HORIZONTAL AND VERTICAL. “According to textbook theories of evolution, the major route of genes moving between organisms is parent to child – whether through sex or asexual cloning – not this sneaky business of escorting genes between unrelated organisms. We must now acknowledge that, even among the most complex organisms, vertical is not the only direction in which genes travel.”
https://aeon.co/essays/genes-that-jump-species-does-this-shake-the-tree-of-life