What causes SPS corals to branch?

[gnikoli]

What stimulates corals to branch and why do they grow in the direction they do? I understand that the character of water flow plays a large role and of course, sunlight contributes a lot to growth habit, but what triggers the tip of a coral to form more than one axial corallite? I have watched one branch continue to grow straight up while another very close to it branches. They looked the same just before that, with the same orientation and as far as I can tell, the light and current was the same for both tips. Pinching back tips doesn't seem to stimulate branching, at least not consistently. After pruning, some will continue to grow without branching and others branch.

Does coral tissue communicate across colonies? For instance, an injury to one tree branch causes a whole-plant, physiological response. If one part of a coral colony is physically injured, does the rest of the colony even notice?

I've Googled these questions and have not been able to find clear answers.

[jdieck]

I really do not know what promotes branching but in my experience corals with a single axial coralite like acroporas will tend to branch at the tip when the single coralite is broken or damaged.
Actually when gragging a coral branch I get several pieces of the same branch. The tip piece continue growing as a single branch while the pieces from the middle of the brach will generate several branches at the exposed tip.

[GQ22]

water flow and the species. if you are going to purchase a cluster formation species it will not branch