• Don Roberson

    Of course this is great stuff, as is everything that Bob Pitman and/or Lisa Ballance do [I’m a big fan having been hired by them 20 years ago to spend 4 months at sea as a bird observer on a cetacean research cruise], but unfortunately this split leaves the Orcas in the rest of the world paraphyletic. Here in Monterey Bay we have 3 types (likely species) of Orca, as summarized from this quote from the MontereyBayWhalewatch site:

    “Three different eco-types of Killer Whales occur in Monterey Bay: 1) Transient Killer Whales (mammal hunting), 2) Resident Killer Whales (fish eating), and 3) Offshore Killer Whales (feeding on fish, sharks, and squid). Each population type is genetically distinct from the others, and they do not interact among types. They have distinct vocalizations, look physically different to the trained person, exhibit different social groupings and hunting tactics, and specialize on different prey. They may eventually each be considered separate species, as they do not intermix.”

    There are surely 3 species of Orca here, of which perhaps 2 may be linked with the species in Antarctica, but that linkage has not yet been studied or, if it has, has not been published.

    The upshot is that there are x number of Orca species in the world — surely “x” is greater than three — but knowing that there are 3 in the Antarctic just leaves the rest of us hanging out in bewildered limbo. What is needed is a comprehensive world-wide look at this…. In my lifetime, please?

  • vladimir dinets

    The idea is nothing new, but I remember reading somewhere that genetic analysis of N Pacific orcas showed no species-level differences, and that all 3 types occasionally interbreed. My understanding is that these differences in mtDNA are about the same as those found between human populations (and, of course, in humans you also find ecotypes often living side by side, but looking, talking and behaving differently, and having only limited genetic exchange).

  • Morgan Churchill

    Just checking in after a long birding trip to NC.

    Regarding Killer Whale speciation, early studies used only very small sections of mitochondrial genes. This is the first study to look at the worldwide pattern with the complete mitochondrial genome, and the genetic differences between the Three main groups (Transient, Resident/N Atlantic, and Antarctic are substanstial. I saw the main genetics person responsible for the study give this talk at last year’s Marine Mammal conference, and I think he advocated keeping the offshore population as a different subspecies. The divergences are fairly shallow within the resident and atlantic clades, and there is probably signficantly more gene flow between offshore and residents then between residents and transient, whose divergence is pretty deep. It’s possible further subdivisions might be needed in the future, the the current taxonomic allocation seems the best fit, as all three groups are morphologically distinct and show widespread sympatry with limited gene flow

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