At 2nd level, the spirit warden gains the ability to channel positive energy as a cleric of her level. Regardless of her alignment, she can only use this ability to harm undead creatures. The spirit warden can use this ability a number of times per day equal to 3 + her Charisma modifier.
This ability replaces the hex gained at 2nd level.
Emphasis added.
I vaguely recall a ruling made some time ago that if an ability references another class ability, it counts as that ability for the purpose of prerequisites (I think it might have been in the context of whether a Witch's familiar counted as a familiar and thus prevented the witch from getting a bonded item) even if the name of the ability is different. However I can't find that reference at the moment. Anyone able to help?
Also, this ability references the cleric's channel energy ability, but is a slightly restricted version (whereas the witches's familiar was an expanded version of the wizard's arcane bond). Does this make a difference for the purpose of prerequisites?
Yes, that would qualify for meeting prerequisites. The precedent is set by Life Oracles channel ability, and SKR, a former designer, explains in this post the reasoning.
Thanks! That post even directly addresses channel energy variants and directly answers my specific question. =)