Answer:
Reproductive isolation
Explanation:
Reproductive isolation is the lack of successful breeding between organisms of related species due to the existence of morphological, physiological, genetic or behavioural barriers.
Reproductive isolation mechanisms are classified into two:
The pre-zygotic mechanisms act to prevent breeding or formation of zygote between organisms of related species while the post-zygotic mechanisms act to ensure that aborted or infertile zygote results in cases where fertilization takes place.
The distinct characteristics observed in the species of butterfly can be viewed as a form of morphological reproductive isolation.