After reading the news about possible tiger subspecies reclassification and research findings, and that the current classification of many subspecies is very old, what current subspecies of certain species in zoos, you think in the future will be regarded as one subspecies and will not be worth of classification and preventing of breeding in zoos? What about: -South-central black rhinoceros (currently around 50 in zoos) same subspecies with the Eastern black rhinoceros and that there is not a really more than one subspecies of black rhinoceros? And phasing-out of south-central black rhinoceros is a big lost for the zoo (Eastern) black rhino captive population? -African lions, and even identical with the Asiatic lion -African leopards -Indian and Sri Lankan leopard -North Chinese and Amur leopard -Northern and Southern white rhinoceros -Splitting of the Bornean orangutan into several subspecies -Southern & Northern (African) and Asiatic cheetah -Splitting of the African bush elephant (Cape, East-African, etc.) -Angolan and Cape giraffe - same subspecies of the species Southern giraffe -Eclectus parrot many subspecies -Western and Eastern Egyptian vulture -Western and Eastern gaboon viper *** -Continential Asian elephant (Indian, Sri Lankan, Malaysian) -Sunda Asian elephant (Bornean, Sumatran, Javan)
Subspecies is even fuzzier than species. You can think of them as like human races in anthropology: no one claims they are properly discrete. What matters is population: if (say) a Malayan tiger is observable different from other tigers, that difference stands regardless of who chooses to label it as whatever: taxonomic labels do not define difference. A slight genetic difference can be important: a population of wall lizards was introduced to an island in the 20th century and quickly evolved adaptations towards herbivory: no one would consider them even a subspecies yet the difference evolved already was arguably more profound than that between two related species. On that note: think of domestic species and remember intensive artificial selection were rare until the early modern era - the difference between a primitive greyhound type and a mastiff evolved naturally. By chance today I was reading about Coregonus extinctions, in European mountain lakes. And looked at the complicated taxonomic mess. And then realised all those subspecies/species aren't extinct at all, but supposedly living on through hybridization in the introduced whitefishes. And things like that strike you as a reminder how arbitrary subspecies and even species taxonomy is. TLDR: this stuff is just fuss. There isn't a real place to draw the line.
I agree with SealPup for the most part (I do, however, take some issue with the statement that "differences between a primitive greyhound type and a mastiff evolved naturally" - there is no evidence that I know of to support such a statement and artificial selection is still artificial selection even if it occurred slowly and not like "modern" artificial selection). There is no universal way to describe a subspecies (or indeed a species). For the purposes of this list, it's far more instructive to address how zoos should manage populations below the species level and how the subspecies/species issues impact conservation decisions.
Well artificial selection is directed and therefore rapid. If you take away the effects of intensive, purposeful engineering, its hard to draw a line between artificial and natural selection in anthropogenic environments AA everyone agrees even stone age people's had some degree of control over their stock. But the distinction I'm making is actually the one between loosely controlled landraces and breeds. People forget the origin of the word race in anthropology comes from the word landrace (in ie. Deniker, Darwin). This is important because differences between human populations, and Holocene evolutionary trends of man, mirror those of domesticates without external selection upon Homo sapiens. Similarly commensals like house mice and sparrows, also show the same evolutionary trends as in domesticates and humans themselves. So at the earliest grade and most of history, adopting anthropogenic habitat was just speciation through ecology like moving into semiaquatic habits (etc) and acquiring a telltale suite of adaptations. Based on anatomy I can't think of a definition of domesticates that excludes man himself and his little commensals and indeed domesticates have domesticated human physiologies ie. lactose tolerance. Artificial selection thus has to be discerned apart from domestication itself, and the initial traits acquired in common by domesticates are naturally acquired. As regards dogs: in the past domestic dogs were thought polyphyletic. Most famously Lorenz and his claim of wolf and jackal dogs, with most dogs being C. aureus derivatives, but at times far more wild dog species were implicated such as harriers from the Simien jackal or dingo from the dhole: because all Canis species integrade to some degree some of these old claims may have some degree of truth. To conceptualize dog differences various Linnean sounding binomial taxa were produced such as "Canis palustris". Interestingly given the similarity of human differences to those between dog races, attempts to name dog species were usually either nonconforming to standards else half-hearted much as racial taxonomy of man diverged from zoological norms whilst paying lip service to them (ie. Baker, Eickstedt). As with racial taxonomy in man it gets confusing as to the hypodigms of the "species": is the dingo-like basenji a living dog of the Turberas or not? And if it was, why was the dingo usually accorded a separate origin. (This nonsense still continues today, in a way, when only certain pariah types are inconsistently regarded as Canis familiaris dingo). Dog origins are not known though they came from a wolf like ancestor and are monophyletic despite introgression confirmed. Since the original ancestor came into domestication the dog's evolution parallels those of wild canids: the slender harriers first appearing in arid northern Africa resembling the Simien jackal, the strong jawed types upon the dire wolf, and even similarities noted between certain "Canis palustris" European Spitz derivatives and the distantly related bush dog and Sardinian "dhole": all of these differences between primitive breeds reflect the local environments or hunting styles as for wild species. If similarities between wild dog species and domestic strains do turn out due to introgression the observation still stands, that the genes acquired came under natural selection whilst in anthropogenic environments. I still stand that dog diversity was initially and largely shaped by natural selection, and aDNA will confirm clades of dog that reflect speciation.
