The Answer is All of the above
They both are the second to last anwsers
Ring species.
When there are neighbouring populations that can interbreed with each other while only two of those populations cannot breed between them, we are standing before a ring species. In the case of Larus gulls what is observed is that several of these species can interbreed, but it comes to two of them that are incompatible - they are probably to<span> distantly related to interbreed. It is considered, that this species may be connected to each other in a line of derivation and is both ends on that line that are incompatible.</span>
