Virgil is our established guide from Inferno. In Purgatorio, he continues to guide to lecture, to answer questions, and to make recommendations, but he’s no longer the authority figure he was in Hell. For one thing, he doesn’t know his way around Mount Purgatory and he has to ask the penitents for directions. He even begins admitting his own shortcomings when Dante begins asking deep questions about the nature of love or the formation of the soul. Being a pagan Virgil lacks the faith needed to fully address such issues. The closer he and Dante get to the top of the mountain, the quieter Virgil grows, especially when Statius is introduced. He cedes a lot of the teaching to Statius and actually goes completely silent in the Earthly Paradise. By the time he vanishes, Virgil has already been a literary non-presence for quite a few cantos.
From the moment Statius enters the scene, we know something’s up. Author-Dante pretty much hails his arrival as the second coming of Christ. He compares Statius to Jesus when introduced. His conversion to Christianity is harped on to no end. Author-Dante goes to great pains to establish him as a writer on the same level as Virgil. We learn it’s for him that the mountain has just trembled, meaning Statius has just purged himself of all his sins and can – conveniently – go to Heaven with Dante, if needed. Character-Dante begins calling both Virgil and Statius his two masters. Then, Virgil lets Statius do some of the teaching. It’s obvious that Statius is Virgil’s replacement, and though he’s pretty quiet in Purgatorio, we expect him to take on a more authoritative role in Paradiso.
Beatrice’s role as guide and mentor is a little less obvious than Virgil’s or Statius’. First of all, she’s a woman. If you haven’t noticed, women were rarely given roles as authority figures in Dante's day. And she’s not a poet of any sort. However, as she begins throwing accusations at Dante and lecturing him mercilessly on a personal level – behavior we’ve never seen from Virgil or Statius – we begin to get the idea that she’s the ultimate mentor, or perhaps she’s more like a confessor. She knows Dante better than any other character and she’s not afraid to call him out on all his faults. In fact, that’s her mission. In the end, she charges Dante with his divine mission: to write about his experiences truly and bring them back to earth. Like Statius, we expect she’ll play a bigger role in Paradiso.