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Anonymous asked in Science & MathematicsBiology · 2 years ago

At what point in its evolution does a subspecies become a species? What is the scientific requirement?

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  • 2 years ago
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    A subspecies is defined as a geographic variant of a species. A subspecies is not necessarily an incipient species, even if some scientists seem to treat them as such. Some species may for example evolve sympatrically (in the same area) as its ancestor, and while it evolved it cannot be classified as a subspecies since it is not a geographical variant. Some populations that eventually become a new species may also not be different enough to be classified as a subspecies.

    In many cases, a population becomes adapted to the local environment and it evolve differences that make it classifiable as a subspecies. However, sometimes a subspecies may be the result of neutral genetic drift and the differences are not adaptive even if it is noticeable enough to make it a different subspecies. For example a population of snakes has a neck ring that is interrupted in the middle, but the other populations have a complete neck ring. It is extremely doubtful that such a trivial character is an adaptation to the environment and therefore it may not be evolving into a different species, but it is nevertheless classifiable as a subspecies. If the adaptation to the local environment is drastic enough then a population may become so different ecologically that if it interbreeds with other populations, the hybrids would not be able to compete with one or both parental species. If so, then the hybrids will not be able to survive and the 2 populations may avoid interbreeding in the future due to natural selection against hybridization. If and when that happens, then a new species has evolved. Reproductive isolation, therefore, is how we can tell if a subspecies or a population (that was not classifiable as a distinct subspecies) has become a new species.

    If a new species has evolved from an isolated population, then if and when it comes into contact with the old species again (secondary contact) they may not recognize each other as different (because they still have the same mating call, mating dance, phermone, or color pattern for example) and therefore they may interbreed at first. Because the hybrids are not as fit as either parental species, the two may then evolve premating reproduction isolation (by evolving different mating calls, dances, or color patterns or phermones for example). Their subsequent unwillingness to interbreed will therefore be good evidence that they are different species. Unfortunately, sometimes two populations that are adapted to different local environments may not come into secondary contact, and in those cases scientists would have to determine whether these 2 are different species or 2 different subspecies by comparing them. For example, the bonobo is geographically isolated from the chimpanzee. For a long time, scientists classified them as different subspecies of the same species. More recently scientists have determined that they are so different that if they meet, they may not interbreed, since the hybrids would be unlikely to fit into the lifestyles of either species. That is why most scientists now classify them as different species instead. It would be easier if these two were to come into contact in nature and inform us through their lack of interbreeding that they are indeed different species. But since they do not come into contact, scientists would have to determine their species status based on how different they are and whether they are different enough to refuse to evolve premating reproductive isolation should they meet in the future. Such determination is unavoidably subjective, but there is no objective means of determining species status in such cases.

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  • Corey
    Lv 5
    2 years ago

    if you wanr some documented examples of speciation look up the faroe island mice and the mosquitos that live in londons subway tunnel.... during the wars in the early 1900s people used the tunnels as bunkers from the bombings and some mosquitoes ended up down there with them, and now like 100 years later the subway mosquitos and the outside mosquitos are no longer able to reproduce due to speciation. It happened that fast because they only live a few days and reach sexual maturity after 2 days...with a new generation every 3 or 4 days if their environment changes, insects can evolve a hell of alot faster that other animals

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  • Anonymous
    2 years ago

    A subspecies of an isolated group becomes a new species when they can no longer reproduce with the parent species.

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  • MARK
    Lv 7
    2 years ago

    This question probably stems from a belief that science is absolutely precise about everything. It is not. We cannot say it takes X generations for a sub-species to evolve. There is no time period over which any stage of evolution occurs.

    There is no eureka moment when scientists claim a new sub-species has evolved. There is also no hard-and-fast rule about what constitutes a sub-species. A lot depends on the knowledge, experience and opinion of taxonomists and they do not always agree.

    It is important to remember that sub-species are usually extremely similar to each other. Until recently the two metapopulations of orang-utan were considered sub-species of the same species: Bornean and Sumatran. Both are now considered species in their own right. However, Bornean and Sumatran orang-utans can breed and produce viable and fertile offspring. Two distinct species are not supposed to be able to inter-breed.

    So there are no sharp definitions. Nature does not always comply with human rules. We come-up with these taxa to classify the world around us and make it more comprehensible. But, that does not mean nature follows what we determine.

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  • 2 years ago

    Thank you, JazSync. The genetic species concept, which geneticists have the hubris to call THE biological one is badly flawed. For one thing, it works for only a small minority of organisms; it's no good for fossils or for organisms that reproduce asexually. For another, some fishes are interfertile across generic lines. Personally, I follow C. Tate Regan's definition, "A species is what a competent biologist working with the group says it is." That sounds flip but it works and is what most of us use.

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  • 2 years ago

    There are no real scientific requirements, other than that a taxonomist champions the "separate species" tag, and such things are subject to bias and stupidity.

    Take for example the third orangutan species. If the same rules used to distinguish the Tapanuli orangutan from Sumatran orangutan were applied to humans, then there would be two extant species of humans. Conversely, if the rules used to "lump" all humans into one subspecies were applied to orangutans, then the Tapanuli orangutans would be a race of Sumatran orangutan, not even a subspecies.

    Your biology teacher will talk about the "biological species concept" which involves populations that wouldn't naturally interbreed in nature. That's not great, because, for example, some canids will readily interbreed to have fertile hybrids. The "red wolf" for example has such significant incursion of genes from coyotes and gray wolves that its existence as a separate species is controversial.

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  • 2 years ago

    Never

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