I have found a great way of doing it. Surround species names with « and ». These are just plain text, so no need to mess with styles. I can build them into existing TextExpanders, so don't need to manually type them. They can easily be searched, can be hidden and I can easily extract text between « and » and save to a new file.
Many thanks for help, and giving me the idea to tag species names as I type, rather than having to locate them post-hoc.