PS - I'm not even sure e-on considers this a bug.  This is the answer I received in response to my bug report:

*"Hi Mari-Anne,

After you have added empty ecosystem layers, just go back to each layer and create your ecosystem. You don't have to populate it at that time.

Then, after you've selected the items for each ecosystem, go back to the lowest layer and populate. Then move up through the layers, from the bottom up and each one will populate.

That way you get your desired effect.

Best regards.
Lee Randall* "