I'm curious, according to your argument all these (sub)species of Galapogos finches interbreed, is that correct?
And when two subspecies interbreed an new one is created, is that correct?
Have there been any new (sub)species recorded since Darwin's first visit?
Why yes, three of them are interbreeding so profusely, they term it merging into one. That they havent yet, officially recognized it as a new one is understandable, being they’ll first argue amongst themselves for years, before finally declaring a new species.
But remember, every single one of those “claimed” species, is no longer the same as what Darwin originally recorded, because of interbreeding.
I’m not sure if you can distinguish the subtlety, but I’ll try. Africans have not inbred for multiple specific traits like we have with dogs. So when an African and Asian mate the difference in offspring is more subtle, but still distinct. Not like dogs which have repeatedly been bred for specific traits. So that when Mastiff and Husky mate, the difference is more dramatic. Each one contains less overall variability.
The same with finches, man has not interfered, so like all animals subspecies tend to mate only within the same subspecies for survival reasons. So when they do interbreed, the differences are also less dramatic.
But why are you asking, read the grants paper yourself.
Or the others where they too observed it right before their eyes. Granted they are simply confused about species and subspecies, but since you asked.
https://evolution.berkeley.edu/evolibrary/news/100201_speciation
But let’s notice with those finches it required a different subspecies to make it happen....