I have recorded some individuals of the genus Calotropis in the Asir province, Saudi Arabia. Shall be grateful if someone can help me determine the exact species and key to identification of both the species.
For Saudi Arabia, Sheila Collenette, in her book An Illustrated Guide to the Flowers of Saudi Arabia (Scorpion Publishing Ltd., London, 1985), cites only Calotropis procera. Your pictures fit very well with that species, which I have seen many times in the Cape Verde Islands and the Canaries. The plant in question was introduced recently to this Spanish archipelago.