Reality, as is usual, doesn't like to comport well with being assigned either or little boxes and hew perfectly to set definitions.
Say you walk from a forest into a swamp, where do you draw the line between, is there such a thing as a swampforest?
;)
Species (and other taxonomic categories) do not exist in nature. They are human-created distinctions we set up to help us categorize things.
IOW, they’re map, not terrain.