Mitochondrial Genome Diversity in Collembola: Phylogeny, Dating and Gene Order

Chiara Leo,Francesco Frati,Francesco Nardi,Antonio Carapelli,Francesco Cicconardi

doi:10.3390/d11090169

Abstract

Collembola (springtails) are an early diverging class of apterygotes, and mark the first substantial radiation of hexapods on land. Despite extensive work, the relationships between major collembolan lineages are still debated and, apart from the Early Devonian fossil Rhyniella praecursor, which demonstrates their antiquity, the time frame of springtail evolution is unknown. In this study, we sequence two new mitochondrial genomes and reanalyze all known Collembola mt-genomes, including selected metagenomic data, to produce an improved phylogenetic hypothesis for the group, develop a tentative time frame for their differentiation, and provide a comprehensive overview of gene order diversity. Our analyses support most taxonomically recognized entities. We find support for an Entomobryomorpha + Symphypleona clade, while the position of Neelipleona could not be assessed with confidence. A Silurian time frame for their basal diversification is recovered, with an indication that divergence times may be fairly old overall. The distribution of mitochondrial gene order indicates the pancrustacean arrangement as plesiomorphic and dominant in the group, with the exception of the family Onychiuridae. We distinguished multiple instances of different arrangements in individual genomes or small clusters. We further discuss the opportunities and drawbacks associated with the inclusion of metagenomic data in a classic study on mitochondrial genome diversity.

Highlights

IntroductionHexapoda and represent the first substantial radiation of the group following the invasion of land
Collembola, commonly referred to as springtails, is an ancient group of primitively winglessHexapoda and represent the first substantial radiation of the group following the invasion of land.During their long evolutionary history, springtails have adapted to almost any ecosystem on Earth, from Antarctic ice-free areas to highlands in the Himalayas and the Australian deserts, dwelling in soil, in leaf litter, or on vegetation [1,2,3]
With costs dropping for Generation Sequencing, and the increasing difficulty in developing morphology-based studies due to the specificity of expertise required, it is foreseeable that the production and availability of mitochondrial metagenomic data for biodiversity studies will increase significantly in the near future

Summary

Introduction

Hexapoda and represent the first substantial radiation of the group following the invasion of land. During their long evolutionary history, springtails have adapted to almost any ecosystem on Earth, from Antarctic ice-free areas to highlands in the Himalayas and the Australian deserts, dwelling in soil, in leaf litter, or on vegetation [1,2,3]. The oldest fossils of Collembola, and hexapods in general, date back to the Early Devonian (~ 400 Millions of years ago, Mya), and were found in the Rhynie chert deposits of Scotland [5,6,7]. The identification of R. praecursor as a collembolan is widely accepted, it remains to be clarified whether the Rhynie chert fossils

Objectives

Methods

Results

Discussion

Conclusion