An elemental ascetic can use his Wisdom modifier instead of his Constitution modifier to determine the DCs of Constitution-based wild talents, the duration of wild talents with a Constitution-based duration, and his bonus on concentration checks for wild talents. This ability alters the key ability scores of wild talents
Forgive me if this is obvious, but does the "can" wording in the first line indicate that the Elemental Ascetic can choose between either Wisdom or Constitution for their wild talents? No other class or archetype I know of allows the player to choose the attribute, hence my confusion about the wording.
Yes, you "can" choose.
Take a look at the Zen Archer. You "may" replace Dex as your to-hit stat with Wis, essentially the same thing. It is permitting you to do so if you choose to do so.
Unlike the Sorcerer Wildblooded Empyreal Bloodline, which says you straight out replace Cha as your casting stat with Wis, and Sage replaces Cha with Int. No "can" or "may", just do.
I wasn't aware the Zen Archer let you choose in the same way- thank you for the clarification!