5 Responses

  1. AreWeThereYeti
    AreWeThereYeti July 1, 2013 at 1:16 pm |

    In a word: fascinating!

  2. mandors
    mandors July 2, 2013 at 9:57 am |

    I am skeptical that the variations between A, B, C and now D truly constitute different species. One can look a Bull Mastiff and a Poodle and see evidence of different species, but they’re not. Here, the differences though extant are not nearly as significant.

  3. AreWeThereYeti
    AreWeThereYeti July 3, 2013 at 10:44 pm |

    @ mandors: Species are generally defined as “groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups.”

    Lions and Tigers, along with all other members of the “Big Cats,” while comprising separate species, CAN successfully be cross-bred in captivity. The same is true for Black, Brown(Grizzly) & Polar bears. In fact, instances of naturally occurring Polar/Grizzly crosses have recently been documented. The resulting hybrids are known as Grolars or Pizzlys.

    Dogs, no matter how dissimilar, are ALL members of the same species: Canis familiaris. As a result, one CANNOT “look a(t) Bull Mastiff and a Poodle and see evidence of different species” – at least not scientifically.

    Which brings us to the disparate groups of Orcas. That they apparently do not interbreed on a regular basis, means they fit the common definition of separate species. The similarities in appearance – or lack of differences, if you prefer – do not preclude them from being recognized separately in scientific nomenclature.

    However, to be fair to your argument, biologists still dispute the details of an all-encompassing definition of species. Throw the matter of subspecies – that is, groups capable of successfully interbreeding, but that usually don’t due to geographic isolation – and the “Orca problem” will likely remain disputed for some time to come.

  4. mandors
    mandors July 6, 2013 at 3:05 pm |

    Yeti, I am aware of the definition of species. I am contesting it’s use here. There are only physical differences and geographic differences cited in the article. Personally, I do not find these determinative. That different groups of Orca do not breed, is very different from them being unable to breed. Tigers and Lions CANNOT be successfully crossbred, because the resulting offspring are sterile. I am aware that different bear species interbreed. I do not know if their offspring are sterile. This leads to the real determination, genetics.

    I am sure that there are blood samples from all four groups of Orcas. I wonder what tests have been done comparing groups A, B, C and D. The article is ambiguous on this point, and I don’t blame Loren. The other articles I’ve read merely make the same observations of physical traits. These like the size between a Mastiff and poodle, as I point out, do NOT indicate different species.

    The highly intelligent nature of the Orcas is an additional factor that could complicate the analysis. Orcas like humans can be very territorial and very discriminating. Pods of the same “species” have been know to shun each other, or worse. So this could likely be a cause of the lack of interbreeding. I wonder whether the differences in the groups of Orca are closer to race in humans than distinctive species. No one would claim that Innuit peoples are a different species of humans simple because they lived separated from other people and did not interbreed with them.

    The question as I see it is again whether there are genetic variations clearly distinguishing the four species of Orcas, other than genomes that determine physical traits, and whether the four type are able to interbreed successfully. The recent disclosure articles about type D do not in my opinion adequately address these issues.

  5. AreWeThereYeti
    AreWeThereYeti July 8, 2013 at 1:43 am |

    @ mandors: Thanks for expounding on the topic. I think I have a better handle on what you were trying to say.

    Clearly, even under the best of circumstances, biologists have had a difficult time nailing-down what, exactly, denotes a species. Although he may have been the first to use the terms Lumpers and Splitters, the concepts predate even Darwin himself!

    For years, all scientists had to go on were physical and territorial differences. Even now, genetic testing may or may not entirely settle the matter. Especially in this case, wherein the various types of Orcas – although physically very similar and assumed to be capable of producing fertile offspring – may “choose” not to breed with other types.

    It plays right into your comment regarding the human “races” – which, BTW, I especially liked. In fact, I think you may have hit the nail on the head! While the human species appears content to divide itself into different races, our egocentric nature seems loathe to allow us to bestow similar labels upon other creatures…

    Any way you look at it, the matter is – and will undoubtedly remain, controversial.

    P.S. I also wanted to clarify a couple points:
    As you correctly noted, MALE “Ligers” (male lion/female tiger) and “Tigons” (male tiger/female lion) cubs are ALWAYS sterile. However, that is NOT the case for the FEMALE cubs; successful matings and resulting viable litters have been documented.

    Also, I looked into it and confirmed that Polar/Grizzly Bear crosses produce viable offspring; i.e., capable, themselves, of successfully reproducing.

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