When you take a playbook advancement and gain a special ability are you restricted to your playbooks options?

When you take a playbook advancement and gain a special ability are you restricted to your playbooks options?

When you take a playbook advancement and gain a special ability are you restricted to your playbooks options? For example, can a Hound take a Spider ability… or is he restricted to Hound?

I haven’t been able to find an answer in the book… maybe I’m blind.