Which of the following does not show ecological diversity?

The correct answer is Option (4) → Rauwolfia vomitoria

Ecological diversity is diversity at the ecosystem level: the number of different kinds of ecosystems in a region.

Option (1) Coral reef — Shows ecological diversity.

Option (2) Alpine meadows — Shows ecological diversity.

Option (3) Wetlands — Shows ecological diversity.

Option (4) Rauwolfia vomitoria — Does not show ecological diversity. This is a single plant species. The variation among its plants in different Himalayan ranges is genetic diversity.

NCERT Extract:
Biodiversity – “… (iii) Ecological diversity : At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway.”
Biodiversity – “… The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces.”