Figure 1: Hepatitis B virus endogenization events during bird evolution.

Presence/absence analyses of zebra finch HBV EVE insertion loci (Supplementary Table S1; for full alignments, see Supplementary Data 1) revealed eZHBV endogenization events in the ancestor of Neoaves, during early passeroid evolution and during recent ploceid evolution. The avian tree of life^13,34 is shown as a simplified chronogram based on molecular dates of interordinal avian relationships¹⁵, as well as relationships within Passeriformes³² and Ploceidae (Supplementary Fig. S1). Based on HASs of the dated EVEs, nucleotide substitution rates (in substitutions/site/year) were calculated (Supplementary Table S3) for the respective parts of eZHBV evolution and denoted above the tree. Endogenization events are depicted as icosahedrons and temporal ranges of insertion events are shown as coloured rectangles (colours correspond to the respective geological epoch in the International Stratigraphic Chart; http://www.stratigraphy.org/ics%20chart/09_2010/StratChart2010.pdf). Although eZHBV_O1 (grey letters) was previously dated⁷, we sampled two missing taxa (Prunella, Chloropsis) that permit a more precise dating.