Two groups of creatures are the same species if, in the wild, there is significant gene flow between the two gene pools

Species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups

Chromosomal analysis suggested that Townsend's grass was an amphidiploid because its chromosomal number, 2n=122, could be derived from the American (2n=62) and European (2n=60) chromosome numbers. Apparently a hybridization occurred on the beaches followed by a chromosomal doubling to produce the current species