Pelophylax esculentus is the fertile hybrid of the Pool Frog (Pelophylax lessonae) and the Marsh Frog (Pelophylax ridibundus), hence the addition of the "kl." (for klepton or synklepton) in the species name. During the ice ages the population of the common ancestor of both species was split into two. These populations diverged, but remained genetically close enough to be able to create fertile hybrids. However, when edible frogs mate with each other, their offspring are often misformed, so there are no pure populations of edible frogs. The hybrid populations are propagated by female edible frogs mating with males of one of the parental species.