What is surrogate species? I was reading this book (pg-16 of link below) and the definition mentioned seem to mean that a surrogate species has the properties of an indicator species, keystone species and an umbrella species! It is a bit strange. Can you explain?

Link:https://books.google.co.in/books?id=oeflCgAAQBAJ&pg=PA16&dq=indicator+species+definition&hl=en&sa=X&redir_esc=y#v=onepage&q=surrogate%20species&f=false