Indigenous species are also known as native species or populated in an area where humans did not intervene. In this topic, it is talking about the native or indigenous species of bees. These (indigenous) bees are pollinating in their original location. They can be seen naturally in their habitat and most of the time have a longer lifespan compared to bees that are introduced to a new place.
The reason is bees that live in their natural habitat are easily adjusted to change of seasons as compared to introduced bees that will take longer to adapt to their new environment. Even though some indigenous bees do not produce honey, they are equally important in pollinating plants.