Specialists

noun

1. Someone who is an expert in, or devoted to, some specific branch of study or research.
2. A physician whose practice is limited to a particular branch of medicine or surgery.
3. Any of several non-commissioned ranks corresponding to that of corporal.
4. An organism that is specialized for a particular environment.

   "The tree Lepidothamnus laxifolius is a high alpine specialist found in high-altitude bog communities and in scrub."