I have something like that growing in my backyard. I have no clue what it is though, it was there when I moved in.
I went out today and collected some ilex cassine leaves, they're much larger than yaupon, like 3-4 inches long. This means one doesn't need to harvest as many leaves or harvest from as many trees. Plus it's evergreen like vomitoria with bright green leaves even in winter. Made a tea that turned black almost instantly after the water began boiling.
One question I have is has anyone used yerba mate as an a ayahuasca additive? How much did you use? I'd like to use the cassine leaves but I'm not sure how much to use to alter the brews effect, but without going overboard on the caffiene.