A proturan Filientomon takanawanum, photo by Makiko Fukui

The early lineages of hexapods (broadly defined insects) have long been debated. Researchers at University of Tsukuba and collaborators critically examined the newly proposed "Protura-sister" phylogenetic hypothesis. This analysis revealed a fundamental flaw in the hypothesis, reinforcing the validity of the previously established "Ellipura" hypothesis.

Tsukuba, Japan—Hexapods, which make up 75% of all animal species, have been a focus of evolutionary debate for over a century. No consensus has been reached on the phylogenetic relationships among the four earliest lineages: Protura, Collembola, Diplura, and Insecta, the latter including all hexapods except the first three groups. To clarify these relationships, researchers have conducted large-scale molecular phylogenetic analyses using extensive gene sequence datasets. These studies have supported the "Ellipura" hypothesis, which proposes the grouping [Ellipura (= Protura + Collembola) + (Diplura + Insecta)], as the most widely accepted theory.

However, the alternative "Protura-sister" hypothesis (Protura + [(Collembola + Diplura) + Insecta]) has emerged based on molecular phylogenetic analysis and garnered substantial attention. However, by examining the non-nucleotide sequence data used to support this hypothesis, researchers identified critical errors resulting from misinterpretation and insufficient analysis.

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This work was supported by the JSPS (Japan Society for the Promotion of Science) KAKENHI: Grant-in-Aid for Scientific Research C, 19K06821 to RM.

Original Paper

Title of original paper:

Embryology cannot establish the "Protura-sister"

Journal:

Proceedings of the National Academy of Sciences of the United States of America

DOI:

10.1073/pnas.2423813122

Correspondence

Visiting Researcher MACHIDA Ryuichiro
Sugadaira Research Station, Mountain Science Center, University of Tsukuba

Associate Professor FUKUI Makiko
Graduate School of Science and Engineering, Ehime University

Researcher TOMIZUKA Shigekazu
Echigo-Matsunoyama Museum of Natural Science "Kyororo"

Assistant Professor IKEDA Yatsukaho
Faculty of Medicine, Oita University

Assistant Professor MASUMOTO Mika
College of Liberal Arts and Sciences, Kitasato University

Related Link

Sugadaira Research Station, Mountain Science Center, University of Tsukuba