﻿Phylogeny and age of cockroaches: a reanalysis of mitogenomes with selective fossil calibrations

Xin-Ran Li

doi:10.3897/dez.69.68373

Abstract

In spite of big data and new techniques, the phylogeny and timing of cockroaches remain in dispute. Apart from sequencing more species, an alternative way to improve the phylogenetic inference and time estimation is to improve the quality of data, calibrations and analytical procedure. This study emphasizes the completeness of data, the reliability of genes (judged via alignment ambiguity and substitution saturation), and the justification for fossil calibrations. Based on published mitochondrial genomes, the Bayesian phylogeny of cockroaches and termites is recovered as: Corydiinae + (((Cryptocercidae + Isoptera) + ((Anaplectidae + Lamproblattidae) + (Tryonicidae + Blattidae))) + (Pseudophyllodromiinae + (Ectobiinae + (Blattellinae + Blaberidae)))). With two fossil calibrations, namely,Valditermes brenanaeandPiniblattella yixianensis, this study dates the crown Dictyoptera to early Jurassic, and crown Blattodea to middle Jurassic. Using the ambiguous ‘roachoid’ fossils to calibrate Dictyoptera+sister pushes these times back to Permian and Triassic. This study also shows that appropriate fossil calibrations are rarer than considered in previous studies.

Highlights

The family-level relationships of cockroaches have been in dispute for decades (Fig. 1; see McKittrick 1964, Klass 2001, Roth 2003)
The present study focuses on true cockroaches (Blattaria), the major component of Dictyoptera
The dating result of two-fossil-calibration analysis is regarded as the formal result of this paper (Fig. 3: middle), suggesting that the age of crown Dictyoptera is 191.08 Ma (95% credibility interval 168.96–218.82 Ma), of crown Blattodea 171.2 Ma

Summary

Introduction

The family-level relationships of cockroaches have been in dispute for decades (Fig. 1; see McKittrick 1964, Klass 2001, Roth 2003). Most recent studies are based on molecular data (e.g., Djernæs et al 2015, Legendre et al 2015, Wang et al 2017, Bourguignon et al 2018, Evangelista et al 2019), or rarely on morphological and ethological data (Klass and Meier 2006, Djernæs et al 2015 in part). The evolutionary pattern of cockroaches remains ambiguous: mitochondrial genomes (Bourguignon et al 2018) suggest the basal splits as (Blaberoidea + Corydioidea) + the blattoid complex (i.e. Blattoidea nesting Isoptera), while the much bigger transcriptome data (Evangelista et al 2019) suggest Blaberoidea + (Corydioidea + blattoid complex), not to mention more incongruent relationships of families and subfamilies. The ‘roachoid’ fossils are a particular point of contention (Tong et al 2015 vs. Kjer et al 2015, Bourguignon et al 2018 per se)

Methods

Results

Discussion

Conclusion