Is domesticated animals considered as a single species or subspecies of its wild ancestor or just a variation from its wild species ??? For example, is domesticated duck and its wild ancestor, Mallard duck are separate species or combine together?
I found your question very interesting and it made me wonder about the taxonomy of the dog. According to Wikipedia the domestic dog was classified as a distinct species (Canis familiaris) until 1993 when it was reclassified as a subspecies of the wolf when it was clear that all dog breeds arose from wolves. "In 1753, the father of modern biological taxonomy, Carl Linnaeus, listed among the types of quadrupeds familiar to him, the Latin word for dog, canis. Among the species within this genus, Linnaeus listed the fox, as Canis vulpes, wolves (Canis lupus), and the domestic dog, (Canis canis; see File:Linnaeus - Regnum Animale (1735).png). In later editions, Linnaeus dropped Canis canis and greatly expanded his list of the Canis genus of quadrupeds, and by 1758 included alongside the foxes, wolves, and jackals and many more terms that are now listed as synonyms for domestic dog, including aegyptius (hairless dog), aquaticus, (water dog), and mustelinus (literally “badger dog)”. Among these were two that later experts have been widely used for domestic dogs as a species: Canis domesticus and, most predominantly, Canis familiaris, the “common” or “familiar” dog.[23] The domestic dog was accepted as a species in its own right until overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single species, the gray wolf, is the common ancestor for all breeds of domestic dogs.[24][25][26] In recognition of this fact, the domestic dog was reclassified in 1993 as Canis lupus familiaris, a subspecies of the gray wolf Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists. C. l. familiaris is listed as the name for the taxon that is broadly used in the scientific community and recommended by ITIS, although Canis familiaris is a recognised synonym.[27] Since that time, C. domesticus and all taxa referring to domestic dogs or subspecies of dog listed by Linnaeus, Johann Friedrich Gmelin in 1792, and Christian Smith in 1839, lost their subspecies status and have been listed as taxonomic synonyms for Canis lupus familiaris [28]" Dog - Wikipedia, the free encyclopedia
In this case domesticated animals considered as the same species as its wild ancestor is because none of the criteria of the species allow to separate domestic form into a new species. Domestic forms are marked like this: Long-tailed chinchilla (Domestic form) – Chinchilla laniger var. dom. Domestic polecat – Mustela putorius var. dom.
it depends on the specific type of domestic animal. Some are considered the same species as their wild ancestor (as [now] in David Brown's dog example, or wild/domestic pigs and wild/domestic ducks) and some are considered to be genetically distinct and hence are treated as a separate species (e.g. domestic vs wild Bactrian camel; also llamas and alpacas are a good example of domestic forms being considered distinct species). Then again, because it's taxonomy, there is not always agreement on whether a given domestic should be considered the same or separate from its wild ancestor (the dog example falls into this category as well, as do horses). Confused?
