Figure 3. Pantropical transfer of AviRTE putatively mediated by insect-borne nematodes.

(a) Diverse geographic origins of seven representatives of AviRTE-bearing birds illustrated on a paleogeographic map of the Earth 20 Myr ago. The Mollweide projection map is copyright to Ronald Blakey (used with permission). (b) Paleobiogeography of the AviRTE phylogeny (see panel c) inferred via statistical dispersal-vicariance (S-DIVA) analysis. We used avifaunal regions sensu Ericson³⁵. For nodes marked with an asterisk, only those areas which received >33% of the ancestral area distribution on this node are shown. Strikingly, the two waves of HT events (cf., Fig. 2a) are not only separated temporally (genome invasion dates of the first and second waves of HT are shown in orange and yellow letters, respectively), but also phylogenetically and biogeographically. (c) The species tree of avian²² and nematode²⁷ hosts (left) is highly incongruent with the AviRTE phylogeny (right; RAxML, GTRCAT model, 1,000 bootstrap replicates, bootstrap values ⩾50% shown) and the assumption of nine HT events (red asterisks) is required to reconcile the two topologies. The AviRTE phylogeny is rooted to several more or less closely related outgroups (Supplementary Fig. 4; cf., Fig. 1c); however, only the closest outgroup is shown for comparability of ingroup internode lengths. Green branches are topologically identical between both trees, implying vertical transmission in species-rich avian lineages. Orange and yellow colours indicate the Oligocene and Miocene waves of HT events, respectively.