So scientists have agreed that they don't agree? I'm confused.
Speciation is a process.
The end point is clear...2 organism populations that do not interbreed in the wild are two different species.
Where the line is drawn during speciation is a flexible concept. Tigers and lions can interbreed with very limited success. They cannot do so in the wild.
In a ring species, the ends of the ring are clearly two species because they do not interbreed in the wild. There is no fixed point along the ring forthe dividing line, though.
No. Scientists agree that there is no single definition for species that works in all cases.