Key words: Stick insect, UK, Loss of sexual reproduction
The insects - found off the coast of Cornwall - reproduce asexually without the need of male sperm.
Clitarchus hookeri - originally from New Zealand - came here by "accident" when plants were brought across.
And it took just 100 generations for the species to evolve "barriers to sexual reproduction".
Biologists in New Zealand took the insects back to find out what happened more closely.
"We know the individuals who moved came from a sexual population - so just one or two eggs could've resulted in the whole population that's surviving there (near Cornwall) now," says Dr Mary Morgan-Richards, from Massey University, who has been studying the species for around 20 years.
This particular stick insect species is found on the Scilly Isles and is "capable of both reproducing sexually - which is the way most multi-cellular organisms reproduce - and also asexually".
"We were able to identify a population that had moved from New Zealand to the UK, left behind males, and in just 100 generations had evolved barriers to sexual reproduction.
"We were also able to identify switches in New Zealand going the other way, where populations that had been asexual reverted back to using sexual reproduction."