Endemism map: how does the map of endemism works?

[preuss96]

I am trying to understand the criteria to make an endemism map, but I didnt found it in documentation.

The criteria was taken in account following some author description in literature? If yes, which?

[lukasbaumbach]

Crisp et al (2001) Endemism in the Australian flora. It's mentioned in the stack_modelling function description at the bottom