This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/evo.14135. This article is protected by copyright. All rights reserved. Evidence for speciation underground in diving beetles (Dytiscidae) from a subterranean archipelago Short running title: Subterranean speciation in diving beetles Barbara L. Langille 1 , Josephine Hyde 1,2 , Kathleen M. Saint 1 , Tessa M. Bradford 1,6 , Danielle N. Stringer 1 , Simon M. Tierney 3 , William F. Humphreys 4,5 , Andrew D. Austin 1,6 , Steven J.B. Cooper 1,6 1 Australian Centre for Evolutionary Biology and Biodiversity, Department of Ecology and Evolutionary Biology, School of Biological Sciences, University of Adelaide, South Australia 5005, Australia. 2 Department of Environmental Sciences, The Connecticut Agricultural Experiment Station, New Haven 06511 CT, USA. 3 Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797 Penrith NSW 2751, Australia. 4 Western Australian Museum, Locked Bag 40, Welshpool DC, WA 6986, Australia. 5 School of Animal Biology, University of Western Australia, Nedlands, Western Australia. 6 Evolutionary Biology Unit, South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia. Corresponding author: Barbara Langille – barbara.langille@adelaide.edu.au Author Contributions BLL was responsible for the bulk of laboratory work, editing of data, data analysis, interpretation of the data, writing, and editing the manuscript. JH was responsible for the shotgun sequencing and editing the manuscript. KMS was involved in the laboratory work. TMB and DNS were responsible for some gene sequencing and editing the manuscript. SMT was involved in the project design, interpretation of the data and edited the manuscript. WFH was responsible for collection of samples and editing the manuscript. ADA was responsible for project planning and editing the manuscript. SJBC was responsible for project planning, the collection of samples, analyses of sequence data, co-manuscript planning, and editing the manuscript. Acknowledgements We would like to thank editor Dr. David Hall, associate editor Dr. Elizabeth Derryberry, and two anonymous reviewers whose constructive criticism greatly improved the manuscript. We would like to thank Julianne Waldock from the Western Australia Museum for technical support and Remko Leijs for providing DNA samples of the stygobiotic species that were used in this study. We would also like to thank Chris Watts and Howard Hamon for the beetle images, and Flora, Peter and Paul Axford, at Sturt Meadows Station, for generously providing accommodation and access to their property. This work was funded by an ARC Discovery grant (DP120102132 and DP180103851) to S.J.B.C., W.F.H. and A.D.A. This work was also funded by an Australian Postgraduate Award and an International Postgraduate Research Scholarship, both awarded to B.L.L.