The authors thank P. Li and P. Scallion (Dalhousie University) for assistance with electron microscopy, M. Dlutek (Dalhousie University) for Illumina sequencing, S. Geisen (Wageningen University) for providing parsed metatranscriptomic data, F. Mahé (CIRAD, Montpellier) for access to and parsing much of the V4 data, M. Brown (Mississippi State) for the seed phylogenomic dataset, A. Sebé-Pedrós (Weizmann Institute of Science) for the seed myosin alignments, M. Kolisko (Institute of Parasitology, Czech Academy of Sciences) for data handling scripts, B. Q. Minh (University of Vienna) for substantial help with phylogenomic analyses and troubleshooting in IQ-TREE, and R. Lewis (Nova Scotia Museum) and B. Francis for advice on Mi’kmaq tradition and language. This work was supported by CIFAR, NSERC grant 298366-2014 to A.G.B.S. and NSERC grant 2016-016792 to A.J.R.

Reviewer information

Nature thanks I. Ruiz-Trillo and the other anonymous reviewer(s) for their contribution to the peer review of this work.