Indeed, that's the point I was trying to make. I just don't know of any non-human examples. If there can be at least three human-populated worlds that are counted as separate members of the Federation, I don't see why there couldn't be, say, several worlds populated by Tellarites that are all separate member states.We Humans may not be so unique in this respect. Could be any number of races that colonized other worlds - some of which have joined the Federation more or less independantly of each other.Do we know that 150 worlds mean 150 separate species, though? In the books, at least, both Mars and Alpha Centauri, both (apparently) with human-majority populations, are depicted as individual members of the Federation, separate from Earth.Out of curiosity, I looked that up. Turns out, 53. Though only 26 are confirmed members as of the 24th century. The rest are believed to be members depite nothing being firmly established one way or the other, those that Mr. Daniels claimed would be members in the 26th century, and members of the Coalition of Planets who likely did become Federation members, though there's nothing canon to say so.
Fun fact.