Chandramohan is correct that the tree Viking Guy posted is definitely not G.xanthochymus - it is an american garcinia (formerly Rheedia which includes G.madruno). Different from the other species pictured in this thread. If we call every yellow fruited garcinia "yellow mangosteen" there would be quite a few different fruits we are calling yellow mangosteen.
G. madruno is an american (new world) garcinia species commonly called 'madrono' in Colombia and 'ocoro' in Bolivia. It is not a 'lemon drop' aka G. intermedia.
Abimael, looks like an old world (india/asia) garcinia species from the photos.
Not sure anyone, including myself, agreed that either of the trees pictured were G.xanthochymus.
I used yellow mangosteen the same way someone would use the word satsuma, perhaps. I wasn't referring specifically to the false mangosteen.
I specified above that mine was G.madruno--which, by the way, is referred to as one of the two lemon drops known, in addition to G.intermedia. When loosely coining any of these, most folks I know just say yellow mangosteen in general. I forget everyone here wants the exact Latin terminology.
Anyways, where did the guy send your tree from? Seeing as you're from Puerto Rico, I find it less likely to originate from India--especially with them irradiating seeds etc.
All my Indian friends and I have to go to great lengths generally to make trades--almost comical, really.
Got me interested now, though. I may have to view this on my computer rather than my phone so I can blow up the photo.