Sentence:  There were a few islets in the sand .... These were at once <WSD>denizened</WSD> by the "Calotropis", "Argemone", "Tamarix", "Gnaphalium luteoalbum" and two other species .... 
Meaning of the word marked with <WSD> tags:  To provide with denizens; to populate with adopted or naturalized occupants.