It's helpful to see how there are fundamental precedents for externally mediated genomic change, which may then give rise to phenotypic ("what we see") or genomic ("the source code of what we see") differences:

Transposons or "jumping genes" [1] are segments of DNA code which can move around within a genome by themselves (autonomously).

Presumably though, over time, enough of these moving in the right place - in combination with some other mutation - might confer some benefit that leads to speciation [2].

edit: length / clarity

[1] - https://en.wikipedia.org/wiki/Transposable_element

[2] - https://www.scientificamerican.com/article/wandering-fly-gen...