Figure I. An example of the lines of evidence used to infer the horizontal transfer of a transposable element family, OposCharlie1 (OC1), across 3 phyla and 3 continents.

(a) Phylogenetic evidence based on a tree showing the patchy distribution and timing of amplification of OC1 across phyla. Presence indicated with an orange lightning bolt, timing of amplification (mya) estimated for vertebrates based on sequence divergence of copies from the consensus shown below tree. (b) Lack of orthologous insertions among taxa illustrated by an alignment showing empty sites at orthologous positions across taxa sharing recently transferred copies of OC1 (target site duplications of insert shown in yellow). (c) Sequence identity shown by a plot of the percent identity at the nucleotide level across all aligned regions of the OC1 consensus sequence across taxa, including the transposase open-reading frame (indicated by the blue rectangle), using 10 bp window and 3 bp steps. (d) Biogeographical evidence represented by a phylogeny of OC1 elements superimposed on a map to illustrate the presumed distribution of the host species at the inferred time of transfer which shows higher identity among geographically overlapping species. (e) Candidate vectors include i. naked DNA or RNA, ii. TEs, iii. viruses, iv. bacteria (e.g., Wolbachia), v. cellular parasites (e.g., trypanosomes), vi. internal parasites (e.g., schistosomes), vii. obligate endoparasitoids (e.g., parasitoid wasps), viii. ectoparasites (e.g., R. prolixus, the blood sucking triatomine bug, which has OC1 copies 95% similar to those found in its preferred host, the opossum [based on Gilbert et al. 2010]).