Classifying chihuahuas and saint bernards

Species ification of the Saint Bernard and the Chihuahua The dog, canis familiaris, is among the 38 species ified as members of the Canidae family and the Carnivora order and is believed to have descended directly from the wolf, canis lupus (Galibert, Quignon, Hitte, & André, 2011, p. 191). The number of estimated dog breeds is large with most possessing different characteristics. For example, the Saint Bernard is up to 100 times heavier than the Chihuahua. Controversy has developed as to whether or not some of the breeds still share the same species classification due to such great differences. This paper explains, supports and proves that the Chihuahuas and the St. Bernard breeds are of the same species.
Artificial selection, which involves cross breeding different dogs, has led to the many and different dog breeds seen today. The Saint Bernard and Chihuahua are good examples of the big difference created as they are extremely different in terms of looks and size. This great difference is only phenotypical and does not affect their gene pool. Phenotypical variation is evident in many animals of the same species and is also evident in humans. Therefore, the difference in look and size between the Saint Bernard and Chihuahua does not prove that they are different species.
Galibert, Quignon, Hitte and André (2011), point out that the need for dogs to perform different tasks was a strong impetus towards artificial selection and the creation of more breeds. This creation, although leading to different phenotype characteristics as evident in the Saint Bernard and Chihuahua, does not change the fact that the dogs are still in the same gene pool. And can therefore, interbreed and have offspring.
In conclusion, although having many phenotypical differences and great visible variations, the Chihuahua and the Saint Bernard are still in the same gene pool and are classified in the same species group, canis familiaris.
References
Galibert, F., Quignon, P., Hitte, C., & André, C. (2011). Toward understanding dog evolutionary and domestication history. Comptes Rendus Biologies. doi: 10. 1016/j. crvi. 2010. 12. 011