Insect phylogenomics: new insights on the relationships of lower neopteran orders (Polyneoptera)

The branching pattern of the diverse lower neopteran insect lineages (Polyneoptera: cockroaches, mantids, earwigs, grasshoppers, phasmids etc.) is the least resolved problem in insect systematics. Despite the accumulation of various morphological and molecular datasets, the proposed phylogenetic relationships within Polyneoptera remain unstable. In this study we investigate these relationships based on a new transcriptome data matrix covering almost all polyneopteran orders, except for Mantophasmatodea, Grylloblattodea and Mantodea. The data conclusively support a monophyletic Polyneoptera, thus corroborating previous findings from (i) recent large gene studies with smaller taxon sampling and (ii) comprehensive protein coding gene analyses across all insect lineages, and, consequently, rejecting the paraphyletic lower neopteran group suggested by various morphological characters and rRNA gene analyses. The inclusion of several phylogenetically ambiguous polyneopteran orders (Zoraptera, Dermaptera, Plecoptera, Phasmatodea and Embioptera) allows us to further test alternative phylogenetic relationships within Polyneoptera. Previously suggested clades are significantly rejected: Parametabola (=Zoraptera+Paraneoptera), Mystroptera (=Embioptera+Zoraptera) and Orthopterida (=Orthoptera+Phasmatodea). Although the lower neopteran orders are so far only supported as a monophyletic group by autapomorphies in wing base characters, phylogenomic analyses consistently provide further strong support. However, despite the use of this large dataset, several polyneopteran orders still show unstable positions within a monophyletic Polyneoptera.