Incoming links: Horizontal gene transfer
Ways in which it can happen:
Graph of life
. Source. horizontal gene transfer transforms the tree of life into the graph of life! Fuck my life.
It is important to note that due to horizontal gene transfer, the early days of life, and still bacteria to this day due to bacterial conjugation, are actually a graph and not a tree, see also: Figure "Graph of life".
Definitely have a look at: coral of life representations.
Current Wikipedia seems to say that this refers specifically to cells taking up DNA from other dead cells as in the Avery-MacLeod-McCarty experiment, excluding other types of horizontal gene transfer like bacterial conjugation
The term is sometimes just used a synonym for horizontal gene transfer in general it seems however.