescale of divergences based on an uncorrelated log-normal relaxed clock model was established among all lineages of winged insects. The inferred timescale for various nodes are congruent with major historical events including the increase of atmospheric oxygen in the Late Silurian and earliest Devonian, the radiation of vascular plants in the Devonian, and with the available fossil record of the stem groups to various insect lineages in the Devonian and Carboniferous.

Highlights

Insecta s. str. (=Ectognatha), comprise the largest and most diversified group of living organisms, accounting for roughly half of the biodiversity on Earth
The results of Bayesian inference (BI) and maximum likelihood (ML) analyses based on five nuclear genes are summarized in Fig. 2 and Supplementary Fig. S1
Our study comprehensively reexamined the applicability of these markers in studies on insect phylogeny at the ordinal level

Summary

Introduction

Insecta s. str. (=Ectognatha), comprise the largest and most diversified group of living organisms, accounting for roughly half of the biodiversity on Earth. Understanding the factors that led to these episodes of diversification and extinction over the more than 400 million years of insect history is vital for any comprehensive perspective on their evolution Crucial to this is a robust estimate of the timing of major events so that they may be placed within the proper paleoecological and paleoclimatological context. There remains a gap of approximately 100 million years between the earliest hexapods and their putative crustacean sister group, clade Xenocarida (=Remipedia +Cephalocarida)[5,6] which has fossils at least as old as the Upper Cambrian, approximately 500 million years ago (Ma)[7] These include improper fossil calibration[13,14], sparse taxonomic sampling[15,16,17], or excessive restrictions on priors that can bias posterior estimates[18,19]

Methods

Results

Conclusion