Species Delimitation and Phylogenetic Relationships in Ectobiid Cockroaches (Dictyoptera, Blattodea) from China

Abstract

We collected Ectobiidae cockroach specimens from 44 locations in the south of the Yangtze valley. We obtained 297 COI sequences specimens and carried out phylogenetic and divergence dating analyses, as well as species delimitation analysis using a General Mixed Yule Coalescent (GMYC) framework. The intraspecific and interspecific sequence divergence in Ectobiidae cockroaches ranged from 0.0 to 7.0% and 4.6 to 30.8%, respectively. GMYC analysis resulted in 53 (confidence interval: 37–65) entities (likelihood ratio = 103.63) including 14 downloaded species. The COI GMYC groups partly corresponded to the ectobiid species and 52 ectobiid species were delimited successfully based on the combination of GMYC result with morphological information. We used the molecular data and 6 cockroach fossil calibrations to obtain a preliminary estimate of the timescale of ectobiid evolution. The major subfamilies in the group were found to have diverged between ~125–110 Ma, and morphospecies pairs were found to have diverged ~10 or more Ma.

Fossil calibrations for the cockroach phylogeny (Insecta, Dictyoptera, Blattodea), comments on the use of wings for their identification, and a redescription of the oldest Bla

“…Only two previous studies (Legendre et al, 2015;Che et al, 2017) have used fossils within the scope of this paper as calibration points. Legendre et al (2015) used four calibration points within Blattodea and Che et al (2017) used five.…”

“…Additionally, there are many genera of cockroaches that have cup-like structures, or pits covering the tegmina (e.g., Lucihormetica, Hemiblabera), and these taxa can frequently be beetle-like (e.g., Colapteroblatta, Eustegasta, Calhypnorna). Che et al (2017) use Epilampra sp. Pongrácz, 1935, Pycnoscelus gardneri Cockerell, 1920, and Zetobora brunneri Scudder, 1890, as calibration bounds for their COI gene tree.…”

“…Molecular phylogenetic studies of cockroaches go back more than 20 years (Kambhampati et al, 1996), but molecular dating of cockroach phylogenies has only begun recently (Djernaes et al, 2015;Legendre et al, 2015;Che et al, 2017). One of the crucial points in divergence time estimation is choosing the correct fossils for age calibration, as these are highly influential on posterior age estimates (e.g., Inoue et al, 2010).…”

“…There have been three molecular phylogenies of Blattodea with fossil-calibrated divergence dates (Djernaes et al, 2015;Legendre et al, 2015;Che et al, 2017), not including those focusing on termites (e.g., Ware et al, 2010). Some studies with larger scope have dated nodes within Dictyoptera as well (Misof et al, 2014;Tong et al, 2015).…”

“…Four of these fossil calibration points were non-termite crown Blattodea, and we evaluate each of these in the current paper. Most recently, Che et al (2017) used five fossil Blaberoidea to date their COI gene tree. We briefly discuss four of these (Piniblattella, Epilampra sp., Pycnoscelus gardneri, Zetobora brunneri) here but do not agree with any of them as calibration points because of their poor phylogenetic justifications.…”