I'd like to start first by saying that I don't believe in creationism at all, nor any non-Darwinian-evolution explanation of the diversity of life on Earth. The theory, the fossil record, and the genetic, morphologic, and biochemical evidence are more than overwhelming in support of it.
Also, I understand that the term 'macro-evolution' is a "weasel word" invented by creationists to make a bogus distinction of two supposed kinds of evolution.
But for this question, I think the term is useful. I'm happy to take any corrections or qualifications in comments or answers.
I wonder if there has been any long-term experiment performed to attempt to induce 'macro' changes in a species-- something that would make this lab-based population considered to be a subspecies, or even a different species, if it were found in the wild.
I'm aware of the long-term E. Coli experiment that resulted in bacteria that developed mutations that allowed them to completely metabolize citric acid. I understand that's a change of a few genes (amongst other recorded changes).
What I'm looking for is something a little larger, more than a new protein. I was thinking something like 1. a new organelle, 2. a new type of cell or tissue, 3. a new organ, or 4. a new type of limb or radically different limb use (something like reptilian jawbones re-purposed in mammalian ears_.
I understand there are numerous incidents of organisms losing useless features, such as eyeballs in dark caves, flight ability, etc. For this experiment I don't think it's enough to show the loss of something-- genes turning off, but novel characteristics must arise. To rebut creationists, I think it's necessary to show 'new' information, not just loss of information (I'm speaking of the genes responsible for morphology).
With my laypersons' imagination, I was thinking of a species with a relatively fast reproductive cycle, put in an environment that had some selective pressures. Perhaps one without much room to fly, not enough food, but plenty of food in a water area where they couldn't normally get to it. Something that might encourage them to adapt to taking to water to exploit a new food resource.