During the 11th and 12th centuries, the Omani coast was in the sphere of influence of the Seljuk Empire. They were expelled in 1154, when the Nabhani dynasty came to power. The Nabhanis ruled as ''muluk'', or kings, while the Imams were reduced to largely symbolic significance. The capital of the dynasty was Bahla. The Banu Nabhan controlled the trade in frankincense on the overland route via Sohar to the Yabrin oasis, and then north to Bahrain, Baghdad and Damascus. The mango-tree was introduced to Oman during the time of Nabhani dynasty, by ElFellah bin Muhsin. The Nabhani dynasty started to deteriorate in 1507 when Portuguese colonisers captured the coastal city of Muscat, and gradually extended their control along the coast up to Sohar in the north and down to Sur in the southeast. Other historians argue that the Nabhani dynasty ended earlier in A.D. 1435 when conflicts between the dynasty and Alhinawis arose, which led to the restoration of the elective Imamate.