Transposable elements modify gene regulation in maize to confer drought tolerance, alter flowering time, and enable plants to grow in toxic aluminum soils.
Insofar as we can track evolution as it has happened, e.g. in dog breeds, it consists overwhelming of breaking genes, the degradation of biological information.
They are not, per the National Academy of Sciences, a “particularly convincing example for speciation.”
“Darwin’s mechanism is dominated by ‘Poison-Pill’ mutations: positively-selected, loss-of-function mutation.” It “squanders genetic information for short-term gain.”
A study in PNAS has gotten tons of affectionate press, probably because puppies are so darned cute.