Reading the press or listening to the TV news you could be forgiven for thinking that these organisations are tied a the hip.
What are the facts?
According to Karen Greenberg in Guardian America CiF:
"According to the National Counterterrorism Centre, al-Shabaab's links to al-Qaida have not reached the organisational level; it can therefore in no way be classified as a strong partner in the al-Qaida network. To quote from the NCC's website:
"While most of [Shabaab's] fighters are predominantly interested in the nationalistic battle against the TFG and not supportive of global jihad, al-Shabaab's senior leadership is affiliated with al-Qaida, and certain extremists aligned with al-Shabaab are believed to have trained and fought in Afghanistan."
A summary report by the Council on Foreign Relations concurs:
"Experts say there are links between individual al-Shabaab leaders and individual members of al-Qaida, but any organizational linkage between the two groups is weak, if it exists at all."