The role of differential selection in determining the geographic distribution of genotypes in hybrid
systems has long been discussed, but not settled. The present study aims to asses the importance of selection in
structuring all-hybrid Pelophylax esculentus populations. These populations, in which the parental species (P. lessonae
with genotype LL and P. ridibundus with genotype RR) are absent, have pond-specific proportions of diploid (LR) and
triploid (LLR and LRR) genotypes.