Step 1: Understanding the Concept
Genetic diversity is the variation in genes among individuals and populations of the same species.
Step 2: Apply to Rauwolfia
Rauwolfia serpentina growing in different Himalayan ranges differs in the potency and amount of its active chemical, reserpine.
Step 3: Conclusion
These are differences within one species, so it is intraspecific diversity.
Final Answer:
Rauwolfia serpentina shows intraspecific diversity.
\[ \boxed{\text{(B) }\text{intraspecific}} \]