Crossbreeding is the process of mating two strains of a particular plant or animal species to produce offspring that display desirable characteristics. This process remains popular within agriculture in particular, because of the phenomenon of heterosis (also known as hybrid vigor), which dictates that the hybrid offspring tend to perform better than their parents. However, mating the hybrid offspring as a new generation is generally less successful, and there is a need to retain the purity of the family line of the original parents for subsequent crossbreeding. Successful heterosis requires a suitable level of complementarity between the specimens. While most large cities of the world contain populations of crossbred dogs, which show the vigorous fertility of so many crossbreeding encounters, there are nevertheless limits to ...